Bench 6.5 digit - most bang for the buck?

[alank2]

SO what do you guys think of the Rigol DM3068 vs. the Agilent 34461A.  If I am understanding the specs/videos I see, it looks like the Rigol might have a higher counts - 2M vs the 1.2M of the Agilent - is this true?  I guess this is one thing that irks me about these things.  One manufacturer claims 6.5 digits and another does and with the "rounding" you don't really know.  In this case log10(1200000)=6.079 digits and log10(2000000)=6.301 digits.

[Macbeth]

I've got a DM3058E which is alright as the lowest possible denominator, but 6.5 digit - forget the DM3068 and go for Keithley 2000 and especially 2015's which are very cheap at the moment because they were sold to the phone companies and are now flooding the second hand market... (Guy in South Korea will let them go for $200 each if you can order a good pile, like 10 off)

And of course a HP 34401A is the classic that all college kids used. But the Keithley is so much better! cheaper! Who doesn't love a Keithley 2000 running up its 10Gohm voltage display?

[smgvbest]

I've got a DM3068 and a HP34401A.   I realize the HP is seen as a much higher quality meter and is serviceable were as the DM3068 is not.   
But side by side in measurements they are often <10mV off of each other on <10V range.  microvolts off usually in the lowest ranges.
In resistance reading 2W a few milli ohms off and 4W they are usually less than 2mOhm off as well.   I realize this can be big for professional and I am not saying the DM3068 is on par with the HP but depending on use the Cost vs function vs accuracy to me seems to be good.

So my question is what I am missing?   Just comparing common features not ones the DM3068 has the 34401A does not and visa-versa.

[commie]

SO what do you guys think of the Rigol DM3068 vs. the Agilent 34461A.

Get the newest Agikent 34461A or the 34465A, if you cant afford one get the Fluke 8808.

[HighVoltage]

I just got a great deal on an Agilent 34410A, probably one of the best 6 1/2 digit meters ever built.
If you look long enough, you can find them in the price range of a 34401A.

Great read on the GellerLabs website between the 34401A and the 34410A
http://www.gellerlabs.com/34401A%20AC%20zero.htm

[rdl]

I've just about talked myself into buying one of those Vici 8145 bench DMMs. At less than $30 per digit it looks hard to beat. I bet it'll be plenty good enough for anything I need to measure. All I have now is a cheap 4000 count rebadge bench style meter and a Fluke 87-III that I don't like to use because it burns through batteries too fast.

[Micke]

I just got a great deal on an Agilent 34410A, probably one of the best 6 1/2 digit meters ever built.
If you look long enough, you can find them in the price range of a 34401A.

Great read on the GellerLabs website between the 34401A and the 34410A
http://www.gellerlabs.com/34401A%20AC%20zero.htm

I also have a 34410A, and it is a great instrument! I had a 34401A before buying it, but sold the 34401A.
They look quite similar, but are quite different if you look closer!
I would say the 34410A is better in all ways except it has a fan with a high pitch irritating sound! (but I put a fan reduction device in my unit, now it is fine)

Extras on the 34410A:
* Better HMI, easier to navigate in menus etc.
* Display has two rows (showing for example Frequency and ACV simultaneously, or showing statistics (max, min, mean etc) simultaneosly with "live" data)
* Capacitance measurement
* Temperature measurement (NTC 2.2k, 5k or 10k or RTD 49R-2.1k)
* Extended AC/DC Amps range down to 100µA (but there are hacks to enable unofficial 10mA ACA range on 34401A, works fine)
* As mentioned before, superior AC measurement with direct sampling (like 3458A), specifications are very conservative! Crest factor up to 10 no problem!
* Resistance measurement to 1GOhm
* Can be used as standalone datalogger with internal non volatile memory of 50000 samples (20µs-3600s sample interval)
* Has LAN interface with built in web server, just surf in to the unit to configure or get readings!

BTW, here is how to enable 10mA AC range on 34401A:
http://www.keysight.com/main/editorial.jspx?cc=SE&lc=swe&ckey=1000001267:epsg:faq&nid=-536902435.536880933.02&id=1000001267:epsg:faq

[alank2]

So guys, what type of calibration document do these units come with:

Keysight 34461A/34465A

Rigol DM3068

If you have one of these and can post it, I'd love to see what they look like, how detailed they are, how close a unit is to ideal, etc.  The Fluke 8845A one I had (before I returned it) was pretty detailed.

[Tom45]

The certificate for my 34465 is attached below. I see I'm due for a new calibration. Not that I'm planning to do it.

[alank2]

Thanks Tom - that is what I was looking for.

[smgvbest]

Rigol doesn't give a test report.  only the certificate part
I'll scan one of mine and post sometime today


(edit: added DM3068 Cal Cert)
(edit: Just for fun I added my DP832 Cal)

Macbeth, Looks like same call equipment on our 832's also

[alank2]

Thanks Sandra.

[Macbeth]

I can confirm Rigol only give the summary sheet and no data.

Sandra, it looks like we got the same Fluke Calibrator, only mine was 11 days later than yours 

Also my DP832 for good measure 

[alank2]

Well guys, I've come to the conclusion that the 8845A is the 6.5 digit meter _I can afford_.  Zoro has 30% off today (still going) and that brought the price to $756 shipped.  On top of that they have a gift promo going where you can get an ipod touch or fluke 116.  So ... I ordered it again.  Hopefully this one won't have the 1 Hz buzzing noise, and at this price, I'll live with the display.  I would have preferred the 34461A, but it is $300 more and no gift.

[dr.diesel]

You've made the right choice, twice, lmao.

[alank2]

twice, lmao.

Oh yeah, this is how I do it.  You know you should have kept something when you miss it after you send it back...

[Micke]

Besides Agilent 34410A, I also have a FLUKE 8846A which I am very happy with.
The 8846A has one very big advantage compared to many other multimeters, it is fanless!
Before modding the fan on my 34410A, I tend to use the 8846A more often due to the irritating fan noise of the 34410A...

On the forum, free_electron has made a great teardown of a 8846A: https://www.eevblog.com/forum/reviews/fluke-8846a-teardown-9409/msg127654/#msg127654
I like those hermetically sealed laser trimmed resistor hybrids!
Other people on the forum have testified the 8845A/8846A is really stable over time, probably those hybrids are a big contribution to that!
Downside on the 8845A/8846A is the VFD display, which quickly fades, and "burns-in". But if you buy the multimeter new, it is likely not a problem, another story with equipment powered on 24/7 in a production line or something...

[HighVoltage]

I never had a 8846A, may be time to get on...

In regards to the 34410A, you are absolutely right, the fan noise is horrible, if you are sitting next to the meter. This was also one of the first mods I did, when I got my first 34410A a couple years ago. It is very simple to install a "quiet" fan and then the meter is perfect. Interesting, that Agilent thought to add the fan, although the 34401A also was a fan-less unit.

[alank2]

Downside on the 8845A/8846A is the VFD display, which quickly fades, and "burns-in". But if you buy the multimeter new, it is likely not a problem, another story with equipment powered on 24/7 in a production line or something...

The other forum member who said Fluke wanted $400 or so to replace the display was not pleasing to me (You can buy the 34461A display online for $60 or so I think I saw), but perhaps the $400 is for the entire display and front panel pcb with input buttons, etc.  I looked through some of the Noritake stuff I picked up when they ran a 50% off sale a year or two ago and I think I actually might have the same glass on one of the VFD modules GU256x64D-7000, so if it dies, I've got a VFD glass I can try down the road.

Just for fun I hooked up the logic analyzer to it to see if I could discern the signal.  These are chip in glass "CIG", but they are not full high level driver in glass.  The CIG is meant to just lower the pin count so it is really some shift registers and grid drivers.  Just enough to reduce pin count, but not more than that.  Noritake has a helpful document on this here:

https://www.noritake-elec.com/display/cig_driver_vfd.htm

But, they actually go further than that - they combined the grid and data spi into a single spi.  The first 256 bits are data, and the final 64 bits are grid.

From GU256X64D

Code: [Select]

pin name description
6 HV 60v
7 gnd
8 gnd
9 vcc 3.3v
10 sig1 4.57k, positive pulse 16us blanking
11 sig2 4.57k, positive pulse 1us latch
12 sig3 2.25k, square wave
13 gnd
14 nc data out?, 800ns wide pulses (1.25MHz clock)
15 nc data out?, 500ns wide pulses (2MHz clock)
16 sig4 data in
17 sig5 clock
18 sigA data or clock ?
19 sigA
20 sigA
21 sigA
22 nc data out?

An entire frame is 14.21 ms so refresh rate is 70.3729.  I wonder if Fluke may be running it slower in their implementation of driving it because out of the corner of my eye I can see it updating sometimes.

So, I exported the data out of the Saleae and wrote a quick C program that converts the captured values to an image to see if I could do it.  It was a bit perplexing as the order of the bits changes between columns.  It has 64 four bit columns.  So a byte is two rows tall.  First it is 7654 with 3210 under it, and then it is 4567 with 0123 under it.  See the Noritake doc, probably has to do with overlapping grid scan.

The bottom line though is that with only a few pins and a microcontroller, one could convert the 256x64 bitmap display output to practically anything.  OLED, LCD, maybe even composite for precision meter meets old school TV output...  Might be a fun project down the road for 8845/8846's with bad displays.

The PNG is from a GU256X64D test screen:

[dr.diesel]

Even if you set the display to say around ~70%, I bet you get 20+ years of acceptable lab use.

By then the 3459A 12.5 digit will be out, sold exclusively at the prestigious Taco Bell T&M division.

 O0

[alank2]

You get low/med/high and it doesn't look like high is full power so I'll bet Fluke has tweaked the firmware in an attempt to make the display last as long as possible.  I read somewhere here that it is supposed to default to "med", but I think the last one I got arrived on low.  We'll see how long it lasts...

[XFDDesign]

Well guys, I've come to the conclusion that the 8845A is the 6.5 digit meter _I can afford_.  Zoro has 30% off today (still going) and that brought the price to $756 shipped.  On top of that they have a gift promo going where you can get an ipod touch or fluke 116.  So ... I ordered it again.  Hopefully this one won't have the 1 Hz buzzing noise, and at this price, I'll live with the display.  I would have preferred the 34461A, but it is $300 more and no gift.

Weren't you disappointed in the display, even neglecting the flicker issue?

[alank2]

Weren't you disappointed in the display, even neglecting the flicker issue?

Yep, it comes down to what is affordable.  I got it for $54 less this time as well.  I would have preferred the keysight 34461A's TFT, but I can't see anywhere to get it for less than $1050 shipped, this was $756 shipped and I will get a gift from Fluke for $150-$250, bring it down to $500-$600.  At that price I can lower my "display" expectations a bit and see how it holds up.

[XFDDesign]

Yep, it comes down to what is affordable.  I got it for $54 less this time as well.  I would have preferred the keysight 34461A's TFT, but I can't see anywhere to get it for less than $1050 shipped, this was $756 shipped and I will get a gift from Fluke for $150-$250, bring it down to $500-$600.  At that price I can lower my "display" expectations a bit and see how it holds up.

If display attractiveness is such a high priority, you're precisely saying you're compromising on your #1 value. How long will it take you to save up the extra cash and get something pretty and makes you happy? As it stands, you've already stated your dislike of the display - so you're going to be dissatisfied from this point forward over saving ~25%.

Consider, "I want to buy a 6.5 digit meter. I don't have $1,300, so I'll spend $1,000 for a 4.5 digit meter instead." It's very literally defeating the original point. 

[alank2]

My primary concern really isn't the attractiveness, but longevity.  I don't want to spend on a piece of equipment that is going to not be usable in a short period of time if i can help it.  5 years from now if it dies, will it become useless or can I make it workable without pouring a ton of money in to a part?  I'm more satisfied now that I can replace it with another type of display if I had to...  Perhaps my expectations are less now...  This $$$ is at the very upper limit of what I want to spend, the additional 30-40% for the 34461a defeats it.