Hi,

I have a problem with my 34410A: everything is OK except Ohmmeter.I tested with 0.01% resistor, 100, 1k, 10k, 100k, 1Meg and 10Meg and used my 34970A for DC current measurement (equivalent to 34401A).

If I execute TEST ALL, I have error 612 (500nA current source FAIL), 613 (DC high voltage divider FAIL) and 621 (pre-charge amp zero FAIL).

I verified current source in the ohmmeter circuit with result below

• 100 Ohms range seem OK: current source was 0.997mA (nominal 1mA)

• 1K range seem OK: current source was 0.997mA (nominal 1mA)

• 10k range near OK: current source was 100.7µA (nominal 100µA)

• 100k range not OK: current source was 11µA (nominal 10µA)

• 1Meg range not OK: current source was 6µA (nominal 5µA)

• 10Meg range not OK: current source was 1.56µA (nominal 500nA)

In fact, I have 1µA too, maybe on all range, but effect appears only on higher range resistance.

I supposed this leakage came from opamp U300 AD706JR, but after replacement, problem was still there.

I don’t know the part number of JFET include in current source (Q313), maybe a 2N5461 (obsolete part), but I'm not sure.

Somebody may help me about this problem... Ohmmeter circuit on page #4 of PDF

Thanks.

Regards

Yves

It seems a little strange that you would use both the 34410A and 34970A for this as both can measure DC current and resistance. In any case, your 34410A is broken and need to go to a Keysight Service Center. Go to https://service.keysight.com/infoline/public/product-service.aspx?laf=mya&pn=34410A&lc=eng&cc=US#