[Boatanchors] DC Voltmeter Calibration

[mikea]

On Thu, Jan 07, 2016 at 11:03:13AM -0500, David C. Hallam wrote:
> I obviously need to calibrate my DC voltmeters.  I was setting the 300 VDC
> B+ on my signal generation after some repairs.  I used 3 voltmeters and got
> a spread of 45V among the 3 of them, low 285V and high330V.  The low was a
> VTVM and the high  DVM.  What is a good standard to use that won't break the
> bank to acquire?  I used to have some mercury batteries but they are a no,
> no any more.

I think you can buy reference supplies which have a band-gap device as the
base standard in the supply. These devices are neat because they really are
invariant, so long as you run them within the stated conditions. 

Here's a data sheet for one band-gap device, with some circuits at the bottom.
The last circuit is a precision 2.5V 100mA max supply, which can serve as the
internal reference for a higher-voltage regulated power supply. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin