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Grounded device measurement using HP4294A + HP42941A

Question asked by ricengnr on Jul 12, 2007
Latest reply on Jul 16, 2007 by ricengnr
I am trying to measure the impedance of a grounded two-port network DUT. 

Currently, I measure the two port Z parameters of the DUT directly using the HP4194A gain/phase analyzer with a voltage probe at the test channel and a current probe for the reference channel. The gain is calculated as the ratio of test/ref, so the result is in units of ohms. 

To measure Z12/Z21, I attach the voltage probe at one port while connecting the HP4194A output at the other port and measuring the output current using a series sense resistor. The negative terminals of both ports of the DUT are connected to ground, so I have a grounded DUT. Thus, I cannot use an auto-balancing bridge to measure the transfer impedances (Z12/Z21). This is why I use the setup I have just described.

I would like to do the same type of measurement using the HP4294A. Unfortunately, it does not have a gain/phase measurement section. The impedance measurement section is an auto-balancing bridge type. However, the Agilent Data Sheet for 4294A says that it is able to measure grounded impedance using the HP 42941A impedance probe.

I do not understand how the 42941 probe works, so I am not sure how the grounded impedance measurement works. What is the proper procedure to measure Z12/Z21 using this instrument?