Questions about reference resistor board at AliExpress

[patchbr]

Reference resistor & capacitor board frequently seen in AliExpress.
Did the first developer described by what device these values were measured by? I think I've seen that before, but I can't remember.
Also, is there a article that tested the accuracy of this board, or a YouTube video? I googled it up, but I couldn't find it.
Thank you.

[radiolistener]

You can't believe these marking. Also there is no guarantee that it uses good quality resistors and capactiors with low temperature coefficient and long term stability.

You can measure it with good quality equipment and write down real values at specific temperature.
But more reliable way is to replace all resistors and capactiors with good quality branded one with low temperature coefficient.

Usually all such kind of DIY reference boards sold on Aliexpress uses fake components (fake REF voltage IC, etc) and is supplied with false measurements, sometimes they just add a paper with printed values which is the same for all instances...

PS: using cheap noname Chinese electrolyte capactior as a reference looks like joke 

[wasedadoc]

Regarding the 10uF capacitor, I think there is no electrolytic that has low temperature coefficient.

[wraper]

Electrolytic for 10uF and (best case X7R) MLCC for 1uf reference is ridiculous to say the least.

[korystoltenberg]

I’m not sure if the first developer specified the device used for measuring the resistor and capacitor values on those boards. You might have seen it mentioned somewhere, but I can’t recall either.

As for accuracy tests, I haven’t come across any specific articles or YouTube videos reviewing this board. It seems like detailed info might be hard to find. You might need to test it yourself or rely on user reviews.

[squadchannel]

The written measurements would not be very reliable either.
guess from the digits that they were measured with a pocket DMM.

Using electrolytic capacitors as a reference is ridiculous.

[squadchannel]

Resistance references better than 0.1% can be purchased cheaply from reliable sources.

As for capacitors, it is a little more difficult. The cheapest ones you can buy are about 1% at best.
Mica and C0G type capacitors are made with more accuracy. Mica capacitors are expensive, but C0G capacitors can be purchased inexpensively.

[wraper]

The written measurements would not be very reliable either.
guess from the digits that they were measured with a pocket DMM.

Using electrolytic capacitors as a reference is ridiculous.

X7R or worse MLCC is not better. Temperature and voltage dependence. Not to say capacitance ageing. It can easily lose 20% of capacitance from fresh or reheated state.

[tatel]

This is what most people here considers appropriate to check handheld DMMs:

https://dmmcheckplus.com/

You can trust the values in the calibration paper; this people measure their products with a calibration certified HP3458 8-1/2 digit bench meter. After a year or so, you can send it back to them for calibration, and so on. If you are in USA/Europe. Otherwise shipping and customs make it difficult/expensive.

For resistance, something like this could be trusted:

https://www.ebay.co.uk/itm/166916383115


But cheap chinese references need to be taken with a pinch of salt. Recently I got this LM399 voltage reference:

https://aliexpress.com/item/1005002791469664.html

After checking it, I would say you can trust it down to milivolt level, because all my meters, handheld and benchtop, coincided to the milivolt digit, even with temperature differences about 10ºC. Not bad for the price, but, an LM399 should be able to provide a couple digits more. To do that, much better resistors should be used, which is not the case.

If you look at the metrology section on this forum, you'll find that not even a $150 Vishay VHP101 resistor is really what these guys want; that would be the "bare minimum". One should look for a $4000 commercial resistance standard instead, or hand select four top-tier resistors from, say, 40, in what would be a "cheap DIY approach".

But, if you are in handheld territory, you could try a Vishay Y1453 that will cost you about $25-30 each. Since it's not in an hermetic metal can it will be affected by humidity. But you can get five for the cost of just one VHP101.

Now you can think what that cheap resistance reference will be able to do at that price. Capacitance and inductance will be the same thing or worse.

Bottom line is, you get what you pay for, and good references are expensive.

On the real cheap side, you would be better getting another DMM to compare against each other. If they more or less agree, fine. If not, you'll have to decide which one is to be trusted. At the end of the day, it's probably cheaper to purchase a new DMM that getting into the rabbit hole of references.

[patchbr]

Thank you to everyone who answered. I'm sorry I couldn't reply to each one.
They helped me a lot, and I realized a lot.
Nevertheless, this board is very cheap, so I'm going to buy one.
Please feel free to let me know if anyone has seen any articles or videos about the accuracy of this board in the future.
Thank you.

[radiolistener]

Recently I got this LM399 voltage reference:

https://aliexpress.com/item/1005002791469664.html

After checking it, I would say you can trust it down to milivolt level, because all my meters, handheld and benchtop, coincided to the milivolt digit, even with temperature differences about 10ºC. Not bad for the price, but, an LM399 should be able to provide a couple digits more. To do that, much better resistors should be used, which is not the case.

Usually, they obtain a cheaper chip with worse specs or a defective Chinese reference chip, then package it with fake markings so it looks like a genuine part. However, there's actually another chip inside. In the best case, it will have worse specifications. In the worst case, it will be defective and may function incorrectly.

They can put any marking and can use almost any package for transistors or IC, so you can't believe it's marking. Some of them even don't care what is inside and just put marking of requested component on any kind of other component, just to sell it.

Once I bought a kit of 0.125W axial resistors on aliexpress, it appears that they have so bad temperature coefficient so it can be used as temperature sensor... 

[Kim Christensen]

I wonder if the silkscreen is done the same way as those fake "handwritten" flyers that I get in my mailbox? 

[Aldo22]

I measured the board in the attached image with the ZT-MD1, which I got today.

Type   Level   Frequency   Value       D
R       0.6V   1000Hz      9.982R      801.9976
R       0.6V   1000Hz      99.99R      1965.5692
R       0.6V   1000Hz      999.8R      306.9142
R       0.6V   1000Hz      9.997kR     1363.9243
R       0.6V   1000Hz      99.89kR     257.0721
C       0.6V   10000Hz     99.4pF      0.0045
C       0.6V   10000Hz     983.8pF     0.0262
C       0.6V   10000Hz     10.24nF     0.0017
C       0.6V   10000Hz     102.8nF     0.0087
C       0.6V   100Hz       973.5nF     0.0176
C       0.6V   100Hz       10.25uF     0.0547

[mawyatt]

See if Josh will sell one of these, they should be more accurate and reliable than the AliEx version.

https://www.eevblog.com/forum/testgear/lcr-cal-test-pcb/

BTW long ago we got a LM399 off AliEx, turns out it was removed from some equipment and damaged as the TC was horrible!! Tossed it and got a few LM399s from Mouser, lesson learned



Best,

[mawyatt]

On the real cheap side, you would be better getting another DMM to compare against each other. If they more or less agree, fine. If not, you'll have to decide which one is to be trusted. At the end of the day, it's probably cheaper to purchase a new DMM that getting into the rabbit hole of references.

Certainly not the cheap solution, but following this down the Rabbit Hole!!

Got our 1st HP34401A long ago, then a AG34401A to check the older HP, (both agree!), then a major project (required verifications) got a new KS34465A (Tan case) to check the others (all 3 agree!), then later another new KS34465A (Dark case) to make sure, yep all 4 agree, then a new SDM3065X (we needed 4~5 DMMs for a major project), then a new DMM6500 (all agree!!), then a new KS34465A arrived by accident (they were BO 1yr, so we got the DMM6500 instead as it was in stock at Newark (preferred the low ohms scale anyway), but forgot to cancel the KS BO which arrive a year latter   so decided to keep it just in case

So we now have SEVEN 6-1/2 digit DMMs that all agree, Classic Rabbit Hole Disease 

Be very careful this is Highly Contagious 

BTW this same Rabbit Hole Disease causes LCR Meter Syndrome as well, don't ask how we know

Best,