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|  MIL-C-14858A (AR)
AMENDMENT 3
APPENDIX A
ANNEX 1
Each pressure level shall be applied three times, either by applying increasing pressure levels in
step a through step c, or by applying one pressure level at a time and returning to zero pressure
before repeating. Electronic system drift and stability shall dictate which method should be used.
If drifting is noticed, the pressure source shall be checked for fluid leaks. Drifting caused by
fluid leakage is too severe for either method to yield acceptable measures. Record the voltage
readings at each pressure level and calculate the average voltage for each pressure level.
A.4.5 Determine the transducer sensitivity (T.S.) for each pressure level by the
following calculations:
a. For picocoulomb per psi, use:
Average Transducer Output (volts) = T.S.
Pressure Input Level (K psi)
b. For psi per volt, use:
Pressure Input Level (K psi) = T.S.
Average Transducer Output (volts)
c. Record the resulting sensitivity in units of either picocolomb/psi or psi/volt. For the
transducer to be acceptable for use, the sensitivity value obtained at each pressure level shall not
be more than 2 percent different from the previously obtained sensitivity at that pressure level
nor more than 10 percent different from the original sensitivity determination for that transducer.
A transducer calibration record must be kept for each transducer. An example is at figure 1.
A.4.6 The transducer linearity shall be determined by the full-scale (F.S.) error band
method used in conjunction with the zero-based best straight line. The following is a description
of this method:
a. Determine the average transducer output voltage for each of these pressure levels:
40,000, 50,000 and 60,000 psi.
b. Determine the straight line, intercepting the origin (0,0), to the data points by
equalizing the error between the points below the line and the points above the line.
c. The + 1 percent Full Scale Error Bands shall be determined for the data group. The
transducer shall be determined to have full range acceptable linearity if all data points fall within
the appropriate error bands. If one or more data points fall outside the error band(s), the
transducer shall be considered to have unacceptable linearity.
A.4.7 An example for determining transducer linearity is at figure 2.
12 (28)
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