MIL-DTL-81963 Servocomponents, Precision Instrument, Rotating, Common Requirements And Tests, General Specification ForThis specification covers common requirements and tests for analog, digital and analog/digital precision instrument rotating servocomponents \(synchros, electrical resolvers, electrical, linear resolvers, transolvers, shaft angle encoders, servomotors, tachometer-generators, servomotor-tachometer generators, stepping motors, and gear heads\). This specification will be used with the applicable general specification, which covers a particular class of servocomponents \(for example, synchros\), together with the documents and the specification sheet that cite MIL-DTL-81963 as a direct reference detailing the specific requirement for the individual servocomponent.

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MIL-DTL-81963C

234.5 = 1/0.00427 (0.00427 is the temperature coefficient of resistance of 100 percent conductivity

IACS � International Annealed Copper Standard � copper at 0 degrees C).

4.9.12 Variation of brush contact resistance. The servocomponent shall be energized from a source of

constant current not to exceed 10 milliamperes and the brush contact resistance variation between

collector rings and brushes as exhibited by a change in voltage between each set of rotor winding

terminals shall be measured. The rotor shall be turned at one rpm. After the third revolution, the

measurement shall be performed through a complete revolution. The variation of brush contact

resistance shall be in accordance with 3.6.12. For qualification approval, the variation of brush contact

resistance shall be determined by the method described in 4.9.12.1.

4.9.12.1 Method of measurement for variation of brush contact resistance. Figure 13 is a basic bridge

circuit. Example shown is for synchro transmitters, receivers, and control transformers. R1 resistor is

adjusted to approximately twice the value of the DC rotor resistance. R4 resistor is set to 0.5 ohms and

will be used for setting the limits on the recorder. R2 and R3 resistors are used to balance the bridge. A

maximum of 10 mA through the rotor winding is recommended unless the applicable documents and the

specification sheet that cite MIL-DTL-81963 as a direct reference specifies a lower current value.

Balancing the bridge is accomplished by using R2 and R3 resistors with a suitable amplification factor set

on the dc amplifier and the center scale dc meter. The sensitivity of both instruments is increased as the

bridge is being balanced in order to produce a good null. If excessive drifting occurs, the rotor current

should be reduced until a steady null is achieved. The sensitivity of the recorder and amplifier are now

set at a level that will give a good reference on the tape when the resistance of R4 is decreased and

increased from the 0.5 ohm setting (0.0 to 1.0). After the reference marks have been established on the

tape, the rotor is turned by the one rpm motor with the recorder chart feed set at 5 mm per second.

4.9.13 Electromagnetic interference. When required by the applicable general specification, the

servocomponent shall be tested for conducted and radiated electromagnetic interference in accordance

with MIL-STD-461, while energized at the standard test voltage on those windings specified in the

applicable general specification and under the conditions of electrical or mechanical load also specified

therein. The conducted and radiated electromagnetic interference shall not exceed the limits as specified

4.9.14 Terminal or wire lead strength (see 3.6.14).

4.9.14.1 Wire leads. The force shall be applied at the extreme end of the lead and in a downward

direction:

a. While the servocomponent is held with its shaft vertically upward, in the case of servocomponents

having leads emerging from the back end of the servocomponent.

b. While the servocomponent is held with its shaft horizontal, in the case of servocomponents having

leads emerging from the housing periphery.

In the latter case, the servocomponent shall be so held that the lead exit is on the under side. For end-

emergent leads, the servocomponent shall then be turned through an angle of 90 degrees so that the

shaft axis is horizontal. While in this position, the housing shall be rotated once in each direction,

clockwise and counterclockwise, about the shaft axis through an angle of 360 degrees. For side-

emergent leads, the servocomponent shall then be turned through an angle of 90 degrees so that the

shaft is vertically upward. While in this position, the housing shall be turned once in each direction,

clockwise and counterclockwise about the axis of emergence of the leads (that is, end over end), through

an angle of 360 degrees. The method of applying force shall be such that the latter is borne by both the

conductor strands and the insulation. Wire lead strength shall be in accordance with 3.6.14.1