MIL-PRF-25435D
4.5.8 High temperature. After performing a scale and friction error test (4.5.3), the transmitter
shall have pressure and power connections made to simulate operational conditions and shall be
connected to the standard indicating unit. The transmitter shall be placed in a temperature
chamber and the temperature brought to 330° ± 3°F for 6 hours. After 6 hours, with the
temperature still at 330° ± 3°F, the transmitter again shall be subjected to the scale and friction
error test (4.5.3).
4.5.9 Electrical characteristics. To verify compliance with the transmitter current, power, and
voltage requirements, a single-phase excitation voltage of 26V, 400 Hz shall be applied across
pins A and B of the transmitter. With pin C open, the transmitter current shall not exceed 160
mA. Transmitter power usage shall not exceed 0.9 W. The voltage between pins A and C and
between B and C shall not exceed 18 V.
4.5.10 Endurance. The transmitter, connected to the standard indicating unit, shall be operated
for 10,000 cycles at a rate of 30 ± 10 cycles per minute (cpm) from 0 indication to 80 ± 5% of
full scale and back to 0 indication. Within 1 hour after conclusion of this test, the transmitter
shall be subjected to the scale and friction error test (4.5.3). Errors shall not exceed the tolerances
in the contract. After 10,000 cycles, the transmitter shall be operated for an additional 60,000
cycles. Within 1 hour after conclusion of this test, the transmitter shall be subjected to the scale
and friction error test (4.5.3). Errors shall not exceed the tolerances in the contract.
4.5.11 Temperature-altitude. After performing a scale and friction error test (4.5.3), the
transmitter shall have pressure and power connections made to simulate operational conditions
and shall be connected to the standard indicating unit. The transmitter shall be placed in an
environmental chamber at ambient temperature and atmospheric pressure. The temperature shall
be reduced to -65° ± 3°F at a rate not exceeding 1.8°F per second. The chamber pressure shall be
adjusted to simulate an altitude of 100,000 feet at a rate not exceeding 3 pounds per square inch
(psi) per second. The transmitter shall be maintained at this temperature and pressure for 1 hour,
and then a scale and friction error test (4.5.3) shall be performed.
4.5.12 Low temperature exposure. After performing a scale and friction error test (4.5.3), the
transmitter shall have pressure and power connections made to simulate operational conditions
and shall be connected to the standard indicating unit. The transmitter shall be placed in a
chamber with the temperature at -80° ± 3°F for a minimum of 48 hours. While still at this
temperature, the transmitter shall be subjected to another scale and friction error test (4.5.3).
After the scale and friction error test, the temperature shall then be raised to -65° ± 3°F for a
minimum 24 hours. The transmitter, while still at this temperature, again shall be subjected to the
scale and friction error test (4.5.3). After the scale and friction error test, the transmitter shall be
brought to ambient temperature for a minimum of 4 hours and again shall be subjected to the
scale and friction error test (4.5.3).
4.5.13 High temperature exposure. The transmitter shall be placed in a chamber and the
temperature brought to 450° ± 3°F for a minimum of 80 hours. After 80 hours, the transmitter
then shall be brought to ambient temperature for a minimum of 4 hours and then subjected to the
scale and friction error test (4.5.3)
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