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Products => Test Equipment => Topic started by: ni.st on November 04, 2018, 02:39:34 am

Title: Agilent 34401A switches from ACV to Resistance Measurement
Post by: ni.st on November 04, 2018, 02:39:34 am

I recently bought an Agilent 34401a which shows some strange behavior. Sometimes if I do VAC measurements it changes unexpectedly to Resistance Measurement.
It passes the selftest without errors.

Does anyone know the reason for this problem?

Thanks for your help
Nicolas

Title: Re: Agilent 34401A switches from ACV to Resistance Measurement
Post by: floobydust on November 04, 2018, 04:40:57 am

The two buttons are next to each other ACV (SW613), 2W ohms (SW614) but different MCU scan lines.
So I would suspect the ohms pushbutton sticking/shorting or a solder bridge on the front panel PCB. Try gently pushing and tapping to see if the ohms button is shorting.

I take these apart and clean up the front panels, toss the keypad in dishsoap and water to clean it up.
Sometimes I find something was spilt inside, or loose strand of copper wire got in.

Title: Re: Agilent 34401A switches from ACV to Resistance Measurement
Post by: ni.st on November 05, 2018, 11:31:19 pm

Thank you for the advice floobydust.

I removed the Frontpanel and cleaned everything, but the problem occured again. While measuring DCV, it also switched to 2W ohms after some time.

Title: Re: Agilent 34401A switches from ACV to Resistance Measurement
Post by: HighVoltage on November 05, 2018, 11:51:14 pm

Leave the front panel disconnected (Remove the cable ) and try to control the instrument over GPIB or RS232 and see if it still switches to 2W Ohm.

Title: Re: Agilent 34401A switches from ACV to Resistance Measurement
Post by: ni.st on November 06, 2018, 12:59:41 am

I tried what you suggested HighVoltage, but It still switches to 2W Ohm after some time with disconnected ribbon cable  and control via RS232.