MIL-DTL-25446E
4.5.6 Insulation resistance. A potential of 100 VDC shall be applied for 1 minute
between each of the connector terminals and any other metal parts of the temperature transmitter
assembly. The insulation resistance shall be not less than 5 megohms.
4.5.7 Temperature gradient. The temperature transmitter shall be inserted in the test
fixture with a temperature at the bottom of the well of 200 ° ±1 °C (392 ° ±2 °F). The test
voltage shall be applied across the temperature transmitter and the resistance measured. The
measured resistance shall be within 1.7 Ω of the resistance value determined in the transmitter
resistance test for the same temperature.
4.5.8 Thermal response. The temperature transmitter shall be inserted in the test fixture
with a temperature at the bottom of the well of approximately 205 °C (400 °F). The transmitter
shall remain in the fixture for a length of time sufficient to insure that the transmitter temperature
has stabilized at the same temperature as the well temperature. The temperature transmitter shall
then be removed from the fixture and air-cooled until the transmitter resistance for 200 °C
(392 °F), as determined in the transmitter resistance test, is reached. The temperature transmitter
shall then immediately be inserted in a second test fixture that has a temperature at the bottom of
the well of 260 ° ±1 °C (500 ° ±2 °F). During the time required to properly insert the transmitter
in the second fixture, the transmitter temperature will drop slightly below 200 °C. The
transmitter temperature in the fixture shall be permitted to rise to 200 °C before response time is
noted. The time required for the transmitter temperature to rise from 200 °C to 250 °C shall be
noted. The resistance values for transmitter temperature determination at 200 °C and 250 °C
shall be those values determined in the test fixture with temperatures, at the bottom of the well of
200 °C and 250 °C. The thermal response of the transmitter shall be considered as an average of
three or more test runs and shall not exceed 20 seconds.
4.5.9 Thermoelectric potential. The temperature transmitter shall be inserted into the test
fixture with a temperature at the bottom of the well of 200 ° ±5 °C (392 ° ±9 °F). The potentials
produced in the transmitter winding shall not exceed one millivolt (mv).
4.5.10 Self-heating. The temperature transmitter shall be inserted into the fixture with a
temperature at the bottom of the well of room temperature (approximately 25 °C (77 °F)). A
current of 50 milliamperes (mA) shall be applied to the transmitter and the rise in resistance
measured. The rise in resistance shall not exceed 3.0 Ω.
4.5.11 Low temperature exposure. The complete temperature transmitter assembly shall
be subjected to a temperature of -65 ° ±2 °C (-85 ° ±3.6 °F) for a period of 48 hours. A
continuity test shall be performed while at this low temperature. No open or short circuit shall
occur and no other damage to the temperature transmitter shall result from this test.
4.5.12 High temperature exposure of lead insulation. The entire temperature transmitter
assembly shall be subjected to a temperature of 175 ° ±2 °C (347 ° ±3.6 °F) for a period of 8
hours. There shall be no failure of the lead insulation, nor any other damage to the temperature
transmitter assembly.
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