[Test-Equipment] Simple DC Voltage Standard?

[Fuqua, Bill L]

Simplest solution to calibrate an analog volt meter is to use a battery, variable voltage divider ( 10k or so) and a cheap digital volt meter across the input to the analog voltmeter.
Any loading effects will not be an issue as long as you don't remove the digital voltmeter. 
Oddly as it may seem the Horbor Freight  $4.95 3.5 digit multimeter is accurate to plus or minus least digit.
I have tried many of these and they seem quite consistant in DC. Not so in AC however.
  One down side to these cheap digital multimeters is that the input resistance is 1MOhm. 
Just set the voltage divider output to the full scale value you want to calibrate your meter with both meters in parallel and set it.
  73
Bill Wa4lav
________________________________________
From: test-equipment-bounces at mailman.qth.net [test-equipment-bounces at mailman.qth.net] On Behalf Of Barry [n4buq at knology.net]
Sent: Monday, February 28, 2011 8:23 PM
To: test-equipment at mailman.qth.net
Subject: [Test-Equipment] Simple DC Voltage Standard?

I recently refurbished an HP-410B and want to perform a simple DC voltage calibration.   The problem is I don't have anything that I'm really certain is all that close to the 1V standard I need.  I have a variable-voltage supply and with a simple voltage divider, I can hit 1V easily but without something to properly measure it, I don't know when it's spot on 1V.

I have a Fluke 25 DMM, an old Triplett 630-NA, and an HP-410C - none of which are in known calibration.  The Fluke and Triplett agree, but the HP410C reads a little lower than either of those for the same voltage.

For example, if I set the variable supply through the divider so that the Fluke and Triplett both see exactly 1V, the HP410C reads about 0.85V.  Of course, without any of them in known calibration, I don't know which one would be correct.

What I was wondering is how close should a fresh AA battery be to exactly 1.5V?  From what I can find online, all the specs state a AA battery's "nominal" voltage is 1.5V but I'm not sure how close to exactly 1.5V is considered "nominal".

Oddly, the HP410C measures a fresh AA batttery at exactly 1.5V while the other two see it as about 1.625V.  I'm pretty sure 1.625V is quite high for a "nominal" AA and perhaps the Fluke and Triplett are both out of calibration about the same amount.

Any suggestions on a "dirty" way to get really close to 1.0V?  I also have a Tek 465B 'scope but that, too, isn't calibrated so not sure how that might help get me where I want to be with this.

Thanks,
Barry - N4BUQ

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