scope:

This specification covers the detail requirements for styles RW70 RW74, RW78, and RW79 resistors.

The type designation shall be in the following form:

The style is identified by the two-letter symbol "RW" followed by a two-digit number; the letters identify power type, wire-wound, fixed resistors, and the number identifies the size, wattage rating, and construction of the resistors.

The characteristic is identified by a single letter that identifies the maximum continuous operating temperature (surface hot spot), the minimum insulation resistance value at the end of the moisture resistance test, and the resistance temperature characteristic in accordance with table I. TABLE I. Characteristic.

Symbol Maximum continuous Minimum insulation Resistance temperature operating resistance at end of characteristic temperature1/ moisture resistance test (percent per degree C) ---------------------------------------------------------------------------------------- °C Megohms U - - - 275 100 ±30 PPm for 10 ohms and above. ±50 PPM for 1 ohm up to but not including 10 ohms. ±990 PPM below 1 ohm. 1/ This temperature is also the maximum permissible hot-spot surface temperature.

The nominal resistance expressed in ohms is identified by four digits; the first three digits represent significant figures and the last digit specifies the number of zeros to follow. When the value. of resistance is less than 100 ohms, or when fractional values of an ohm are required, the letter "R" shall be substituted for one of the significant digits to represent the decimal point. When the letter "R" is used, succeeding digits of the group represent significant figures. The resistance-value designations are shown in table II. The standard resistance values for every decade shall follow the sequence demonstrated for 10 to 100 decade in table III. TABLE II. Designation of resistance values.

Designation Resistance ------------------------------------------------------------------- ohms R100 to R976 - - - - - 0.10 to 0.976 incl 1R00 to 9R76 - - - - - 1.0 to 9.76 incl 10R0 to 97R6 incl- - 10.0 to 97.6 incl 1000 to 9760 incl- - - 100 to 976 incl 1001 to 9761 incl- - - 1,000 to 9,760 incl 1002 to 9092 incl- - - 10,000 to 90,000 incl

TABLE III. Standard resistance values for the 10 to 100 decade. 1/

10.0 14.7 21.5 31.6 46.4 68.1 10.2 15.0 22.1 32.4 47.5 69.8 10.5 15.4 22.6 33.2 48.7 71.5 10.7 15.8 23.2 34.0 49.9 73.2 11.0 16.2 23.7 34.8 51.1 75.0 11.3 16.5 24.3 35.7 52.3 76.8 11.5 16.9 24.9 36.5 53.6 78.7 11.8 17.4 25.5 37.4 54.9 80.6 12.1 17.8 26.1 38.3 56.2 82.5 12.4 18.2 26.7 39.2 57.6 84.5 12.7 18.7 27.4 40.2 59.0 86.6 13.0 19.1 28.0 41.2 60.4 88.7 13.3 19.6 28.7 42.2 61.9 90.9 13.7 20.0 29.4 43.2 63.4 93.1 14.0 20.5 30.1 44.2 64.9 95.3 14.3 21.0 30.9 45.3 66.5 97.6 1/ These values are applicable to all resistance tolerances.

It is preferred that resistance values be selected as specified in table III. However, if it is impracticable to do so, then any value (within specification limits) may be specified and these values shall be considered as .conforming to the specification (see table IV). TABLE IV. Designation of resistance values. 1/

Designation Resistance value 2/ ------------------------------------------------------------------------------------------------------ ohms R100 to R999 incl- - - 0.10 to 0.999 incl 1R00 to 9R99 incl- - - 1.0 to 9.99 incl 10R0 to 99R9 incl- - - 10.0 to 99.9 incl 1000 to 9990 incl- - - 100 to 999 incl 1001 to 9991 incl- - - 1,000 to 9,999 incl 1002 to maximum- - - - 10,000 to maximum 1/ Applicable to 0.1 and 0.5 percent tolerances and for replacement and maintenance as required (see 1.2.1.3.1). 2/ Minimum value for .1 percent tolerance shall be .499 ohm.

The resistance tolerance is identified by a single letter in accordance with table V. TABLE V. Resistance tolerance.

Symbol Resistance tolerance ----------------------------------------- percent (±) B - - - - - 0.1 D - - - - - 0.5 F - - - - - 1.0