MIL-DTL-16034B
4.5.2 Zero adjustment. The range of zero adjustment above and below the zero mark shall be determined. A
determination shall also be made as to whether the zero adjuster can be rotated through 360 degrees without damage to
the device or any part of the meter or without becoming inoperative or any part becoming adrift. Zero adjustment
devices not capable of rotation through 360 degrees shall be tested as follows: A screwdriver or similarly shaped tool
shall be prepared by shaping the point for maximum snug engagement with the zero adjust device. This tool shall be
mounted in a torque wrench which indicates torque of 10 inch-ounces. Ten ounces of torque shall be applied in both
clockwise and counter-clockwise direction. Distortion, damage or jamming in either direction shall be cause for
rejection.
4.5.3 Position influence (balance). The pointer shall be set to the center of the zero scale division with the meter
in the normal operating position. The meter shall then be tilted 60 degrees from this position in any direction, and the
deviation of the pointer noted (see 3.9).
4.5.4 Initial accuracy. Meters shall be checked for accuracy as specified in 4.5.4.1 or 4.5.4.2, as applicable.
4.5.4.1 Qualification test. After preliminary conditioning in the test circuit for 30 minutes at two-thirds scale
deflection, readings shall be taken and compared with corresponding reading of the standard meter. The test shall be
4.5.4.1.1 Direct-current reversal error. The change in indication produced by reversing the polarity of a DC
source of energy shall be determined for portable meters of 0.25 percent accuracy class designed for both AC and DC
measurement (AD meters). (see 3.10.1)
4.5.4.1.2 Wave-form effect. The change in indication produced by an abnormal wave form shall be determined
on portable meters of 0.25 percent accuracy class designed for both AC and DC measurement (AD meters). For this
test, a wave having the same rms value of a sine wave but a crest factor of not less than 2.4 shall be used. This wave
shape can be obtained by combining, in equal parts and proper phase relationship, the fundamental and the third and
fifth harmonics (see 3.10.2).
4.5.4.1.3 Selector-switch effect. After determining the initial accuracy, portable meters provided with a range
selector switch shall have the range selector switch subjected to a life test of 10,000 continuous no-load operations.
Each operation shall consist of making contact with each position, and returning to the starting position by reversing
the direction of rotation. The rate of operation shall be between 0.25 and 1 second per contact position. Upon
completion of the life test, the initial accuracy of the meter shall again be determined (see 3.6.4.1.1).
4.5.4.2 Conformance inspection. The conformance inspection of initial accuracy shall be performed under the test
conditions specified in 4.2 without preliminary conditioning (see 3.10).
4.5.5 Damping factor. Electric power sufficient to produce momentary end-scale deflection shall be applied to the
meter. The maximum momentary deflection shall be observed and recorded. After the pointer has come to rest, the
steady deflection shall be observed and recorded. When making this test, the circuit resistance shall be not less than
100,000 ohms and such that no additional damping is added to the system. The damping factor shall be taken as the
ratio of the steady deflection (in angular units) to the difference between the maximum momentary deflection and the
steady deflection in angular units. Example: If the maximum momentary deflection is 90 angular degrees and the
steady deflection is 75 angular degrees, the difference between the two is 15 degrees, and the damping factor (the ratio
of 75 degrees to 15 degrees) is 5 degrees (see 3.11).
4.5.6 Response time. Steady electric power sufficient to produce momentary end-scale deflection shall be applied
to the meter. The length of time, in seconds, required for the pointer to come to apparent rest shall be recorded. The
pointer shall be considered as having come to apparent rest when it has obtained the actual point of rest within one-half
the initial-accuracy requirement. The test shall be repeated five times, and the average length of time recorded for all
measurements shall be considered as the response time of the meter (see 3.12).
4.5.7 Power consumption. The power consumption shall be measured at end-scale deflection and recorded in
terms of current, voltage, voltamperes, or ohms, as applicable (see 3.13).
4.5.8 Frequency range. Unless otherwise specified (see 3.1), AC meters having a nominal frequency of 60 cycles
per second shall be tested for satisfactory operation at the extreme operating frequencies specified (see 3.14).
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