(71B) HP 3421A DATA AQUISTION/CONTROL UNIT calibration

[Dave Frederickson]

Hi Erwin,

Be aware that the manual temperature calibration procedure uses the internal voltmeter of the 3421A. For the temperature calibration to be accurate, the DC volts needs to calibrated first.

Edit: The temperature calibration procedure makes resistance measurements which is part of the voltmeter calibration, so resistance needs to be calibrated also, after DC volts.

Edit #2: Before diving into what is now becoming a much bigger task, are your batteries good? The CAL Data battery can be replaced with a Panasonic BR-2/3AE5SPN, Digi-Key P226-ND. The 6V 3.2Ah SLA battery can be replaced with a Powersonic PS-632. There's a nice procedure for replacing the CAL battery here: http://www.eevblog.com/forum/repair/owon...t=prev#new
Note: This is exactly the same battery as the one in the 3468 DMM.

Dave