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Dinosaur

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Joined: 12/08/2011
Location: Australia
Posts: 331

Posted: 08:30am 26 Jun 2025

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Hi All

Working on improving my Lithium charging electronics and software.
To be able confirm accurately what the voltage is (3.200 to 3.600) I need the confidence
that my meter is correct.

I have about 6 different meters and they vary from one to the other by up to 30mV.
Just recently purchased an Internal Resistance meter for reading the Cells,
but being Chinese I have no confidence in it's accuracy either.
Yes I trust the milli-ohm readings, but not the voltage.

The way to solve that, is to have a calibrated Voltage device.

The other way is to have a calibrated voltage regulator that is set to say 2.500V
once plugged into a 240V supply.
But you still need confidence in the meter that you use to setup the 2.500V supply.

Do any members have any experience in using off the shelf batteries that have a very reliable voltage when new.?

Any suggestions ?

Regards
Hervey Bay Qld.

CaptainBoing

Guru

Joined: 07/09/2016
Location: United Kingdom
Posts: 2170

Posted: 08:33am 26 Jun 2025

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can't get better than this for "maker" purposes

https://geoffg.net/Voltage_Reference.html

I have this along with a 6.144000MHz TCXO (0.1ppm) in a die-cast box fixed above my bench so I can calibrate DC voltage and Hz quickly and precisely
Edited 2025-06-26 18:44 by CaptainBoing

Dinosaur

Guru

Joined: 12/08/2011
Location: Australia
Posts: 331

Posted: 09:18am 26 Jun 2025

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Hi All

Simplicity in itself.
I like it, now just have to source it locally without waiting for 3 weeks.

Edit: Obsolete and hard to get.
But ordered this on two day delivery locally.
LM404 +-0.1% accuracy of O/P voltage, which will allow me to pick the best of my multi meters.
Edited 2025-06-26 20:09 by Dinosaur

Regards
Hervey Bay Qld.

KeepIS

Guru

Joined: 13/10/2014
Location: Australia
Posts: 1861

Posted: 12:48am 27 Jun 2025

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I had the same problem a wile back, and using a slightly different voltage reference, the problem was that while I could calibrate various meters at low voltage reference, they were all different at higher voltages.

I bit the bullet and bought a recent version of the 5.5 digit meter in Geoff's notes.

FYI I purchased a hand held ZOYI ZT-703S 50MHz dual channel Oscilloscope Multimeter, and I was surprised at how accurate the voltage calibration is.

A big beautiful display in Multimeter mode, one of the best I've seen, and really great DSO response and display, it accurately displays the same HF transients and waveforms as a 100Mhz bench top DSO, for the first time, something that's built and feels like a high cost quality device.
Edited 2025-06-27 10:50 by KeepIS

NANO Inverter: Full download - Only Hex Ver 8.1Ks

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