MIL-PRF-23648F
e. When two climate chambers are used: The thermistors may be transferred from one chamber to
another, in which case, they shall be kept at room temperature for not less than 10 minutes and
not more than 15 minutes between exposure, to the extreme temperatures.
f. Measurement after cycling: Not less than 1 hour, but within a 24 hour period after the last cycle,
zero power resistance shall be measured outside the chamber as specified in 4.8.2.
g. Inspection after the test: Thermistors shall be inspected for evidence of mechanical damage.
4.8.14.1 Beads, beads in rods, and beads in probes. The thermistor shall be preconditioned by being
immersed in water at a temperature of 100°C +0°C, -5°C for a minimum of 15 seconds. Immediately
upon conclusion of the precondition time, the thermistor shall be transferred to water at a temperature of
0°C +5°C, -0°C. The temperature shall remain at low temperature for minimum of 5 seconds. Then
transferred to water at a temperature of 100°C +0°C, -5°C. The thermistor shall remain at the high
temperature for a minimum of 15 seconds. Transfer time between baths shall be less than 3 seconds.
The duration of this test shall be 5 complete cycles.
4.8.15 Resistance to soldering heat (see 3.1 and 3.17). Thermistors shall be tested in accordance with
method 201 of MIL-STD-202. The following details and exceptions shall apply:
a. Measurement before test: Zero power resistance shall be measured as specified in 4.8.2.
b. Special preparation of specimen: Sample units shall not have been soldered during any of the
previous tests.
c. Depth of immersion in the molten solder: To a point .125 inch to .1875 inch (3.17 mm to 4.7625
mm) from the thermistor body.
d. Temperature of solder: 300°C ±10°C.
e. Duration of immersion: 2 seconds ±0.5 second.
f. Cooling time prior to final inspections and measurements: 24 hours ±4 hours.
g. Inspection and measurement after test: Thermistors shall be inspected for evidence of
mechanical damage and zero power resistance shall be measured as specified in 4.8.2.
4.8.16 Moisture resistance (see 3.18). Thermistors shall be tested in accordance with accordance with
method 106 of MIL-STD-202. The following exceptions shall apply:
a. Mounting: Thermistors shall be soldered by their leads to insulated stand off terminals on a
suitable panel so that there will be at least 1 inch (25.4 mm) of free air space around each
thermistor. The spacing of the mounts shall be such that the length of each thermistor lead is .750
inch (maximum) (19.05 mm) when measured from the edge of the supporting terminal to the
thermistor body.
b. Initial measurements: Not less than one and one half hours after thermistors have been removed
from the drying oven, the resistance shall be measured at 25°C as specified in 4.8.2.
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