Precision in different multimeter readings...

[Externet]

Greetings.
Readings of a battery showed 14.4V, 13.9V, 15.5V, 14.7V with four different high impedance 'modern' digital voltmeters for general use (not professional bench instruments).
Probably other scales and measurements are also imprecise.

How to discern which reading - instrument is more reliable as I think cannot be user calibrated -never seen a manual with calibration instructions-
Any way to make/obtain a home-made decent voltage reference ? Would a fresh-new carbon-zinc cell be decent ? What for higher voltage scales ?
How do you and how often check accuracy of your daily use multimeters ?

Checking against a decent oscilloscope falls also to the same uncertainty of such reference being precise. What % of error is reasonable to accept ? Sometimes I charge lithium cells and prefer to avoid errors as their maximum voltage is not very forgiving.

For resistance measurements, perhaps there is a reference kit in the market you prefer to use ? What would you get without breaking the wallet ?

 

[D.A.(Tony)Stewart]

It depends on your test method. Is it static DC only, AC ripple will add error.

the scope has a calibration ref. no? And specs... read them

If the DMM's have no specs or manual, then not very reliable.
I would expect <1% error

 

[danadakk]

Precision V references :

https://www.analog.com/media/en/technical-documentation/data-sheets/1021fc.pdf

https://www.ti.com/lit/pdf/SLYT183

https://www.youtube.com/results?search_query=diy+voltage+reference

Regards, Dana.

 

[Easy peasy]

You don't state how many seconds between readings ! also any ripple will affect a non true rms meter.

 

[D.A.(Tony)Stewart]

If there is radiated RF, twist the leads to see if it changes.
Show your DMM's and what did you measure?
car?

 

[BradtheRad]

Certain IC instructions told me about built-in reference voltages. Example, 3914 (popular bargraph IC) makes a default volt separation between each level. Example, TL431 produces its own 2.495V reference.

I used the above when I wished to calibrate my meters. A year or two ago I picked up a Craftsman DMM on sale at Sears. I compared its new readings with my other meters. The differences were slight, so I'm happy.

For as long as I remember a 12V car battery (according to electronics articles) in good health is really 12.6V after resting half a warm day. Supposedly your meter can read 12.4-12.8 and still be within two percent.