Troubleshooting HP 34401a Voltage Meter Load

[ttsky]

Hi every one,

I have a HP 34401a meter that is causing some issues with a high impedance sensor input.

when I place only the ground wire ( black ) to the input circuit ground, the sensor reading jumps quiet dramatically, this does not happen if i place only the Red wire.

I have tried an AMPROBE 30XR-A with no issues, but it is not sensitive enough for this.

can anyone think of why this could happen. I can provide schematics of the input circuitry if needed, the sensor input is connected to an instrumentation amp.

many thanks.

 

[Baluncore]

Are you measuring Voltage?

Do you have two leads to make the measurement?
What happens if you connect both leads to the transducer?

Have you selected the input resistance in the Measurement Menu?

 

[ttsky]

Are you measuring Voltage?

Do you have two leads to make the measurement?
What happens if you connect both leads to the transducer?

Have you selected the input resistance in the Measurement Menu?

Yes two leads, when both are connected i see a rise in sensor reading from the analyzer, and when i take both leads off the reading drops. i can recreate this with only the ground lead. i have selected between 10M and >10G ohms input resistance on the meter, both with same results. it feels as if the meter is at a slightly higher reference ground, and it is effecting the analyzer circuit. but i am not sure if that is possible with only one lead.

 

[Baluncore]

We really need more information here.
What does the sensor measure. We need to know the make / model of the sensor.
What instrument, make / model, is receiving the signal from the sensor.

 

[alphy]

As a scientist, my first step would be to thoroughly examine the schematics of the input circuitry and the HP 34401a meter to understand how the instrument is designed to function. I would also review any available documentation or manuals for the meter to see if there are any known issues or troubleshooting steps for high impedance sensor inputs.

I would then conduct a series of controlled experiments to isolate and identify the source of the issue. This could include testing the meter with different inputs, using a known good sensor, and comparing the results to the AMPROBE 30XR-A. I would also test the meter in different environments and conditions to see if there are any external factors affecting its performance.

Based on the results of these experiments, I would be able to determine if the issue lies with the meter itself or with the input circuitry. If it is determined that the meter is causing the issue, I would recommend contacting the manufacturer for further assistance or possibly sending the meter in for repairs.

In addition, I would also suggest checking for any firmware updates or software patches that may address this issue. It may also be helpful to consult with other colleagues or experts in the field to see if they have encountered similar issues with the HP 34401a meter.

Overall, it is important to approach troubleshooting in a systematic and scientific manner to accurately identify and resolve the issue.