MIL-PRF-23648F
6.6 Flammability. It should be noted that this specification contains no requirements concerning the
flammability of the material used in construction of the thermistors. Users should take this into
consideration when a particular application involves this requirement.
6.7 Mounting for shock and vibration. Where thermistor bodies are restrained from movement under
conditions of shock and vibration, consideration must be given to the restraining techniques effect upon
the thermal characteristics of the thermistor.
6.8 Definitions.
6.8.1 Thermistor. A thermistor is a thermally sensitive resistor whose primary function is to exhibit a
change in electrical resistance with a change in body temperature.
6.8.2 Standard reference temperature. The standard reference temperature is the thermistor body
temperature at which nominal zero power resistance is specified (25°C).
6.8.3 Zero power resistance (RT). The zero power resistance is the dc resistance value of a thermistor
measured at a specified temperature with a power dissipation by the thermistor low enough that any
further decrease in power will result in not more than 0.1 percent (or .100 inch (2.54 mm) of the specified
measurement tolerance, whichever is smaller) change in zero power resistance.
6.8.4 Resistance ratio characteristic. The resistance ratio characteristic identifies the ratio of the zero
power resistance of a thermistor measured at 25°C to that resistance measured at 125°C (see 4.8.3).
6.8.5 Zero power temperature coefficient of resistance (alpha aT). The zero power temperature
coefficient of resistance is the ratio at a specified temperature (T), of the rate of change of zero power
resistance with temperature to the zero power resistance of the thermistor.
1 (dR T)
aT =
RT (dT)
6.8.5.1 Negative temperature coefficient (NTC). A NTC thermistor is one which the zero power
resistance decreases with an increase in temperature.
6.8.5.2 Positive temperature coefficient (PTC). A PTC thermistor is one which the zero power
resistance increases with an increase in temperature.
6.8.6 Maximum operating temperature. The maximum operating temperature is the maximum body
temperature at which the thermistor will operate for an extended period of time with acceptable stability of
its characteristics. This temperature is the result of the internal or external heating, or both, and should
not exceed the maximum value specified (see 3.1).
6.8.7 Maximum power rating. The maximum power rating of a thermistor is the maximum power which
a thermistor will dissipate for an extended period of time with acceptable stability of its characteristics
(see 3.1).
6.8.8 Dissipation constant. The dissipation constant is the ratio, (in milliwatts per degree C) at a
specified ambient temperature, of a change in power dissipation in a thermistor to the resultant body
temperature change.
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