MIL-DTL-16034B
4.5.9 Frequency influence. Alternating current meters shall be calibrated at nominal frequency, then at
frequencies 10 percent above and 10 percent below the nominal frequency, and the change in indication determined
(see 3.15).
4.5.10 External-field influence. This test applies to all switchboard meters and to 0.25 percent accuracy class
portable meters. The meter shall be placed at the center of a four-turn coil, 50 centimeters in diameter, carrying a
current of 50 amperes of the same kind and frequency as that which actuates the meter mechanism, and which
produces a field of approximately 5 oersteds at the center of the coil. Readings shall be taken with the meter at various
positions in the center of the field (see 3.16).
TABLE VI. Procedure for determining heat effect at 65 °C.
Cycle number
Period (hours)
Step number
Procedure
1
Take initial reading at reference temperature.
Place meter in chamber at 65 °C and maintain that temperature
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2
for the remainder of that period.
1
3
Read meter while at 65 °C at the end of step 2.
Allow chamber and meter to cool down to the reference
8
4
temperature during this period.
5
Read meter while at reference temperature at the end of step 4.
Raise temperature of chamber and meter as rapidly as possible to
16
6
65 °C and maintain that temperature for the remainder of the
period.
2
7
Read meter while at 65 °C at the end of step 6.
Allow chamber and meter to cool down to the reference
8
8
temperature during this period.
9
Read meter while at reference temperature at the end of step 8.
Raise temperature of chamber and meter as rapidly as possible to
16
10
65 °C and maintain that temperature for the remainder of the
period.
3
11
Read meter while at 65 °C at the end of step 10.
Allow chamber and meter to cool down to be the reference
8
12
temperature during this period.
13
Read meter while at reference temperature at the end of step 12.
NOTE:
1. It is the intent to specify a test coil, which will produce a uniform field of approximately 5 oersteds through the
case of the meter. Therefore, coils of other size are equally suitable if an equivalent electrical field is produced.
4.5.11 Heat effect at 65 °C. Meters shall be maintained at reference temperature for a sufficient time (not less
than 2 hours) to attain thermal stability, and shall then be subjected to the three successive cycles of temperature
change listed in table VI. During this test, meters shall indicate freely (see 6.6.9) at all parts of the scale (see 3.17).
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