Pressure sensor with full Wheatstone bridge configuration

Hi all!

I would like to use a mV output pressure sensor to one of my projects. Internally the sensor uses a resistive full (4 active arms) Wheatstone bridge configuration. The output of the sensor is a differential signal from pins V(+) and V(-).

What I would like to ask is if there is any chance that the output of the sensor goes below zero, although keeping the mentioned polarity for the output pins. Thus, if there is any chance that V(+)-V(-) < 0. This is a general question regarding the sensors that integrate a full bridge configuration. At least to me, this is not obvious. And note, it is important to know this in order to to design correctly the amplification stage circuit.

I hope that someone knows the answer.

Re: Pressure sensor with full Wheatstone bridge configuratio

Generally, this sensors have data sheets and specifications. They tell about the circuit and the electrical data. At zero pressure
(assuming you have a relative pressure sensor), the differential output voltage can be slightly negative due to offsets (-> specification).

For simple measurement applications, a single OP differential amplifier is most likely sufficient, a three OP true instrumentation
amplifier gives better performance.

Re: Pressure sensor with full Wheatstone bridge configuratio

FvM, thanks for your reply.

Yes you have right. This information is indeed written in the datasheet. For example it says that at zero pressure, the output is +/- 2mV. However, it is an absolute pressure sensors and I guess that the zero pressure will not be a real situation. What I really wanted to say with my question is if there is a possibility to have a negative output during the normal operation (not at zero pressure). For example, the datasheet says that the Span output is 100mV (typical). Nothing is said about negative. I know that the best is to ask the manufacturer. However, I really wanted to ask the same question at the forum.

Regarding the measurements, I intend to use a three OpAmp instrumentation amplifier. My only concern is whether I have to apply any offset voltage at the output or not. Note, that this issue is due to the single voltage supply of the design.

Re: Pressure sensor with full Wheatstone bridge configuratio

If zero pressure is not included in the used range, you don't need an offset. Applying near to zero pressure can be a good
method for sensor zero calibration, however. Only applies, if you need a zero calibration and have a suitable vacuum pump.