This circuit is design allows only a small diaphragm deflection sin it has limited elasticity, and this produces only a very small output signal, only about 1% modulation of the bridge resistance elements. This circuit is based on LM4041. This is the figure of the circuit.
The A2 circuit provides for the precision adjustment, via DCP1, of any transducer initial null offset error. To accomplish this, the bridge excitation voltage is programmable attenuated by the R2, R3, R4, R5 network and applied to DCP1. Boosting the ~10mV/psi bridge signal by 100x to a convenient 1V/psi output level is the job of the A3 non-inverting amplifier via its feedback and calibration network consisting of R7 through R9 and DCP2. The range for the zero adjustment voltage is from +22mV to –22mV. The resolution is 172uV and is proportional to the bridge excitation voltage, thus improving the temperature stability of the zero adjustment.
The net result of the combination of transducer and the Figure 4 circuitry is a signal conditioned precision pressure sensor that is compatible (thanks to DCP1 and 2) with full automation of the calibration process, is very low in total power draw (< 1 milli ampere, most of which goes to transducer excitation), and (equally important) is low in cost.
