  Impedance measurements provide a useful probe of the physics of bolometers
and calorimeters. We describe a method for measuring the complex impedance of
these devices. In previous work, stray impedances and readout electronics of
the measurement apparatus have resulted in artifacts in the impedance data. The
new technique allows experimenters to find an independent Thevenin or Norton
equivalent circuit for each frequency. This method allows experimenters to
easily isolate the device impedance from the effects of parasitic impedances
and frequency dependent gains in amplifiers.
