MIL-DTL-52869C
APPENDIX A
TEST METHOD 2
PERFORMANCE TEST
1.
TEST APPARATUS:
a. Power supply, dc (2 required) - constant voltage, adjustable from 20
to 30 Vdc, 100 mA minimum current capacity, line and load regulation 0.5
percent or less, ripple and noise 1 mV P-P.
b. Sound level meter (with microphone) - capable of measuring single
frequency radiated ultrasonic energy at frequencies from 10 to 40 kHz,
calibrated to measure sound pressure level (SPL) in dB referenced to 0.0002
microbars.
c. Wideband ultrasonic signal generator (WUSG) - capable of radiating
ultrasonic acoustic energy, continuous wave (CW) and in bursts of CW for
durations of 40 milliseconds (ms) and 5 seconds, at adjustable amplitude from
30 to 80 dB above RSPL over a frequency range from 10 to 40 kHz.
d.
Oscilloscope (scope) - general purpose.
e.
Signal generator - sine wave of 26.3 kHz, 1 V rms into 600 ohms.
f. AC voltmeter - true rms, calibrated to display the rms value of a
waveform and the corresponding dBm (decibels with respect to 1 milliwatt for
600 ohm load), accuracy 1 percent of full scale.
g.
Frequency counter - range, 10 to 40 kHz.
2.
TEST PROCEDURE:
2.1
Alarm criteria.
a. Place 19 of 20 receivers in an acoustically quiet area.
One test
receiver shall be excited by the ultrasonic test signals.
b. Connect all 20 receivers to terminal board TB2 of the processor by
500 feet of cable.
c. Set the processor sensitivity to maximum (position 5) and the test
receiver gain to 10 dB below maximum (position 7).
d. Apply 30 (+0, -0.3) Vdc through 2.7k ohms across processor terminals
TB1-1 and TB1-2 and connect oscilloscope across these terminals to monitor
alarm function.
e. Place the PUS in operation by applying 20 ±0.3 Vdc to processor
terminals TB1-7 (positive) and TB1-8.
f. Set up the wideband ultrasonic signal generator so that ultrasonic
test signals may be generated at any frequency or swept over the range of
frequencies between 10 and 40 kHz and at output levels that produce the
desired SPL at the receiver microphone. The SPL shall be monitored by placing
the sound level meter microphone as close to the receiver as possible and
reading SPL at that point.
g. Apply a 5-second burst of ultrasonic test signal at 25.5 kHz and an
SPL at the receiver microphone of 60 dB above a reference sound pressure level
(RSPL) of 0.0002 microbar. The PUS shall alarm.
h. Apply a 40 ms burst of test signal at 25.5 kHz and 60 dB above the
RSPL every 4 seconds. The PUS shall alarm on the fourth burst. As indicated
on the oscilloscope, the alarm duration shall be from 0.5 to 1.5 seconds.
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