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Model 4277A
SECTION III
3-71.
EXTERNAL DC BIAS
3-74. EXTERNAL TRIGGERING
3-72.
The
special
biasing
circuits
and
procedures for using external voltage or current
bias
(required
for
certain
capacitance
or
inductance measurements) are given in Figure
3-23.
The
figures
show
sample
circuits
appropriate
for
4277A
applications.
When
applying a dc voltage to capacitors, be sure the
applied voltage does not exceed the maximum
specified voltage of the capacitor and that the
capacitor is connected with correct polarity.
Note that the externally applied bias voltage is
present at the
Hpot
and
Hcur
terminals.
3-73.
Bias
Voltage
Settling
Time:
When
a
measurement with do bias voltage superposed is
performed, it takes some time for the voltage
across sample to reach a certain percentage of
the applied (desired) voltage. Typical values of
dc bias voltage settling time are listed in Table
1-2 as reference data.
3-75. The 4277A can be externally triggered by
connecting an external triggering device to the
EXT TRIGGER connector on the rear panel and
setting the TRIGGER control on the front panel
to MAN/EXT on front panel. The instrument is
triggered (measurement is made) each time a
positive-going TTL level pulse is applied to this
connector
(refer
to
Figure
3-22).
External
triggering
can
be
also
done
by
alternately
shorting and opening the center conductor of the
EXT TRIGGER connector to ground (chassis).
Input Levels:
Pulse Width:
Trigger Timing:
VrL<0.4V
2.4V<Vih
Tp>100us
Leading Edge
Figure 3-22. External Trigger Pulse.
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