MIL-PRF-23648F
6.8.9 Thermal time constant. The thermal time constant is the time required for a thermistor to change
to 63.2 percent of the total difference between its initial and final body temperature when subjected to a
step function change in temperature under zero power conditions.
6.8.10 Resistance temperature characteristic. The resistance temperature characteristics is the
relationship between the zero power resistance of a thermistor and its body temperature (see 3.1).
6.8.11 Temperature wattage characteristic. The temperature wattage characteristic of a thermistor is
the relationship at a specified ambient temperature between the thermistor temperature and the applied
steady state wattage.
6.8.12 Current time characteristic. The current time characteristic is the relationship at a specified
ambient temperature between the current through a thermistor and time, upon application or interruption
of voltage to it.
6.8.13 Stability. The stability of a thermistor is the ability of a thermistor to retain specified
characteristics after being to designated environment or electrical test conditions.
6.9 Tin plated finishes. Tin plating is prohibited (see 3.3.3) since it may result in tin whisker growth.
Tin whisker growth could adversely affect the operation of electronic equipment systems. For additional
information on this matter refer to ASTM B545.
6.10 Environmentally preferable material. Environmentally preferable materials should be used to the
maximum extent possible that the material meets or exceeds the operational and maintenance
requirements, and promotes economically advantageous life cycle costs. Table X lists the Environmental
Protection Agency (EPA) top seventeen hazardous materials targeted for major usage reduction. If any
of these hazardous materials are required, it is recommended that it be used only when other materials
cannot meet performance requirements.
TABLE X. EPA top seventeen hazardous materials.
Benzene
Dichloromethane
Tetrachloroethylene
Cadmium and
Lead and Compounds
Toluene
Compounds
Carbon Tetrachoride
Mercury and
1,1,1
Compounds
Trichloroethane
Chloroform
Methyl Ethyle Ketone
Trichloroethyene
Chromium and
Methyl Isobutyl Ketone
Xylenes
Compounds
Cyanide and Compounds
Nickel and Compounds
6.11 Subject term (key word) listing.
Coefficient, negative temperature
Coefficient, positive temperature
Dissipation constant
Thermal time constant
Zero power resistance
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