Bias - Protek 9216A User Manual

Figure 3-1. Normalized Voltage Across DUT vs. DUT Impedance

Bias

Internal or external DC bias voltages can be applied to capacitors. Electrolytic
and tantalum capacitors need a positive bias for accurate measurements,
although the meter bipolar test voltage will not typically be enough to damage
them. The 2 VDC internal or up to 40 VDC external bias voltage allows
measurements to be made while approximating actual operating conditions. The
external bias capability also allows C-V measurements to be made on
semiconductor devices.
Notice: Always be certain that the capacitor being tested is inserted with the
correct polarity. The bias voltage is always positive to the right and is marked on
the meter. Failing to observe the correct polarity can result in the destruction of
the component under test and possibility injury. Beware that capacitors can hold
their charge for a long time if removed from the fixture without discharging the DC
bias voltage.
Warning: Care must be taken to discharge the capacitor after making
measurements, especially when using a high external bias voltage. Failing to
discharge the device can result in damage to the device, damage to the meter, or
possible injury. The meter is protected internally against discharging capacitors
with up to 1 joule of stored energy (C*V/2).
The internal and external bias circuitry will work only if the unit is in the C+D or
C+R mode. Bias voltage cannot be applied if the meter is in the R+Q, L+Q or
AUTO mode.
The error message "bias for c" will appear if the bias button is pressed in an
inappropriate mode. Whenever the bias circuitry is active, the meter is in the
constant voltage mode, so that the voltage across the capacitor under test will
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