MIL-DTL-62741A(AT)
4.2.3.5 Input channel Mux select. To determine conformance to 3.3.5, for each (+, -)
input pair specified in table II, the corresponding bit pattern shall be applied to BUS 0 through
BUS 5 (P1-21 through P1-26) and control signals conforming to the waveforms shown in
figure 3. A dc voltage (within the input voltage range specified) shall be applied to the specified
input and the input signal, times the attenuation ratio, shall be verified to be present at U10 pins
1 (+) and 3 (-).
4.2.3.6 Input channel attenuation. To determine conformance to 3.3.6, the channels listed
in table II that have an attention ratio greater than 1:1 shall be selected. For each, the attenuation
ratio shall be verified to be within the tolerance shown in table II using the procedure in paragraph
4.2.3.5.
4.2.3.7 Signal processing.
4.2.3.7.1 Instrumentation amplifier. To determine conformance to 3.3.7.1, the tests of
4.2.3.7.1.1 and 4.2.3.7.1.2 shall be performed.
4.2.3.7.1.1 Gain adjust. Select the first Mux channel listed in table II. Select a gain of 1
as listed in table III. Select filter -3dB frequency of 6 kHz as listed in table IV. Ground pins
P1-65 and P1-67. Apply a variable voltage dc source to P1-68 and adjust the voltage until the
voltage at U12-7 is 0.000 Vdc. Remove P1-65 and P1-67 from ground. Apply 3.5 Vrms ac at
100 Hz to P1-65 (+) and P1-67 (-). Measure the voltage between P1-65 and P1-67 and note the
value. Adjust R3 (gain adjust) until the ac voltage at U12-7 is equal to the previously noted
value.
4.2.3.7.1.2 CMRR adjust. Select the input channel P1-55/P1-53 as listed in table II.
Ground pins P1-55 and P1-53. Select gain of 60 as listed in table III. Select a filter -3dB
frequency of 6 kHz as listed in table IV. Apply a variable voltage dc source to P1-68 and adjust
for 0.000 Vdc at U12-7. Disconnect P1-55 and P1-53 from ground. Apply 14.14 Volts root
mean square (Vrms) alternating current (ac) at 100 Hz to P1-55/P1-53 (both connected to plus),
and a ground. Adjust R10 for minimum ac voltage at U12-7. Verify that the ac voltage at U12-7.
Verify that the ac voltage after adjustment is no greater than 8.4 millivolts root mean square
(mVrms).
4.2.3.7.2 Summing amplifier. To determine conformance to 3.3.7.2, the following test
shall be performed. Select the first Mux channel as listed in table II. Ground P1-67 and P1-68.
Apply a variable voltage dc supply to P1-65. Adjust the voltage at P1-65 until the voltage at
U10-7 is 0.000 Vdc. Verify that the summing amplifier offset voltage at U12-14 is not more than
+11 mVdc. Adjust the voltage at P1-65 until the voltage at U10-7 is +5.000 Vdc. Verify that the
voltage at U12-14 is +5.000 + 0.01 Vdc when the previously measured summing amplifier offset
voltage is subtracted. Remove P1-68 from ground. Apply +5.000 Vdc to P1-68. Adjust the
voltage at P1-65 until the voltage at U10-7 is 0.000 Vdc. Verify that the voltage is U12-14 is
-5.000 + 0.005 Vdc after the summing amplifier offset voltage is subtracted.
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