MIL-PRF-23648F
6. NOTES
(This section contains information of a general or explanatory nature that may be helpful, but is not
mandatory.)
6.1 Intended use. Thermistors covered by this specification are intended for use in electronic
equipment, and are used for stringent environmental and electrical requirements. Thermistors covered
by this specification are unique due to the fact that these devices must be able to operate satisfactorily in
military systems under the following demanding conditions: 20 Gs of high frequency vibration, 100 Gs of
shock (specified pulse), and undergo moisture resistance test. In addition these military requirements are
verified under a qualification system.. Commercial components are not designed to withstand these
military environmental conditions.
6.2 Acquisition requirements. Acquisition documents must specify the following:
a. Title, number, and date of this date of this specification, the applicable associated specification,
and the complete PIN.
b. Unless otherwise specified (see 2.1), the versions of the individual documents referenced will be
those in effect on the date of release of the solicitation.
c. Packaging requirements (see 5.1).
6.3 Qualification. With respect to products requiring qualification, awards will be made only for
products which are, at the time set for opening of bids, qualified for inclusion in the applicable QPL
whether or not such products have actually been so listed by that date. The attention of the contractors is
called to these requirements, and manufacturers are urged to arrange to have the products that they
propose to offer to the Federal Government tested for qualification in order that they may be eligible to be
awards contracts or orders for the products covered by this specification. The activity responsible for the
QPL is the Defense Supply Center, Columbus, DSCC-VQP, Post Office Box 3990, Columbus, OH 43218-
3990.
6.4 Critical voltage (applicable to NTC thermistors). The current voltage characteristic curve of NTC
thermistors indicates that the voltage increases with increase in current normally up to a critical voltage
point. Heat produced by the current at this point causes the resistance of the thermistor to decrease,
thereby resulting in a voltage drop as the current increases further. A limiting series resistor
(approximately 0.100 of nominal resistance value of thermistor) is used in circuits where the maximum
operating temperature might be exceeded.
6.5 Materials. There are many material grades used for construction of negative temperature
coefficient thermistors, for example:
a. Composed of manganese and nickel oxides.
b. Composed of manganese, nickel, and cobalt oxides.
The conductivity of each grade is characteristic of the chemical proportion of each element, and of
temperature. Other semiconductor materials such as silicon or boron are used for positive temperature
coefficient thermistors. The intent of this specification is not to limit the types of materials used in the
construction of thermistors. However, the units must comply with the performance requirements
specified.
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