MIL-DTL-16034B
4.5.12 Temperature influence. Meters shall be tested at temperatures 20 °C above and below the reference
temperature. Reading shall be taken at not less than four points on the scale, one of which is at or near the maximum
scale value and the temperature influence computed. The temperature influence shall be considered one-half the
percentage change in indication caused by the 20 °C departures from the reference temperature. If the influences
above and below the reference temperature are not equal, the greater value shall be considered the temperature
influence (see 3.18).
4.5.13 Low-temperature exposure. Meters shall be exposed to a temperature of 0 °C for 16 hours, and at the end
of the period meter readings shall be taken. It shall be observed whether or not the meter indicated freely at all parts of
the scale while at 0 °C. Meters shall then be maintained at room temperature for sufficient time to attain thermal
stability, and meter readings repeated. The permanent change in indication resulting from the low-temperature
exposure shall be noted (see 3.19).
4.5.14 Overload.
4.5.14.1 Momentary overload. The current circuits of AC and DC meters shall be subjected to 10 applications of
current equal to 10 times end-scale value. The current shall be applied nine times for a period of one-half second each
time, with 1-minute intervals between successive applications, then followed by one application for a 5-second period
(making a total of 10 applications during an elapsed period of 9 minutes, 9½ seconds), during which time current is
applied for a total of 9½ seconds. (If the meter is provided with a voltage circuit, normal voltage shall be applied to the
meter during the whole period of test.) After 1 hour at reference temperature following the above test, the pointer shall
be reset to zero and the change in indication determined. This test should not be applied to external shunts (see 3.20.1).
4.5.14.2 Sustained overload. Meters shall be subjected for 8 hours to an application of energy 20 percent greater
than end-scale value. Immediately after the load is withdrawn at the end of the 8-hour period, the temporary zero shift
shall be determined. Sixteen hours after completion of the 8-hour overload period, the permanent zero shift shall be
noted. The pointer shall then be set to zero and the permanent change in indication determined (see 3.20.2).
4.5.15 Dielectric stress. When performing this test, portable meters with nonmetallic cases shall be placed on a
metallic platform; switchboard meters with nonmetallic cases shall be mounted on a metallic panel. All meters shall be
subjected to a voltage of 2,600 volts rms applied between all external live parts of meter and:
a.
The metallic platform or panel on which the meter is placed or mounted, or the meter case, if the case is
metallic
b.
The zero-adjuster, and range selector switch, when applicable
c.
All exposed metal parts not a live part of the meter
The voltage shall be nominal 60 cycles per second in frequency and shall approximate, as closely as possible, a
true sine wave in form. The voltage shall be applied continuously for a period of 60 seconds. The test voltage shall be
measured by the voltmeter method whereby the measuring meter derives its voltage from the high-potential circuit,
either directly or by means of a voltmeter coil placed in the testing transformer. To avoid voltage surges, the applied
voltage shall be raised to its full value gradually, and upon completion of the 60-second test period shall be gradually
reduced. The test shall be made using high-potential test prods having not less than ⅛-inch radius tips. Any damage or
flash-over shall be noted (see 3.21).
4.5.16 Insulation resistance. Meters shall be placed on a metallic platform or mounted on a metallic panel as
specified in 4.5.15. Using a potential of 500 volts direct current, the insulation resistance shall be determined between
all external live parts and the metallic platform or panel on which the meter is placed or mounted, or the meter case, if
the case is metallic (see 3.22).
Note: For conformance inspections of meters furnished with external accessories as an integral part, the
complete meter (meter with accessories) shall be tested.
4.5.17 Vibration. Meters shall be mounted in various positions upon a vibration platform and subjected to
vibration for a total period for 24 hours. The construction of the vibration platform shall be such as to give simple
harmonic motion at a frequency of 400 cycles per minute, and with a maximum amplitude of 1/16-inch (1/8-inch maximum
total excursion) at the horizontal centerline of the meter. The change in indication shall then be determined (see 3.23).
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