MIL-PRF-94G
6. NOTES
(This section contains information of a general or explanatory nature that may be helpful, but is not mandatory).
6.1 Intended use. The resistors covered by this specification are military unique due to the fact that these devices
must be able to operate satisfactorily in military systems under the following demanding conditions: 15 g's of high
frequency vibration, 100 g's of shock (specified pulse), 25,000 cycles of endurance at the maximum temperature,
thermal shock (with no more than 5 percent deviation in initial resistance), low temperature coefficient of resistance,
and resistant to salt corrosion. In addition, these military requirements are verified under a qualification system.
Commercial components are not designed to withstand these military environmental conditions.
6.2 Acquisition requirements. Acquisition documents must specify the following.
a.
Title, number, and date of this specification, and the complete PIN (see 1.2).
b.
If not otherwise specified (see 2.1), the versions of the individual documents referenced will be those in
effect on the date of release of the solicitation.
Packaging instructions (see 5.1).
c.
d.
Hardware, whether assembled on resistor (see 3.4.6.1).
6.3 Qualification. With respect to products requiring qualification, awards will be made only for products which are,
at the time of award of contract, qualified for inclusion in the Qualified Products List whether or not such products
have actually been so listed by that date. The attention of the contractors is called to these requirements, and
manufacturers are urged to arrange to have the products that they propose to offer to the Federal Government tested
for qualification in order that they may be eligible to be awarded contracts or orders for the products covered by this
specification. Information pertaining to qualification of products may be obtained from Defense Supply Center,
Columbus, ATTN: DSCC-VQP, 3990 East Broad Street, Columbus, Ohio 43218-3990.
6.4 Tin whisker growth. The use of alloys with tin content greater than 97 percent, by mass, may exhibit tin
whisker growth problems after manufacture. Tin whiskers may occur anytime from a day to years after manufacture
and can develop under typical operating conditions, on products that use such materials. Conformal coatings applied
over top of a whisker-prone surface will not prevent the formation of tin whiskers. Alloys of 3 percent lead, by mass,
have shown to inhibit the growth of tin whiskers. For additional information on this matter, refer to ASTM-B545
(Standard Specification for Electrodeposited Coatings of Tin).
6.5 Supplementary insulation. Resistors should not be used at potentials to ground greater than a peak voltage of
500 volts, or 200 volts for aircraft equipment, unless supplementary insulation is provided.
6.6 Soldering. Care should be taken in soldering resistors, since all properties of a composition resistor may be
seriously affected when soldering irons are applied to terminals for too long.
6.7 Hum pickup. Design engineers confronted with the problems of hum pickup by resistors from attached
switches in any particular application should specify separate switches at an appropriate distance from the resistor.
6.8 Shaft locking device. Locking devices are commercially available which may be readily attached to any
standard bushing type resistor covered by this specification. These locking devices permit any degree of torque from
normal to complete locking of the operating shaft of the resistor. The locking bushing type resistor specified herein
provides the shaft locking feature without additional equipment.
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6.9 Derating. If it is desired to operate these resistors at ambient temperature greater than 70 C. The resistor
should be derated in accordance with figure 7.
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