[volt-nuts] PWM voltage divider / now "Voltage divider"

Bill Ezell wje at quackers.net
Wed Jan 8 13:26:36 EST 2014

A PWM divider was used in the excellent Datron 4910 voltage standard, 
sub-ppm accuracy (and stability).
It included a multi-pole active LPF (5? 7? don't remember) to eliminate 
switching noise in the output.
The reference/divider topology they used pretty much eliminated any temp 
drift from any component other than the voltage ref itself (LTZ1000).
There are schematics online in various places.

I have two of them, I used to send them out alternatley for cal (by 
Fluke) whenever the out-of-cal one had an average diff from the 
calibrated one of more than 1uv. I haven't had to send either out for a 
few years now. Going long distances down the aging curve is a wonderful 
thing. Of course, they could both be aging at exactly the same rate now. 
:) They're both on continuously, and have been for the 8 years I've had 
them. I have no idea how many thousands of hours they had on them before 
I got them.

Bill Ezell
They said 'Windows or better'
so I used Linux.

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