Opamp for converting signal from pressure transducer to direct readout on voltmeter

[rkovach12]

I am trying to use an opamp to convert the signal from a pressure transducer to a direct readout on a voltmeter. The pressure transducer has an output from .5 to 4.5 volts and is linear to 5 volts referance voltage supplied to it. At 0 psi, the output is .5 volts and at 500 psi, the output is 4.5 volts. I have designed the circuit with LTspice, and the simulator works as it should. .5 volts in reads 0 volts at meter and 4.5 volts in reads 5.00 volts at meter. If I input any other value and read the output, .9 volts in reads .50 volts at meter for example, everything works as designed. The problem I am having is that after building the circuit, the readings do not match the simulator. At .5 volts input, the reading at the output is 0 volts as expected. Also at 4.5 volts input the reading at the output is 5.00 volts as expected. If I input a voltage between this range the output is not the same as the simulator shows. If I input 2.5 volts, the output should read 2.50 volts as the simulator shows. What I am reading at the output is 2.35 volts. Is this because the simulator uses an "ideal" opamp and I am useing a 741 opamp? If a differant opamp will fix my problem, can anyone recommend what I shoud use?

 

[BurnOut_tesla]

Re: Opamp circuit

Try to use opamp with unity gain configuration

 

[albbg]

Re: Opamp circuit

I think you are using the op-amp as a subtracting amplifier with gain 1.25 and offset 500 mV. It should works without any problem. Did you take into account the output impedance of the transducer ? Could you show the schematic ?

 

[alfredop]

Opamp circuit

Are you minimizing the input offset voltage by using the proper resistance between pins 5 and 1? This is something that you probably didn't have to do in simulations but that may be required in your prototype. The input offset voltage amplifies along with your signal and it will change your expected DC output level.