MIL-PRF-38230D
4.5.1 Scale and friction test. The transmitter shall be connected as shown in figure 1 to the
standard indicating unit through 300 feet of No. 20 AWG stranded copper. The transmitter
shall be subjected to the scale and friction error test of MIL-PRF-25435 at the test points in
table 1 herein. Tolerances for the scale error and friction test, performed alone or as
accept/reject criteria for other tests, shall be those in tables I and II.
4.5.1.1 Example. To verify that the transmitter meets the scale error tolerance after performing
the overpressure test, refer to the Note 2 column and select a test point. If 20 psi is selected, the
tolerance is ±1.75 psi. The standard indicating unit shall read 18.25 to 21.75 psi when
performing the scale error test. The friction error allowed for this test is ±0.5 psi as shown in
table II. Friction error is the difference in readings observed before and after tapping the
transmitter while applying the test pressure of 20 psi.
4.5.2 Vibration. The transmitter shall be subjected to the vibration test in MIL-PRF-25435.
The pointer oscillation and variation tolerances for the vibration error in table II shall be verified
while conducting the vibration test.
4.5.3 Reliability. The reliability test is required for qualification unless waived in the
acquisition document (see 6.2). See MIL-HDBK-781 for guidance.
4.5.3.1 Preparation. The transmitter shall be mounted directly to a vibration exciter without
vibration isolators and shall be placed in a chamber for temperature cycling. The transmitter
shall be connected to electrical power and the standard indicating unit as shown in figure 1.
Pressure shall be applied to the transmitter as required for a standard indicating unit reading in
the range of 40 to 60 psi.
4.5.3.2 Test. Rated power (see figure 1) and pressure shall be applied to the transmitter for 4
hours. The transmitter shall be subjected to random vibration for a minimum of 10 minutes
during each hour when power is applied. The level of the acceleration power spectral density
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(APSD) shall be: 0.025 g /Hz at 15 Hz increasing at a rate of 6 dB/Octave to 0.3 g /Hz at 52 Hz;
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maintain 0.3 g /Hz from 52 to 852 Hz; decrease at a rate of -12 dB/Octave to 0.01 g /Hz at 2,000
Hz. The axis of vibration shall be longitudal. Temperature cycling shall be conducted as follows:
the transmitter shall be brought to -65°F and maintained at that temperature for 4 hours; increase
the transmitter temperature to 330°F at a minimum rate of 9°F per minute and maintain at that
temperature for 4 hours; decrease the transmitter temperature to -65°F at a minimum rate of 9°F
per minute and maintain at that temperature for 4 hours. Continue this sequence during the
reliability test. The electrical power shall be turned off for 10 minutes after each 4 hours with
power applied to the transmitter. Testing shall be halted and the transmitter shall be subjected to
the scale error and friction test in MIL-PRF-25435 after each 250 hours of testing. The tolerances
shall not exceed 150% of the ambient temperature tolerances in tables I and II. Transmitter
malfunctions shall be recorded and repairs made. The transmitters shall not be recalibrated
during the reliability test. The reliability test shall demonstrate a transmitter MTBF of 2,000
hours with a confidence level of 90% and a discrimination ratio of 1.5.
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