scope:

This specification covers the general requirements for established reliability, insulated, fixed resistors having a composition resistance element consisting of a mixture of carbon, insulating material, and suitable binders, either molded together or applied as a thin layer of conducting material on an insulating form. Resistors covered by this specification have failure rates ranging from 1.0 to 0.001 percent per 1,000 hours (see 1.2.1.5) at 50 percent full-load operation at an ambient temperature of 70°C (see table I). These failure rates are established at a 60 percent confidence level on the basis of life tests. The failure rate, identified by the appropriate symbol, is referred to operation at rated temperature and at a voltage equivalent to 50 percent of rated wattage (with a permissible resistance change of ±15 percent). A part per million (PPM) quality system is used for documenting and reporting the average outgoing quality of resistors supplied to this specification. Statistical

The Part or Identifying Number is in the following form, and as specified (see 3.1, 6.1, and 6.12): Beneficial comments (recommendations, additions, deletions) and any (pertinent data which may be of use in improving this document should be addressed to: US Army Laboratory Command ATTN: SLCET-R-S, Fort Monmouth, NJ 07703-5000 by using the self-addressed Standardization Document Improvement (DD Form 1426) appearing at the end of this document or by letter.

The style is identified by the three-letter symbol "RCR" followed by a two-digit number; the letters identify established reliability, insulated, composition, fixed resistors, and the number identifies the size and power rating of the resistors.

The characteristic is identified by a single letter in accordance with table I.

The nominal resistance value expressed in ohms is identified by three-digit number; the first two digits represent significant figures and the last digit specifies the number of zeros to follow. When resistance values less than 10 ohms are required, the letter "R" is substituted for one of the significant digits to represent the decimal point. When the letter "R" is used, succeeding digits of the group represent figures as shown in the following example:

2R7 = 2.7 ohms

Minimum and maximum resistance values shall be as specified (see 3.1). The standard values for every decade shall follow the sequence demonstrated for the "10 to 100" decade in accordance with MS90178.

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

Symbol Resistance tolerance --------------------------------- Percent (±) J 5 K 10

The failure rate designation as shown in table III is signified by a single letter (M, P, R, S), which identifies the failure rate level for which the resistor is qualified (see 4.4). TABLE III. Failure rate level (at 50 percent rated wattage).

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