scope:

This specification covers the general requirements for power type, wire-wound fixed resistors which utilize the principal of heat dissipation through a metal mounting surface. The resistors have an initial resistance tolerance of ±1 percent. These resistors are suitable for continuous full load operation at an ambient temperature of +25°C, and when derated up to +275°C (see figure 1). These resistors should not be used in circuits where their ac performance is of critical importance in the operation of such circuits. However, provisions have been made in particular styles to minimize inductance (see 3.1). These resistors will have life failure rate levels ranging from 1.0 to 0.001 percent per 1,000 hours (see 1.2.1.4). These failure rate levels are established at a 60-percent confidence on the basis of the life tests. The failure rate level, identified by the appropriate symbol, is referred to operation at full rated wattage at +25°C, with a permissible change in resistance of ±2 percent as the criteria for failure. Table I of supplement 1 provides a summary of performance characteristics for these resistors. 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. 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 by using the self-addressed Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.

The term Part or Identifying Number (PIN) is equivalent to the term (part number, identification number, and type designator) which was previously used in this specification. The PIN shall be in the following form, and as specified (see 3.1 and 6.5).

The style is identified by the three-letter symbol "RER" followed by a two digit number; the letters identify established reliability, chassis mounted, power type, wire-wound, fixed resistor, and the number identifies the size and power rating of the resistor.

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

Symbol Resistance tolerance ----------------------------------- percent ± F 1.00

The nominal resistance value expressed in ohms is identified by a four digit number; the first three represent significant figures, and the last digit specifies the number of zeros to follow. Where fractional values of an ohm, and values of less than 100 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, the succeeding digits become significant. The following are examples of symbols for resistance values:

R100 = 0.10 ohm 1R00 = 1.00 ohm 10R0 = 10.0 ohms 1000 = 100 ohms 1001 = 1,000 ohms 1002 = 10,000 ohms

Minimum and maximum nominal resistance values shall be as specified (see 3.1). The standard resistance values for every decade shall follow the sequence demonstrated for the "1 to 10" decade (see table II). TABLE II. Standard resistance values for the 1 to 10 decade. 1/

1.00 1.47 2.15 3.16 4.64 6.81 1.02 1.50 2.21 3.24 4.75 6.98 1.05 1.54 2.26 3.32 4.87 7.15 1.07 1.58 2.32 3.40 4.99 7.32 1.10 1.62 2.37 3.48 5.11 7.50 1.13 1.65 2.43 3.57 5.23 7.68 1.15 1.69 2.49 3.65 5.36 7.87 1.18 1.74 2.55 3.74 5.49 8.06 1.21 1.78 2.61 3.83 5.62 8.25 1.24 1.82 2.67 3.92 5.76 8.45 1.27 1.87 2.74 4.02 5.90 8.66 1.30 1.91 2.80 4.12 6.04 8.87 1.33 1.96 2.87 4.22 6.19 9.09 1.37 2.00 2.94 4.32 6.34 9.31 1.40 2.05 3.01 4.42 6.49 9.53 1.43 2.10 3.09 4.53 6.65 9.76 1/ Resistors having resistance values not listed herein, or in any other decade, shall be considered as not conforming to the specification.

The life failure rate designation as shown in table III is signified by a single letter (M, P, R, S), which identifies the life failure rate level for which the resistor is qualified (see 4.5). TABLE III. Life failure rate level (established at 60-percent confidence).

Failure rate level Failure rate level designation -------------------------------------------- M 1.0 P 0.1 R 0.01 S 0.001