Boonton Electronics 71A, 71AR - Page 27

added for the low Q check. However .. if it is necessary to
use this method .. it is suggested that the capacitance stand-
ard be in the order of 100 pF and that the capacitance of
the resistor be assumed to be 0.5 pF. This also has the
advantage of requiring a resistor of sufficiently low value
(approximately 5000 ohms) so that the effective 1 Mc resist-
ance will be very nearly the dc value.
If a capacitance standard of substantially higher value is
used.. the greater correction for error stemming from series
inductance jeopardizes the accuracy of calibration (see
paragraph 3.4.3.).
Prior to calibration the "eOMP ADJ" peaking adjustment
should be performed as follows:
(a) Attach the standard to the "TEST" posts .. using the
shortest practical lengths of coaxial cable.
(b) Set the "RANGE" selector to the lowest value on
which .. by adjustment of the "e ZERO" control .. a
reading of approximately 75% of full scale is
possible.
(c) Adjust the "COMP ADJ" control for a peak reading.
(Readjust the "e ZERO" control to keep deflections
on-scale if necessary).
(d) Disconnect the coaxial cable from the "LO-" test
terminal and zero the meter using the "e ZERO"
control.
Following the adjustment of the "COMP ADJ" control .. proceed
with the calibration check as follows:
(a) with the standard connected to the "TEST" terminals ..
set the "RANGE
II
selector to produce the greatest
on-scale deflection. The meter should read the value
of the standard.
(b) Shunt the standard with the resistor to simulate a
Q of 3. The meter should read the value of the
standard plus 0.5 pF (the capacitance of the shunt-
ing resistor). If both tests yield the appropriate
values.. the instrument is in calibration. Other-
wise, the following calibration adjustments should
be performed:
3-15
7lA