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

4.7.7 Insulation resistance (see 3.11). Resistors shall be tested in accordance with method 302 of

MIL-STD-202 with the following exceptions:

a. Special preparation for wire lead resistors: Resistors shall be clamped in the trough of a 90° metallic V-block of such size that the body of the resistor does not extend beyond the extremities of the block. The resistor leads shall be so positioned that one of the points of contact of the periphery of the resistor with the V-block is the point at which the distance from the surface of the resistor leads to the periphery of the resistor body is a minimum. The minimum distance to the periphery of the resistor body shall be measured from the point of emergence of the resistor lead.

b. Test condition: A or B, whichever is greater.

c. Points of measurement: Between the resistor terminals connected together and the mounting strap.

4.7.8 Moisture resistance (see 3.12). Resistors shall be tested in accordance with method 106 of

MIL-STD-202 . The following details and exceptions shall apply:

a. Mounting for wire lead terminal resistors: Resistors shall be soldered by their leads to rigid mounts or terminal lugs. The spacing of the mounts shall be such that the length of each resistor lead is approximately .375 inch (9.53 mm) when measured from the edge of the supporting terminal to the resistor body. One half of the specimens shall be covered with a V-shaped strap whose width is such that the resistor shall not extend more than 0.5 inch (12.7 mm) beyond the edge of the strap. The strap shall be made of a corrosion resistant metal and shall be kept in contact with the resistor body by supporting the resistor body as indicated on figure 2, with a nonconducting, noncorrosive support whose width is less than that of the body and which will not act as a moisture trap. The mounting straps may be individual for each resistor or continuous for all resistors.

b. Initial measurements: Immediately following the initial drying period, the dc resistance shall be measured as specified in 4.7.2.

FIGURE 2. Mounting strap for wire lead terminal resistors.