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Pressure Sensor Resistance Variation

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dansteinb

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I'm making use of a pressure sensor to produce an output voltage range depending on pressure but the sensor to sensor resistance variation is throwing off the output range.

Is there an analog compensation method for the varying resistances of Wheatstone bridge sensors?
 

The whole point of a Wheatstone bridge is that it's the RATIO of the resistors that matters, not the absolute resistance. What kind of sensor are you using?
 
I'm using the sensor linked below:
**broken link removed**
Sensor.jpg

I've attached the schematic for the circuit. The problem that I'm running into is that the output voltage range is different for each sensor. I would like to find a method to keep the output voltage range stable for any sensor used.
 

The variation of values between components of a given manufacturing lot is expected within a tolerance range. The calibration process at the firmware side, or addition of extra resistors in series are possible solutions to minimize the effect of this variation from part to part.
 
It's a little difficult to tell what's going on with that sensor from the data sheet. Is it a half-bridge? Full-bridge? quarter-bridge? It LOOKS like it's a full bridge, in which case, as I said, the absolute resistance shouldn't matter. However, it looks like the SPAN variation is enormous, i.e., the first column has "2.5...5.4"-That's greater than 100% tolerance. Does that mean the value for a particular sensor is 'somewhere' in that range? If so, you'll have to calibrate each unit.

And why are you using 741 opamps? Those are about 40 years old. I think you want a more modern precision opamp.
 
Hi,

If I remember right then there are "signal conditioning ICs" with non volatile calibration features especially for bridge sensors.
But I don't remember the name.

But I think the cheaper and more flexible solution is a microcontroller.

Klaus
 
Hi,
this is a stainless steel sensor with a great variance in offset an span. There is no other way than to do an an individual calibration for each sensor or to buy a calibrated and compensated sensor.
Do you need a stainless stell product ?
 

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