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TM 55-4920-383-13&P
b.
The Test Set performs four basic functions. They are as follows:
—
(1) Capacitance measurement
(2) Capacitance simulation
(3) Insulation resistance measurement
(4) Capacitance and resistance self test
c.
Capacitance measurement and capacitance simulation are under the control of the
CAPACITANCE FUNCTION switch (1, figure 2-1). A tank unit applied across the COAX A
and UNSH B input connectors (18) and a compensator applied across the COAX A and COMP C
input connectors (18) are measured by routing the capacitance signals through the
CAPACITANCE FUNCTION switch (1) and applying them to the capacitance-to-dc converter.
The capacitance-to-dc converter generates a dc voltage proportional to either the tank unit
or compensator being measured. This DC voltage is scaled by the CAPACITANCE RANGE
switch (6). The scaled voltage is applied to the analog-to-digital converter when the
DISPLAY SELECT switch (8) is in the CAP (pF) position. The analog-to-digital converter
converts the dc voltage (which is proportional to the capacitance being measured) to a digital
code.
This code is applied to the digital display (7) which, in turn, displays the value of
the capacitance being measured (in picofarads). Measurement of the Test Set capacitance
simulators (tank unit and compensator) is also under the control of the CAPACITANCE
FUNCTION switch (1), with the measurement process being identical to that previously
described for the aircraft-located tank components applied to the UNSH B, COAX A and
COMP C Test Set connectors (18).
d.
The capacitance simulators for tank unit and compensator are applied to the indicator
under test through the UNSH, COAX and COMP Test Set connectors (21). The simulator
signals are routed through the CAPACITANCE FUNCTION switch (1) to the aforementioned
Test Set connectors.
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