56-101-00901 Revision F
Page 10
C. Precautions
1. Do NOT press either pushbutton with test clips connected to the aircraft indicator. The
current applied may damage the indicator.
2. Do NOT connect test clips to an energized circuit. Although the TT1000A is provided with
protective devices, not all damaging potentials can be made completely safe.
3. Allow sufficient time for test clips to stabilize to the temperature of the terminals to which
they are connected for temperature tests.
4. Measure system and thermocouple resistance with a cold engine for greatest accuracy.
5. To conserve battery power, place ON / OFF switch to OFF when the test set is not in use.
6. BAT warning displayed indicates that about 10% battery life of the six 1.5V batteries
remains and the batteries should be replaced.
7. Perform insulation battery check (refer to section
on page 9 before taking measurements). Voltage should be 45 volts or greater.
D. Hot Engine Testing
A hot engine will cause thermocouple to generate a small potential which will produce
errors in measured resistance values.
This effect is inherent in any type of resistance
measuring instrument.
The effect can be circumvented by taking two measurements; the first with test leads connected
in one polarity, and then reversing the lead connections for the second measurement. The true
value is equal to the average of the two readings (i.e., add the two readings and divide by two).
The two readings must be taken in quick succession so that the thermocouple temperature will
be the same for both readings. If the thermocouple are too hot, the readings will be too far from
nominal to provide sufficient accuracy. In this case, wait for the engine to further cool.
3. SYSTEM LEAD RESISTANCE TEST PROCEDURE
A. Disconnect thermocouple leads from system temperature indicator.
B. Carefully connect test lead clips to each of the lead wires insuring a good electrical connection.
C. Rotate the FUNCTION selector to RESISTANCE MEASURE.
D.
Rotate the RESISTANCE RANGE selector to 20Ω.
E. Place the ON / OFF switch to ON and depress the BLACK pushbutton switch.
F. The d
isplay will indicate resistance in ohms to within ±0.01Ω.
G. If a "1_.__
" is displayed, select 200 Ω on the RESISTANCE RANGE switch. If a "1__._" is
displayed, resistance is greater than
199.9 Ω or there is an open circuit.
H. Swap the RED and BLACK test clip connections and the display should repeat when the
BLACK pushbutton is depressed. If the reading does not repeat, the engine thermocouple may
be hot (refer to paragraph. 2.D.
Note:
Resistance must be within manufacturer's specifications. If results are slightly outside
limits, repeat entire procedure to ensure test failure is not due to human error.
I. Place the ON / OFF switch to OFF.