MIL-PRF-22097J
e.
Operating conditions: Rated dc or ac continuous working voltage at commercial line frequency and
waveform (see 3.1), shall be applied intermittently to the end terminal of the resistors, 1.5 hours "on", a half
hour off, for a total of 1,000 hours, at the test temperature. Each resistor shall dissipate rated wattage, but
shall not exceed maximum voltage. Adequate precaution shall be taken to maintain constant voltage on the
resistor.
f.
Test condition D.
g.
Measurement during test: While resistors are still in the oven, resistance shall be measured between the
end terminals at the end of the half hour "off" periods after 50 hours ±4 hours, 100 hours ±8 hours, 250
hours ±12 hours, 500 hours ±12 hours, 750 hours ±12 hours, and 1,000 hours ±12 hours have elapsed and
compared to the similar readings taken 4.7.15d.
h.
Measurement outside of chamber: When measurements are made outside the chamber, resistor shall be
outside of the chamber for a minimum of 45 minutes and stabilized before measurement.
i.
Measurement after test: After resistors have been removed from the oven and returned to room
temperature, setting stability and total resistance shall be measured as specified in 4.7.8.1 and 4.7.2.1,
respectively, and compared to the similar readings taken in 4.7.15c. Dielectric withstanding voltage (at
atmospheric pressure), and torque shall be measured as specified in 4.7.5.1 and 4.7.7.1, respectively.
j.
Inspection after test: Resistors shall be inspected for evidence of mechanical damage.
4.7.16 Low temperature operation (see 3.21).
4.7.16.1 Mounting. Resistors shall be mounted in such a manner as to allow electrical connections to be made to
the terminals.
4.7.16.2 Procedure. Total resistance shall be measured as specified in 4.7.2.1 and 4.7.8.1, respectively. The
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resistor shall be placed in a chamber at room temperature. The temperature shall be gradually decreased to -55 C
+0OC, -5OC within a period "off" not less than one and one half hours. After 1 hour of stabilization at this temperature,
setting stability shall be measured as specified 4.7.8.1. Full rated continuous working voltage (see 3.1 and 3.6) shall
be applied for 45 minutes. The resistors may be loaded individually or in parallel. Fifteen minutes +5 minutes, -0
minutes after removal of voltage, setting stability shall be measured as specified in 4.7.8.1. The temperature in the
chamber shall be gradually increased to room temperature within a period of not more than 8 hours. The resistors
shall be removed from the chamber, and maintained at a temperature of 25 C ±5 C for a period of approximately 24
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hours. Total resistance shall be measured as specified in 4.7.2.1. Resistors shall be examined for evidence of
mechanical damage.
4.7.17 High temperature exposure (see 3.22).
4.7.17.1 Mounting. Resistors shall be examined in such a manner as to allow electrical connections to be made to
the terminals.
4.7.17.2 Procedure. Total resistance and setting stability shall then be measured as specified in 4.7.2.1 and
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4.7.8.1, respectively. The resistors shall then be exposed to an ambient temperature of 125 C +5 C, -0 C for
characteristic A, and 150 C +5 C, -0 C for characteristic C and characteristic F for a period of 250 hours ±8 hours.
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Not less than 2 hours after the end of the exposure period, setting stability and total resistance shall be measured in
4.7.8.1 and 4.7.2.1, respectively. Torque shall be measured as specified in 4.7.7.1, except that it shall be determined
during the movement of the contact arm from the position for setting stability to the position for total resistance.
Dielectric withstanding voltage (at atmospheric pressure), and insulation resistance shall be measured as specified in
4.7.5.1 and 4.7.6, respectively. Resistors shall then be examined for evidence of mechanical damage.
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