DMMCheck Plus Multimeter Reference(and other References) - Experiences..

[Martin72]

Hi,

Welectron offer this board together with the L/C option, it sounds very promising...
AC/DC current, AC/DC voltage, resistance, capacity, inductance - everything together in one box.

The DMMCheck Plus provides the following test circuits:

Resistance: 100Ω / 1.00 kΩ / 10.0 kΩ / 100 kΩ (±0.1%, 10ppm precision resistors)
DC voltage: 5V, ± 0.007% voltage reference
DC current: 1mA, ±0.1% current source
AC voltage: 5V RMS, bipolar (+5V, -5V) square wave, ±0.1% voltage source
AC current: 1mA RMS, ±0.2% current source
Frequency: 100 Hz / 10 kHz, ±0.02% signal source
Duty Cycle: 100Hz, 5V RMS, signal source has 50% ± 0.05% duty cycle
Capacitance (with pre-installed L/C option): 1nF / 10nF / 100nF / 1µF (±0,05% precision capacitors)
Inductance (with pre-installed L/C option): 1µH / 10µH / 100µH / 1mH (±0,05%)

https://www.welectron.com/DMMCheck-Plus-Multimeter-Calibration-Reference-with-L-C-Option

Before I hit the buy button, what are your thoughts ?
Thanks in advance..

[sokoloff]

I bought one and am happy with it. I don’t have the L/C option, but the others all indicate that my meters aren’t crazy off. I don’t know how I’d be “sure” how calibrated it is, but based on the paperwork I got with it, I’m inclined to believe it is as-specified and as-measured.

[Martin72]

but based on the paperwork I got with it,

I would trust that in this case, based on the technical data of the components used.
Welectron offers an additional calibration, once according to ISO standard or even DakkS (globally accepted standard) standard.
Would be another 85 or 115 € in addition, does not necessarily have to be...For now.

[KungFuJosh]

Have you looked at purchasing it directly? Assuming the shipping isn't crazy, it should cost a lot less.

https://dmmcheckplus.com/shop/ols/products/dmmcheck-plus-without-enclosure

[J-R]

I've had the main board for about 5 years and the L/C board for about 2 years.  If you don't have any references/standards already, it can be a great way to kick start things and get a bunch all at once.  However, it needs to be shipped off for a yearly calibration to be of much use, IMHO.  It is going to drift a little over time, and my calibration data reflects that.  But also I think that is the main advantage of it.  It's very small and can be shipped around for very little money (relatively speaking).

The main shortcoming is the limited output values.  So what are you planning to do with this?

[bdunham7]

However, it needs to be shipped off for a yearly calibration to be of much use, IMHO.  It is going to drift a little over time, and my calibration data reflects that. 

How much drift do you see?  I can't imagine using these for anything beyond the 4.5-digit level--am I wrong?

[tautech]

However, it needs to be shipped off for a yearly calibration to be of much use, IMHO.  It is going to drift a little over time, and my calibration data reflects that. 

How much drift do you see?  I can't imagine using these for anything beyond the 4.5-digit level--am I wrong?

Doug has been making these for a good while now and keeps his 8.5 digit Calibration DMM in Cal.
I suspect you can calibrate a 6.5 digit meter with confidence with these.
He also offers a cheap recalibration service:
https://dmmcheckplus.com/technical-information

[bdunham7]

Doug has been making these for a good while now and keeps his 8.5 digit Calibration DMM in Cal.
I suspect you can calibrate a 6.5 digit meter with confidence with these.
He also offers a cheap recalibration service:
https://dmmcheckplus.com/technical-information

DMMCheck is not the same as voltagestandard.com, although apparently they used to be the same.  Doug's 10V reference is 24ppm and indeed is good enough for a reference to check a 6.5-digit DMM, but the DMM-Check product is nowhere near that accurate AFAIK.

[tautech]

FWIW we supplied a tech EDU with 15 units 15B Fluke DMM's and HOD got a DMMCheck Plus to monitor their aging which after 1 year two units were 1 LSD from the other 13 but all still within spec.

However, students being what students are, all DMM's need measure exactly the same so those 2 units were adjusted as you can with a 15B so they all showed the exact same values = no classroom arguments !   

[J-R]

I purchased my DMMCheck Plus from Doug, but as stated he sold that one specific product to Russ a while ago.  I've had no issues with either individuals.

After about 15 months from purchase, the 5VDC reference had drifted up to approximately 5.000,37V.  Two years after that I don't have the as-received, unfortunately.  One year after that (now) and it is 4.999,95V.  I'm adding one extra digit because I can, but the calibration printout will only have 5.000,0V for example.

As for the standards, it depends, and actually I've had three add-on boards overall.  First was just the capacitance standards, then the first L/C board (VERY low serial number) which was replaced at the next calibration for reasons I can't recall, maybe a component was damaged.

The resistors are about 5 years old at this point and the drift is minimal.  I'd say the 5th digit on your 4.5 digit DMM will be within 1-2 counts, generally speaking.

The free calibration for the first two years may only apply to US customers.  But again, a primary aspect of this unit is being able to easily ship it for regular calibrations.

[Domitronic]

Before I hit the buy button, what are your thoughts ?
Thanks in advance..

I think it is nice but i don't see the use case for me. If you have multiple DMMs you can compare them to see if they are drifting. If you only have one then you could buy another one for that price or send the one for calibration.

I could not justify to buy the DMMCheckPlus for two reasons. One is that i don't do anything at home where high accuracy is required. The other one is that i could check my multimeters by comparing them to a calibrated 6.5 digit DMM at work.

[Fungus]

Before I hit the buy button, what are your thoughts ?

Have you seen these?

https://www.aliexpress.com/item/1005002190676191.html
https://www.aliexpress.com/item/1005004219629979.html
https://www.aliexpress.com/item/1005004221641169.html

(random examples)

https://www.eevblog.com/forum/testgear/cheap-chinese-ad584-voltage-reference-legit-cal-data-let_s-find-out!/

[J-R]

With a freshly calibrated DMMCheck Plus, you could put a 6.5 digit DMM through (some of) its paces.  You get a full page of trust-worthy numbers to compare against.

Can you use it to calibrate/adjust any of your test equipment?  Well, generally not really, although there are perhaps rare exceptions.  Specifically, I used it to adjust the 5V range on my BM869s, which really made the 500,000 count DCV mode significantly more useful.  I also do recall using the four resistors to calibrate a Fluke 8842A.

And maybe a less-common tactic is to leverage known-good values along with Ohm's law in various ways to expand the range of usefulness of the references.

[KungFuJosh]

Before I hit the buy button, what are your thoughts ?

Have you seen these?

https://www.aliexpress.com/item/1005002190676191.html
https://www.aliexpress.com/item/1005004219629979.html
https://www.aliexpress.com/item/1005004221641169.html

(random examples)

Those random examples are all trash. I bought them (thankfully they're inexpensive trash 😉). Most of them don't come with any reference values written. NONE of them come with any form of certification for the values written. The one unit I received that had values written, was mostly bs. I think 3 out of all the written numbers were accurate (checked across multiple meters with higher digit counts than the reference numbers).

The only value for any devices like these are if you know they're measured/calibrated from a reliable source.

[Martin72]

Hi,

Thank you so far for all the hints and advices.
What I like on this board is to have not only voltage references, but also having current references - I would check my tek probe with them (plus several windings through the probe).
And having LCR references.
The combination of R-C-L references, voltage, current and frequency references I only found with this board.
Further comments are welcome..

[rhb]

I've had the DMMCheckPlus and the 10 V reference for several years.  Quite happy with them, though they  need a recal.  I did by mine directly from Doug.

I'll adjust it when I get the USA Cal Kit round 3 package.  I know of no turnkey option that is as good without being 10-100x the price.  If something happened to mine I'd buy another unless I'd picked up a Fluke or HPAK voltage rcalibrator.

I do notice the price has roughly doubled IIRC.

BTW  At the level of your "drift" you need to record the temperature and measure the tempco.  fpr buget precision voltage references used LM399s are the best deal if you want to build a bespoke calibrator or reference.

https://www.ebay.com/itm/121069770252

They have much lower aging rates from many years of use.

Have Fun!
Reg

[KungFuJosh]

You might want to wait or email before buying them. I think I saw an ad on their header banner about a new high precision device coming soon.

[tomud]

With a freshly calibrated DMMCheck Plus, you could put a 6.5 digit DMM through (some of) its paces.  You get a full page of trust-worthy numbers to compare against.

IMHO not very useful equipment ... Unfortunately, one voltage and only one current source is not enough to test the DMM in any meaningful way. In fact, it will work only on one measuring range (which does not tell us much about the multimeter because the tested measurement range may be ok, and the problem may occur on other ranges) 

Unfortunately, the equipment is poorly thought out, even if we are talking about a simple DMM test, not to mention calibration... To tell the truth, I would rather spend these over 200 euros, for example, on the purchase of ultra high precision z-foil resistors etc.

[tatel]

Have you looked at purchasing it directly? Assuming the shipping isn't crazy, it should cost a lot less.

https://dmmcheckplus.com/shop/ols/products/dmmcheck-plus-without-enclosure

If you are on Europe, the full-blown version with LC, dual frequency, enclosure, etc, sets you back €239 on welectron, shipped, and you can have it ISO calibrated for €85 (plus shipping, I guess).

On the page you provided, a similarly equiped deviced would be $197.50 plus shipping. Shipping from the US to Europe is often ridiculously expensive so I bet it's cheaper to purchase it in Welectron. Not to mention that you would also have to pay VAT for item's price + shipping. Not to mention the piratic fees Western couriers charge for customs paperwork. Probably €50 more for an import in that price range. If you send it back to the US for calibration, you'll have to deal again with customs... probably twice. So, to purchase it in the US? Thanks but no, thanks.

Certainly it's not cheap, but since I didn't have any referencies, and those doesn't seem to be cheap either, it seemed a reasonable deal to me. So I got one to check all my multimeters. To me, main advantage is the availability of a calibration service in Europe. Should my multimeters disagree, I will not need to wonder which one(s) drifted, but I will know it for sure. Or so I hope.

However, I'm not planning to have it calibrated yearly. I'm planning to do it only if I'm seeing my meters disagree unreasonably. Now I have HP 3456A, Brymen 869s, DER DE-5000 (from Eleshop, not gray market -ouch!), UT61E and UT210E. While Uni-T meters are cheaper than DMMCheck calibration, I don't think replacing the better ones if they disagree is a very sensible option.

I think it would be also useful to get one of these multiple voltage references from some guy in the UK... but then we are again dealing with customs and Western courier/pirates, so... no. I would need to be able to have it purchased and calibrated within European Union before pulling that trigger

I wonder how I could get those referencies and get them calibrated without becoming a volts-nut and expending even more money in the long run. After having some looks at the Metrology section, I really got scared. So, to me, it's purchasing DMMCheck and perhaps some similar, voltage-related COTS product and to have it calibrated if and when deemed strictly necessary. For my needs and skills, that's probably already overkill.

[KungFuJosh]

After having some looks at the Metrology section, I really got scared.

That's why I avoid that area. 😉

[Martin72]

If you are on Europe, the full-blown version with LC, dual frequency, enclosure, etc, sets you back €239 on welectron, shipped, and you can have it ISO calibrated for €85 (plus shipping, I guess).

This is the point.
Importing the item from the states will cost nearly the same when buying it here from welectron.
Plus the US website explicitly tells you to buy from welectron if you are based in Europe.
I had used welectron's calibration service on my Brymen 869s and did not regret it.
Our calibration service that we use from work only states.
If something is out of tolerance, it is sent back blocked.
The service from Welectron determines AND readjusts it...Very good.

Certainly it's not cheap, but since I didn't have any referencies, and those doesn't seem to be cheap either, it seemed a reasonable deal to me.

I feel the same way.
The reference may not meet higher demands, but if my multimeters already show "strange" values on it, then that is enough to become active.
Currently, I am very strongly inclined to buy the device.

[rsjsouza]

I have one of these purchased in 2019 from Doug (non-LC version). Excellent for a quick sanity check of the various meters I have - something that seems to agree with your expected usage as well.

[J-R]

Yes, absolutely the DMMCheck Plus is limited at face value, but it's trivial to transfer the confidence around your bench to other devices and also generate further permutations with Ohm's law as I mentioned (solve for the unknown).

I don't think that gets enough attention, and it's one of the tricks so to speak that I personally use to check things from multiple angles.

Example:  I could verify some of my DMMs using the 1mA and 5V references, then connect those DMMs up to a DC supply and go to town on checking resistors.  I'd feel really confident from about 100-5K Ohms in this setup.  How many digits you consider valid will depend on your equipment and you do want to calculate some worse-case values to get an idea of what is sensible.  As I proved in another thread, even the junkiest of equipment ($50 PSU and $30 DMM) can be used to verify low-value resistors at 3 digits using the Kelvin method.


Contemplating this more, I do think the calibrated passives are probably the best bang for the buck feature on the DMMCheck Plus.


For primarily voltage and current it's probably more sensible to just have a couple decent DMMs sent out for calibration and then use them along with a bench supply to generate what you need.  I've found most bench supplies are more stable in voltage regulation than current regulation, so I use that even when generating a precise current.  You monitor the current using the DMM...

[Electro Fan]

The comments above regarding how accurate they are and continue to be are pretty consistent with my experience.

I bought 3 of their products way back in the day and was/have been happy with all of them (two are marked 2011-12 Rev 1, and one is 2008 R4).

Since then there have been various improvements.

Overall, it's mostly a function of your TEA to budget ratio, so YMMV.   

Having said all that, Doug is a good guy making good products, so I'd say if in doubt but you can afford it, go for it. 

[Fungus]

Those random examples are all trash.

I've measured mine on various multimeters and it seems legit.

There were quite a few in that thread I linked to that were legit, too.

The comments above regarding how accurate they are and continue to be are pretty consistent with my experience.

I bought 3 of their products way back in the day and was/have been happy with all of them (two are marked 2011-12 Rev 1, and one is 2008 R4).

The hardware in those devices seems OK, it's the calibration where some sellers are cutting corners.

I'm sure you can get a good one if you take the time to go through all the Aliexpress comments/ratings. I just posted a few random listing to give an idea of prices.

nb. The references in them are probably pulled from old devices. The silver lining is that they'll be well burned-in.