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34401A Loading

Question asked by misterdrew on Oct 9, 2015
Latest reply on Oct 12, 2015 by Dr_Frank
Hello, I could use some assistance fixing an issue. A little background first: my company is asking me to automate some testing but I have no experience doing so. I am learning as I go and so far have found some success. I am using some Agilent 33401A multimeters as well as some newer Agilent multimeters. I am using Labview for the software control. 

My problem is with the 33401A multimeters specifically. I hook everything up the same way on my newer DMMs and do not experience this issue. I have the V+, LO, and I(current) terminals hooked up. I have my software connect and take measurements. Everything reads correctly until I switch to read voltage. When I do this the voltage reads too high and my input power is therefore increased. The voltage is reading about 1.6V high on about 500mA of current. 

As soon as I switch back to current reading mode the input power drops back down to where it should be. So the issue is likely somewhere in the voltage measurement. I understand that there will be some load by the DMM but it seems to be unreasonably large with these multimeters. Again, this does not happen in the exact same set up with my newer DMMs. 

Are there any settings I can change or anything I can do to help bring this loading down to a more reasonable level? I've tried changing the ranging and resolution to no avail. The problem always comes back when I switch to voltage reading mode.

Sorry for my inexperience, I'd appreciate any help!

Drew  

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