scope:

This specification covers the general requirements for axial lead precision, power type, wire-wound, fixed resistors having a +25°C ambient operating temperature derated to zero load at +275°C for use in electrical, electronic communication, and associated equipment. These resistors have initial resistance tolerances of ±.5, ±.1, and ±1 percent, and a resistance temperature characteristic as given in table VII. Resistors covered by this specification shall have failure rates ranging from 1 to .001 percent per 1,000 hours (see 1.2.1.5). These failure rates are established at 60 percent confidence on the basis of life tests (permissible resistance change of 1.0 percent). The failure rate, identified by the appropriate symbol (see 1.2.1.5) refers to operation at full rated wattage (or voltage) at +25°C ambient temperature (see 6.1). Table I of supplement 1 provides a summary of performance characteristics for these resistors. Resistors which are noninductively wound with solderable terminals are designated by a terminal designated "N" and "Z". Terminals designated by the letters "S" and "W" are inductively wound with solderable and weldable terminals (see 1.2.1.2). A part per million (PPM) quality system is used for documenting and reporting the average outgoing quality of resistors supplied to this specification. Statistical process control (SPC) techniques are required in the manufacturing process to minimize variation in production of resistors supplied to the requirements of this specification.

The PIN shall be in the following format, and as specified (see 3.1 and 6.1):

The style shall be identified by the three-letter symbol "RWR" followed by a two digit number; the letters identify established-reliability, axial-lead, power type, wire-wound, fixed resistors, and the number identifies the size, wattage rating, and construction of the resistors. Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: U.S. Army Laboratory Command, ATTN: SLCET-R-S, Fort Monmouth, NJ 07703-5000 by using the self-addressed Standardization Document Proposal (DD Form 1426) appearing at the end of this document or by letter.

The terminal capability and inductive or noninductive winding designation are identified by a single letter in accordance with table I. TABLE I. Terminal and winding.

Symbol Terminal and winding ----------------------------------------------- S Solderable, inductively wound W Weldable, inductively wound N Solderable, noninductively wound 1/ Z Weldable, noninductively wound 1/ 1/ Wound using Ayrton-Perry method.

The nominal resistance is expressed in ohms and 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. Minimum and maximum resistance values shall be as specified (see 3.1). The standard resistance values for every decade shall follow the sequence demonstrated for 10 to 100 decade as specified in table III. For resistance tolerances F and D, only those resistance values which follow the sequence of values listed in the 10 to 100 decade specified in table III shall be considered as conforming to this specification. TABLE II. Designation of resistance values.

Designation Resistance (ohms) ----------------------------------------------------------- 1R00 to 9R88 inclusive 1 to 9.88 inclusive 10R0 to 98R8 inclusive 10 to 98.8 inclusive 1000 to 9880 inclusive 100 to 988 inclusive 1001 to 9881 inclusive 1,000 to 9,880 inclusive 1002 to 4022 inclusive 10,000 to 40,200 inclusive

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

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

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 this specification (see table V and 3.1). TABLE V. Designation of resistance values (0.1- and 0.5-percent tolerances).

Designation Resistance value ----------------------------------------------------------- R100 to R999 inclusive .1 to .9 inclusive 1R00 to 9R99 inclusive 1 to 9 inclusive 10R0 to 99R9 inclusive 10 to 99 inclusive 1000 to 9990 inclusive 100 to 999 inclusive 1001 to 9991 inclusive 1,000 to 9,999 inclusive 1002 to maximum 10,000 to maximum

The failure rate is identified by a single letter in accordance with table VI. TABLE VI. Failure rate (60-percent confidence).

Failure-rate-level Failure rate designation percent/1,000 hours ------------------------------------------ M 1.0 P 0.1 R 0.01 S 0.001