MIL-R-93 Resistors, Fixed, Wire-Wound, Accurate, General Specification ForThis specification covers the general requirements for accurate, wire-wound, fixed resistors having a maximum resistance tolerance of 1 percent, with the winding protected against high humidity. The resistors are rated for continuous full load operation at any ambient temperature up to 125 Degrees C, and derated up to 145 Degrees C. They are not capable for application where alternating current ac characteristics are of critical importance. Performance characteristics are in accordance with table I.

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MIL-R-93F

4.7.12  Resistance temperature characteristic (see 3.16).  Resistors shall be tested in accordance with method 304 of MIL-STD-202.  The following detail shall apply:

Test temperature - In accordance with table XII.

TABLE XII.  Temperature for resistance temperature characteristic test.

1/  This temperature shall be considered the reference temperature for each of the succeeding temperatures.

4.7.13  Low temperature storage (see 3.17).

a.  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 in 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.

b.  Procedure:  DC resistance shall be measured as specified in 4.7.2.  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 4.7.2.  Resistors shall then be examined for evidence of mechanical damage.

4.7.14  Low temperature operation (see 3.18).  Following the final dc resistance measurement specified in 4.7.13, the resistors, mounted as specified in 4.7.13a, shall again be placed in a cold chamber at room temperature.  The temperature shall be gradually decreased to -55°C +0°C, -0°C within a period of not less than 1 hour 30 minutes.  After 1 hour of stabilization at this temperature, full rated continuous

working voltage as specified in 3.5 shall be applied for 45 minutes.  The resistors may be loaded

individually or in parallel.  Fifteen minutes +5 minutes, -0 minutes after the removal of voltage, the temperature in the chamber shall be gradually increased to room temperature within a period of not more than 8 hours.  The resistors shall then be removed from the chamber and maintained at 25°C ±5°C for a period of approximately 24 hours; the dc resistance shall again be measured as specified in 4.7.2. Resistors shall then be examined for evidence of mechanical damage.

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