Decent benchtop multimeter for beginner?

[live2fish88]

Hey guys. Looking for a new bench top meter. I don’t feel comfortable buying used unless from a reputable seller (but still prefer new). I have handhelds but would like a dedicated bench top unit. Trying to keep the price $300 or below.

[KungFuJosh]

For $300, you're better off getting something used. For $400, you can get a brand new SDM3045X.

[wasedadoc]

Do you want a benchtop for extra digits or just better aesthetics and ergonomics? Bigger, brighter digits etc.

[nctnico]

I'm planning on getting / trying a UT8805E from Uni-T. Otherwise the cheaper VC8145 is a good choice for being a no-nonsense bench DMM although the auto-ranging is a bit slow on these. I have been using the VC8145 for over a decade already as a daily driver.

[live2fish88]

I saw the 3045x, 3055 and uni-t 8803e. Was wondering if cheaper was worth it or if I should pay more.

[wraper]

I suggest you don't bother with these whatsoever. Budget bench multimeters are significantly worse than portable meters sold for the same price. For example UNI-T UT8803E that was mentioned is about as good as $40 or even cheaper portable meter.

[KungFuJosh]

The SDM3045X is an EXCELLENT meter. I have mine upgraded to SDM3055X-E, but that's not possible (yet?) on all hardware versions (newer versions have a different firmware requirement).

In either case, it's a serious meter.

[nctnico]

I suggest you don't bother with these whatsoever. Budget bench multimeters are significantly worse than portable meters sold for the same price. For example UNI-T UT8803E that was mentioned is about as good as $40 or even cheaper portable meter.

The point is not the features but having a stackable, mains powered meter. Ofcourse you are going to pay extra for the bigger casing and mains power supply. And likely the volumes are lower so your share of the NRE costs are higher.

[BeBuLamar]

If I want a benchtop it's for accuracy otherwise I prefer the handheld. More convenient to use.

[wraper]

I suggest you don't bother with these whatsoever. Budget bench multimeters are significantly worse than portable meters sold for the same price. For example UNI-T UT8803E that was mentioned is about as good as $40 or even cheaper portable meter.

The point is not the features but having a stackable, mains powered meter. Ofcourse you are going to pay extra for the bigger casing and mains power supply.

OP did not say why he wants one, IMHO a beginner does not need one, especially on a tight budget. Mains powered is barely in advantage, batteries last for a very long time. And you'll make even less space on your likely cramped bench. There way more sensible tools that money can be spent on.

[wraper]

If I want a benchtop it's for accuracy otherwise I prefer the handheld. More convenient to use.

It's literally less accuracy for the price. Unless you spend at least double of your budget, there won't be better accuracy than in portable meters.

[wasedadoc]

Things like the $100 Owon XDM1041/1241 are a half way house. Not too big but easy to read upright display. More digits than a typical handheld but not in the $400 league.

[KungFuJosh]

It's literally less accuracy for the price. Unless you spend at least double of your budget, there won't be better accuracy than in portable meters.

The SDM3045X is a 66,000 count DMM firmware limited on what's actually 220,000 count hardware. DC accuracy is 0.06% + 8 counts. AC accuracy depends on voltage range and frequency, but the worst accuracy is 3% + 40 counts; best case is 0.6% + 10 counts.

The Fluke 87V, is 6,000 counts standard, 19,999 counts in high-resolution mode. DC accuracy is +/- 0.05% + 1 count. AC accuracy is +/- 0.7% + 2 counts. They don't give more detailed accuracy than that, I'm sure they only listed their best accuracy. I'd love to know the true range of accuracy for it.

Bottom line, the Fluke 87V costs more, and is maybe a tiny bit more accurate in a best case scenario, while also giving up other benefits of the less expensive bench meter.

If you match the price of the Fluke 87V, you can buy the SDM3055 instead. 220,000 counts. DC accuracy of 0.015% + 0.004 count. AC accuracy best case 0.2% + 0.05 count; worst case 3% + 0.05 count.

I do agree that doubling his budget gets a much better device. The SDM3065X is 2,200,000 counts. Accuracy± (% of Reading + % of Range). Worst DC accuracy is 0.0055+0.0008.  Best AC accuracy is 0.06+0.04, and worst is 4.00+0.50.

[Phil1977]

Things like the $100 Owon XDM1041/1241 are a half way house. Not too big but easy to read upright display. More digits than a typical handheld but not in the $400 league.

Yes, the Owon 1x41 are nice with only two serious drawbacks:
- The Autorange is of the "stupid" kind. If a range is exceeded, it first shows Overload, then switches the range, then it shows 0.000, then it shows the actual value. Better meters get this done much faster.
- The AC-ranges switch to zero below 1% of their full range.

Beside that it´s a really convenient form factor. I like especially the 1241 because it needs no power cord and just sits on the table where you need it with a very clear and easy to read display.

What´s also nice in this price class is the SCPI interface.

[Fungus]

- The AC-ranges switch to zero below 1% of their full range.

Many meters do that (or should do that) TRMS converters are inaccurate at low voltage levels.

[Fungus]

I have been using the VC8145 for over a decade already as a daily driver.

What  do you think is lacking in that meter? Why do you want to change?

[wraper]

The SDM3045X is a 66,000 count DMM firmware limited on what's actually 220,000 count hardware. DC accuracy is 0.06% + 8 counts. AC accuracy depends on voltage range and frequency, but the worst accuracy is 3% + 40 counts; best case is 0.6% + 10 counts.

And you can buy Brymen BM869S for a little bit more than half the price of SDM3045X. With better resolution, precision and more robust input protection.

The Fluke 87V, is 6,000 counts standard, 19,999 counts in high-resolution mode. DC accuracy is +/- 0.05% + 1 count. AC accuracy is +/- 0.7% + 2 counts. They don't give more detailed accuracy than that, I'm sure they only listed their best accuracy. I'd love to know the true range of accuracy for it.

Comparing Siglent bench meter with Fluke handheld in this context is disingenuous to say the least.

[KungFuJosh]

The SDM3045X is a 66,000 count DMM firmware limited on what's actually 220,000 count hardware. DC accuracy is 0.06% + 8 counts. AC accuracy depends on voltage range and frequency, but the worst accuracy is 3% + 40 counts; best case is 0.6% + 10 counts.

And you can buy Brymen BM869S for a little bit more than half the price of SDM3045X. With better resolution, precision and more robust input protection.

Agreed, the BM869S is a well respected meter. Again, I think they only list the best case accuracy. I would still like to see accuracy shown across the ranges like Siglent shows. I don't believe for a second these handhelds accuracies are equal across all ranges.

The Fluke 87V, is 6,000 counts standard, 19,999 counts in high-resolution mode. DC accuracy is +/- 0.05% + 1 count. AC accuracy is +/- 0.7% + 2 counts. They don't give more detailed accuracy than that, I'm sure they only listed their best accuracy. I'd love to know the true range of accuracy for it.

Comparing Siglent bench meter with Fluke handheld in this context is disingenuous to say the least.

Why? Because it sucks? It's the most popular handheld DMM. Or because all Flukes are overpriced? Fair enough. 😉

All that said, I personally prefer the bench format, as I'm almost always...on my bench.

[nctnico]

I have been using the VC8145 for over a decade already as a daily driver.

What  do you think is lacking in that meter? Why do you want to change?

The slow autoranging is becoming a bit of a nuisance. Other than that there is nothing wrong with it. I'm having quite a hard time finding a replacement without setting a budget.

[wraper]

The Fluke 87V, is 6,000 counts standard, 19,999 counts in high-resolution mode. DC accuracy is +/- 0.05% + 1 count. AC accuracy is +/- 0.7% + 2 counts. They don't give more detailed accuracy than that, I'm sure they only listed their best accuracy. I'd love to know the true range of accuracy for it.

Comparing Siglent bench meter with Fluke handheld in this context is disingenuous to say the least.

Why? Because it sucks? It's the most popular handheld DMM. Or because all Flukes are overpriced? Fair enough. 😉

All that said, I personally prefer the bench format, as I'm almost always...on my bench.

Because you compare premium priced industrial (largely electricians) portable meter where precision not a priority with Chinese bench meter.

[wraper]

- The AC-ranges switch to zero below 1% of their full range.

Many meters do that (or should do that) TRMS converters are inaccurate at low voltage levels.

They shouldn't do that, as it's just lying to try appear better.

[KungFuJosh]

Because you compare premium priced industrial (largely electricians) portable meter where precision not a priority with Chinese bench meter.

Oh, it sucks because it's Chinese. Gotcha. Flukes are also made in Asia. They're "assembled" in the USA. Another part of the Fluke scam. 😉

Anyway, none of it matters since the OP specifically asked for a bench meter. 🤷

[wraper]

Agreed, the BM869S is a well respected meter. Again, I think they only list the best case accuracy. I would still like to see accuracy shown across the ranges like Siglent shows. I don't believe for a second these handhelds accuracies are equal across all ranges.\

You're right, that table shows base accuracy. Here is the full spec http://www.brymen.com/images/ProductsList/BM860s_List/BM860s_Catalog.pdf
SDM3045X is actually better over the range. However it's also over the stated budget quite a bit. There is no chance buying as accurate bench meter for the price of BM869.

[KungFuJosh]

Agreed, the BM869S is a well respected meter. Again, I think they only list the best case accuracy. I would still like to see accuracy shown across the ranges like Siglent shows. I don't believe for a second these handhelds accuracies are equal across all ranges.\

You're right, that table shows base accuracy. Here is the full spec http://www.brymen.com/images/ProductsList/BM860s_List/BM860s_Catalog.pdf
SDM3045X is actually better over the range. However it's also over the stated budget quite a bit. There is no chance buying as accurate bench meter for the price of BM869.

Fair enough. But it's a great bench meter for the money. I wouldn't trade any of my bench meters for handhelds...unless I need to bring them somewhere with me. 😉

Another great thing about the Siglent meters, if you can find one used, but still within the 3-year warranty, it can be a great buy.

[wraper]

Because you compare premium priced industrial (largely electricians) portable meter where precision not a priority with Chinese bench meter.

Oh, it sucks because it's Chinese. Gotcha. Flukes are also made in Asia. They're "assembled" in the USA. Another part of the Fluke scam. 😉

Nope, because you compare very differently priced market segments. It's like comparing AMD Server CPU with Intel desktop CPU and making a conclusion that Intel offers more performance for the price.

Anyway, none of it matters since the OP specifically asked for a bench meter. 🤷

Op said he prefers a handheld meter but wants a bench meter for more accuracy. Which is an opposite of what you'll get for the money if you buy a bench meter within his budget.It was not OP

[nctnico]

Op said he prefers a handheld meter but wants a bench meter for more accuracy.

Where does the OP write that? I can't find it... 
To me the opening post reads more like the OP is looking for a stationary DMM and is fed up by using handhelds. 

[live2fish88]

I currently have a fluke 179, TPI 194 II, Fluke 374, a Klein and a kaiweets. The latter are just throw in the car or in the toolbox for a throw around meter. I’d like a dedicated bench top meter for the larger display, somewhat permanent location and the ability for it not to fall down lol. It seems the stands on handhelds are never wide enough to provide good stability, one wrong move with the leads and they fall down. Sometimes it’s hard to see the display without a backlight… the list goes on.

[nctnico]

I currently have a fluke 179, TPI 194 II, Fluke 374, a Klein and a kaiweets. The latter are just throw in the car or in the toolbox for a throw around meter. I’d like a dedicated bench top meter for the larger display, somewhat permanent location and the ability for it not to fall down lol. It seems the stands on handhelds are never wide enough to provide good stability, one wrong move with the leads and they fall down. Sometimes it’s hard to see the display without a backlight… the list goes on.

I totally get that. Those reasons are why I switched to bench DMMs about 2 decades ago. To many bench DMMs are all about precission though; don't let yourself get distracted by that.

[wraper]

Op said he prefers a handheld meter but wants a bench meter for more accuracy.

Where does the OP write that? I can't find it... 
To me the opening post reads more like the OP is looking for a stationary DMM and is fed up by using handhelds. 

I thought it was OP who said that but it was another user in reply #8.

[Fungus]

Agreed, the BM869S is a well respected meter. Again, I think they only list the best case accuracy.

Actually worst case.

I would still like to see accuracy shown across the ranges like Siglent shows. I don't believe for a second these handhelds accuracies are equal across all ranges.

Brymen clearly show accuracy on all ranges.

Datasheet here:
https://brymen.eu/wp-content/uploads/biall/102092/102092.KARTA_EN..2015-07-09.1.pdf

[bdunham7]

Hey guys. Looking for a new bench top meter. I don’t feel comfortable buying used unless from a reputable seller (but still prefer new). I have handhelds but would like a dedicated bench top unit. Trying to keep the price $300 or below.

Before you decide you should have a look at what capabilities you can get in a bench meter over and above what your handhelds have and determine if any of those might be useful to you.  I'd also think about either bumping your budget, reconsidering used or both.  For example, prices of the 34401A have been cooling a bit and you can get something like this:

https://www.ebay.com/itm/365031591932?epid=710140765

Some advantages of getting a halfway-decent bench meter include the high-impedance input mode, much greater AC bandwidth (over what you have now) and of course much greater accuracy.  Convenient data logging (can be always connected to a computer) is also a handy feature on many newer bench models.  $300 is a tough price point, there's a lot of junk down there.

[live2fish88]

Ok so let’s say I go up to 3045x pricing, is the extra 45$ for the 3055 worth it?

[KungFuJosh]

Ok so let’s say I go up to 3045x pricing, is the extra 45$ for the 3055 worth it?

That depends. I used to own both, but I sold the 3055. It didn't do anything for me that my 3045X (upgraded to 3055X-E) couldn't do. I liked the 3045X better because it doesn't have a fan, so it was quieter.

Technically, the 3055 hardware is superior, but in practice it was the least stable of my 3 bench DMMs. It was still good, but not better (to me), and no thanks to the fan noise.

Now I just have the 3055X-E and the 3065X. I still use both, and if I want it quiet, I use the 3055X-E.

Just keep in mind that if you have a different firmware/hardware range, you won't be able to upgrade the 3045X (at least not yet).

Normally, there's a $100 difference between the two. If you think you'd prefer the 5.5 digits, then I'd spend the extra $45. If you'd prefer it to be quiet, get the 3045X.

The main other thing I would consider is the counts. I do prefer the 5.5 digits (220,000 vs 66,000 on the 4.5 digit meter). The ranges make more sense to me, but YMMV.

[uargo]

Ok so let’s say I go up to 3045x pricing, is the extra 45$ for the 3055 worth it?

Absolutely yes, at that price for $45 extra the SDM3055 has better hardware (resistive divider, voltage reference etc), better precision 0.06 vs 0.015, 1 more digit 4.5 vs 5.5, higher frequency measurement 500KHZ vs 1MHZ and some other things.

[uargo]

Ok so let’s say I go up to 3045x pricing, is the extra 45$ for the 3055 worth it?

That depends. I used to own both, but I sold the 3055. It didn't do anything for me that my 3045X (upgraded to 3055X-E) couldn't do. I liked the 3045X better because it doesn't have a fan, so it was quieter.

3045X (updated to 3055X-E), adds 1 more digit, but still has the same hardware and the same 0.06 precision of the SDM3045X

[live2fish88]

I don’t get what you guys mean by 3055x. I haven’t seen that model on their website?

[uargo]

I don’t get what you guys mean by 3055x. I haven’t seen that model on their website?

It is a Chinese firmware that can be installed (I think it is not possible anymore) on the SDM3045X to convert it into SDM3055X-E, which is a version that is only sold in China, which is an SDM3045X with the same precision of 0.06, but it adds 1 more digit.
But I repeat, it still has the same hardware and the same precision of 0.06 as the SDM3045X.

[KungFuJosh]

3045X (updated to 3055X-E), adds 1 more digit, but still has the same hardware and the same 0.06 precision of the SDM3045X

I did mention that the 3055 hardware is superior. However, the correct way to look at it is that the 3045X is crippled by the firmware. Whether or not somebody needs higher accuracy is a different question.

I don’t get what you guys mean by 3055x. I haven’t seen that model on their website?

The SDM3055X-E is a China market only variant. They took the exact same meter, reduced the capabilities via the firmware, and put a different sticker on it to create the SDM3045X.

[uargo]

There is also a custom firmware for the SDM3055 on this forum by a user that gives you 8.5 digits and you can put it on, but the thing is that the digits have to be correlated with the precision of the hardware, that is, the SDM3055 has the precision for 5.5 digits, from there on the rest of the digits will show inaccurate data, for example the 6th digit will be inaccurate, the 7th very inaccurate, the 8th and following digits will show garbage.
Why do you think the SDM3065X costs 250€ more than the SDM3055?
Because of the extra precision it needs to show the 6th digit correctly

[uargo]

In summary what I mean is that the SDM3045X upgraded to SDM3055X-E will show you 5.5 digits and will look very cool. But it will never have the same precision (accuracy) in measurement as the SDM3055.
And for $45 difference it is certainly worth it.

[KungFuJosh]

No question, it's worth the difference in money...unless fan noise drives you crazy. 😉

To be fair, if I didn't get the 3065X, I would have kept the 3055. When I need the accuracy I have it. When I don't care if a 250VDC measurement is off by less than 2V (0.06% = 1.5V), then I go for the quiet one.

[robert.rozee]

I currently have a fluke 179, TPI 194 II, Fluke 374, a Klein and a kaiweets. The latter are just throw in the car or in the toolbox for a throw around meter. I’d like a dedicated bench top meter for the larger display, somewhat permanent location and the ability for it not to fall down lol. It seems the stands on handhelds are never wide enough to provide good stability, one wrong move with the leads and they fall down. Sometimes it’s hard to see the display without a backlight… the list goes on.

on the basis of the above, a Fluke 37 may be a good match, such as this one for us$50 on ebay:
https://www.ebay.com/itm/185960963771

can be run on a plugpack, although has enough space inside to fill it up with more than enough battery capacity to run for several years. if it is not heavy enough, place some chunks of lead inside. the only thing lacking is a backlit display - has anyone added this to a 37?

or a Fluke 45 if you could get one at a sane price (and it had a good condition VFD).


cheers,
rob   :-)

[Phil1977]

- The AC-ranges switch to zero below 1% of their full range.

Many meters do that (or should do that) TRMS converters are inaccurate at low voltage levels.

As it was also stated on this forum: Digital TRMS converters as in the Owon are by far not that inaccurate that it is justified to throw away the lower 1% of the range.

It´s okay to specify no accuracy for < 1% - but to hard switch the display to 0.000 is just good for idiot operators who are confused by a little zero noise. Many better meters like Keysight DON'T do this, but probably they can afford a customer support that explains the IOs why they don't see zero if they cross the probe tips.

[Kleinstein]

The SDM3045 has some quirks with internal range switching at some 2 V and 0.2 V. This because the hardware is made for 0.2 / 2 / 20 V ranges and they have made it 0.6 / 6 V in software for some marketing reasons. This can add an "unexpected" discontinuity and maybe even change in the input impedance at some 2 V (6 V range).
The FW change to the 3055E version on some older units would also fix this issue, not just show 1 more digit.
Given the more stable hardware (and thus better accuracy) and better firmware and no more easy hack to SDM3055E, I would consider $45 more worth it for the 3055.

Dropping the AC reading to zero below some 1% is sometimes found - ideally there would be an extra warning on low accuracy. However this makes mainly sense with analog RMS that has some issues at low amplitude, though the limit should be a bit lower. The digital RMS as in the XDM1041 should ideally not have such an issue. So that is more like a software bug, not caused by using digital RMS. It is more of the opposite and digital RMS (without the bug) can handle the low readings better. The problem with lower end digital RMS is more a limited bandwidth (e.g. 1 or 5 KHz).

There are different reasons for a bench meter and not all bench meters have the full features:
Better visibilty
mains power (no battery)
4 Wire ohms  (rarely found with handhelds)
PC interface
high impedance ranges (rarely found with handhelds)

If it is mainly about good visibilty and a PC interface the XDM1041 is not such a bad choise.

[uargo]

The OWON XDM1041 is very good value for money overall, but it has several things:
1 - Worse accuracy 0.05 at best (in general it has much worse accuracy)
2 - It only measures AC voltage up to 1KHz and AC current is not even specified (which makes me think that maybe it only reaches 100Hz)
3 - 4.5 digits
4 - Very very slow in auto range
5 - Very limited dual display (only for frequency)
6 - It does not have a histogram
7 - It does not have a trend chart
8 - It does not have 4-wire measurement
9 - It does not have a trigger synchronization input
10 - It does not have an RJ45

Don't get me wrong, for that price it offers great value for money. But it is not on par with the SDM3055.

But if you don't need or don't care about the things I have listed, it is a good value for money option

[Phil1977]

I don't think the SDM3055 really competes with the XDM1041.

If you need a "real" benchtop DMM then the SDM3055 is a clear winner.

If you want a "hybrid", semi-portable DMM for the table, then especially the XDM1241 with it´s integrated battery (>10h runtime) is a fantastically convenient tool with the visibility of a benchtop DMM and the portability of a handhold device. For the same reason I often use it for logging purposes together with a PC. It´s just easier to setup than the heavy and large "real" benchtops.

AC voltage and current are both stable up to ca. 10kHz - but I can't quantify the accuracy, it´s definitely not the right tool to do AC characterizations over a broad frequency range.

[live2fish88]

I was sent some clearance rack stuff…
Siglent 3045x and the Rigol 3058E are close enough in price to each other.
Which would be the more solid unit?

[live2fish88]

How is the Rigol DM858E?

[KungFuJosh]

While I hate Rigol in general, I'll put that aside to say:

The display is lame on the 3058E.
The display looks a lot nicer on the DM858.

I can't tell you anything else about the Rigols, other than the DM858 series is a different form factor, which you may or may not like compared to normal bench DMMs.

[live2fish88]

Ok! I think I’m going to keep an eye on the siglent clearance page and if an 8055 comes up I’ll snatch  that.

[KungFuJosh]

Ok! I think I’m going to keep an eye on the siglent clearance page and if an 8055 comes up I’ll snatch  that.

I don't know if I would go that route. That clearance page can supply you with something out of calibration (which costs $200 for the 3055), or sometimes a lower warranty, maybe only 1 year at best.

The normal Siglent warranty is 3 years.

If you want to save money, I would look on eBay or facebook marketplace. You can ask the seller the purchase date, and/or email the serial number to Siglent support to find out if the DMM is still in warranty/calibration.

[bdunham7]

How is the Rigol DM858E?

Apparently pretty bad unless they've fixed the issues mentioned in this thread:

https://www.eevblog.com/forum/testgear/rigol-dmm-dm858-comparison-thread/msg5417507/#msg5417507

If you are allergic to used and want new, modern gear only then the SDM3055 is probably a good choice.  If you aren't in a hurry you can stalk Amazon for a deal--they run sales occasionally and sometimes on Prime Day or Black Friday you can get an exceptional deal.  I believe Siglent is currently selling directly on Amazon, so you won't be dealing with questionable third parties.

[J-R]

The performance of Siglent products is only covered by a 1 year warranty even if the product itself is under a 3 year warranty.  So you'd still need to pay for yearly calibrations on a new DMM if that is important to you.

An aged DMM with a new calibration is a popular go-to solution and probably a better route.

But now you're at a much higher price point.

[KungFuJosh]

The performance of Siglent products is only covered by a 1 year warranty even if the product itself is under a 3 year warranty.  So you'd still need to pay for yearly calibrations on a new DMM if that is important to you.

That's misleading. The warranty is 3 years. Calibration is 1 year. They don't guarantee calibrated performance for more than the calibrated period. That seems like something that should be obvious.

[J-R]

The performance of Siglent products is only covered by a 1 year warranty even if the product itself is under a 3 year warranty.  So you'd still need to pay for yearly calibrations on a new DMM if that is important to you.

That's misleading. The warranty is 3 years. Calibration is 1 year. They don't guarantee calibrated performance for more than the calibrated period. That seems like something that should be obvious.

You seemed to be trying to make the point that a new product would be a better purchase than clearance in the context of calibration, and I'm saying it seems they're essentially identical.

Personally, I'd rather have a clearance/refurbished product direct from the manufacturer than other used purchase options.

[nctnico]

The performance of Siglent products is only covered by a 1 year warranty even if the product itself is under a 3 year warranty.  So you'd still need to pay for yearly calibrations on a new DMM if that is important to you.

An aged DMM with a new calibration is a popular go-to solution and probably a better route.

That makes no sense. Old or new, all test equipment has set calibration intervals which don't change with age. So if you want to be sure the measurement result are traceable to a calibration standard, you need to stick to the prescribed calibration intervals. But keep in mind that equipment may fail so you'll need to the a pre and post check when doing measurements which are important.

[J-R]

The performance of Siglent products is only covered by a 1 year warranty even if the product itself is under a 3 year warranty.  So you'd still need to pay for yearly calibrations on a new DMM if that is important to you.

An aged DMM with a new calibration is a popular go-to solution and probably a better route.

That makes no sense. Old or new, all test equipment has set calibration intervals which don't change with age. So if you want to be sure the measurement result are traceable to a calibration standard, you need to stick to the prescribed calibration intervals. But keep in mind that equipment may fail so you'll need to the a pre and post check when doing measurements which are important.

Of course it makes sense and you know why.

[live2fish88]

So many options!
Let’s say under $500. It’s funny to put a budget on something only to realize you don’t really get your moneys worth in quality until a certain price point.
I do random projects and repairs here and there and my biggest pet peeves are slow refresh, I need at least 3 digits after the decimal. Resistance, continuity, voltage, amps, diode are really all I use. I don’t mind spending the money for when I get more involved years down the road. Slow meters drive me nuts. Low continuity buzzers drive me nuts. Resistance is important. The cheaper $200 from what I’ve read in this thread don’t refresh fast enough.

I know I’m all over the place in the thread but between price and options, it’s a lot! I don’t work in a lab environment so spending the money once is important to me. I really only need one set of probes on the meter, I see some you can apply two sets. Though it seems in the $400-500 range you get that feature regardless. I was hesitant to get the owon, Kaiweets, etc because all my other meters with the exception of my throw around ones are good quality and I tend to spend to the best of my ability. I like the siglent display. I don’t do the type of work that requires HIGH accuracy as far as something being +-.05 to something being +-.015 it won’t matter in my application, but I appreciate high accuracy. I tend to use the TPI 194 due to the display and the extra digits over the fluke, but I use the fluke for the continuity buzzer and for AC type applications more. I’d like the bench unit to be a sit down at my work area and probe away. I could have used it today actually. I feel like if I’m spending 150-250 on a cheaper owon, Kaiweets, uni-t, etc that I’ll probably regret buying id rather spend twice that and buy once. I just want the BEST for my money. And yes new, I’m one of those weird people who want to know my money went towards something new that hasn’t been messed with, though I don’t mind factory refurbished.

[KungFuJosh]

You seemed to be trying to make the point that a new product would be a better purchase than clearance in the context of calibration, and I'm saying it seems they're essentially identical.

Personally, I'd rather have a clearance/refurbished product direct from the manufacturer than other used purchase options.

I never said that. I did say 1. I prefer a warranty; and 2. figure calibration into the cost.

I don't see the benefit of buying on clearance from the manufacturer if you lose every benefit of buying from the manufacturer. If they have it on their clearance page in cal with a 3 year warranty, I would absolutely prefer that. But if it's out of cal, and only has 1 year warranty, it's not worth it.

Simple example: they had an SDM3065X on sale for $600 something on their clearance section with a 1 year warranty, and no statement of calibration...in other words, very likely out of cal. Siglent charges $295 for calibration, or you can get it done from Trescal directly around $200 plus shipping costs. So tell me how it's a good deal to lose 2 years worth of warranty, and need to spend more money on calibration than what you save in the first place?

[KungFuJosh]

So many options!
Let’s say under $500. It’s funny to put a budget on something only to realize you don’t really get your moneys worth in quality until a certain price point.

New: get the SDM3055. Used: be patient and get a good deal on an SDM3065X. IMO that's the best bet for the money.

[live2fish88]

Is Ali express legit?
https://www.aliexpress.us/item/3256806417536519.html?src=google&aff_fcid=552b5cb0b38c429d8292f81a744a1dc7-1721577183452-07993-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=552b5cb0b38c429d8292f81a744a1dc7-1721577183452-07993-UneMJZVf&terminal_id=dc38be48f2bf4b389ee4a2ebb6d24988&afSmartRedirect=n&gatewayAdapt=glo2usa

[J-R]

No more speculation, I e-mailed Siglent to ask them the calibration status of that clearance DMM.

The OP's original price target was $300, and despite the recent budget uplift, I do not see them having a need for a $500 DMM plus $200 per year in calibrations.  So a $300 open-box DMM direct from Siglent that you sanity check every so often against your other DMMs really seems the most logical to me.  I read all of the OP's posts to date (35) and everything I'm reading aligns with that.

But obviously we can all buy what we desire.


Tony has a comparison of the three Siglent units here:

[KungFuJosh]

I'm not really disagreeing with you there either. If that meter is in cal, it's a killer deal for $300. The only reason I care about receiving a (new to me) meter in cal is to know I can trust it to begin with.

For example, if I have 3 meters, and 2 agree but one doesn't, the 2 agreeing don't mean a lot if they're the ones out of cal. Whether he ever renews cal again is up to his needs.

If your meter is in cal when you get it, you can use standards to monitor drift over time.

[Fungus]

For example, if I have 3 meters, and 2 agree but one doesn't, the 2 agreeing don't mean a lot if they're the ones out of cal.

If they both agree down to the last digit and that's all you have, then... maybe it's the third one.

If your meter is in cal when you get it, you can use standards to monitor drift over time.

These meters really don't go out of spec. They're designed not to, and have all sorts of tricks to ensure it.

You can buy a really good standard (or two) for less than the price of a $200 calibration.

Yearly, paid-for calibration is mostly for people with legal liabilities.

[EEVblog]

I currently have a fluke 179, TPI 194 II, Fluke 374, a Klein and a kaiweets. The latter are just throw in the car or in the toolbox for a throw around meter. I’d like a dedicated bench top meter for the larger display, somewhat permanent location and the ability for it not to fall down lol. It seems the stands on handhelds are never wide enough to provide good stability, one wrong move with the leads and they fall down. Sometimes it’s hard to see the display without a backlight… the list goes on.

In that case there is no need to pay for an expensive bench meter, sounds like even a 4.5 digit benchtop will do the job.
Probably the majority of people buy bench meters for the extra accuracy and resolution, e.g. 5.5 or 6.5 digit. But there are 4.5 digit benchtops that cater to thoe that just prefer the bechtop form factor.
Uni-T have an affordable 4.5 digit one, but no idea if it's any good.
https://instruments.uni-trend.com/UT8804E

[EEVblog]

Is Ali express legit?
https://www.aliexpress.us/item/3256806417536519.html?src=google&aff_fcid=552b5cb0b38c429d8292f81a744a1dc7-1721577183452-07993-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=552b5cb0b38c429d8292f81a744a1dc7-1721577183452-07993-UneMJZVf&terminal_id=dc38be48f2bf4b389ee4a2ebb6d24988&afSmartRedirect=n&gatewayAdapt=glo2usa

AliExpress is legit, personally had no problems myself. But it's really up to the individual seller.

[krish2487]

If you dont mind getting a used one.. why not something like the venerable 3478a?
You get good deals under 100 bucks..
granted you might need to spend a little effort with the rifa caps replacement and the battery replacement.. but it is still a solid piece of kit as any.
Choose one that passes the self test, so that you know the cal constants are still present.
And of course, if you are up for it, then do a fram mod on the unit to dispense with the battery forever.
Id wager those 3478a are much likely to be on par and in spec as any of the UniT and rigols.

[J-R]

I'm confident the OP is not looking for an old, used $100-price point DMM.

But still, the HP3478A seems like an iffy recommendation due to the extensive list of missing features.  The go-to beginner oldie at that price point has to be the Fluke 45?

Not sure about all countries, but for North America Siglent has a disclaimer on their warranty page essentially stating if you don't buy from them or an authorized distributor, then they won't provide any warranty coverage.  You would need to deal with the seller instead: https://siglentna.com/service-and-support/warranty-information/

The UT8804E feels like a step back for a bench DMM due to the 11-position selector knob.  There is the UT8805E, but it's almost $500 USD.

[tszaboo]

I currently have a fluke 179, TPI 194 II, Fluke 374, a Klein and a kaiweets. The latter are just throw in the car or in the toolbox for a throw around meter. I’d like a dedicated bench top meter for the larger display, somewhat permanent location and the ability for it not to fall down lol. It seems the stands on handhelds are never wide enough to provide good stability, one wrong move with the leads and they fall down. Sometimes it’s hard to see the display without a backlight… the list goes on.

In that case there is no need to pay for an expensive bench meter, sounds like even a 4.5 digit benchtop will do the job.
Probably the majority of people buy bench meters for the extra accuracy and resolution, e.g. 5.5 or 6.5 digit. But there are 4.5 digit benchtops that cater to thoe that just prefer the bechtop form factor.
Uni-T have an affordable 4.5 digit one, but no idea if it's any good.
https://instruments.uni-trend.com/UT8804E

I personally would never consider a benchtop DMM with a manual range switch.
If you ever want to do any kind of automation, that switch limits you. And it's a moving part.
And it makes it 100% certain that the meter is just a handheld meter in a desktop chassis. Even the Rigol DM858E is that based on the teardowns.
It would need to be a lot cheaper that that for me to even consider it. At least that's my 2 cents.

[nctnico]

I currently have a fluke 179, TPI 194 II, Fluke 374, a Klein and a kaiweets. The latter are just throw in the car or in the toolbox for a throw around meter. I’d like a dedicated bench top meter for the larger display, somewhat permanent location and the ability for it not to fall down lol. It seems the stands on handhelds are never wide enough to provide good stability, one wrong move with the leads and they fall down. Sometimes it’s hard to see the display without a backlight… the list goes on.

In that case there is no need to pay for an expensive bench meter, sounds like even a 4.5 digit benchtop will do the job.
Probably the majority of people buy bench meters for the extra accuracy and resolution, e.g. 5.5 or 6.5 digit. But there are 4.5 digit benchtops that cater to thoe that just prefer the bechtop form factor.
Uni-T have an affordable 4.5 digit one, but no idea if it's any good.
https://instruments.uni-trend.com/UT8804E

I personally would never consider a benchtop DMM with a manual range switch.
If you ever want to do any kind of automation, that switch limits you. And it's a moving part.
And it makes it 100% certain that the meter is just a handheld meter in a desktop chassis. Even the Rigol DM858E is that based on the teardowns.

The manual range switch is a personal preference. I wouldn't like it either but maybe other people find that easier compared to having function button.

I disagree though on the never ending hand-held in a desktop chassis argument. For general purpose use you actually want a handheld DMM in a desktop chassis which is mains powered. A lot of higher end bench DMMs are not a good 1 on 1 replacement for a handheld because they are optimised for different use cases. Take continuity testing and startup time for example. For a quick measurement you don't want to wait 2 minutes for a DMM to boot. And continuity is often software defined and slower instead of faster. Also consider power consumption and fan noise. In this case more is actually less.

[Phil1977]

I disagree though on the never ending hand-held in a desktop chassis argument. For general purpose use you actually want a handheld DMM in a desktop chassis which is mains powered. A lot of higher end bench DMMs are not a good 1 on 1 replacement for a handheld because they are optimised for different use cases. Take continuity testing and startup time for example. For a quick measurement you don't want to wait 2 minutes for a DMM to boot. And continuity is often software defined and slower instead of faster. Also consider power consumption and fan noise. In this case more is actually less.

Isn't it the only reason for having a mains powered DMM to let it switched on all time you are working or even always? If you switch it on and off a battery lasts eternities (think of the Fluke 37) and a mains power cable is only annoying. Make it at least a USB-C power input instead of a mains socket if you only need a few Watts.

[tszaboo]

I disagree though on the never ending hand-held in a desktop chassis argument. For general purpose use you actually want a handheld DMM in a desktop chassis which is mains powered. A lot of higher end bench DMMs are not a good 1 on 1 replacement for a handheld because they are optimised for different use cases. Take continuity testing and startup time for example. For a quick measurement you don't want to wait 2 minutes for a DMM to boot. And continuity is often software defined and slower instead of faster. Also consider power consumption and fan noise. In this case more is actually less.

I get it, you want fast continuity. I just have an Uni-t 61E on my desk, that I grab most of the time to take quick measurements, not the desktop one.

[live2fish88]

It's too bad nobody offers a modular multimeter yet..

[Kleinstein]

There were modular multimeters in the past, with optional board for Ohms and RMS or similar. Today this makes little sense, as the costs for the AC part or ohms part are relatively low and the extra connectors pose a problem for the protection and leakage.
One may sill get some options / versions with GPIB interface or a scanner, though more like a choose at order.

The internal construction can be modular, but the is more thing for the manufacturer with little help for the user. E.g. the case and display part for the SDM3045/55/65 are essentially the same. A benefit for the user is a similar UI and maybe slightly better spare part availabilty.

[bdunham7]

It's too bad nobody offers a modular multimeter yet..

Be careful what you ask for!

https://www.ebay.com/itm/404613379451

These were truly mix-and-match devices that could be configured as needed even after sale.  Modern devices are much, much less expensive and there's little demand for such flexibility.

[Fungus]

In that case there is no need to pay for an expensive bench meter, sounds like even a 4.5 digit benchtop will do the job.

I think the requirement is for something that runs on mains with fast autoranging.

All the talk of traceable calibration is a red herring.

[Fungus]

I get it, you want fast continuity. I just have an Uni-t 61E on my desk, that I grab most of the time to take quick measurements, not the desktop one.

If you want fast continuity get a $7 Aneng DT9205A.

https://www.aliexpress.com/item/1005005221439318.html

It also has a really bright continuity LED on the front, bright enough to be useful, and it's as fast as anything else I own even with the supplied probes.

nb. There's another meter with the same model number. The one I have is square with colored side panels, not colored top/bottom.

(I should maybe get on of the others to see if it's the same)

[bdunham7]

I think the requirement is for something that runs on mains with fast autoranging.

OK, then I guess he wants a Fluke 8842A set to the "M" reading rate...

[Aldo22]

If you want fast continuity get a $7 Aneng DT9205A.

Or ut123.

https://youtu.be/s8mRZVx4m6k?t=630

[nctnico]

I get it, you want fast continuity. I just have an Uni-t 61E on my desk, that I grab most of the time to take quick measurements, not the desktop one.

If you want fast continuity get a $7 Aneng DT9205A.

Both suggestions completely ignore what the OP is looking for 

[uargo]

If you find the OWON XDM3041 for less than 350€ it can be a good option (be careful not to find the XDM2041)
The XDM3041 4.5 digits, precision 0.02, AC voltage to 100khz, AC current to 10khz, Bar meter, histogram, trend chart, Max. Min. value, average value, standard deviation,
DB / DBm, Pass / Fail
external trigger, 4-wire measurements, RJ45.

For 400€ the Siglent SDM3045X is better

For 400€ you also have the Rigol DM858E 5.5 digits precision 0.06, AC voltage and current only 8khz, only measures up to 3 A, I see it cut down but it does have a huge touch screen

and for a little more the SDM3055 is the best

[J-R]

The Rigol DM800 series still has major unresolved bugs, some in hardware, so should not be a recommendation.

[corey]

Question, related but doesn't help the OP: I see a whole lot of 2nd hand Keysight/HP benchtop DMMs on Ebay for ~AU$1000-1500 (incl postage), such as the 34401A, U3402A, etc. Why would anyone buy one of those (old) units when one could buy a SDM3055 for ~AU$730? I haven't compared the specs but is it just in the accuracy/tracking?

[KungFuJosh]

Question, related but doesn't help the OP: I see a whole lot of 2nd hand Keysight/HP benchtop DMMs on Ebay for ~AU$1000-1500 (incl postage), such as the 34401A, U3402A, etc. Why would anyone buy one of those (old) units when one could buy a SDM3055 for ~AU$730? I haven't compared the specs but is it just in the accuracy/tracking?

Mostly just eBay insanity. I would never spend that much for old used and abused gear with less going for them.

You could buy a new SDM3065X or a new DMM6500 for what people are asking for lesser old gear.

[Fungus]

Both suggestions completely ignore what the OP is looking for 

I wasn't replying to OP, I was replying to "I keep a UT61E around for continuity testing" guy.

[CaptainBucko]

The OWON XDM1041 is very good value for money overall, but it has several things:
...
Don't get me wrong, for that price it offers great value for money. But it is not on par with the SDM3055.

I own an Owon 1041. Yes the auto range speed is a bit annoying, so I mostly leave it in fast update mode.
I bought it because of its small form factor (I wanted a DMM to be permanently mounted on the wall board of my work bench), and easy to read display.
The Owon 1401 was $159 AUD from Amazon. The Siglent is $726 AUD. So it's a bit of a Fiat vs Ferrari decision.

[J-R]

Question, related but doesn't help the OP: I see a whole lot of 2nd hand Keysight/HP benchtop DMMs on Ebay for ~AU$1000-1500 (incl postage), such as the 34401A, U3402A, etc. Why would anyone buy one of those (old) units when one could buy a SDM3055 for ~AU$730? I haven't compared the specs but is it just in the accuracy/tracking?

It's not unusual for an item no longer made to increase in value, whether it's test equipment, cars or whatever.  The 34401A has a long history, is discussed on the forums quite a bit, and there are valid reasons why someone would be willing to pay a bit more for one, primarily accuracy and stability due to aging, but also maybe just nostalgia.  Common prices are $350-$500 USD.  Higher prices could be due to a recent calibration or a model in good condition, and of course in the case of eBay there are always listings that are inflated for the common go-to reasons you can read about online.

The DMM6500 goes for $1,600 USD, so not sure how that would be a reasonable comparison.
SDM3065X is $745 USD, but it's known that Siglent uses an un-aged LM399 so there could be some drift over time.  This is probably fine if you pay for yearly calibrations, but it probably defeats the purpose of those digits if you don't (or have a way to verify it).

There are a wide range of forum users here, and not everyone is looking for the same thing.  Which can lead to some unnecessary back and forth, so it's important to list out priorities when asking for purchasing advice.

[EEVblog]

I'll just drop this here 

[ledtester]

Is Ali express legit?
https://www.aliexpress.us/item/3256806417536519.html?src=google&aff_fcid=552b5cb0b38c429d8292f81a744a1dc7-1721577183452-07993-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=552b5cb0b38c429d8292f81a744a1dc7-1721577183452-07993-UneMJZVf&terminal_id=dc38be48f2bf4b389ee4a2ebb6d24988&afSmartRedirect=n&gatewayAdapt=glo2usa

AliExpress is legit, personally had no problems myself. But it's really up to the individual seller.

AliExpress is legit but if the unit is defective the best you are going to get is financial compensation - which might be 100% (probably doesn't include shipping) but that's really up to the vendor. And don't expect to be able to return it just because you don't like it.

[tszaboo]

Question, related but doesn't help the OP: I see a whole lot of 2nd hand Keysight/HP benchtop DMMs on Ebay for ~AU$1000-1500 (incl postage), such as the 34401A, U3402A, etc. Why would anyone buy one of those (old) units when one could buy a SDM3055 for ~AU$730? I haven't compared the specs but is it just in the accuracy/tracking?

They have two targets. One is looking for a perfect condition calibrated gear to replace a failed one in a test setup. They are willing to pay more because writing test scripts changing cables is expensive.
The other is people who want to have a decent DMM at home to take measurements. These are sold for ~400 EUR.

[J-R]

Some other new options under $500:

GW Instek GDM-8341 and GDM-8342
https://www.gwinstek.com/en-US/products/detail/GDM-8342_GDM-8341
https://www.tequipment.net/InstekGDM-8341.html
https://www.tequipment.net/InstekGDM-8342.html

B&K Precision Model 2831E:
https://www.bkprecision.com/products/multimeters/2831E
https://www.digikey.com/en/products/detail/b-k-precision/2831E/2280305

[Phil1977]

Question, related but doesn't help the OP: I see a whole lot of 2nd hand Keysight/HP benchtop DMMs on Ebay for ~AU$1000-1500 (incl postage), such as the 34401A, U3402A, etc. Why would anyone buy one of those (old) units when one could buy a SDM3055 for ~AU$730? I haven't compared the specs but is it just in the accuracy/tracking?

They have two targets. One is looking for a perfect condition calibrated gear to replace a failed one in a test setup. They are willing to pay more because writing test scripts changing cables is expensive.
The other is people who want to have a decent DMM at home to take measurements. These are sold for ~400 EUR.

And many customers just want you to use certain type of measuring equipment. If you say you did some qualification tests with e.g. a Siglent then your results are automatically doubted. Some people trust names more than calibration certificates.

[coromonadalix]

you had Micronta bench meters, you had 2 version of them,  compact bench meters and useful

and can be purchased for low prices outside the vintage effect plaguing many sites

https://www.ebay.com/itm/315655169172?

or unless you're driven mad getting more digits ??

3468 3478 ... 3478 with enhanced functions ... thread here ...


but as soon you get outside 4.5 digits, you'll see price rise pretty fast ... unless  you stick  for the uni-t  vichy victor  kinda cheap ones  ...

establish your needs, and save money to get yourself a good one ...  but keep in mind there is no perfect meter with all functions

but if you need calibrated stuff,  you'll need to go with known brands $$    but repair side is another story

[maralb]

GW-Instek GDM-8245 might be another option.

https://www.gwinstek.com/en-US/products/detail/GDM-8245

It suits the budget. If you don't need any gimmicks it is a decent device.

[KungFuJosh]

Why do companies still make bench DMMs with those terrible screens? I hate that. Information display is terrible.

How about the ability to track statistics?

Or take screenshots?

Or connect to a program like TestController and track data over time remotely?

[KungFuJosh]

Really I’d like the Siglent 3065x

That's an excellent choice. I've been very happy with mine, and the stability/accuracy are excellent.

[live2fish88]

This is my solution until I can settle on a bench top meter. Designed it in CAD and printed it on my 3D printer. Can be attached using double sided adhesive or screws.

[BeBuLamar]

I have the Fluke 8050A which is just about as accurate as my best handheld Flluke 289. It's cheap. Just doesn't have a lot of function but generally enough for what I need.

[Antonio90]

I have the Fluke 8050A which is just about as accurate as my best handheld Flluke 289. It's cheap. Just doesn't have a lot of function but generally enough for what I need.

I have one, and it is good at what it does. It lacks continuity though, otherwise it would probably be used much more.
I's also ridiculously expensive in Europe. Someone in Italy seems to think it is worth around €130-150, plus shipping, go figure.
For less than $50 and working, it's a nice, very stable meter for the price.

[BeBuLamar]

I have the Fluke 8050A which is just about as accurate as my best handheld Flluke 289. It's cheap. Just doesn't have a lot of function but generally enough for what I need.

I have one, and it is good at what it does. It lacks continuity though, otherwise it would probably be used much more.
I's also ridiculously expensive in Europe. Someone in Italy seems to think it is worth around €130-150, plus shipping, go figure.
For less than $50 and working, it's a nice, very stable meter for the price.

I got mine around 1995 for $25 from a company that made telephone switchboard which went out of business. I never had it calibrated but it was calibrated a few months before I got it.

[skander36]

...

For example, if I have 3 meters, and 2 agree but one doesn't, the 2 agreeing don't mean a lot if they're the ones out of cal. Whether he ever renews cal again is up to his needs.

...

If the two meters  that agreed and not in cal are 34465A and DMM6500 and the third is a Siglent 3065X which is in cal but disagree with the other two, you can bet that the Siglent is wrong ...    ... my case. 
The two meters were verified with pdvs2 mini in calibration period.

[nctnico]

...

For example, if I have 3 meters, and 2 agree but one doesn't, the 2 agreeing don't mean a lot if they're the ones out of cal. Whether he ever renews cal again is up to his needs.

...

If the two meters  that agreed and not in cal are 34465A and DMM6500 and the third is a Siglent 3065X which is in cal but disagree with the other two, you can bet that the Siglent is wrong ...    ... my case. 
The two meters were verified with pdvs2 mini in calibration period.

Agreed, calibration is nothing more than taking a snapshot (like a photo) from the situation at a single point in time. Equipment can and will break which is why you need to do checks using known sources before and after measuring a DUT if you need to be very sure the results are correct.

Another point I have not seen mentioned in this thread is that some handhelds can give false readings when the batteries run low. And this is not only a problem for the $5 meters but I've seen (ballpark) $200 BK 'Precission' handhelds go wrong as well.

[EEVblog]

...
For example, if I have 3 meters, and 2 agree but one doesn't, the 2 agreeing don't mean a lot if they're the ones out of cal. Whether he ever renews cal again is up to his needs.
...

If the two meters  that agreed and not in cal are 34465A and DMM6500 and the third is a Siglent 3065X which is in cal but disagree with the other two, you can bet that the Siglent is wrong ...    ... my case. 
The two meters were verified with pdvs2 mini in calibration period.

It's basic statistics. The odds of two random meters agreeing to the last digit adds value above and beyond any "calibration". Especially so if they have agreed for years and not drifed from each other, in which case, bingo, you've started to add some "tracability" and "measurement confidence" with those two meters.


For those interested:

[Martin72]

If the two meters  that agreed and not in cal are 34465A and DMM6500 and the third is a Siglent 3065X which is in cal but disagree with the other two, you can bet that the Siglent is wrong ...    ... my case. 

I don't think so.
If a calibration laboratory, which is incomparably “better” equipped than you, determines that a multimeter is within its tolerances, then the device is OK.
The point is not that it should display something that you expect.
Exaggerated example:
If 10V is fed in and you expect a “nice” 10.00000V to be displayed, but the device “only” displays 9.99999V, but that is within the tolerance, then that is OK.
You can stand on your head, but that's the way it is.
If other meters then show the hoped-for 10.00000V, then they are not “better” or more OK, then they just show 10.00000V, because these meters also have a range from...to...
Then you have to make sure that the 10.00000V is actually 10.00000V.
This also varies, although not as “strongly” as with the meters.
This fluctuates and the “true” value is not known anyway.
A snapshot.

[nctnico]

I'm pretty sure skander36 is not argueing about the 6th digit. But more like 2 meters saying the voltage is 10.00V and the third saying it is 9.90V. Then 9.90V is more likely to be wrong than right no matter whether that third meter was calibrated 5 minutes ago.

[skander36]

@Martin72, If two meters that are out of period of calibration show a similar value confirmed by a voltage reference and a third meter show a consistently different value even if is freshly calibrated, for me is wrong for a 6,5 meter. For a handheld this can be tolerable.

[Fungus]

If 10V is fed in and you expect a “nice” 10.00000V to be displayed, but the device “only” displays 9.99999V, but that is within the tolerance, then that is OK.

I hate that.

10.00001 is perfectly fine but 9.99999 is really annoying. 

[Martin72]

I can well imagine that.
But things usually work differently.
If I want a meter that definitely displays 10.00000V when 10.00000V is actually present (don't forget that), then I have to buy one that can do that.
Then you won't get far with 6.5 digits, regardless of the brand.
An SDM3065X with its 0.0015% tolerance(look at the tolerances of other 6.5 digit meters) can fluctuate between 9.99985 and 10.01500.
If it's within that range, it's not broken or bad, it's just “in there”.
If I don't want that, I have to buy a 7.5 digit or higher meter.
Incidentally, in my opinion, the cheap voltage references that are freely available are all unsuitable for estimating a 6.5 digit meter.
If you really want to know, you must at least have your meter calibrated to ISO.
It costs about 150€ here, I can't buy a suitable reference for that.

[tautech]

Well there's Calibration and there's Calibration and what I've seen and learnt in the last few days was a real eye opener. 
Clean room, all working with equipment wore antistatic clothes, hats and booties and so so so many new units were having automated calibrations performed at once, meters, scopes, AWG's PSU, analyzers and so on.

But consider this, should just a single measurement in each measurement range be performed or many within each range ?
Some instruments took several hours to have the full calibration process complete. 

So so many top of the line calibration instruments performing these tasks was a sight to behold and will be etched in my mind like a good cal for the rest of my days.

It need be done properly or you're 

[Fungus]

Incidentally, in my opinion, the cheap voltage references that are freely available are all unsuitable for estimating a 6.5 digit meter.

Obviously... you need temperature control for that many digits.

[Phil1977]

Maybe a blasphemy question, but what do you need 6-digit absolute accuracy for - except for calibrating other instruments?

All validation/qualification labs I know had basic requirements of 0.1% or in rare cases 0.05%. If your meter should be one order of magnitude better than your specification you get to 0.005% - these are 4 1/2 digits.

Of course you can use 7 or more digits for relative purposes. Seeing small changes also over a large timespan is a great feature, so the instrument should have sufficient stability. From a pragmatic point of view this stability can also be ensured by tracking an external standard instead of going through the exhaustive and expensive complete calibration process.

What are real life applications for 6 digit absolute accuracy and not only stability? I´m curious.

[uargo]

Well, you will see in precision applications (medical, industrial, military, satellite, etc.) that you need to capture 3.3v or 1.8v from a sensor with a 24-bit ADC. We are talking about precisions of up to 107 nanovolts (1.8v / 2^24 = 0.000000107v). Any noise greater than 0.0000001 will distort the measurement, and if you are designing that circuit, you need to measure with that precision to mitigate the noise as much as possible.

[Kleinstein]

It is indeed very rare that one needs the high resolution. One point would be checking the linearity of a slow DAC / ADC or maybe DC amplifier. This usually does not need an accurate absolute scale.
Another point can be checking resistors or voltage references if they are really stable. For this one may want to see changes of only a few ppm.
A point here can be that the resistance ranges may not as stable / low noise as the preferred DC volt range.

A more common point is looking at really small signals, like a thermocouple voltage. For this one may want 1 µV or maybe 0.1 µV resolution. With a 100/200 mV range this would need 5 or 6 digit resolution. A few meters offer smaller ranges like 20 mV or 2 mV, but not very many. In this respect the old but still comming up used HP3478 can be a good pick with a 30 mV range and 5.5 digits.

The number of digits is really not the only thing to look at. There can be other points that can be important, like small ranges, speed, readability, having 4 wire ohms, high impedance to a certain voltage, frequency range for AC, PC interface, calibration. It really depends on the expected use which features are important and where one can compromise. A beginner tends to not need the calibration paper-work.

[robert.rozee]

[...] If your meter should be one order of magnitude better than your specification you get to 0.005% - these are 4 1/2 digits [...]

depending on how you view things, the above (0.005% for a 4.5 digit meter) may be out by a factor of 10, or even 100...

consider my 3.5 digit meter: it can at best be used to measure an arbitrary input to a 0.5% resolution. the limiting factor is where i want to measure, for example, 2.01 volts. this is too much to measure using the 2v range, so i need to use the 20v range instead. this can yield readings of 2.00 (a little low) or 2.01 (spot on) or 2.02 (a little high), giving a 0.5% usable resolution. while i could have my 3.5 digit meter adjusted to significantly better than 0.5% accuracy, this would be relatively pointless as the meter is unable to display results to anything better than 1 part in 200 (0.5%).

my 4.5 digit meter can, by extension, resolve an arbitrary input to within 0.05%, and hence is it pointless to have it adjusted to anything significantly better. my 5.5 digit meter can do 0.005%, while my 6.5 digit meter can do 0.0005%


now lets work the numbers backwards. lets say i want to measure something that is between 1.9 and 2.1 volts using my 3.5 digit meter.

if i see the number "2.01" displayed, what can i confidently say about the measurement that i am observing? it is fair to say that the actual voltage being measured could be anywhere between (just over) 2.005 and (just under) 2.015 volts - assuming the meter is spot on (0.0% accuracy error). but then we need to factor in the 0.5% level of accuracy we already arrived at above - this gives us an expanded range of 1.994975 to 2.025075 volts for what we are trying to measure, and possible displays of "1.99", "2.00", "2.01", "2.02", or "2.03".

this rather wide range gives me little confidence in that ".01" i'm seeing! i feel that i need at least to see one more digit to be confident - or that i need to downgrade the accuracy i'm willing to ascribe to my measurements by a factor of 2. i would be far more comfortable if i was looking at a display showing "1.990", as then i can happily dismiss the last digit and say "this is within 0.5% of 1.99 volts" with an air of certainty!

hence, when making arbitrary measurements, we really would like a 'guard digit' that we can throw out. while this could be a half-digit on the right (where the rightmost digit on our meter can only be either "0" or "5"), the marketing department prefers that every displayed digit beyond the first can cover the full range of "0".."9". instead, when we see the display of "2.01" we need to take that as being something between "1.99" and "2.03" - even if the reference and resistor divider of our meter is good for 0.5% accuracy, the reading we see displayed only has a +/-1% useful accuracy (what we might decide to call 'confidence').

by extension:
our 4.5 digit meter has a maximum useful accuracy of 0.1%,
our 5.5 digit meter has a maximum useful accuracy of 0.01%,
our 6.5 digit meter has a maximum useful accuracy of 0.001%.

and in cases of there being a little noise within our measurement system (as happens with 5.5 and more digit meters), we may wish to instead take a full decimal digit as the 'guard'. then we get:
our 5.5 digit meter having a maximum useful accuracy of 0.05%,
our 6.5 digit meter having a maximum useful accuracy of 0.005%.


cheers,
rob   :-)

[Fungus]

Well, you will see in precision applications (medical, industrial, military, satellite, etc.) that you need to capture 3.3v or 1.8v from a sensor with a 24-bit ADC. We are talking about precisions of up to 107 nanovolts (1.8v / 2^24 = 0.000000107v). Any noise greater than 0.0000001 will distort the measurement, and if you are designing that circuit, you need to measure with that precision to mitigate the noise as much as possible.

Nobody's arguing against having precision. The question was about accuracy:

Maybe a blasphemy question, but what do you need 6-digit absolute accuracy for - except for calibrating other instruments?

[Fungus]

consider my 3.5 digit meter: it can at best be used to measure an arbitrary input to a 0.5% resolution. the limiting factor is where i want to measure, for example, 2.01 volts. this is too much to measure using the 2v range, so i need to use the 20v range instead. this can yield readings of 2.00 (a little low) or 2.01 (spot on) or 2.02 (a little high), giving a 0.5% usable resolution. while i could have my 3.5 digit meter adjusted to significantly better than 0.5% accuracy, this would be relatively pointless as the meter is unable to display results to anything better than 1 part in 200 (0.5%).

Benford's law: https://en.wikipedia.org/wiki/Benford%27s_law

[Martin72]

Well there's Calibration and there's Calibration and what I've seen and learnt in the last few days was a real eye opener. 
Clean room, all working with equipment wore antistatic clothes, hats and booties and so so so many new units were having automated calibrations performed at once, meters, scopes, AWG's PSU, analyzers and so on.

But consider this, should just a single measurement in each measurement range be performed or many within each range ?
Some instruments took several hours to have the full calibration process complete. 

So so many top of the line calibration instruments performing these tasks was a sight to behold and will be etched in my mind like a good cal for the rest of my days.

It need be done properly or you're 

What you saw was a mass calibration, there is no other way with the quantities.
The good thing is that Siglent does not “throw away” the data obtained, even if the (cost-effective) devices are only accompanied by a one-page declaration that they have been successfully calibrated.
This is how I got the complete protocol for my SDM3065X in a roundabout way, which was important for me, because this is the only way to see trends and where the journey is going with each further calibration.
Incidentally, the protocol for an SSG3000X is a whopping 14 pages long...
Privately, these efforts are more than sufficient, for us they are null and void.
We have different standards and every piece of measuring equipment we purchase is calibrated by an accredited measuring laboratory before it is used.
Even if they basically do nothing other than what I have already described.
Is the device within its own tolerances yes/no.
But this is documented and completely traceable.
To be able to calibrate according to ISO, for example, the references used must be calibrated according to DakkS, the higher standard.
This in turn must also be completely traceable, the laboratory must be listed, otherwise their protocols can be contested.
And that is why a calibration by the manufacturer is null and void.

Maybe a blasphemy question, but what do you need 6-digit absolute accuracy for - except for calibrating other instruments?

Well....
I would like to see the person who has a private project going on where his resolution is really necessary.
There are probably not many people who own a 6 digit or more instrument.
At work, we sometimes have projects that require voltage adjustment to 1mV, which is very precise.
Anyone can work out what resolution is sufficient for us.
As a MIL, AERO and ISO certified company, we do not have a 6.5 digit instrument in our inventory.
If you buy something like this privately, 90% of the time it will go to the dog.
Or according to the dog question.
Why does he lick his balls?
Because he can.

[tautech]

Well there's Calibration and there's Calibration and what I've seen and learnt in the last few days was a real eye opener. 
Clean room, all working with equipment wore antistatic clothes, hats and booties and so so so many new units were having automated calibrations performed at once, meters, scopes, AWG's PSU, analyzers and so on.

But consider this, should just a single measurement in each measurement range be performed or many within each range ?
Some instruments took several hours to have the full calibration process complete. 

So so many top of the line calibration instruments performing these tasks was a sight to behold and will be etched in my mind like a good cal for the rest of my days.

It need be done properly or you're 

What you saw was a mass calibration, there is no other way with the quantities.
The good thing is that Siglent does not “throw away” the data obtained, even if the (cost-effective) devices are only accompanied by a one-page declaration that they have been successfully calibrated.
This is how I got the complete protocol for my SDM3065X in a roundabout way, which was important for me, because this is the only way to see trends and where the journey is going with each further calibration.
Incidentally, the protocol for an SSG3000X is a whopping 14 pages long...
Privately, these efforts are more than sufficient, for us they are null and void.
We have different standards and every piece of measuring equipment we purchase is calibrated by an accredited measuring laboratory before it is used.
Even if they basically do nothing other than what I have already described.
Is the device within its own tolerances yes/no.
But this is documented and completely traceable.
To be able to calibrate according to ISO, for example, the references used must be calibrated according to DakkS, the higher standard.
This in turn must also be completely traceable, the laboratory must be listed, otherwise their protocols can be contested.
And that is why a calibration by the manufacturer is null and void.

Check my current sig. 

I was not about to take pics of the several multiple calibration stations but I can add I've seen the high end Fluke universal calibrators elsewhere but those I saw at HQ were next level and many had leveling heads where they were connected to the DUC.
This alone indicated calibration was done to a very high standard.

[Martin72]

I was not about to take pics of the several multiple calibration stations but I can add I've seen the high end Fluke universal calibrators elsewhere but those I saw at HQ were next level and many had leveling heads where they were connected to the DUC.
This alone indicated calibration was done to a very high standard.

That is clear, because if you also offer high-precision instruments like Siglent, the calibration references have to be higher, otherwise it won't work.
But no quality auditor will say, OK, a certificate directly from the manufacturer is enough for me.
It has to be confirmed independently.
Professionals like Siglent know that.
But that's the game in the industry, siglent says our devices meet the self-imposed standards, we have tested EVERYTHING accordingly.
And an independent measurement laboratory then says “right”.

[Fungus]

I'm still unclear how "calibration" provides a guarantee unless it's done before and after each critical measurement.

Sending these devices through the abusive transport system for calibration or saying "it was calibrated six months ago" doesn't seem enough.

I'm more of a "I have two or three decent meters and they all agree to within a digit" sort of a guy.

This is something that calibration doesn't provide, per se.

[KungFuJosh]

I'm more of a "I have two or three decent meters and they all agree to within a digit" sort of a guy.

This is something that calibration doesn't provide, per se.

The best way to deal with that logic is to have a calibrated reference.

[J-R]

At a basic level, a hobbyist can use whatever method they want to obtain a desired result, but this is not realistic in a company/manufacturing context.  You can't just give an employee three DMMs and tell them to figure things out.  That leads to extra labor cost, mistakes, poor knowledge transfer, etc.  So you go with set procedures and automation along with calibration and multiple levels of QC to provide a statistically desirable result.

Fungus, how do you think you were able to obtain three completely DMMs that agree with each other???  Calibration...

[EEVblog]

I'm more of a "I have two or three decent meters and they all agree to within a digit" sort of a guy.
This is something that calibration doesn't provide, per se.

The best way to deal with that logic is to have a calibrated reference.

Multimeters are "calibrated references" in their own right.

[EEVblog]

I'm still unclear how "calibration" provides a guarantee unless it's done before and after each critical measurement.

Technically, it doesn't.
That's what "tracability" and "measurement confidence" are all about.

[KungFuJosh]

Multimeters are "calibrated references" in their own right.

If they're calibrated. 😉

[EEVblog]

Multimeters are "calibrated references" in their own right.

If they're calibrated. 😉

Don't confuse "calibration" with a good stable reference. The best reference is one that doesn't drift. It's better to have a reference that is out by say 0.1% and doesn't drift than an expensive "calibrated" reference that might have measured bang on when it was "calibrated", but then drifts over the next year.

[KungFuJosh]

Don't confuse "calibration" with a good stable reference. The best reference is one that doesn't drift. It's better to have a reference that is out by say 0.1% and doesn't drift than an expensive "calibrated" reference that might have measured bang on when it was "calibrated", but then drifts over the next year.

Of course not. But you can have your good stable reference calibrated. If you have 5 meters, it costs much less to have 1 reference calibrated and see how well your meters agree with that.

[EEVblog]

Of course not. But you can have your good stable reference calibrated. If you have 5 meters, it costs much less to have 1 reference calibrated and see how well your meters agree with that.

That "good stable reference" can be your multimeter. After all, it literally contains a stable reference chip.

[KungFuJosh]

That "good stable reference" can be your multimeter. After all, it literally contains a stable reference chip.

Agreed. But in context of the conversation:

I'm more of a "I have two or three decent meters and they all agree to within a digit" sort of a guy.

This is something that calibration doesn't provide, per se.

If you don't want to calibrate your meters, then calibrate something that all your meters can benefit from. Or don't care, because it doesn't matter for most hobbyists. 😉

[Fungus]

Fungus, how do you think you were able to obtain three completely DMMs that agree with each other???  Calibration...

Adjustment.

[J-R]

Fungus, how do you think you were able to obtain three completely DMMs that agree with each other???  Calibration...

Adjustment.

So you adjusted all three so they match, got it.

[tszaboo]

I'm still unclear how "calibration" provides a guarantee unless it's done before and after each critical measurement.

Technically, it doesn't.
That's what "tracability" and "measurement confidence" are all about.

Exactly this. Some time ago we had tthis calibrated shunt for 50A that was used as a transfer standard for calibrating the equipment we were selling. The shunt failed one calibration a year. We checked the relevant standard and the procedure is that you have to recall every equipment calibrated with it since the last passed calibration.

[Phil1977]

I would like to see the person who has a private project going on where his resolution is really necessary.
There are probably not many people who own a 6 digit or more instrument.
At work, we sometimes have projects that require voltage adjustment to 1mV, which is very precise.
Anyone can work out what resolution is sufficient for us.
As a MIL, AERO and ISO certified company, we do not have a 6.5 digit instrument in our inventory.
If you buy something like this privately, 90% of the time it will go to the dog.
Or according to the dog question.
Why does he lick his balls?
Because he can.

Very well said 

My question was not about hobbyists. Hobbies can be crazy, I´d even say they must be crazy. No further details needed.

But professionally - where do you need it?

I professionally often work with photometry. In that field, even the best equipped quality departments with 2m-Ulbricht-Spheres and dedicated black painted 25m long halls for goniometers struggle to get stability of better than 1% for some kind of light sources. In most datasheets of internationally leading suppliers the equipment specified for the performance measurement is required to be of 5% or 10% tolerance.

Anyhow measurements are done. You carefully track standards and multiple golden samples of the product type you are analysing. You sometimes use different standards that are routinely swapped between locations.

If you want to have an accuracy better than 5% then you usually can't buy a better instrument, you have to care for the accuracy by doing lots of comparisons and doing the math.

I perfectly get the point that in electronic metrology many things get much easier if you have a 7.5 digit DMM that always can be trusted for 4 digits relevant for your measurement. But where is it needed professionally? I´d just be curious for examples like: Doing ageing tests of batteries - if the ESR starts to fall for 5ppm then this is and indicator for something (This example was fictional - probably it's so much harder to measure the temperature of a battery than it´s ESR)

[EEVblog]

Fungus, how do you think you were able to obtain three completely DMMs that agree with each other???  Calibration...

Adjustment.

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
You have to specifically ask for a "calibration adjustment" if you want this.
And "adjustment" is not something that is normally done in any environment that takes calibration seriously. Why? Because you have just reset all of your tracable history and hence "measurement confidence" of this meter.
It sounds silly, as you just adjusted it to "spot on", but if you understand what tracable calibration is this is something you usually don't want. The tracabe history is usually more important than the absolute value.

[EEVblog]

I would like to see the person who has a private project going on where his resolution is really necessary.

Can be as simple as tracing shorts.

[Phil1977]

resolution != accuracy

That high resolution and a basic stability are super valuable is probably undoubted.

[tautech]

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
You have to specifically ask for a "calibration adjustment" if you want this.

Yes and yes but why the industry has retained Calibration as general terminology when it is too simply misunderstood and the fault of the industry.

Instead there need be a change of wording used to Performance Verification and Calibration Adjustment, both of which should never be misunderstood as their meanings are very clear.

[Kleinstein]

For using a meter as a voltage reference, there may be more drift in a DMM than just the internal voltage reference. For many meters there is additional ADC gain and possibly extra dividers / amplifiers. So the meters have it a bit more difficult to be as stable as a reference source. The market for stable ref. sources is relatively small though and a good meter may be easier to get than a ref. source. So using a meter as reference point is still a valid option.

Especially for hobby use one does not care that much about the absolute scale. One still wants the meter to be reliable, stable and linear.

For the short tracing one only needs the ability to resolve small voltages, not really the larger number of digits. Still a higher resolution meter may be a way to get that resolution.

[EEVblog]

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
You have to specifically ask for a "calibration adjustment" if you want this.

Yes and yes but why the industry has retained Calibration as general terminology when it is too simply misunderstood and the fault of the industry.
Instead there need be a change of wording used to Performance Verification and Calibration Adjustment, both of which should never be misunderstood as their meanings are very clear.

The industry has gotten by just fine as it is.
Most who take it seriously and pay money for proper tracable calibration know what it is and why they do it.

[Furna]

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
You have to specifically ask for a "calibration adjustment" if you want this.

Yes and yes but why the industry has retained Calibration as general terminology when it is too simply misunderstood and the fault of the industry.
Instead there need be a change of wording used to Performance Verification and Calibration Adjustment, both of which should never be misunderstood as their meanings are very clear.

The industry has gotten by just fine as it is.
Most who take it seriously and pay money for proper tracable calibration know what it is and why they do it.

If most (as opposed to all) of the people that pay money know what it is .. then it is definitely ambiguous   

[nctnico]

But professionally - where do you need it?

As Kleinstein noted, a quality DMM is easier to get than a good reference. And a DMM is more versatile as it can measure currents and resistances accurately as well. I'm using a Keysight 6.5 digit DMM to measure initial values of voltage references and reference resistors. The parts I'm using have low drift, low tempco but the initial value can vary more than required so they need calibration to increase absolute accuracy. I bought the Keysight DMM specifically for this purpose alone.

[skander36]

For using a meter as a voltage reference, there may be more drift in a DMM than just the internal voltage reference. For many meters there is additional ADC gain and possibly extra dividers / amplifiers. So the meters have it a bit more difficult to be as stable as a reference source.

...

Indeed! For example:



With some DMM's one have to be quick to catch the "opportunuty window" ...

[slavoy]

And this is where Siglent steps in, offering user adjustment through a .csv file while preserving the factory calibration so traceability remains 

[skander36]

And this is where Siglent steps in, offering user adjustment through a .csv file while preserving the factory calibration so traceability remains 

As Kelinstein said this is about stability. whatever calibration you will do, the descent curve will manifest. This measurement was in about 1:45 minutes, and the decay were in progress.

[slavoy]

And this is where Siglent steps in, offering user adjustment through a .csv file while preserving the factory calibration so traceability remains 

As Kelinstein said this is about stability. whatever calibration you will do, the descent curve will manifest. This measurement was in about 1:45 minutes, and the decay were in progress.

I was reffering to Dave's post to be precise.

Fungus, how do you think you were able to obtain three completely DMMs that agree with each other???  Calibration...

Adjustment.

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
You have to specifically ask for a "calibration adjustment" if you want this.
And "adjustment" is not something that is normally done in any environment that takes calibration seriously. Why? Because you have just reset all of your tracable history and hence "measurement confidence" of this meter.
It sounds silly, as you just adjusted it to "spot on", but if you understand what tracable calibration is this is something you usually don't want. The tracabe history is usually more important than the absolute value.

[skander36]

I was reffering to Dave's post to be precise.

Then our posts became interlaced in time.
This is why is good to quote the post referred.

[watchmaker]

This was dealt with by navigation centuries ago in the days of mechanical chronometers.  These were at sea for 3 years at a stretch and had to be consistent (and were, as proved by successful trade and naval maneuvers).

FWIW, these were so successful the USN did not retire mech chrons until GPS was perfected in 1989 even though they had first deployed quartz during WWII.  The quartz did not hold up well at sea.  Now of course, the USN would like some back.

All capital ships carried three chronometers.  Use one and it went rogue, SOL.  Use two and one went rogue, you were guessing.  Use three and one went rogue, you knew which one was bad.

These were calibrated and adjusted to Greenwich at the service depot every three years.  In use they were only wound, never adjusted for time.

Each carried a certificate that provided the calibration error determined over 30 days of observation.  The instruments used an escapement that is remarkably stable over 3 to 5 years and did not use oil (especially important in the days when whale oil thickened over time).

The navigator did not care about the "accuracy" of the dial time.  He used the calibration error to calculate the adjusted dial time so he could determine the actual time back in Greenwich.

Application to meters:

The absolute reading is not as important as knowing the deviation from "reality" on a consistent basis.  As in chronometers, consistency is far more important.

For this and statistical reasons, I agree with Dave that if three random DMMs consistently provide readings that agree to whatever precision is "good enough", then it can be assumed they are reliable.  And an aged instrument has likely reached its highest level of stability (chronometers were run for a year to allow the balance spring of the oscillator to age, and the consistency tended to approve over the 50 to 100 years of service).

Like a navigator, someone working in a high liability position needs annual calibration.  If concerned about changes within that period, they can spot check readings with another calibrated instrument.  Again though, the rule of three would seem to apply.

For the amateur, consistency would seem to be the goal and she/he can assume agreement among 3 DMMs means the readings are likely valid.  This is one approach to assessing convergent validity.

The amateur can also check their DMM by going back to basics, using Ohm's law to determine the expected reading.

I never paid more than $125 shipped for my DMMs, most of the time far less.  All agree within a couple counts on the last 2 digits.  My work range is 120 vac and below; so all but my Agilent 1252 are at least 15 years old with the electronics well aged and stable.

For the amateur buying a used instrument, Ohm's law at delivery is your friend.  Of course, a vetted second instrument is also your friend.  And who does not need at least 2 or 3 DMMs?

[BeBuLamar]

I think the OP doesn't want a benchtop for more resolution or accuracy than his handheld DMM. I think he just want the form factor of a benchtop unit.

[coromonadalix]

since OP has not appeared in HIS thread for a while  loll

[skander36]

And he has received in the beginning some good recommendations from Josh, Nico and Dave ...

[Aldo22]

since OP has not appeared in HIS thread for a while  loll

He showed that he did something with the 3D printer:
https://www.eevblog.com/forum/testgear/decent-benchtop-multimeter-for-beginner/msg5604207/#msg5604207

[coromonadalix]

oh sorry  thks  missed that one

i retract myself

[Kleinstein]

The comparison of the 34465 DMM6500 and SDM3065 is for the stabilization after turn on. Most of this should be a thermal effect and the 3 meters use the same LM399 reference that should have rather low TC. So the drift observed in the graph is mainly from the extra drift components, not the reference.
The TC of meters can scatter quite a bit between units - so with 3 other units of the same meter types the curves can look quite different (though the same time scale).

For precision use one anyway lets the meter warm up before use - so this initial phase is less relevant. There is however also a chance that longer time drift can happen at the same parts involved in thermal drift.

For the more low price range one can not expect that level of stability (at least from a new one).

[skander36]

...
For precision use one anyway lets the meter warm up before use - so this initial phase is less relevant. There is however also a chance that longer time drift can happen at the same parts involved in thermal drift.
....

After 1h:45 min Siglent still drift.  You want to say that it cannot be used for 2 hours ?
Why the others two are so stable?
Siglent is the older (about 5 years) and is the only calibrated and adjusted (last year) by Siglent in Germany. 

[nctnico]

...
For precision use one anyway lets the meter warm up before use - so this initial phase is less relevant. There is however also a chance that longer time drift can happen at the same parts involved in thermal drift.
....

After 1h:45 min Siglent still drift.  You want to say that it cannot be used for 2 hours ?
Why the others two are so stable?

Pedigree. Knowing how to age voltage references and knowing how to build a DMM properly.

[Fungus]

Fungus, how do you think you were able to obtain three completely DMMs that agree with each other???  Calibration...

Adjustment.

So you adjusted all three so they match, got it.

You adjust them so they match a reference, yes.

[Fungus]

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.
You have to specifically ask for a "calibration adjustment" if you want this.
And "adjustment" is not something that is normally done in any environment that takes calibration seriously. Why? Because you have just reset all of your tracable history and hence "measurement confidence" of this meter.

You could do it with a new meter if it doesn't agree with your other meters too well when it arrives. 

[Kleinstein]

...
For precision use one anyway lets the meter warm up before use - so this initial phase is less relevant. There is however also a chance that longer time drift can happen at the same parts involved in thermal drift.
....

After 1h:45 min Siglent still drift.  You want to say that it cannot be used for 2 hours ?
Why the others two are so stable?
Siglent is the older (about 5 years) and is the only calibrated and adjusted (last year) by Siglent in Germany.

If you want good accuracy it is standard to wait some time for the temperature to stabilize. The SDM3065 example may be an especially bad unit. The stabilization looks quite slow - maybe a bad or disabled fan ? It's is not the larger magnitude of the drift, but also looks like a longer time constant.

Many of the meter instruction call for some 2 hour warmup before doing critical measuments (e.g. do the calibration). That is not unusual. One can still use the meter before that, just don't expect the specified accuracy. One can not use it for the first minute or so, because many modern meters take quite some time for boot and an initial power on test. For a really serious meter I would even want a good self test to be run after at least some (e.g. 30 min) warmup, so it can be more stringent than right after turn on when things are naturally still drifting. A power on self test can be more tricky and may need to add extra tolerances for a possibly cold meter.

[2N3055]

Can somebody say how long it takes for KS 34401 to stabilise after power on, please?

[bdunham7]

Can somebody say how long it takes for KS 34401 to stabilise after power on, please?

 

Completely stabilize?  Never, unless you hold the ambient temp to better than +/- 1C.  Stabilize to well within specs, assuming 73C ambient and the meter being in that ambient for a while (48-72 hour) prior to power on?  30 minutes or so.  Stabilize to 1-2 counts?  2 to 4 hours.  All assuming a nominal 10V reference and the 10VDC range.  I've never really tried to test one for other functions, but since AC/ohms/current and the higher/lower DC volts all have worse specs I would think that the power on settling would be less signficant.  And this is all assuming you don't move or reorient the 34401A in any way.

Now ask me about the F8846A. 

[skander36]

If you want good accuracy it is standard to wait some time for the temperature to stabilize. The SDM3065 example may be an especially bad unit. The stabilization looks quite slow - maybe a bad or disabled fan ? It's is not the larger magnitude of the drift, but also looks like a longer time constant.

Many of the meter instruction call for some 2 hour warmup before doing critical measuments (e.g. do the calibration). That is not unusual. One can still use the meter before that, just don't expect the specified accuracy. One can not use it for the first minute or so, because many modern meters take quite some time for boot and an initial power on test. For a really serious meter I would even want a good self test to be run after at least some (e.g. 30 min) warmup, so it can be more stringent than right after turn on when things are naturally still drifting. A power on self test can be more tricky and may need to add extra tolerances for a possibly cold meter.

The meter was come back from Siglent, calibrated and validated as good with a calibration certficate from them. You can see that in the beginning the meter agree with the other two. But then it drift from the initial value while the others two dmm's keep reading in the same time/conditions as 3065X. If this is a defect then Siglent has failed verification and calibration, which I'm  really doubt. My point is that 3065X has not the best design for a 6.5 DMM. 
The fan is working well. Sellf test always pass, the meter was never broken or malfunctioned.

[Kleinstein]

The point of the calibration is to have the meter after warm up to meat it's specs, not just after turn on. The calibration instruction usually call for some 2 hours of warm up. If it only meets the specs directly after turn on, in a cold state, that would be fail. The overall change is also quite large - so maybe a rather poor unit or really weak fan / blocked air flow. Chances are this meter would also have a rather large (negative) TC for the 20 V range.

[skander36]

The point of the calibration is to have the meter after warm up to meat it's specs, not just after turn on. The calibration instruction usually call for some 2 hours of warm up. If it only meets the specs directly after turn on, in a cold state, that would be fail. The overall change is also quite large - so maybe a rather poor unit or really weak fan / blocked air flow. Chances are this meter would also have a rather large (negative) TC for the 20 V range.

As I said before, the fan is ok.

[BILLPOD]

 

[Martin72]

Pedigree. Knowing how to age voltage references and knowing how to build a DMM properly.

If the device drifts out of its own tolerance, something is defective, quite simply.

[skander36]

Pedigree. Knowing how to age voltage references and knowing how to build a DMM properly.

If the device drifts out of its own tolerance, something is defective, quite simply.

That is correct! But Siglent said that is ok and in tolerance ...  .. who knows?
Anyway my point was to show the difference between this three meters on drifting.
Having this meter as a single precission DMM make any user happy, but when a second meter is coming, the difference became obvious.

[Martin72]

Many people think when you send you meter in for "calibration" that they actually adjust it to be spot on, this is untrue, they just check it and give you a report on the values and whether it's within spec or not.

That's exactly how it is.
This is how an accredited (listed) calibration laboratory does it.
Either it passes or it is blocked with a query as to whether it should be adjusted or not.
As a rule, the devices are then sent to the manufacturer, and after re-adjustment they are sent back to the calibration laboratory.
However:

You have to specifically ask for a "calibration adjustment" if you want this.
And "adjustment" is not something that is normally done in any environment that takes calibration seriously. Why? Because you have just reset all of your tracable history and hence "measurement confidence" of this meter.
It sounds silly, as you just adjusted it to "spot on", but if you understand what tracable calibration is this is something you usually don't want. The tracabe history is usually more important than the absolute value.

Spot on again.
This is a popular question from auditors to us (me as the person responsible for the test field and to my measuring equipment representative, who is in charge of calibration and maintains the database of our test equipment):
Regular traceable calibration is all well and good, but what do you then do with the logs and, above all, with the results from them?
Do you simply file them away and only react when a calibration has failed?
What does your reaction look like then?
I can say that if a calibration fails, that would be FATAL.
And that's what the auditor is getting at.
If a measuring device passed calibration last year and now it hasn't, that doesn't mean it's OK, so we have it checked by the manufacturer and then calibrated again.
That means :
- What was measured with the device in the last 12 months after the last calibration, which products.
- Since nobody can say whether the device went out of tolerance after day 1 after calibration or only on day 364 before the next calibration, everything that was measured with it must be questioned.
- Are the products measured with it still in the company? You were lucky.
But rather not, they have already been delivered, then recall actions must be started, with the corresponding consequences such as economic and of course “loss of face”.
This must be prevented at all costs.
Therefore, the task is not only to manage the calibration results but also to check exactly where the trend of the measured values is heading.
In order to be able to intervene in good time if the trend turns negative.

[Martin72]

That is correct! But Siglent said that is ok and in tolerance ...  .. who knows?
Anyway my point was to show the difference between this three meters on drifting.
Having this meter as a single precission DMM make any user happy, but when a second meter is coming, the difference became obvious.

You would have to create a long-term graph and see whether the drift actually goes “out”.
If the drift remains within 0.0015%, this may be unpleasant for personal perception, but not a technical flaw.
If 10V are present, the measured value may be between 9.985 and 10.015V, roughly speaking.
If this is the case, then “unfortunately” everything is fine, you get what you bought.
If I remember correctly, the tendency of an SDM3065X is rather constant “downwards”, at least constant and not up/down.
The behavior opens up possibilities to “improve” this.
Or not, because it is within tolerance.
Or buy something that doesn't “annoy” you so much.

[nctnico]

That is correct! But Siglent said that is ok and in tolerance ...  .. who knows?
Anyway my point was to show the difference between this three meters on drifting.
Having this meter as a single precission DMM make any user happy, but when a second meter is coming, the difference became obvious.

You would have to create a long-term graph and see whether the drift actually goes “out”.
If the drift remains within 0.0015%, this may be unpleasant for personal perception, but not a technical flaw.
If 10V are present, the measured value may be between 9.985 and 10.015V, roughly speaking.

You might have a two decimal places wrong here  . 0.0015% = 15ppm. For 10V this means +/-150uV so between 9.99985V and 10.00015V

If you calculate your numbers back to a percentage, you get to 0.15%.

[Martin72]

My mistake, but the intention behind it remains the same.
As long as you're in, you're in.
If you're not, you're not and then it's a mistake that needs to be corrected.

[KungFuJosh]

He needs his starting voltage, and the mean voltages from the other meters to determine that. It isn't 10V exactly on any of the meters.

If the reference is 9.9998 then 9.9998 x 0.9985 = 9.9848. Or 9.9999 source voltage would be 9.9849. Both of those would be within threshold, no?

ETA: I would like to see data via TestController for an extended period of time, like a couple days or more.

[tautech]

He needs his starting voltage, and the mean voltages from the other meters to determine that. It isn't 10V exactly on any of the meters.

If the reference is 9.9998 then 9.9998 x 0.9985 = 9.9848. Or 9.9999 source voltage would be 9.9849. Both of those would be within threshold, no?

ETA: I would like to see data via TestController for an extended period of time, like a couple days or more.

Can you do one Josh ?
TIA

[KungFuJosh]

ETA: I would like to see data via TestController for an extended period of time, like a couple days or more.

Can you do one Josh ?
TIA

My computer and workbench stuff all get shut off at night. I could probably do one for 12 hours or so. I would let the reference and meter warm up first though.

[Kleinstein]

The drift shown for the SDM3055 is for the warm up period. There are usually no specs for this, the accuracy specs are valid only after warm up for 1 or 2 hours. A rather strong drift after turn on is inconvenient, but not a fault per se. There are usually no hard spec limits for this.

Much of the warm up drift is from the meters TC and the temperature rise for the frist 1 or 2 hours after turn on. So the large shift after warm up points to likely a large TC and this may be outside the specs or at least borderline. The observed change is some 50 ppm and with a 5 ppm/K spec this would mean a 10 K temperature rise. This sounds reasonable and it may not need an out of spec TC to reach that level of turn on drift.

[skander36]

The reason for there are 3  DMM's is comparison.
This is the idea. TWO meters are stable from ther beginning and ONE not so stable. Not the precission.
SDM3065X is not defect. Is just inferior as design.



P.S. Reference value is 10.000005

[tautech]

The reason for there are 3  DMM's is comparison.
This is the idea. TWO meters are stable from ther beginning and ONE not so stable. Not the precission.
SDM3065X is not defect. Is just inferior as design.



P.S. Reference value is 10.000005

And the time scale is ?
us, ms, s ? ? ?

[skander36]

The reason for there are 3  DMM's is comparison.
This is the idea. TWO meters are stable from ther beginning and ONE not so stable. Not the precission.
SDM3065X is not defect. Is just inferior as design.



P.S. Reference value is 10.000005

And the time scale is ?
us, ms, s ? ? ?

I've said before Rob. about 1H45min.

[KungFuJosh]

The reason for there are 3  DMM's is comparison.
This is the idea. TWO meters are stable from ther beginning and ONE not so stable. Not the precission.
SDM3065X is not defect. Is just inferior as design.



P.S. Reference value is 10.000005

Not one of your meters agrees with that reference value.

As has been said, no bench meters are expected to be perfect at power on. If two more expensive meters are more stable at power on, cool. Buy more expensive meters.

One of the reasons the SDM3065X costs less is because the LM399 is not burned in ahead of time. If you want stability faster, put at least a thousand hours on the chip.

Another question I have is regarding the setup. Which meter was tested first? Was the reference warmed up? I imagine your reference also needs warm up time before it's stable. I know mine do.

If your variables aren't consistent, your comparison isn't useful. Give equal warmup time to the reference, and to the meters, and then see what the results are.

[bdunham7]

P.S. Reference value is 10.000005

What is it and how do you know its value to better than 0.5ppm?

[bdunham7]

Not one of your meters agrees with that reference value.

Although the difference is more than I might expect for the Keysight (assuming his reference value is accurate) the Keithley and KS are both within their stated specfications.  The Siglent is not.

As has been said, no bench meters are expected to be perfect at power on. If two more expensive meters are more stable at power on, cool. Buy more expensive meters.

Sure, but being "better" in terms of stability and warmup performance is a much different issue than "meeting specifications" vs "not meeting specifications".  My HP 34401A also has significant power-on drift and is roughly 15-20ppm low at power-up.  But it is still well within specs even though it is 30 years old and has never been adjusted.

One of the reasons the SDM3065X costs less is because the LM399 is not burned in ahead of time. If you want stability faster, put at least a thousand hours on the chip.

That makes them useless or even dangerous (in a liability sort of way) in many professional applications.  See the post by tzaboo earlier.  Drifting out of tolerance before the first calibration interval is an unmitigated disaster in some instances and IMO is completely unacceptable for a professional-grade instrument.  As you say, you get what you pay for (if you're lucky).  However, none of this has anything to do with the particular behavior of this meter and Siglent's calibration practices.  This isn't the first story involving shortcomings on both of those fronts:

https://www.eevblog.com/forum/testgear/siglent-sdm3065x-issues/

Another question I have is regarding the setup. Which meter was tested first?

I'm assuming they were all tested simultaneously in parallel.  If not, then we need some details.

[KungFuJosh]

Although the difference is more than I might expect for the Keysight (assuming his reference value is accurate) the Keithley and KS are both within their stated specfications.  The Siglent is not.

I don't agree, and I won't assume anything, because the stated value of the reference is very likely BS. Not one of the meters agree with it, and how many digits would the meter to certify that value need to be? If we're playing the throw out the last digit rule, then you need an 8.5 digit meter to certify the ref as stated.

If you average the 2 more expensive meters, or choose either of them, and accept that as the ref value, then the Siglent is well within it's accuracy range:

If the reference is 9.9998 then 9.9998 x 0.9985 = 9.9848. Or 9.9999 source voltage would be 9.9849. Both of those would be within threshold, no?

ETA: Let's pretend that an 8.5 digit DMM meter was used to certify the ref, and that the DMM was also traceably calibrated. What conditions were required to meet that value? How long was warmup time for the ref and the meter? What was the temperature and humidity? Were any of those guidelines followed here? We know the answer is no, they were not, so the best we can do is average 2 or 3 of the 6.5 digit meters available to find a reasonable value.

[bdunham7]

If you average the 2 more expensive meters, or choose either of them, and accept that as the ref value, then the Siglent is well within it's accuracy range:

I'm perfectly OK with not assuming the reference is accurate, but even if you opt to believe that the Keysight is exactly accurate--an assumption that would most benefit the Siglent--there's still a ~50ppm discrepancy in the Siglent readings after the 1:45 warmup time.  That's not within spec, is it?

Now if you assume the Keithley and Keysight are reading high near the top of their tolerances and the reference is actually much lower (say 25ppm below 10V) then the Siglent might be in-spec albeit still quite drifty.  However, that's what I think Scott Adams refers to as "pretzel logic" and I think the answer here is very simple:  The meter has excessive power-on drift (perhaps due to a TC or TC compensation issue) and it was calibrated cold.  This is very similar to what happened to KG7AMV in the thread I linked.

Hopefully skander36 will fill us in on the details of the reference and whether these meters were all tested simultaneously.

[skander36]

Josh, you write a lot of personal assumptions (AKA BS).

The point is not he performance but a comparison between them.
The meters was tested in the same time. As KS and KT was able to keep a reasonable reading, so Siglent should stay aside. If not in my opinion is inferior. You may have your personal opinion of course.
-No, none of the meters doesn't show the actual value of the reference, they can't as they are 6.5 digit and this value is from a 3458A used for calibration. Actually the real value is 10.000001 after adjustement. 10.000005 was before (after 1 year and 8 month from fabrication) see picture from adjustement.
The drift will eventually stop after 3 about hours - see attached.

[skander36]

P.S. Reference value is 10.000005

What is it and how do you know its value to better than 0.5ppm?

I  said before, is a PDVS2 mini, calibrated in January this year.

[Kleinstein]

...
One of the reasons the SDM3065X costs less is because the LM399 is not burned in ahead of time. If you want stability faster, put at least a thousand hours on the chip.

The drift directly after turn on and the long term drift are different issues. It is common practice to have a mains powered meter powered up for an extended time (e.g. > 2h , possibly more in a fan-less design) before counting on the accuracy. So the calibration should also be for the later value, not the initial value. The initial drift can also vary quite a bit between units. So that SDM3065 could be an especially bad one - others can be much better. It would need more units to really make a point from it.

The design is different and the way the SDM3065 is build the 20 V range is not the most stable. Chances are the 2 V range can be more stable with the SDM3065 and the 1 V range of the DMM6500 and KS34465 are likely less stable than the 10 V range. A comparison at 1 V may go the other way.
Want the SDM3065 to look good: do the comparison at 15 or 20 V.

The reference with little burn in is a different issue and effect the long term drift. This a downside of the SDM3065 and makes the claimed accuracy a bit dubious for the initial phase and may requite an adjustment with the 1st calibration to really get it accurate. With the lower grade 34460 version from KS (still more expensive than the Sigilent), I am not so sure they get a proper burn in - maybe the rejects from the better meters. It would not need a few 1000 hours, just 1 week could do a lot.

[skander36]

One of the reasons the SDM3065X costs less is because the LM399 is not burned in ahead of time. If you want stability faster, put at least a thousand hours on the chip.

The meter is about 6 years old, and last year Siglent has certified /calibrated as good.

[KungFuJosh]

That's not within spec, is it?

Yes, it's still in range based on the 0.0015% I mentioned above. Which is wrong. Apparently that accuracy applies only to the 2V range (within 24 hour relative to calibration standards).

The meter is about 6 years old, and last year Siglent has certified /calibrated as good.

Skander's meter is 6 years old, and calibrated about a year ago. 20V range: 0.0040% of reading, + 0.0004% of range is the relevant stated accuracy. Even if we pretend it's within 24 hours (which we know is not true) that would be 0.0020 + 0.0003. In either of those cases, it's well within those ranges.

Skander, I'd like to see what it looks like if you let the meter and the standard warm up for 1 hour and then record the data over a long period and see how much drift there is.

I did the same warm up, and I'm recording data now with TestController (I'll follow up in the regular SDM meter thread).

If your meter shows to drift significantly when correctly warmed up and setup, then Siglent should absolutely correct it.

[bdunham7]

I  said before, is a PDVS2 mini, calibrated in January this year.

OK, I must have missed that.  In any case, that is a 5ppm (typical) reference not 0.5ppm, so that needs to be taken into account when analyzing your results.  I don't think it makes much difference to the conclusion though.

[bdunham7]

In either of those cases, it's well within those ranges.

I think one of us is reading that chart wrong.  What do you see the SDM3065X reading at the 1:45 (end of the chart) point?  How many ppm below 10.00000V is that?

I'm seeing about 9.99933V, which is 670uV or 67ppm below 10V.

[KungFuJosh]

In either of those cases, it's well within those ranges.

I think one of us is reading that chart wrong.  What do you see the SDM3065X reading at the 1:45 (end of the chart) point?  How many ppm below 10.00000V is that?

The incorrectly stated accuracy was +/- 0.0015%. 10.00000000000000000000000000 x 0.9985 = 9.985. At no point in the chart does the measure value drop below 9.9992. It is within that incorrect range.

The correct accuracy for his meter in the 20V range is 0.0040%. That would place the bottom range: 10.00000000000000000000000000000000000000000000000000 x 0.996 = 9.9960. The meter is clearly within the accuracy spec.

[Kleinstein]

After warm up the SDM3065 seems to be some 65 ppm off the nominal 10 V from the reference and some 50 ppm lower than the other 2 meters. Both would be outside the 1 year specs (40 ppm of 10 V + 8 ppm of fixed part). So the reading should be between 9.99952 and 10.00048.  It is not far off, so maybe still in the gray zone where we can not for sure say it is out, but more likely out than in.

Given the time of year, part of the problem could also be the temperature - it may not be close to 23 C. A high temperature could explain a lower reading. An extra 10 K would allow for an extra 50 ppm.

There is a certain problem with the usual calibration practice to only check against the spec limit (e.g. for 1 year). Ideally there should be a warning if the meter just passes the 1 year specs, but not the shorter (e.g. 90 day) specs. This would indicate that the meter was OK for the past, but has a chance to drift outside in the next year or so. So one would either need to include correction factors or do an adjustment to make the meter direct read good values again. For the future it is just not good enough to just pass the 1 year limits, one needs some headroom for future drift and temperature variations.

[zepto]

I'm surprised by the minimal warm-up drift of the other 2 meters, but I do not have any experience with either of those models.

I recently tested some old meters from hp, fluke, advantest, and keithley with possible intent of adjusting. Despite some being 40 years old they all decided a high quality reference was within 40 ppm of 10V, the two oldest suggested it was within <10ppm. Most of them had not been turned on in the last year, I have no idea when they were last calibrated. I bought them used and untested beyond power on. I have never worked on any of them and they are better off for that fact.

I was under the impression that HP's spec sheets for multimeters served as a guarantee and they were liable for damages.

I do not recommend to hobbyists that they buy an old LCR meter like pm3603, hp4261a,esi252 etc when DE-5000 exists. There is not a similar device that makes precision multimeters from the past obsolete. Even older devices that lacked digital interfaces could have their usefulness extended with a $15 mcu dev board and a little bit of effort. The graphing capability of modern meters is inferior to properly processing the data on a computer, and they don't offer anything over older meters if you just want to take a series of 1 plc or 10 plc readings.

Recommending sdm3045x for $400 to a hobbyist in the USA seems malicious.

[skander36]

I see you like it
The source csv file from Test controller (the one and only).

[bdunham7]

The correct accuracy for his meter in the 20V range is 0.0040%. That would place the bottom range: 10.00000000000000000000000000000000000000000000000000 x 0.996 = 9.9960. The meter is clearly within the accuracy spec.

Your math is one or two decimal places off depending on where you look.  100.0000% - .0040% = 99.9960% or 0.999960.  4 nines.  The lower threshold would be 10V x 0.999960 = 9.99960V.  The lowest readings appear to be about 9.99933V, well below the threshold.

[nctnico]

I'm surprised by the minimal warm-up drift of the other 2 meters, but I do not have any experience with either of those models.

The Keysight one Skander36 tested has a temperature coefficient compensation mode. Likely that is enabled. My guess is the Keithley DMM6500 has a similar feature.

[Kleinstein]

The KS meter is a quite high grade part and the actual performance can also vary. The main part to expect is temperature rise (e.g. some 10 K as a crude estimate for meter with a fan) times TC  (2 ppm/K spec limit for the 34465). So one should expect less than some 20 ppm or the grid spacing in the graph. The actual TC is often quite a bit smaller as actually measuring the TC is difficult and thus some design headroom needed.
Some of the initial drift (the first few minutes) are likely missed with the meters, as they take quite some time to boot and than may come added time to actually start the test. The curve looks like it is not that steep to start with and thus some initial part missing - the first few minutes can make quite a difference to the look.
The actual turn on drift can also vary quite a bit between units and there can be some lucky ones with really low drift.

The more relevant parameter may actually be the TC, so the effect of a change in the room temperature.


The $300 price range for a new bench meter is tricky. One can get some 4.5 digits based one a chip set for hand helds for some $200 or even less, but these often miss on 4 wire ohms and high impedance. Due to the low volume the bench versions tend to be more expensive than a comparble hand held version and no accuracy advantage at the lower end.

Bench meters with 4 Wire ohms and high impedance mode start at more like $400, like with the SDM3045, but there are a few alternatives too.
The SDM3045 is a bit 2 sided thing. One the one side it is kind of based on a 5.5 digit design (SDM3055E is essentially the same harware) that is software crippled. One still gets relatively good noise performance. The crippling however causes some issues with the ranges that can be really anoying. So one may consider the not that much more expensive SDM3055 as the proper 5.5 digit version.

Some $300 is the range where one may get a used 6 digit meter in the US - maybe no longer a HP34401, but still some reasonable used bench meter around in the US. One issue with a used DMM can be the PC interface: the old ones often come with GPIB and a GPIB card / adapter add to the costs.

[slavoy]

I see you like it
The source csv file from Test controller (the one and only).

Noticeably outside the specification, but I’m not knowledgeable enough in metrology to calculate the uncertainty of your method. Siglent might just as well be right on the low edge.

[KungFuJosh]

Okaaaay, I did not understand how the accuracy was supposed to be calculated. It's pretty goofy the way it works. It's like there's an extra step just to confuse me. 😉

So the real accuracy is supposed to be:
0.0040 + 0.0004 = 10 x (0.0040 / 100) + 10 x (0.0004 / 100) = +/-0.00044
.0004 + .00004 = .00044

That makes the lower number 9.99996, but that's only assuming that the calibrated reference really matches the calibrated number in his environment, which it does not, according to three 6.5 digit DMMs.

I saw Skander's calibration post, and the Siglent was usually above the nominal value, but now it's under. That's not awesome.

However, since the meter is 6 years old, it's not under warranty anyway. Maybe it would be better to let an independent lab calibrate / adjust the meter?

SiglentNA quoted me $300 just to calibrate. Trescal told me $200, and a couple smaller but still certified/traceable labs quoted me around there, including the data. I would rather an independent lab calibrate it anyway; I would certainly never pay the manufacturer extra for a potentially biases cal. 😉

I would still like to see longer data after everything is properly warmed up.

[bdunham7]

That makes the lower number 9.99996,

Now you have FIVE nines!     When it gets confusing, using the same number of digits as appear on the display can be helpful. 9.99960 is what you are looking for, or 40 counts.  Actually you'd use 9.99952, another 8 counts lower, since there is the additional 4ppm of range and the range is 20V. 

I saw Skander's calibration post, and the Siglent was usually above the nominal value, but now it's under. That's not awesome.

If I'm looking at the same post you are, that measurement was at 18V, not 10 so linearity could be an issue.  That much non-linearity would, IMO, truly be "not awesome" but still a possibility.  I don't think there is an INL spec for the SDM3065X.

You posted a screenshot in another thread showing your SDM3065X with about 2ppm p-p noise over a 30-minute period.  What was it measuring on cold power-up with the reference warmed up?  Do you get anywhere near as much power-up settling as skander36?

[Kleinstein]

It is indeed odd to see high values in the calibration report and low values here. There are a few points that can cause such effects: a rather high TC and different temperatures, an offset error (e.g. zero adjust too soon after trun on or at a much different temperature) or a linearity problem as the calibration is at 18 V  and not at 10 V. Another possible issue can be EMI, e.g. from interference between the meters or some local source.

The full scale for the SDM3065 is 20 V to the 40+4 ppm makes it  400 µV + 80 µV = 480 µV or 48 ppm of the 10 V signal.

The rather high costs for calibration are a problem with many more budget meters. This is not only the Sigilent. Here the DMM6500 may have a slight edge with specs for 2 years, not just 1year. For hobby use one usually not really needs the calibration as an extra expensive piece of paper to tell that is meter was supposedly OK at the test points.

[skander36]

However, since the meter is 6 years old, it's not under warranty anyway. Maybe it would be better to let an independent lab calibrate / adjust the meter?

This is not gonna happen. I already paid 200E plus shipping to Germany in the hope that this meter will came close to the other two DMM's. If I'm not getting money from DMM I will not calibrate it again.
It had this behavior from the first day when it arrived from calibration.
It will stabilize itself, as I said after 3-4 hours, when I can generate a calibration file to use it as user calibration, but at this interval is no use for me, as I have the other two DMM's that can stabilize faster.

[bdunham7]

It had this behavior from the first day when it arrived from calibration.

Any idea what its behavior or measurements were before calibration?

[skander36]

It had this behavior from the first day when it arrived from calibration.

Any idea what its behavior or measurements were before calibration?

About the same curve drift. This was the reason for sending to calibration.

[KungFuJosh]

You posted a screenshot in another thread showing your SDM3065X with about 2ppm p-p noise over a 30-minute period.  What was it measuring on cold power-up with the reference warmed up?  Do you get anywhere near as much power-up settling as skander36?

Wasn't that 27ppm noise?

I didn't test cold power up at all since it's sort of pointless. Ignoring warmup times for both the ref and the meter doesn't make any sense to me.

I could try another time if you think it matters, but the meter's been on for 7 hours so far today, so no cold start info for a while.

[KungFuJosh]

This is not gonna happen. I already paid 200E plus shipping to Germany in the hope that this meter will came close to the other two DMM's. If I'm not getting money from DMM I will not calibrate it again.
It had this behavior from the first day when it arrived from calibration.
It will stabilize itself, as I said after 3-4 hours, when I can generate a calibration file to use it as user calibration, but at this interval is no use for me, as I have the other two DMM's that can stabilize faster.

Understandable, and that makes sense. In the other thread Defpom said:

It is FAIRLY settled after an hour, it is still warming up for about 4 hours, after that although there is still some movement but it is small.

So I posted my first 4 hours in that thread, then I reset the data, and I'm going to post the following 4 hours when it's done. P-P was 0.000042 for the first 4 hours, and then after two hours on the new test it's currently holding at 0.000030 P-P.

I don't know how many hours of on-time your SDM has had, but I assume more than mine. I think mine is still in the low hundreds of hours at most.

You could always just leave your meter powered on forever. Then problem solved. 😉

If you feel like doing the same test as me, I would love to see that info. 1 hour warmup, 4 hours tracked, then reset data and continue tracking for 4 hours. I want to see how your PP compares. 🤣🤣🤣🤣🤣

[skander36]

...

If you feel like doing the same test as me, I would love to see that info. 1 hour warmup, 4 hours tracked, then reset data and continue tracking for 4 hours. I want to see how your PP compares. 🤣🤣🤣🤣🤣

This doesn't make any sense to me. My point was a compare between three different DMM's.

[G0HZU]

Maybe a blasphemy question, but what do you need 6-digit absolute accuracy for - except for calibrating other instruments?

All validation/qualification labs I know had basic requirements of 0.1% or in rare cases 0.05%. If your meter should be one order of magnitude better than your specification you get to 0.005% - these are 4 1/2 digits.

Of course you can use 7 or more digits for relative purposes. Seeing small changes also over a large timespan is a great feature, so the instrument should have sufficient stability. From a pragmatic point of view this stability can also be ensured by tracking an external standard instead of going through the exhaustive and expensive complete calibration process.

What are real life applications for 6 digit absolute accuracy and not only stability? I´m curious.

Few professional people will need the absolute accuracy, but because DVM technology has been 'boringly brilliant' for several decades now, the internal reference accuracy and stability justifies 6.5 digits or maybe more for a decent bench multimeter.

In my experience, 6.5 digit meters generally offer other features making them very attractive for professional ATE systems. They offer fast read rates and various inbuilt math functions and they offer GPIB and/or USB and/or LAN interfaces.

In all my years at work, I have never seen any engineer get excited when a decent DMM was returned from calibration. Also, I don't think I've ever seen an engineer check two 6.5 digit DMMs against each other in the way many hobbyists do obsessively. Many of them seem to progress to obsessing over state of the art voltage references and calibrators.

Don't ask me what they think they need this stuff for, but in other hobbies there will always be people who want either the titanium/platinum/silver/gold version of whatever widget(s) the hobby demands. I think it's partly a status thing, partly a FOMO thing and partly an OCD thing.

[KungFuJosh]

...

If you feel like doing the same test as me, I would love to see that info. 1 hour warmup, 4 hours tracked, then reset data and continue tracking for 4 hours. I want to see how your PP compares. 🤣🤣🤣🤣🤣

This doesn't make any sense to me. My point was a compare between three different DMM's.

You compared the 3 devices from cold start. I'm curious about the actual stability of your DMM, which requires warmup time first. You could still measure all 3 if you want to compare.

Comparing between 3 DMMs is fun, but if you want to see if there's an actual problem with one of them, you have to test it properly.

I just saw this post:

Josh, you write a lot of personal assumptions (AKA BS).

The point is not he performance but a comparison between them.
The meters was tested in the same time. As KS and KT was able to keep a reasonable reading, so Siglent should stay aside. If not in my opinion is inferior. You may have your personal opinion of course.
-No, none of the meters doesn't show the actual value of the reference, they can't as they are 6.5 digit and this value is from a 3458A used for calibration. Actually the real value is 10.000001 after adjustement. 10.000005 was before (after 1 year and 8 month from fabrication) see picture from adjustement.
The drift will eventually stop after 3 about hours - see attached.

That's what I correctly assumed, an 8.5 digit meter. That number also has to take into account temperature and humidity. Did you when you tested your 3 meters? You will never match that number otherwise.

Your results are BS if you wanted to test or compare anything besides cold start drift. It's simply not accurate to claim you have a problem based on cold start. That's not an opinion or an assumption. Every device requires warmup time to meet specs.

I'm not saying the Siglent isn't inferior to the other two meters. I would love to have a DMM6500 if I could afford it. That doesn't make my Siglent a piece of crap; it's just not as nice as the meter that costs twice as much. I'm not shocked by that.

[bdunham7]

Wasn't that 27ppm noise?

No, that would be terrible.  27µV is what is displayed in the box, that's 2.7ppm. 

I didn't test cold power up at all since it's sort of pointless. Ignoring warmup times for both the ref and the meter doesn't make any sense to me.

First, characterizing your meter so you know how it behaves can be helpful because then you'll know how long you have to let it warm up before you can get a certain level of accuracy.  Second, the power-on settling data can give you some idea of what the TC of the unit will be like.  An hour is an arbitrary time, regardless of whether or not it appears in a manual.  You might discover that for all practical purposes your meter is spot-on after 5 minutes or you might find that it is not even well within spec until an hour goes by.  Either result may be technically acceptable and no cause for complaint, but it is still useful to know.

[KungFuJosh]

I suppose I should be less lazy. I might have been using an online calculator that said 0.000027 = 27ppm. Ok, 27uV is 2.7ppm. Cool. I assume there's some context as to why there's a discrepancy.

Fair enough. I often use my DMM with 1 minute of warmup, I haven't had any issues. I also don't usually test anything that cares about uV resolution.

Tomorrow I'll test both from cold start. Or should I warm up the ref first, to separate that? It makes sense to me to warm up the ref first remove the ref's drift from the test.

ETA: removing the ref's drift might prove difficult if I can't keep my room consistent as my other test showed (even if it was obvious).

Thanks,
Josh

[bdunham7]

Tomorrow I'll test both from cold start. Or should I warm up the ref first, to separate that? It makes sense to me to warm up the ref first remove the ref's drift from the test.

Ideally you'd do it both ways--with the ref warmed up and meter cold then vice versa.  But try it the first way first.  IDK what I'd do if I had to shut my power off nightly--I have multiple references and instruments that stay on for months on end.  I may have missed it if you said earlier, but what is your reference?

[skander36]

That's what I correctly assumed, an 8.5 digit meter. That number also has to take into account temperature and humidity. Did you when you tested your 3 meters? You will never match that number otherwise.

Your results are BS if you wanted to test or compare anything besides cold start drift. It's simply not accurate to claim you have a problem based on cold start. That's not an opinion or an assumption. Every device requires warmup time to meet specs.

I'm not saying the Siglent isn't inferior to the other two meters. I would love to have a DMM6500 if I could afford it. That doesn't make my Siglent a piece of crap; it's just not as nice as the meter that costs twice as much. I'm not shocked by that.

Actually you said that

...

I don't agree, and I won't assume anything, because the stated value of the reference is very likely BS.

I proved that the referece value is not BS.

The other meters can provide a trusty reading no mater the conditions, while the Siglent not.  This is the idea.

[tautech]

That's what I correctly assumed, an 8.5 digit meter. That number also has to take into account temperature and humidity. Did you when you tested your 3 meters? You will never match that number otherwise.

Your results are BS if you wanted to test or compare anything besides cold start drift. It's simply not accurate to claim you have a problem based on cold start. That's not an opinion or an assumption. Every device requires warmup time to meet specs.

I'm not saying the Siglent isn't inferior to the other two meters. I would love to have a DMM6500 if I could afford it. That doesn't make my Siglent a piece of crap; it's just not as nice as the meter that costs twice as much. I'm not shocked by that.

Actually you said that

...

I don't agree, and I won't assume anything, because the stated value of the reference is very likely BS.

I proved that the referece value is not BS.

The other meters can provide a trusty reading no mater the conditions, while the my Siglent not.  This is the idea.

FTFY

I have no idea why yours seems to be a problem child and even though you've had it recently checked it drifts outta spec. 

[2N3055]

...The other meters can provide a trusty reading no mater the conditions.....

I presume what you wanted to say, but this statement is highly doubtful..

I'm sure I could provide conditions to make them show numbers highly different from what you expect...

[KungFuJosh]

Ideally you'd do it both ways--with the ref warmed up and meter cold then vice versa.  But try it the first way first.  IDK what I'd do if I had to shut my power off nightly--I have multiple references and instruments that stay on for months on end.  I may have missed it if you said earlier, but what is your reference?

I attached a photo from the aliexpress listing for the ref I have. The stated values are (surprisingly) not the same as the piece of paper that came with mine. 😉

I have the ref warming up now, I'll turn on the meter soon and do the cold start test.

If I had solar I might leave stuff on, but my electric bills are already way too high as it is.

[robert.rozee]

I attached a photo from the aliexpress listing for the ref I have [...]

 

[nctnico]

I'm wondering how they measured the resistors on that board so accurately...  But they don't look like low tempco, low drift resistors anyway. Also, the AD584 isn't the best reference out there. There are so many better choices.

[KungFuJosh]

Make fun all you want, it's pretty damn good for $20. 

[Aldo22]

Make fun all you want, it's pretty damn good for $20. 

I ordered something similar for CHF 6.
Apparently it uses an AD584L which is supposed to be reasonably accurate (+- 5mV @ 10V).

According to the pictures in the comments, it's measured with a 34401A.


Let's see, I don't have it yet.
For this price you can give it a try.
It's just for fun, I only have an AN870.

[bdunham7]

I have the ref warming up now, I'll turn on the meter soon and do the cold start test.

The TC of that reference is probably not great, so keeping it at a constant temperature is more important than a long warmup.  It's still an experiment worth doing, as well as the inverse with a stabilized meter.  How good is the temperature stability of your lab/room/bench?

[KungFuJosh]

Make fun all you want, it's pretty damn good for $20. 

I ordered something similar for CHF 6.
Apparently it uses an AD584L which is supposed to be reasonably accurate (+- 5mV @ 10V).

According to the pictures in the comments, it's measured with a 34401A.

Let's see, I don't have it yet.
For this price you can give it a try.
It's just for fun, I only have an AN870.

I have a couple others similar to those (maybe the same one also?). They give the same printout with every one of them, no value changes. That's why I commented about the values for mine not being the same as the photo, as that's rare on aliexpress.

I don't remember who, but another member on here told me about the purple one I ordered. It's the best I've seen of these cheaper references.

[Aldo22]

I have a couple others similar to those (maybe the same one also?). They give the same printout with every one of them, no value changes. That's why I commented about the values for mine not being the same as the photo, as that's rare on aliexpress.

I don't remember who, but another member on here told me about the purple one I ordered. It's the best I've seen of these cheaper references.

I also have my doubts about these "individual" measurements.
But the AD584L is supposed to be a bit better than the "J" or "K" variants.
Should arrive next week.

[KungFuJosh]

I also have my doubts about these "individual" measurements.
But the AD584L is supposed to be a bit better than the "J" or "K" variants.
Should arrive next week.

Most of the ones that I bought was advertised as AD584L. 🤷

I also got a couple from Amazon and eBay.

[Aldo22]

Most of the ones that I bought was advertised as AD584L. 🤷

OK, but if it does what it promises, it's good enough for my purpose (+- 5mV @10V), even if it wasn't measured individually.
That's what I meant.

[KungFuJosh]

Most of the ones that I bought was advertised as AD584L. 🤷

OK, but if it does what it promises, it's good enough for my purpose (+- 5mV @10V), even if it wasn't measured individually.
That's what I meant.

Oh, I'm not arguing with you. I agree, they're generally good enough for my purposed too, but the purple one has been the best (living up to the claims etc).

Some people will obviously laugh at these references, but if they want to buy us $400 references, that would be fine with me too. 😉

The seller I got the purple ref from has these now instead: https://www.aliexpress.us/item/3256806626314478.html

I guess they ran out of the 584Ls. I have no idea if those are any good, but he also has some other interesting ref boards for L, C, R individually.

[skander36]

I attached a photo from the aliexpress listing for the ref I have. The stated values are (surprisingly) not the same as the piece of paper that came with mine. 😉

I have the ref warming up now, I'll turn on the meter soon and do the cold start test.

If I had solar I might leave stuff on, but my electric bills are already way too high as it is.

I would recommend you a reference with LM399. there are plenity on Aliexpress at an affordable price.
You can also build one, but from my experience you really need to put quality components to achieve high stability.

[KungFuJosh]

I would recommend you a reference with LM399. there are plenity on Aliexpress at an affordable price.
You can also build one, but from my experience you really need to put quality components to achieve high stability.

When I convince myself I need a better ref, and if it's in stock at that exact moment, I'll buy a VREF10-001 r9. It's hard for those two things to line up tho. 😉

[skander36]

When I convince myself I need a better ref, and if it's in stock at that exact moment, I'll buy a VREF10-001 r9. It's hard for those two things to line up tho. 😉

Testing a 6.5 DMM isn't enough reason?

[KungFuJosh]

Testing a 6.5 DMM isn't enough reason?

Not for me. The $22 ref I have is fine for my needs. It's stable enough to show that my DMMs are also stable. I rarely need more than mV resolution, so it's sort of silly. Maybe if somebody wants to sell me a used one I'd buy it. 😉

I am about to test my ref from cold start with the DMM warmed up. I might also point a hot air wand at the ref to see how that affects the voltage. I'll post the results in the SDM thread.

[EEVblog]

Testing a 6.5 DMM isn't enough reason?

Not for me. The $22 ref I have is fine for my needs. It's stable enough to show that my DMMs are also stable. I rarely need more than mV resolution, so it's sort of silly. Maybe if somebody wants to sell me a used one I'd buy it. 😉

If "stability" is your main goal then that's what two mulitmeters you can reference against each other gives, you don't need a reference.
i.e. it's unlikley that both meter would drift in the same direction by the same amount
But of course, not having a third meter or reference means if one of the two meters drifts, you don't know which one it is.

[KungFuJosh]

But of course, not having a third meter or reference means if one of the two meters drifts, you don't know which one it is.

So I should buy a 3rd bench meter, and a calibrated reference. Fiiiiiiiiiine. Eventually. 😉

[Fungus]

Here's my BM857 and Fluke 187 measuring the cheapo reference I got from China:


I know they're only 4.5 digit meters but I figure as long as they both agree to the last digit on a randomly-purchased reference then I'm good. No need to get a cal lab involved.

Looking at the prices of those references I think the chips must be second hand, so... they're probably well burnt-in. 

[Aldo22]

A bit off-topic, but aren't we anyway? 
I just found out that my very old USSR multimeter (1978) can do something that my modern DMMs cannot: It can measure AC voltage at 20kHz. Even at 100kHz it is still within 3dB.
In the picture it should show 1.77Vrms. The reading is about 1.78Vrms @20kHz sine (5Vpp).
My An870 is completely useless at 3kHz already.

So every little meter has its raison d'être. 

[MiroS]

So every little meter has its raison d'être. 

They were sold on local market for 2-3 EUR some time ago. I think they all finished in trash.
AN270 is high-tech rocket comparing to 'that'. I do not think it is RMS mutimerer, most likely not at all.
USSR technology was modern in building tanks, prisons, spy factories, atom bombs terror,  poisons,
economical exploataion occupied countries,  but never in area of multimeters.
I would not touch this device, this plastic can be toxic, USSR did not care for such little things like heath.

[Fungus]

A bit off-topic, but aren't we anyway? 
I just found out that my very old USSR multimeter (1978) can do something that my modern DMMs cannot: It can measure AC voltage at 20kHz. Even at 100kHz it is still within 3dB.

Simple reason: Inertia.

The needle can't move that fast... 

[Aldo22]

They were sold on local market for 2-3 EUR some time ago. I think they all finished in trash.
AN270 is high-tech rocket comparing to 'that'. I do not think it is RMS mutimerer, most likely not at all.
USSR technology was modern in building tanks, prisons, spy factories, atom bombs terror,  poisons,
economical exploataion occupied countries,  but never in area of multimeters.
I would not touch this device, this plastic can be toxic, USSR did not care for such little things like heath.

Oh yeah, it's old, ugly and it stinks, but it pretty much shows the same values ​​as the oscilloscope for Vrms up to 50kHz.
That's definitely something the AN870 does not.

[MiroS]

Oh yeah, it's old, ugly and it stinks, but it pretty much shows the same values ​​as the oscilloscope for Vrms up to 50kHz.
That's definitely something the AN870 does not.

Vrms? My guess is that this is not the case. AN870 can do RMS at least up to 1-3 kHz. That one most likely only for 0 Hz.
Btw using it would be like hearing German radio from III Reich era with big black eagle on front panel. 
Personaly I do not see the difference between both regims and their artifacts.

[Aldo22]

Vrms? My guess is that this is not the case. AN870 can do RMS at least up to 1-3 kHz. That one most likely only for 0 Hz.

It certainly matches the VRMS value for sine (Not True RMS).
Perhaps "average rectified value" is more appropriate?
https://en.wikipedia.org/wiki/Average_rectified_value

[tszaboo]

A bit off-topic, but aren't we anyway? 
I just found out that my very old USSR multimeter (1978) can do something that my modern DMMs cannot: It can measure AC voltage at 20kHz. Even at 100kHz it is still within 3dB.
In the picture it should show 1.77Vrms. The reading is about 1.78Vrms @20kHz sine (5Vpp).
My An870 is completely useless at 3kHz already.

So every little meter has its raison d'être. 

Even a 34401A is going to measure 300KHz with 4% accuracy. 100KHz is 0.5% or 0.04dB.

[Aldo22]

Even a 34401A is going to measure 300KHz with 4% accuracy. 100KHz is 0.5% or 0.04dB.

I don't know what you're trying to say.
I'm talking about a rotten 50 year old analog meter sitting in the basement and you're talking about a $1000 top of the line DMM.
What's the connection?

[MiroS]

Even a 34401A is going to measure 300KHz with 4% accuracy. 100KHz is 0.5% or 0.04dB.

I don't know what you're trying to say.
I'm talking about a rotten 50 year old analog meter sitting in the basement and you're talking about a $1000 top of the line DMM.
What's the connection?

I think 'old bad 'vs 'old good'.

'Old good' can be not that wrong way, actualy often best way to go. With some patient they can be really cheap.
I have a few old lab multimeters lacking plenty of fetures, but most  of them are substituded by Python GUI & scritps woking over old good GPIB. That way you can design your own irtual multimeter.

[Aldo22]

I think 'old bad 'vs 'old good'.

I don't know what you mean by "good" and "bad", but I would describe a measuring device that cost maybe CHF 35.- some 46 years ago and still measures the same today as it did on the first day as a "good" device. But of course it is now outdated.

P.S. I understand that you (still) hate the USSR (as a Polish citizen I probably would too), but this has nothing to do with it.

[Kleinstein]

I also have exactly that type of russian meter. Not bad for an analog meter and reasonabe priced at the time. I nice point was that it came with schematics and even spare diodes and taut band.  I remember a nasty issue when measuring higher frequency AC - at some resonant frequency I get essentially the same deflection (~ 75% at my test) in all ranges including the 900 V range. Maybe it was just may unit or exactly a resonance or had some common mode effect.

The meter has the usual "simple" passive rectifier circuit (the version with 2 diodes and 2 resistors instead of the normal 4 diode bridge). This can work well for high frequencies, but is of cause not true RMS and gives a nonlinear scale. Higher frequency true RMS can be a bit tricky and the better converter chips get quite expensive.

[Gyro]

My second ever multimeter too. The internal construction is a thing of beauty - once you get past the stamped pitch seal on one of the screws! Mine came with non standard NiCd button cells, which I had to build a charger for. It's a shame the Red scales faded so easily in sunlight.

[tszaboo]

Even a 34401A is going to measure 300KHz with 4% accuracy. 100KHz is 0.5% or 0.04dB.

I don't know what you're trying to say.
I'm talking about a rotten 50 year old analog meter sitting in the basement and you're talking about a $1000 top of the line DMM.
What's the connection?

The 34401A is a 25 year old, now obsolete meter.
Saying that an analog meter can do x unlike digital meters, then getting upset because it's not true?

[Aldo22]

The 34401A is a 25 year old, now obsolete meter.
Saying that an analog meter can do x unlike digital meters, then getting upset because it's not true?

I'm not upset at all, and I never said that.
I said: "I just found out that my very old USSR multimeter (1978) can do something that my modern DMMs cannot: "
I just didn't understand what the comparison was supposed to mean.

[J-R]

Yikes, I go away for a bit and this thread has gone off the rails...


With regard to the Siglent clearance DMM, Siglent played dumb with my query about the calibration status.  They said "We do not monitor the status of instruments in the Clearance products" and they offered to calibrate it for a fee.  However, I did look up the serial number on their Warranty Status page and inferred that it was manufactured and calibrated the end of November 2023.  So the person that bought it should be a happy customer.  Side note: it's been reported in other threads that Siglent and their dealers open up equipment before shipment to spot-check or otherwise verify the calibration, even if it's still within the 1 year factory calibration period.  Also, Siglent doesn't seem to state calibration specs past 1 year.

I think that the OP should have gone for that.  It was a good deal and you get a decently modern UI.  Calibration and accuracy shouldn't be such a major concern given the OP's requirements.  My opinion is that any time a hobbyist can save some money and use it to buy other TE they should go for it.


As mentioned by Dave, references are typically not adjusted, and this is to avoid disturbing them physically.  But from what I've seen, test equipment with closed-case calibration is commonly adjusted, especially if it has a display that you're looking at all day.  And it's also common to refer to the adjustment as a part/component of the calibration procedure, and Keysight for example does speak of it that way.  Then there is the performance verification terminology that honestly for some equipment could be considered identical to the calibration procedure.

In a metrology context, I can see the point of not making any changes to any of your equipment just to make historical data tracking easier, but for a typical hobbyist or professional it makes more sense to have bench equipment that is adjusted to a reasonably-tight tolerance.  If I bother to send in my bench DMM and pay for calibration, I'm going to pay to have it fully adjusted along with the pre and post calibration data so that when it comes back I don't have to incessantly look at the cal data printout while I'm using it.  10V is 10.00000V, and I can just mentally be safe and throw away the last digit without having to refer to the cal data.  If I'm REALLY looking at digits, I'll pull out all the cal data for all the equipment involved and scrutinize the conditions.  As seen in various bench DMM performance specs, you might have the last THREE digits be off by some amount yet it's still within calibration tolerance.  How annoying would that be to use on a daily basis??


For anyone interested in turning into a volt-nut or similar, you will want to dig deep into the metrology board to map your path forward.  While not the only path, a common tactic is to purchase older gear that has aged and stabilized.  You can have it calibrated & adjusted once and then just self-verify it regularly afterwards.  With new gear, you're probably going to have to pay for calibration & adjustment many times as it ages, leading to extra costs.

Spot checking offers some information, but it's so far away from anything proper that it's kind of pointless in this context.  The BM857 has over 50 calibration points, for example, covering every function and range.  So one photo at 5V is not showing much of anything.  If you have a decent bench DMM that is in-calibration, then that can be used to compare against other, lesser DMMs, assuming you can generate the appropriate signals.

For hobby references, the DMMCheckPlus is probably the minimum worth considering, since you can at least check a handful of things, and you can use the precision current source and resistors to tease out a few more values.

Ultimately, it's a pretty big shift if you're going to go down this road.

[uargo]

I have found what I think may be the best value for money, at least in Europe.
Owon XDM3051, 5.5 digits, 150 readings/s, precision 0.015±0.004
ACV up to 100Khz, AC current 10Khz, USB, RJ45, external trigger
Bar chart, column chart, trend chart, max/min value, average value, standard deviation, relative value,
DB/DBm, and Pass/Fail
And all this for 415€ with taxes included. What do you think?

https://eleshop.eu/owon-xdm3051.html




https://static.eleshop.nl/mage/media/downloads/xdm3051_datasheet.pdf

[Fungus]

The BM857 has over 50 calibration points, for example, covering every function and range.  So one photo at 5V is not showing much of anything.

FWIW my BM857s and Fluke 187 agree within a digit or so on every range except small currents*.

Both meters have laser trimmed precision resistor arrays which basically don't drift. All measurements are derived internally from voltage measurements so if the voltage ranges are good then the rest of the meter probably is, too.

(*) the current thing might be burden voltage but I haven't really investigated deeply. They're within a couple of dozen counts of each other even on those ranges, so...     The temperature of the room is probably a bigger factor for absolute accuracy.

BM857s teardown:

[Mahagam]

I have found what I think may be the best value for money, at least in Europe.
Owon XDM3051, 5.5 digits, 150 readings/s, precision 0.015±0.004

And all this for 415€ with taxes included. What do you think?

It looks very, very strange, but the accuracy of this DMM is fully consistent with Siglent SDM3055. Absolutely the same values for all parameters! How is this possible?

Maybe they were just rewritten from a competitor's datasheet so as not to look worse?

[Muttley Snickers]

I have found what I think may be the best value for money, at least in Europe.
Owon XDM3051, 5.5 digits, 150 readings/s, precision 0.015±0.004

And all this for 415€ with taxes included. What do you think?

It looks very, very strange, but the accuracy of this DMM is fully consistent with Siglent SDM3055. Absolutely the same values for all parameters! How is this possible?

Maybe they were just rewritten from a competitor's datasheet so as not to look worse?

I'm yet to understand how some people even attempt to compare a brand such as Siglent with Owon, it's too silly for words so I won't even bother.   

SIGLENT >>> SUPPORT >>> SERVICE >>> SUPERIOR.
OWON >>> LILLIPUT >>> A FANTASY LAND.

[uargo]

I'm not comparing anything, I'm just trying to answer the purpose of this thread, instead of rambling about whether my multimeter is more accurate than yours, or who has a bigger one.

[Kleinstein]

Aiming for the specs that a main competitor offers is not such an exception. Quite a lot of 6.5 digit meters have specs very similar to the HP34401. They kind of set the standard.
The specs for a meter are also more like limits that they think they are compftable with. Especially for the long term drift part there is no measurement or definitive way to tell what specs a given meter should get. Its only the TC and linearity part that can be checked relatively easy. It usually takes many years before it turns out if a meter usually is more stable or tends to drift more than expected.

Another point is that often similar (or in part identical) parts are used, so one ends up with similar specs. These modern 5.5 digit usually use a bandgap reference and SD ADC chip which leads to a best range of some 2 V, that usually offers high impedance.
At least the SDM3055 uses a relatively good ADC chip, that others may as well use for 6.5 digits.

[Mahagam]

Quite a lot of 6.5 digit meters have specs very similar to the HP34401. They kind of set the standard.

"Similar" is not "the same".
Owon specs is absolutely the same as for Siglent. For every type of measurement and for every range.

[KungFuJosh]

"Similar" is not "the same".
Owon specs is absolutely the same as for Siglent. For every type of measurement and for every range.

Some people get paid to copy and paste. 🤷

[Kleinstein]

There is a good chance they took the specs of an existing 5.5 digit meter as the design goal and the design team was spot on.
The sigilent meter has more detailed specs on different DC ranges - so not absolutely the same, but very close and possible matching a different DS version.

How good the meter will actually perform, especially over the longer time is a thing that only time will tell.
Anway a 5.5 digit meter is usually not bought because of it's accuracy - it is more for PC control,  the noise, the ability to measure small voltages and have 4 wire ohms. If accuracy matters one often directly goes to 6 digits.

[coromonadalix]

It's too bad nobody offers a modular multimeter yet..

well you do have pci  pxi pxie  meter card   loll   not modular enough  loll

[J-R]

The BM857 has over 50 calibration points, for example, covering every function and range.  So one photo at 5V is not showing much of anything.

FWIW my BM857s and Fluke 187 agree within a digit or so on every range except small currents*.

Both meters have laser trimmed precision resistor arrays which basically don't drift. All measurements are derived internally from voltage measurements so if the voltage ranges are good then the rest of the meter probably is, too.

There is absolutely plenty of opportunity for drift.  Checking one point is just not a valid method for this.  If those two DMMs haven't drifted, then that is great, but what you're saying is not something that can be applied and the photo isn't proof of the method.

Some DMMs DO follow a principle adjacent to this where they know which components are leveraged for each measurement path.  So a performance verification procedure will heavily leverage that in order to reduce the number of tests that need to be performed by the operator.

The protection circuits can also make an impact depending on the voltage you are applying, so each range will still need to be checked.


Edit:
Link to the Fluke 187 calibration guide: https://www.tonyplaza.nl/download/YT251/187cal.pdf
There are 64 performance verification test steps.
There are 38 calibration inputs required.

[Fungus]

There is absolutely plenty of opportunity for drift.  Checking one point is just not a valid method for this.  If those two DMMs haven't drifted, then that is great, but what you're saying is not something that can be applied and the photo isn't proof of the method.

I didn't check just one point, I checked many, but I only uploaded one photo, OK?

The only point I was making is that if two good quality meters from completely different backgrounds agree with other to within a digit, it makes a very strong case for trusting those meters.

[W4HBM]

Hello Sir or Madam,

Some years ago YAESU introduced its FT-5000 series radio that had two small OLED displays in addition to the main display. The OLED displays were crapping out very fast, and many people returned their DOA transceivers. Then, Agilent came out with a hanheld portable DMM with an OLED display, and guess what? Even those displays were turning into cheese too soon. You can find an Agilent DMM with an OLED display pretty regularly, here and there, but that doesn't make up for the inherent lack of quality to make these displays bulletproof.

The Rigol DM858 display seems relatively trouble-free, but I'm sure if there's a smelly one in the pile I'm about to get it when UPS gets here with it.

Or maybe not. It would be wonderful to kickstart a new '858 and find the main display clear and concise, and for it to stay that way for a long while.
<My decades-old Fluke Handhelds are drifting apart, and their readings can't be trusted, and according to Fluke, there are no repairs! (89-IV, 279)
And I've sure come to despise LCD B&W displays that need me to be within 6 inches to read.