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4294A Precision Impedance Analyzer - "Bridge Unbalanced"

Question asked by chaazums on Aug 18, 2011
My question is in regards to our 4-terminal proprietary test cell using the Agilent 4294A meter.

We are trying to obtain DK and DF for a  material and continue to have issues in getting normal Cp values.

The Cp after running through the calibration procedure should be 44 picoFarads +/- 10%.
We continue to get 50 to 55 after calibration.

Even if we continue to test our material with this number, we do not get good DK/DF values for our material at any frequency (100 Hz and 1 kHz).

One thing that is happening is that the 4294A screens reads “Caution:  Bridge Unbalanced” during calibration.

From what we understand, if the loss measurement is high during calibration, It sounds like there is a short with plates touching or a conductive path between the guards and the electrodes.  We checked this and it is not the case. 
We also ran a test with the equipment on another cell and a new set of electrodes to see if the bridge balance was OK.  It was not.
We suspected that either the leads or the equipment may be bad..ie. leakage in the leads. 
Any other advice??  

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