Made a voltage standard using zener diodes.

[Texasmark]

I used 1k resistors and an assortment of zener diodes

Ranging from 12v to 3v.
Only had time to check one of my Free HF EVOM. Free, HF used to give them away as a gift.
I'm surprised using the 20v range all my HF meter voltage readings were less than + or - 1% of full scale readings. I think that is good enough for working on my old tractors.
I think the condition of the 9v battery may play a big part in the Free meter's accuracy.

If I recall, 50+ years ago when I calibrated VOMs at crane naval, the accuracy of the old simpson 260 were + or - 2% of full scale on the DCV. 3% on the ACV. I may be wrong, 50 years ago was a long time ago.
So if measuring DCV on the 150v range the simpson was considered good if all the readings were + or - 3v, if the simpson was 2% accurate. So 150v reading could be anywhere between 147 and 153 volts.
75 volts could be good reading anywhere 72v and 78v.

It's hard to find specs on new EVOMS and are those specs + or - the max reading on the particular scale you are using..

And it's disappointing that some new meters don't measure 10 DC amps.

Santa isn't bringing me a new meter this year.
My Free meters work for me when measuring DCV.

The Free HF meter are different story when measuring ohm.
I need an Ohmmeter that can tell the difference between a 1.25 and a 1.5 ohm ballast.

This picture is 5 meters with the leads shorted together on the lowest resistance range, 200. Notice the meters don't show zero ohms and no zero adjustment like like the old analog meters.

I hope you can tell why I don't trust using my HF meters when measuring resistance.

If you own an ohmmeter that can accurately tell the difference between a 1.25 and a 1.50 ballast please post the make and model.
I don't want Santa to take out a loan to buy the meter.

I find it more reliable to measure the voltage across a ballast and current, then using Ohm's law to calculate the ohms.

I put 3 ammeters in series and their reading are within 1% of each other.
Do you have a way to calibrate an ammeter?

Your ability to get a good solid connection for zeroing..er-ah seeing what your lead resistance is, depends on how good a connection you get when you touch the leads together. I have several of the older yellow HFs and several of the new red ones like yours and all read 0.4 Ohms lead resistance if I do a good job of touching the leads together.

If 10 DC Amps is a requirement why not buy a precision shunt off the www?

 

[Cliff(VA)]

I need to be able to precisely measure 1 to 5 ohm resistors to 0.01 ohms. I read reviews where some of the best meters on the market can measure to .01 ohms. So I measure voltage and current and use Ohm's law.
I'm happy with my zener setup. Does what I want.
Please post pictures of your voltage standard.
Mine has 15 different test points. Works for me..
I'm amazed I have 7 free HF meters that have the exact same readings. Like they are clones.
I also have a pile of junk HF meters. No biggie, they were gifts back when HF was giving them away. Those days are gone. I don't go to HF anymore.

When you are trying to measure milli-Ohms, the leads, component platings, and even exactly where you are touching the probe can make significant difference. It also helps to do a 4-wire measurement instead of the normal 2-wire. There are so many sources of error including esoteric effects like thermocouple voltage offsets between miss-matched metals. I used to have access to a bench meter I would trust to make these measurements with its special 4-wire probes. I would not trust anyone's 2-wire hand held meter for accurate readings including my good Fluke.

Regards,

Cliff(VA) now (NC) working Electronics Engineer.