Measurement methods
There are many measuring methods to choose for measuring
impedance, each of which has advantages and disadvantages. You
must consider your measurement requirements and conditions, and
then choose the most appropriate method, while considering such
factors as frequency coverage, measurement range, measurement
accuracy, and ease of operation. Your choice will require you to make
trade-off, as there is not a single measurement method that includes all
measurement capabilities.
Auto balancing bridge method is a common impedance measurement
method for low frequencies. It use on this instrument provides increased
accuracy, while easing operation.
Figure-18 shows auto balancing bridge method. The current,
flowing through the DUT (Device Under Test), also flows through
resistor R. The potential at the “sense L” point is maintained at zero
volts (thus called a “virtual ground”), because the current through R
balances with the DUT current by operation of the IV converter amplifier.
The DUT impedance is calculated using voltage measurement at
“Sense H” point and that across R.
Figure- 18. Auto balancing bridge method
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