Boonton Electronics 71A, 71AR - Remote Capacitance Measurements

3.4 Remote Capacitance Measurements
3.4.1 Connections for Remote Measurements
A test specimen or a test fixture m~cted to the
"TEST" terminals by coaxial cables. RG-62 is particularly
recommended for this purpose because 0 its low capacitance.
To minimize errors in measurement resulting from the series
inductance of the coaxial cable, the length of each of the
two cables should be less than approximately 5 feet on the
1, 3, and 10 pF ranges, with shorter lengths on higher
ranges. Figure 3-1, which indicates correction factors for
cable inductance, may be used as a guide in selecting prac-
tical cable lengths.
3.4.2 Initial Adjustment for Remote Measurements
There are three controls whose adjustment should be checked
before making remote measurements with this instrument:
(a) "1000 pF ZERO"
(b)
"COMP ADJ"
(c) rIC ZERO"
3.4.2.1 "1000 pF ZERO" Adjustment
The "1000 pF ZERO" control is located at the rear panel.
Its setting is checked by switching to the 1000 pF range
and, with no specimen attached at the "TEST" terminals,
observing the rest position of the pointer. If it does
not read zero, follow the adjustment procedure outlined
in paragraph 3.1.4, (f) and (g).
3.4.2.2 "COMP ADJ" Peaking Adjustment
Prior to measuring remotely, the "COMP ADJ" peaking adjust-
ment must be performed as follows:
(a) Connect the coaxial cables and test fixture (if
any) to be used in subsequent measurements to
the "TEST" terminals. Set the range selector
to the 1 pF range.
(b) Adjust the "e ZERO" control for a reading of
approximately 75% of full scale.
3-6
7lA