MIL-DTL-27188C
4.5.7 Vibration. The indicator shall be subjected to a vibration test in accordance with
MIL-STD-810, method 514.2, equipment category b.1, procedure I, curve B. A synchro signal
shall be maintained on the stators of the indicator synchro to provide an indication of 45 psi.
Pointer oscillation shall not exceed 5 psi double amplitude. Upon completion of this test, the
indicator shall be subjected to the scale error test at room temperature. The scale errors shall not
exceed the tolerances specified in table II.
4.5.8 Low temperature. The indicator shall be subjected to a temperature of -55 °C ± 2 °C
for a period of 4 hours. While at this temperature, it shall be checked for friction and scale errors
and shall not exceed those specified in table III. The response time shall not exceed 3 seconds.
4.5.9 High temperature. The indicator shall be subjected to a temperature of 71 °C for a
period of 4 hours. While at this temperature, the indicator shall be checked for scale errors. The
scale error and friction tolerances shall not exceed the values specified in table III. The response
time shall not exceed 3 seconds.
4.5.10 Fogging. The indicator shall be placed in a controlled ambient temperature of
85 °C ± 5 °C for a minimum period of 2 hours. Within 10 seconds after removal from the oven, the
indicator shall be immersed to a depth of 1/4 inch in an ice water bath maintained at 0 °C to
7 °C. After 3 minutes, the indicator shall be removed from the fluid bath and quickly wiped dry
(compressed air shall not be used). The cover glass and dial shall immediately be inspected and
any evidence of fogging or damage shall be cause for rejection.
4.5.11 Secondary voltage. The maximum open circuit voltage shall be measured between
any two secondary leads and shall be 11.8V ± 3 percent. The variation between the three
maximum secondary voltages on the indicator synchro as measured between any two stator leads
shall not exceed 0.2V.
4.5.12 Magnetic effect. The indicator, first not operating and second, operating on rated
voltage, shall be rotated in a vertical plane around a short bar magnet compass with the nearest
part of the indicator 5-1/2 inches from the compass and magnetically east or west of the center of
the compass. Starting directly under the compass, the indicator shall be held in positions of
0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees and
315 degrees from the initial position. At each of these positions, the indicator shall be rotated on
its own horizontal axis until it is in its normal upright position. The horizontal magnetic field
intensity shall be 0.17 oersted to 0.19 oersted. Deflection of the compass at any of the specified
positions shall not exceed 3 degrees.
4.5.13 Effect of lead length. The indicator shall not change more than 1 degree of arc
when the lead length between the indicator and transmitter is changed from 5 feet to 500 feet
using number 20 AWG wire. Equivalent resistances may be substituted for the added wire
length. The ground lead shall be kept short.
4.5.14 Temperature-altitude. The temperature-altitude test shall be conducted in accordance
with MIL-STD-810, method 504, Procedure I (except the temperature shall be -55 °C) with a
chamber pressure equivalent to an altitude of 100,000 feet. The rate of pressure change shall not
exceed an average of 3 psi per second while under these conditions and at the end of 1-hour period, a
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