MIL-PRF-23648F
e. The vertical travel of the thermistor shall be 4 inches ± 1 inch (101.6 mm ±25.4 mm) from the
surface of the liquid bath.
f. Start measuring time at the instant the thermistor bead (contained in the probe or rod) leaves the
surface of the bath. Note the time from this instant to the time when bridge null is reached.
NOTE: A low persistence screen oscilloscope with graduated time scale may be used.
g. Record this time: This is the time constant of the thermistor.
4.8.12 Terminal strength (see 3.14).
4.8.12.1 Disk and all bead type thermistors. Zero power resistance shall be measured at 25°C as
specified in 4.8.2. Thermistors shall then be firmly clamped, and a pull as specified (see 3.1) shall be
applied to each terminal, (one at a time) in accordance with method 211 of MIL-STD-202, test condition
A. Zero power resistance shall be again measured as specified in 4.8.2. Thermistors shall be inspected
for evidence of mechanical damage.
4.8.12.2 Rod type thermistors. Zero power resistance shall be measured in 4.8.2. Thermistors shall
then be firmly clamped and a pull as specified (see 3.1) shall be applied to each terminal (one at a time)
resistance shall again be measured as specified 4.8.2; the thermistor shall then be inspected for evidence
of mechanical damage.
4.8.13 Resistance temperature characteristic (see 3.15). The thermistors shall be stabilized at each of
the ambient temperatures listed in table III. Zero power resistance measurements shall be made in
accordance with 4.8.2 at each specified temperature, after a stabilization time equal to or not less than
ten times the applicable thermal time constant (see 3.1). Zero power resistance shall be tabulated for
each measurement.
STD-202. The following details and exceptions shall apply:
a. Mounting: See 4.8.2.3.a.
b. Measurement before cycling: Zero power resistance shall be measured at 25°C as specified in
c. Test condition letter: B for thermistors rated at 125°C; C- for thermistors rated at 200°C;
C for thermistors rated at 275°C.
d. Climate chamber: The rate of temperature change within the climate chamber shall not be less
than 2°C per minute. The temperature shall be maintained at each of the extreme temperatures
by means of circulating air. The air temperature shall be measured by a suitable method and as
near the center of the group of thermistors as possible.
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