Siglent Bench DMMs SDM3065X, SDM3055 and SDM3045X

[klausES]

For the 3055 there is also a new firmware. V1.01.01.25 (Release Date 08.06.21)

I am excited... 

[Peter_O]

3055 update just installed without problems. At a first glance no obvious changes visible.

[Mortymore]

SDM3065X Firmware - V3.01.01.10 (Release Date 08.09.21 ) that is, 9th Aug 2021

https://siglentna.com/service-and-support/firmware-software/digital-multimeters/#sdm3065x-series

[kcbrown]

So I've got an SDM3055.  Great meter.  Been fantastic for my needs so far.   The one substantial gripe I have with it (and it's not a dealbreaker) is that the amount of time it displays a measured value in "hold" mode is far too short (it needs to be at least 5 seconds, or until the next measurement is made, whichever comes first).

But that's not related to the question I have here.  The question I have here is with respect to 2-wire resistance mode. 

Specifically, what I get when I short my leads.  I'm using Probemaster leads, FWIW (excellent leads, these).   When I short them together, I get a negative value for the resistance.

The question is: is that to be expected?  I would think it's unexpected.  I would think that the resistance value should always be some positive number no matter what.  But that's not the case with mine, and it makes me wonder whether or not my unit is truly properly calibrated.

Yes, this is with the meter in a stable state.  It has been running continuously for weeks in a reasonably well-controlled climate (indoors with air conditioning).

Thoughts?

[bdunham7]

Have you tried a 4 wire short?  What is the lowest ohms range and how negative does it read?  If the error does not exceed specs, then you may just need to zero it before taking a reading.  Some meters have two separate ohms zero adjustments, one semi-permanent and one readily accessed from the user menu that resets at least every power cycle.

I would think that the resistance value should always be some positive number no matter what.

The meter in resistance mode is just measuring voltage, with a separate part supplying a test current.  Approximately the same uncertainties apply to this voltage measurement as would any other.  That includes the possibility that a very small positive voltage plus an offset error within tolerances would result in a negative value being displayed. 

[tautech]

So I've got an SDM3055.  Great meter.  Been fantastic for my needs so far.   The one substantial gripe I have with it (and it's not a dealbreaker) is that the amount of time it displays a measured value in "hold" mode is far too short (it needs to be at least 5 seconds, or until the next measurement is made, whichever comes first).

Submitted to Siglent as a feature request a few weeks back.

The question I have here is with respect to 2-wire resistance mode. 

Specifically, what I get when I short my leads.  I'm using Probemaster leads, FWIW (excellent leads, these).   When I short them together, I get a negative value for the resistance.

The question is: is that to be expected?  I would think it's unexpected.  I would think that the resistance value should always be some positive number no matter what.  But that's not the case with mine, and it makes me wonder whether or not my unit is truly properly calibrated.

Do you have Rel and/or Auto zero engaged ?

[kcbrown]

Do you have Rel and/or Auto zero engaged ?

Sigh.  Yes, this was user error.  I didn't even notice that I had rel mode engaged.  Explains a lot.  Meter reads as expected when I turned that off.

 

[Bad_Driver]

I got my new SDM3065x today after hesitating a long time with the decision.
I did the firmware update and let it run for 3 hours together with my
old and in unknown calibration status but reliable 34401a.

Voltage source is an old analog and 723 based lab PSU.
First impression: 2x Wow! See attached photos.
slow acquisition mode on both DMMs, 100 PLC.

wow #1 for my 25 y old 34401a that it so nearby the new device.
wow #2 for the new 3065. Hope it keeps it calibration as long as the HP 

[bdunham7]

I did the firmware update and let it run for 3 hours together with my
old and in unknown calibration status but reliable 34401a.

For an additional comparison, try leaving the PSU and one meter on overnight, then switching on the other meter and logging or observing its warmup curve relative to the other one.  Then the next day do the same thing but reverse their roles.  It will give you an idea of the tempco of the two units.  You also now have a good way of guestimating the initial drift of your SDM3065X and I'd be very curious to see how it does over the next year.

[Bad_Driver]

Good idea, thanks.
This is my first try with the new out of the box 3065x.

It will take same days since real life implication needs my attention 
I have TestController by the hand, I will try your setup.

[mawyatt]

Those old 34401As are absolutely amazing!! We have a couple.

What was the calibration date on your new SDM3065X? Ours was 2/2020 

We've been watching for significant drift (another thread indicated a possible drift issue) after the SDM arrived last Saturday. The setup is a KS34465A, and a pair of 34401As, (HP & Agilent), the reference is based on an aged (~10,000hrs) LM399 and LTZ1000 (~500hrs) 10V sources. So far the SDM has shown ~80uv high reading and over the past few days drifted up to ~100uv and seems to be setting in ~100uv high.

Best,

[Bad_Driver]

Calibration date was 2021-01-21.
I follow you on the other board and your measurements were the final push for me to get the SDM.
 
Yes, the 34401A are impressive. I was looking for a second one instead of the 3065x , but prices exploded during the
last years. Since sellers expect 400+€ for a device in unknown condition and I got my 3065 offered for a very good price
I decided for the new one. Hope (all fingers crossed) that it will be as good as the other Siglent devices I own (SDG 2042
and SDS 2014x+ both with forum improvement).

Update after 24h running: the 3065x is now 40 uV above the readings of the 34401a at 10 volts.

[Bad_Driver]

I kept both units (34401a and 3065X) running for one week now.
After 24h the 3065x was a little bit above the HP, but starting with day #2 till today (day #7) its is about 40...50 uV below the HP (or the HP above the Siglent) and stays at this level.

The question is now, which device is more accurate  I can see clearly the rabbit hole in front of me....

That looks very promising! Just for fun I placed my preferred handheld meter (UT181) and my old Fluke 87 (first generation, switched to 4.5 digit mode) because I read in the other SDM-issue thread about
such kind of comparison.

I played with the device during this week and it seems to be better than expected (but with the price I paid in mind).
Menus are not that intuitive but that I can learn. The display is great! And the fan noise is much lower than I expected after some comments here.
It's on the same level as my SDG2042X.

some issues and wishes that came up after playing with it:


#1 as mentioned by others the second measurement value is to small on the display - why??
#2 Trend chart is nice but I found no way to get access to the data or to go to a special time point on the time line
#3 I expected a kind of simple "Recording" function with file save on USB stick or internal as I have it with my UT181 (a nice copy of the Fluke 187 but faster and with much better display...and some other issues) see photo.
     (I know that this is not the typical case for a bench DMM since there is all the PC software available but it should be easy to implement and very handy for simple measurement recording. Or have I overseen something?
#4 why the DMM needs 3 watts when powered of? Is it keeping the reference heated???

Edit:
o.k. I now found out that the DMM is storing measurements in 7 digits ongoing on an USB stick but the behavior is not really clear to me. Thanks to the great handbook! 
How to use it best? With external trigger? With run/stop? Can someone give me advice? Is there a time stamp available?

A final question to Tautech:

My device has a certificate of 2021-01-21 but warranty (from the siglent web) till 2024-05-03, why this difference?
It has the hardware revision 02-02-00-05-00
I assume that manufacturing date is short before date of certification ?

[bdunham7]

I kept both units (34401a and 3065X) running for one week now.
After 24h the 3065x was a little bit above the HP, but starting with day #2 till today (day #7) its is about 40...50 uV below the HP (or the HP above the Siglent) and stays at this level.

The question is now, which device is more accurate  I can see clearly the rabbit hole in front of me....

I've no way to know which one is more accurate, but I'll bet money that the Siglent is the one drifting.  At that price point perhaps some shortcuts are required, but the problem with not doing a thorough burning-in of the LM399s before shipping the meters is that not only are they not fully stabilized, but they also cannot be selected.  So your long-term prospects are limited to the statistical characteristics of a random box of new LM399 (-A hopefully) and the best guaranteed spec (from the datasheet, perhaps big customers can get a different deal) appears to be if you order them with the guaranteed 20ppm/(kH)^0.5 drift spec.

[Bad_Driver]

It was a joke, I also believe that the 34401a has settled down to a stable state after 25y.

Let‘s see what next year brings. I have to redo all my lab cabling and than I can do some more serious tests.

[Kleinstein]

For most parts the 34401 would be more stable, at least compared to a new meter.

The 20 V example may be a little different: the SDM3065 can still use the 20 V range, while the 34401 must use the 100 V range, which is quite a lot less stable than the 10 V range.
A little more burn in may be a good idea. No need for 1000 hours, but some 20-50 hours would already help quite a bit to get more value to the initial calibration.
It is not only the reference, there are also some resistors / dividers than can effect the result, at least for some ranges.

[Bad_Driver]

Yes, I will keep it running another week, than it run for 320h on my bench. This 14 watts are affordable, even inGermany.

Unfortunately my PSU is a little bit noisy, I need a better reference. I‘m heading the rabbit hole….

[Kleinstein]

For a simple comparison of 2 meters a simple alkaline battery could be used as a short time stable and low noise voltage source. Put the battery in some padding to reduce external disturbance from temperature and mechanical effects.

[tautech]

A final question to Tautech:

My device has a certificate of 2021-01-21 but warranty (from the siglent web) till 2024-05-03, why this difference?
It has the hardware revision 02-02-00-05-00
I assume that manufacturing date is short before date of certification ?

Siglent's EU warranty overrides factory warranty.
https://www.siglenteu.com/service-and-support/warranty-information/

3. The warranty period starts from the date of the valid certificate of purchase (receipt or invoice). If the invoice cannot be offered, the starting date will adopt the manufacturer’s delivery date.

[mawyatt]

For a simple comparison of 2 meters a simple alkaline battery could be used as a short time stable and low noise voltage source. Put the battery in some padding to reduce external disturbance from temperature and mechanical effects.

This is a good, quick, short term stable (few minutes) reference source for comparisons. We often use the cheap 9V type, the ones used in handheld meters and they usually produce ~10V

Be sure and set all the meters to the high Z state, so they don't draw any current.  Since 10Mohm at 10V is 1ua, and you have 3 meters for comparing, then 3ua!! This level of current will cause the battery voltage to creep down, so always use the high Z state. We also wrap the battery in a wash cloth to shield from any temperature variations (large in our lab bench).

Best,

[mawyatt]

#4 why the DMM needs 3 watts when powered of? Is it keeping the reference heated???

That's a good question, would be nice to know if Siglent kept the reference powered

Best,

[Bad_Driver]

The same idea I got this night. I have now a 9V block in a thermal enclosure and I think I let the DMM run for another 2 weeks.
The temperature in my lab is always around 23...24 degrees, so no big changes.

Because the SDM is now on power for 8 days it has been running about 500h at the end of the 3 weeks..
Let's see what comes up.

Mawyatt: How is your SDM3065 doing after 2 weeks?

And can someone be so kind to explain how this measurement recording on an USB stick works? I tried it with a 10 mHz sinoid signal for 100 seconds (one wave) and got about 4000 values (with 100PLC).
The behavior is not clear to me  But why should it be simple when you can make it more difficult?

[mawyatt]

The same idea I got this night. I have now a 9V block in a thermal enclosure and I think I let the DMM run for another 2 weeks.

Don't understand, what's the 9V block??

Mawyatt: How is your SDM3065 doing after 2 weeks?

It's been stable around 100~110uv high reading on a 10V source. It starts off at ~50uv high upon power up, rises to ~80uv high in a minute, then ~100uv high after 5 minutes, then ~110uv after 1/2 hr. It's been very consistent at 100~110uv high after initial warmup for the past week. I've been powering up in the morning and down in the evening since this is how the DMM will be used, so not left continuously powered on. The voltage references we use are powered on all the time though, one of the LM399 sources has over 10,000 hours. Theses references will be repackaged into a proper shielded enclosure with better output terminals when time permits, but likely not soon.

The readings provided are just for comparison between the two 34401As, the KS34465A DMMs, and the SDM3065, so no claim for absolute accuracy should be considered, only relative measurements.

Edit: All this begs the question has Siglent done something clever with the SDM3065? If they are powering the internal LM399 when the instrument is off but still has AC applied, then this could be a clever means to acquire "aging" on the LM399 while in the instrument. Without the fan howling, and the high power ASICs & display consuming, the other internal components aren't subjected to a thermal level when the instrument is "off", so not much different that being completely "off" for these "other" components. Sure this isn't as good as what KS does with the LM399/LTZ1000 pre-aging and premium selection, but IMO better than just completely shutting down all power when powered down. Maybe someone that's opened up the SDM3065 can comment, I haven't "yet"

Best,

[bdunham7]

The readings provided are just for comparison between the two 34401As, the KS34465A DMMs, and the SDM3065, so no claim for absolute accuracy should be considered, only relative measurements.

Hmmm.  How closely do the three HPAK models agree, how old are they and when/where were they last calibrated?

[Bad_Driver]

9V block = a 9 Volts battery.

Let‘s hope that the 3 watts in power off are not bad design