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

[Martin72]

There was a difference if I used the TL leads from fluke or the probemaster from home.
It makes also a difference depending on how the probe tips are pressed against the test points, from which side, etc.
It is simply not 100% firm contact.
As for the clips :
For current/voltage it was OK, but for resistors I had more resistance ( albeit in small form) than when I used the probe tips.
I don't think the short term soldering brings any disadvantages, differences in ambient temperature are enough to create "more" deviations.
Speaking of ambient temperature, I had refrained from performing the measurements until now.
By heatrun tests we have in the test field at present approx. 31°C...

[KungFuJosh]

There was a difference if I used the TL leads from fluke or the probemaster from home.
It makes also a difference depending on how the probe tips are pressed against the test points, from which side, etc.
It is simply not 100% firm contact.
As for the clips :
For current/voltage it was OK, but for resistors I had more resistance ( albeit in small form) than when I used the probe tips.
I don't think the short term soldering brings any disadvantages, differences in ambient temperature are enough to create "more" deviations.
Speaking of ambient temperature, I had refrained from performing the measurements until now.
By heatrun tests we have in the test field at present approx. 31°C...

The precise value doesn't matter independently when you're comparing devices. The only thing that matters is you remove inconsistencies in the testing method. If you use the same probes/clips for all meters, you eliminate the inconsistencies of your test setup. In other words, if the clips you're using altered resistance by .001Ω, it doesn't matter, it will have the same altered value for all devices.

If you solder wires on to the reference, you (semi) permanently alter the cal values. Then if you connect with different probes to those leads, you still have an inconsistent test setup.

[Martin72]

Then if you connect with different probes to those leads,

Why should I do this..
By soldering I have made a better contact, this could well lead to the calibration no longer being correct, if more or less contact-safe clips were used when calibrating, that is true.
However, I will soon send the checker with these solid leads for recalibration.
Then no one has to worry about it anymore.

[Martin72]

Speaking of ambient temperature, I had refrained from performing the measurements until now.
By heatrun tests we have in the test field at present approx. 31°C..

On Saturday we still had 25.5°C, but I was curious....
I had already measured last week with the Keysight, for this I had used the test leads from Fluke and it was loosely 4 kelvin cooler in the test field.
Here are the values I had measured at that time:

DCV: 4.9997V
DCA: 1.00049 mA
ACV: 5.0000V
ACA: 1.0001 mA
Freq.: 100.003 Hz
The pictures show the current measured values with the soldered leads and just at 25.5°C.
Now you can wonder if the deviations are caused by the temperature, by the soldered leads or by the measurement uncertainty...

[J-R]

For the DMMCheck Plus voltage and current measurements, the probes or clips you use do not matter, for the reason I proved earlier using Ohm's law.  You can put a decade resistance box in series with your DMM and crank up the resistance to see for yourself.  A common resistance to encounter when using test leads/probes/etc. is going to be under 1 Ohm, typically around 0.1 Ohms if you're shorting them directly.  The contact resistance would have to be very high such as 100 Ohms or more to be an issue.

However, for resistance measurements, YES, the type of probe and lead you use and how you hold it makes a big difference in a 2-wire configuration, but the accepted solution is a 4-wire/Kelvin connection.

Soldering on the reference invalidates the calibration, and there is just no way around that.  Will all the values be different or "wrong"??  That is up for speculation and it would really require another calibration with an 8.5 digit DMM to "know" one way or another.  But again the fact remains the previous calibration is no longer trustworthy.

The 34450A is not a good enough DMM for analyzing the performance of the DMMCheck Plus.  One year 10V range accuracy spec is 0.015% reading + 0.005% range.  So 5V could display between 4.9988V and ‭5.0013V.
However, I've commented before on applying too much value to published specifications, so without the calibration data we shouldn't speculate too far on the actual performance of this 34450A.
But comparing the before and after measurements, and given the performance class that the 34450A is targeted for, it would be unwise to put much trust into the last digit of the display regardless.

I recently received my DMMCheck Plus back from calibration:
34401A: 5.000,00V
34461A: 4.999,98V
K2010: 4.999,995V - 4.999,997V
For verification, I also got identical readings from my PDVS2mini @ 5V.

For 1mA DC, my calibration sheet states 1.0009mA and I observed:
34401A: 1.000,94mA
34461A: 1.000,863mA
K2010: 1.000,779mA

I would put more stock into the value provided by the 34461A since it has a 1mA range while the other two only have 10mA.

[Martin72]

But again the fact remains the previous calibration is no longer trustworthy.

The test points are "miles" away from the circuit, it cannot have been heated along with it by the very short term soldering.

[Veteran68]

They are now taking pre-orders for the new DMMCheckPlus units that include all options. So the enclosure, LC board, and dual frequencies are included at one fixed price now. I guess it makes it easier for them to manage fewer SKUs and also pads their margins a bit more, I'm sure.

I placed an order since I'd been wanting one for awhile. I really wanted Ian's PDVS2 Mini but can't justify 2x the cost.

I accepted the default dual frequencies of 100Hz and 10Khz as I wasn't really sure what else to choose. Being in the US, should I have gone with 120Hz instead of 100Hz, or is that even relevant in this scenario? That didn't occur to me until after I ordered. What are some of the reasons to choose different frequencies on a voltage standard like this? I assumed it's just for testing different AC bandwidth ranges of test equipment.

[mwb1100]

I emailed DMMCheck about their fancy new higher accuracy product, and this was their response:

"Thank for your interest in our products. When available, the new higher stability model will be higher in price but will include all options. The current model you pick and choose options which affects cost. The new LT1021 has higher stability due to the unit being always on and no longer being exposed to ambient air. I hope this helps."

They are now taking pre-orders for the new DMMCheckPlus units that include all options. So the enclosure, LC board, and dual frequencies are included at one fixed price now. I guess it makes it easier for them to manage fewer SKUs and also pads their margins a bit more, I'm sure.

Is this the "new higher stability model"? Or is is just a step in that direction (old model but with all options included)?

[dophuc]

Using what I have, calibrate the Owon P4305 linear DC power supply with the Keysight 34410A to use as a source for testing handheld multimeters and lower precision devices.
@10V
https://youtu.be/wZA3xZyQqnY
@30V
https://youtu.be/r7gR1pGJB1A

[Veteran68]

I emailed DMMCheck about their fancy new higher accuracy product, and this was their response:

"Thank for your interest in our products. When available, the new higher stability model will be higher in price but will include all options. The current model you pick and choose options which affects cost. The new LT1021 has higher stability due to the unit being always on and no longer being exposed to ambient air. I hope this helps."

They are now taking pre-orders for the new DMMCheckPlus units that include all options. So the enclosure, LC board, and dual frequencies are included at one fixed price now. I guess it makes it easier for them to manage fewer SKUs and also pads their margins a bit more, I'm sure.

Is this the "new higher stability model"? Or is is just a step in that direction (old model but with all options included)?

Not sure, but I hope it's the improved model. I didn't see where they actually say anything about the new model on their site. They just changed the banner to say they're now taking pre-orders, and changed the product order page to not charge extra for the add-ons (even though they still have the drop-down selection controls for them as if they're optional). I added everything including dual frequencies and the price didn't change.

[mwb1100]

I didn't see where they actually say anything about the new model on their site.

There was some period of time (around July 10 it seems) where the website's banner teased a new product in the pipeline.  No details given, but @KungFuJosh got a few via email.

[Veteran68]

I didn't see where they actually say anything about the new model on their site.

There was some period of time (around July 10 it seems) where the website's banner teased a new product in the pipeline.  No details given, but @KungFuJosh got a few via email.

Yeah, the banner has been saying for some time that pre-orders for new boards would begin Sept 1. On Sept 1 I sent them a message through their contact form asking for details. I haven't got a response yet (it was a holiday weekend here in the states), then when I saw the banner had changed to now accepting orders, I placed mine. Other than all options now included there's no mention of improvements or other details.

[Martin72]

Hi,

I will send the device for a new calibration, calibration is done according to ISO*.
The L/C option will also be calibrated.
I was sent a sample calibration certificate, so the protocol will look like afterwards.
But I still wonder, should I send it away with the soldered leads, or not - And ask instead, with which test leads / clips they have performed the calibration, to then measure with later with the same...

*(Calibration according to DakkS is also possible, costs 30€ more)

[J-R]

I'm curious, did you solder the wires to the turret terminals, or remove the turrets and solder the wires to the PCB?  And which ones were modified?

[Martin72]

Hi,

To the turrets and then voltage/current.

[KungFuJosh]

I got one of these AD584JH voltage refs in, and it seems to work fine. It was advertised as an AD584L, which I'm not surprised was a lie. They didn't bother to include the fake calibration either.

On my SDM3055X-E I got:
10.0009V
07.5013V
05.0004V
02.5001V

That seems pretty good. The 7.5V and 10V takes a while to get up to their voltage range. After that it seems like it takes some time for the voltages to settle on their targets. Once settled, the voltage is stable.

Anybody else have the same behavior with their similar reference?

Right now I'm leaving the 7.5V test on to see if it gets any closer to 7.5000. 7.5013 was still stable after an hour.

Thanks,
Josh

[Veteran68]

My Agilent 34401A and SDM3065X all get to a stable voltage within a second or two. If you continue to hold the probes, they will creep up very slowly, like one count every 4-5 seconds.

I just tested against the following standards consisting of 3x AD584s (2x LH and 1x KH), a LM399, and a LB02A process calibrator. The AD584LH that looks like yours (that takes the funky 15V battery) came with the fake cal sheet that everyone else has seen. The others seem to have genuine values that measure within about 1mV on both meters.

[KungFuJosh]

If you continue to hold the probes, they will creep up very slowly, like one count every 4-5 seconds.

Ah, weird! I was using probes clipped to the ref, and it took a minute or two to get to 10V. I turned it on without probes connected this time, then tested and it got to the voltage in a few seconds. 🙄

Where did you get that purple AD584LH board from?

[Veteran68]

Where did you get that purple AD584LH board from?

https://www.aliexpress.us/item/3256804431053626.html

[Veteran68]

Not sure, but I hope it's the improved model. I didn't see where they actually say anything about the new model on their site. They just changed the banner to say they're now taking pre-orders, and changed the product order page to not charge extra for the add-ons (even though they still have the drop-down selection controls for them as if they're optional). I added everything including dual frequencies and the price didn't change.

So I sent them an email today asking for any details about this "new" version and when pre-orders would ship. Russ responded this evening:

"This is the Rev 6 version with all the options, meaning the new LC daughter board introduced last year (installed), dual frequencies of 100 Hz and 10 kHz, the enclosure with acrylic top and a free calibration if you send it back within two years. Shipping will commence after their 250 hour burn-in, which improves the stability of the voltage reference."

So other than all options included, nothing about any design changes or improvements.

[Martin72]

Hi,

Any recommendations for really good "state of the art" test leads/clips ?
Except for the set from Probemaster I have found nothing...

[dmmguy]

My Agilent 34401A and SDM3065X all get to a stable voltage within a second or two. If you continue to hold the probes, they will creep up very slowly, like one count every 4-5 seconds.

I just tested against the following standards consisting of 3x AD584s (2x LH and 1x KH), a LM399, and a LB02A process calibrator. The AD584LH that looks like yours (that takes the funky 15V battery) came with the fake cal sheet that everyone else has seen. The others seem to have genuine values that measure within about 1mV on both meters.

They (AD584) take about 3 hours o more to reach an "acceptable stable" status, I always keep them working for more than 72 hours the very first time. I sell those boards with a cal cert measured with a Agilent/Keysight 34461A, it is not the best but may be useful for 4.5 and 5.5 digits and even for 6.5 if used at approx same cal temp.

https://www.ebay.ca/itm/155763974742

[KungFuJosh]

Any recommendations for really good "state of the art" test leads/clips ?
Except for the set from Probemaster I have found nothing...

Almost all of my test leads are from probemaster. Their kits/accessories are excellent.

Are you looking for something they don't offer?

[Veteran68]

They (AD584) take about 3 hours o more to reach an "acceptable stable" status, I always keep them working for more than 72 hours the very first time. I sell those boards with a cal cert measured with a Agilent/Keysight 34461A, it is not the best but may be useful for 4.5 and 5.5 digits and even for 6.5 if used at approx same cal temp.

https://www.ebay.ca/itm/155763974742

Interesting. Are you building these boards yourself, or reselling imported boards?

My understanding as the AD584's in these imported boards are mostly pulls from old equipment, so already at various stages of aging. It would be nice to have some idea of provenance at least.

I do wish that particular board was built for a more practical battery, such as the A23 12V battery the purple board has. The 15V square batteries are expensive and hard to find. I bought two of the green Chinese 10F20 batteries on eBay for around $10 and one was flat within a year. The other I haven't bothered unwrapping, it may be dead too. The Exell branded ones are probably better quality but go for $20 each! So I was using it with a DC barrel plug from my bench PS, but since this board had the bogus cal sheet that just about everyone else got, it was pretty much useless for its intended purpose. My favorite among those AD584 variants is the one with the purple board, as it has a practical battery, the option to use a DC plug, and includes reference resistor measurements also. However now that I have a DMMCheckPlus rev6 on order with all options, these will be relegated to backup or consensus/sanity check purposes.

[Veteran68]

Any recommendations for really good "state of the art" test leads/clips ?
Except for the set from Probemaster I have found nothing...

Almost all of my test leads are from probemaster. Their kits/accessories are excellent.

Are you looking for something they don't offer?

I second the Probe Master recommendation, at least for bench use. I have 3 sets for my bench meters, including one set of the spring-loaded needle tip variety. I don't like them as much for portable DMM use, as the probes are quite a bit bulkier than the typical slim probes, though they do feel great in the hand.

My next favorite have been the Brymen leads. I ordered an extra couple of sets to use in good handheld DMMs that came with shitty leads, like the super stiff TL75 PVC leads that came with the Fluke 117. I even ordered a set of TL71 leads for it which are softer but the probes still feel cheap and had inconsistent contact even after cleaning. BTW, Fluke's website still advertises the 117 as shipping with silicone leads. Lies! (sorry for the OT Fluke rant)