[Test-Equipment] Simple DC Voltage Standard?

[Ron]

You may wish to consider building yourself a voltage standard. 
Take a quick look at the LM385-1.2 -- a 1.235V (typical) diode. 
Adding a resistor will make a voltage standard with roughly 1% 
basic accuracy. 

-- Ron




________________________________
From: Barry <n4buq at knology.net>
To: test-equipment at mailman.qth.net
Sent: Mon, February 28, 2011 8:23:58 PM
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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