Good day! I have THREE 34401As with the exact same overarching fault: ACI doesn't work. Tested 6 digit range w/1mA, 100Hz source.
I've tested the following on all three:
- Self Test: Pass
- ACV & DCV @ 5V and 50V
- DCI @ 1mA
- Freq @ 100Hz
- Resistance @ 100, 1000, 10,000, and 100,000 ohms
- Front & Rear Jacks for consistency
- Checked R120 & R121 for grins
All of the above tests had great results... Tried all the different filters for AC... same issue.
I also tested the resistance across Lo & I input terminals: about 0.65ohm resistance when in ACI (all three of the 34401A)...0.75ohm on a 34461A in 3A range
Looking through the schematics and theory of operation, I am not seeing a clear failure mode for this situation - it's not a relay, as all of the other working modes exercise each of them successfully
All I can think of is that *I* am doing something wrong, but I've checked myself with:
- 34461A reports ACI @ ~1mA (that's what I am giving it)
- 3458A reports ACI @ ~1mA
- Fluke 189 reports ACI @ ~1mA
I know I went overkill on validating my source, but really... I have three bad ones, so might as well prove it's not *ME* three times! I mean, how on earth can I end up with three of these things (from different sellers) with the same symptom?
Any words of wisdom on this?
Thank you!