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3-1 INTRODUCTION. This chapter contains a functional description of the pressure and differential pressure
transducer.
3-2 FUNCTIONAL DESCRIPTION. The transducers consist of a piezoresistive strain gage
transducer/electronic assembly characterized for temperature variations. The sensor is vented to atmosphere for
gauge pressure less than 600 psi, and all compound ranges. For gauge pressures of 600 psi and greater and for gauge
ranges that specify psis references, the sensor is referenced to 14.6 psi. For all absolute pressures, the sensor is
referenced to 30 inches of Hg. vacuum.
3-2.1 The 4-20 mA dc output pressure transducer receives a 28 Vdc input power on the pin A (+ signal) and
pin B (- signal) on the MS connector. The housing is grounded through pin C on the MS connector.
The 0-5 V dc output pressure transducer receives a 28 V dc input power on the pin A (+ power) and pin B (-
power) on the MS connector. Pin D is the (+) voltage out signal lead and pin E is the (-) voltage output lead. The
housing is grounded through pin C on the MS connector.
The ground wire of the pressure transducer, pin C of the MS connector, must be
connected to earth ground to insure proper operation of the pressure transducer. In order
to avoid "Ground Loop" conditions, there should only be one earth ground to a loop.
3-2.2 Input power and signal are EMI protected by two filters and capacitors mounted on the RFI assembly in
the transducer housing. The output voltage is also EMI protected with two filters.
3-2.3 Input pressure is applied through a MS 16142, 1/4 inch O.D. connection to a diaphragm in the sensor
assembly. Pressure on the diaphragm causes the strain gage to change resistance proportionally to the pressure
applied. The pressure transducer's electronic circuit converts this resistance change into an electrical (4-20 mA dc) or
( 0-5 V dc), depending on option, signal that varies in proportion to the applied pressure.
3-1
CHAPTER 3
FUNCTIONAL DESCRIPTION
NOTE
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