I'm making project where I would like to read from stain gauge sensor. It will use only one 1k ohm (or 350 ohm) strain gauge and 3 dummy resistors to complete bridge (1k or 348 ohm). I'd lik to feed signal from bridge to A8237 ICF amplifier and I'd like to know what is better way of remiving initial bridge offset Like there: First Way


Second Way

What I mean by sesnod way is that I'll connect DAC output with RA to one of bridge signals and adjust voltage.

Which one is better?

  • \$\begingroup\$ What is your acceptance criteria? \$\endgroup\$ Mar 26 '19 at 18:21
  • \$\begingroup\$ What do You mean by acceptance criteria in that case? \$\endgroup\$
    – Anrzej
    Mar 26 '19 at 19:40
  • \$\begingroup\$ How will you know if a solution is good if you have no criteria or specs? \$\endgroup\$ Mar 26 '19 at 20:12
  • \$\begingroup\$ What I mean... I have situation similar to the example in "First Way" website, and I'd like to decide which way of removing offset will give me better results at ADC. \$\endgroup\$
    – Anrzej
    Mar 27 '19 at 6:56
  • \$\begingroup\$ auto-calibration to flash memory? \$\endgroup\$ Mar 27 '19 at 9:41

Resistor tolerance error is likely to be many times the signal from one measly strain gauge, so an offset adjustment at the bridge will be needed. You can connect a DAC as shown for autozero function. Looking at the circuit again, the DAC should drive the input to A2.

  • \$\begingroup\$ Why I should drive A2 with DAC? I'm not even using A2, that only purpose is to set reference to half the supply voltage, I'm using just voltage divider to achieve that. "You can connect a DAC as shown for autozero function" - You mean to FB pin through RA, or to one or bridge signals through Ra? \$\endgroup\$
    – Anrzej
    Mar 27 '19 at 6:59
  • \$\begingroup\$ You can connect the DAC through Ra to the bridge or the voltage divider, I would avoid any feedback nodes. By autozero I meant software controlled zero. The DAC will be useless if the Amp is saturated. \$\endgroup\$
    – EinarA
    Mar 27 '19 at 23:14

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