MIL-PRF-39005 Resistors, Fixed, Wirewound \(Accurate\), Nonestablished Reliability, Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\), established reliability \(ER\), accurate, wire-wound, fixed resistors that have a maximum resistance tolerance of 1 percent and a high degree of stability with respect to time under specified environmental conditions. The resistors are capable for continuous full-load \(or voltage\) operation at any ambient temperature up to 125??C, and when derated, up to 145??C \(see 6.5\). They are not capable for application where the alternating current \(ac\) characteristics are of critical importance. ER resistors have life failure rates \(FR\) ranging from 1.0 percent to 0.001 percent per 1,000 hours \(see 1.2.1.5\). These FR are established at 60-percent confidence level on the basis of the life tests. The FR, identified by the appropriate symbol, is referred to operation at full rated voltage and temperature.

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MIL-PRF-39005G

4.8.14 Resistance temperature characteristic (see 3.18). Resistors shall be tested in accordance with

method 304 of MIL-STD-202. The following detail shall apply: Test temperature: In accordance with

table XVI.

TABLE XVI. Temperatures for resistance temperature characteristic test.

Sequence

Temperature �C 1/

Conformance inspection

Qualification inspection

-15

-55 +0, -3

-65 +0, -3

105

125 +15, -0

145 +15, -0

1/ At the option of the manufacturer the reverse sequence may be as follows:

1. Room temperature 2/

2. +125 �3

3. Room temperature 2/

4. -55 �3.

2/ This temperature shall be considered the reference temperature for each of

the temperatures in sequences 2 through 5 inclusive.

3/ This temperature shall be considered the reference temperature for each of

the temperatures in sequences 7 through 10 inclusive.

4.8.15 Low temperature storage (see 3.19).

4.8.15.1 Mounting. Resistors shall be mounted by their normal mounting means, in such a manner

that there is at least 1 inch of free air space around each resistor, and is such a position with respect to

the air stream that the mounting offers substantially no obstruction to the flow of air across and around

the resistors.

4.8.15.2 Procedure. DC resistance shall be measured as specified in 4.8.5. Within 1 hour after this

measurement, the resistors shall be placed in a cold chamber at -65�C +0�C, -3�C. Twenty-four hours

after the resistors have reached this temperature; the temperature of the chamber shall be gradually

increased to room temperature within a period of not more than 8 hours. The resistors shall be removed

from the chamber and maintained at a temperature of 25�C �5�C for a period of approximately 24 hours;

the dc resistance shall again be measured as specified in 4.8.5. Resistors shall then be examined for

evidence of mechanical damage.