Question 4.56: A small pressure transducer has the characteristics shown in......
A small pressure transducer has the characteristics shown in Figure P4-56. Design an interface that will operate between 7- and 32-psi. An input of 7 psi should produce –5 V and 32 psi should produce 5 V. The transducer is modeled as a voltage source in series with a 500 Ω resistor that can vary ± 75 Ω depending on the pressure.
The OP AMPs you must use have a maximum closedloop gain of 2000. Your available bias source is 5 V.
Using MATLAB, determine the gain and bias required to complete the interface. We can find the gain and bias by solving a pair of linear equations relating the input and output specifications.
Script File
clear all
syms K vBias
% 7 psi: 1000 microV input maps to a -5 V output
% 32 psi: 400 microV input maps to a 5 V output
Eqn1 = '-5 - (K*1000e-6 + vBias)';
Eqn2 = '5 - (K*400e-6 + vBias)';
Soln = solve(Eqn1,Eqn2,'K','vBias')
K = double(Soln.K)
vBias = double(Soln.vBias)
Soln =
K: [1x1 sym]
vBias: [1x1 sym]
K =
-16.6667e+003
vBias =
11.6667e+000
The gain is K = -16667 and the bias voltage is 11.667 V. The following circuit will meet the specifications for the interface. Note that the bias source is inverted so that the output bias has the correct sign.
