Hi Group,
Just started a new measurement, with two 34461A an a 34401A, all three more than 24 houre's on before the measurement started.
First this, this is a nice link on the website of Gellerlabs about tempco of DMM's
http://www.gellerlabs.com/DMMtempco.htmSome pictures of 4 instruments measuring a 10V Reference, is uses a quad heathed LT1021-5V TO ic's
First picture meters are in "Null" state, showing the difference for 2 hour.
2x 34461A, The top meter drift a llittledown and the bottom meter drift a little up.
Cal december 2014 and cal 30-jan 2015
One of my TEK DMM4050 DMM's.
Almost no drift, only noise, verry stable meter on 10V range.
Cal Nov 2013, 10 V DC, stil spot on.
This is my old 34401, a view months late for its cal.
It a verry stable meter, but for the last digits it has to be on fore at least 16 hours.
The meters are compared bij a freshly calibrated 3458A.
Now I have a 3458A, and two calibration reports of these meter, one from the beginning of december 2014 and one at the end of December 2014.
You can almost never be sure, that if you measure 10V DC reference, is accurate to within 3 ppm of NIST and PTB.
There are so many variables, cables, connectors, DMM drift etc.
Probably you can really have a little confidence, if you have 3x 3458a and a Fluke 732a.
If you look at the drift specifications of the calibrators used for my 3458a, you will not be happy...
I know the specifications and the reputation of the drift makes it a lot better than specifications.
But still, it gives me no good feeling.
All I can do, is difference measurements, with multiple instruments to see if my circuit drift. Live sucks
Kind regarts,
Blackdog