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Many force transducers like this one are made up of Wheatstone bridges and they have sensitivity which relates the force/stimulus change to the voltage change. This small voltage change then is amplified by an instrumentation amplifier.

But I hear sometimes a phrase called "temperature compensation". Is it something done by a circuit in the amplifier or done mechanically in the transducer? I read couple of articles I have some information but I'm not sure I got it what it is all about. The reason is some of people I know talk things like "is the force transducer temperature compensated?" I'm not sure if they know what they talk about so I was trying to learn the meaning of it.

Below figure is from a text:

enter image description here

Is it nonsense to say: "Is this strain gauge(or a Wheatstone bridge sensor) temperature compensated"?

Can compensation only be done by a circuitry in the amplifier stage(not in sensor/Wheatstone/force transducer stage) which both sense the temperature and regulates the sensitivity? How is it done?

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  • \$\begingroup\$ hbm.com/en/6725/… Normally compensation is for known errors in temp coefficients. Yours are unknown. Consider Uref =5V or consider a constant current source that yields 5V nom. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 20 '18 at 0:30
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No it is not nonsense to say "Is this strain gauge(or a Wheatstone bridge sensor) temperature compensated?"

The strain gauge (bridge) has a temperature coefficient of gain. i.e at a fixed stain and Ve, Vout will change with temperature. But Vout also changes proportional to Ve. So if we change Ve with temperature we can compensate and keep Vout constant.

In practice this means putting a thermistor + fixed resistor/s in series with Ve. So the block labelled "temperature compensating network" is probably a thermistor + series and parrallel fixed resistors

You can compensate in the amplifier, or more practically, in software after digitising. But regardless, you need to know the temperature at the actual strain gauge e.g. by putting a thermistor at the strain gauge

Thermistor linearising and compensating networks are something that is cheap and quite easy to do, when you have a production system. But a bit of a nightmare for one offs. A pressure sensor factory finds it is a cheap way to do it. End users of uncompensated gauges would do digital compensation.

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  • \$\begingroup\$ How is the compensation done? Is it done inside the gauge by thermistor adjusting the Ve across the bridge? Did you mean that? \$\endgroup\$ – user16307 Mar 20 '18 at 11:00
  • \$\begingroup\$ Yes. Thermistor is inside the gauge. E is a fixed voltage. Ve changes with temperature as the thermistor resistance changes. \$\endgroup\$ – Henry Crun Mar 20 '18 at 19:03
  • \$\begingroup\$ I would love to see any paper about this. I couldn't find any when I googled the terms together: "temperature compensation" "Thermistor" "bridge" \$\endgroup\$ – user16307 Mar 20 '18 at 19:07
  • \$\begingroup\$ Thermistor companies do publish info about linearising thermistors - generally for use as a linear temperature sensor. Companies that make products that they linearise themselves (pressure sensors, crystal oscillators TCXOs) tend tokeep it as a trade secret. TCXO's are done by temperature testing each one, and swapping components. It is quite possible that gauges are predictable enough to have a single set of components that are fixed for all gauges. Or maybe not, depending on how much you pay for the quality of the compensation... \$\endgroup\$ – Henry Crun Mar 20 '18 at 19:28

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