Chapter 2 Operation
DTF measurement
22166183 R001 PSD90-3 Universal AC/DC Fuel Quantity Test Set Operation Manual FINAL
April 2023 Subject to Export Control; see Cover Page for details. 2 - 29
8. Turn the MEG MODE SIMULATE SELECT switch to either A/C, TU & (COMP); TU &
(COMP); or TU, AUX & (COMP) to simulate the appropriate conditions.
9. The SIMULATOR COURSE switch will still adjust the TU, COMP or AUX simulators
while in simulate mode. The corresponding FINE knob still adjusts the simulators.
The display will indicate DVM voltage measurement.
2.7 DTF measurement
2.7.1 DTF measurement mode
1. Connect CHASSIS jack to Airframe.
2. Turn POWER switch to REV DC (DC+), DC CAP (DC-) or AC CAP. Allow one minute
for test set to stabilize.
3. Check battery condition. If "% CHARGE" on the digital display is 10% or less,
recharge batteries.
4. Connect TANK UNITS LO Z, HI Z and COMP connectors to the interface box with the
appropriate interface cable.
5. Without the aircraft interface connected to the aircraft, place the function select
switch in DTF mode.
6. When the unit nulls all stray capacitance, 0ρF will be indicated on the units display.
NOTE
The TU AND AUX setting shows the total of the two combined simulation values.
NOTE
Any adjustments made in TU, AUX & (COMP) will only affect the AUX simulation value
and not the TU value.
NOTE
Connecting test harnesses and interface boxes should not add capacitance to the
system. However, if the cable is suspect, connect only the cable to MEASURE LO-Z,
MEASURE HI-Z, and MEASURE COMP and read its capacitance per measurement
procedure. If cable capacitance is less than 1 ρF above displayed reading with no
cables connected to test set, subtract its capacitance from the amount being simulated.
If over 1 ρF, repair cable; shields are probably improperly terminated.
NOTE
The AIRCRAFT ONLY position disconnects all internal simulators. This is used when
delta values are simulated, and actual dry aircraft tanks are used for empty.
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