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I want to accurately measure the resistance of a single strain gauge, unaffected by lead wire resistance and with ratiometric ADC conversion to compensate for excitation drifts. I know for RTD measurements its common to use a simple circuit like below:

schematic

simulate this circuit – Schematic created using CircuitLab

Unfortunately this works poorly for strain gauges, since the full swing of the signal is very low, on the order of V_exc/2 +- 10 mV, so a lot of the usable signal vanishes into ADC noise.

Naturally a bridge configuation + instrumentation amplifier comes to mind, but after trying for quite some time I just cannot come up with a decent 4-wire connection. Best I can find is a 3-wire one like this: enter image description here

Since there a a lot of 4-wire strain gauge setups available commercially, there must be solution to this that I cannot find. Can someone point me in the right direction here?

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  • \$\begingroup\$ This site is not product commercials, however what you are seeking is load cell amplifier or load cell front end with ADC. This one might fulfil your requests: aliexpress.com/i/4000385663309.html \$\endgroup\$ Commented Jul 24, 2020 at 16:33
  • \$\begingroup\$ Thanks for your answer Marko, but thats not what I'm looking for since it needs 4 remote gauges (or 2 + 2 resistors) if Im not mistaken \$\endgroup\$
    – Miomio
    Commented Jul 24, 2020 at 16:50

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I found a solution that works by copying the voltage difference at the gauge into a bridge through high input impedance op amps. Might not be the most elegant way but I think it should be OK.

4 Wire Strain Gauge Circuit

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