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I have designed a sensor board which gives a strain o/p based on wheatstone bridge principle(change in stress is measured through change in resistance).

But the starting value is not at zero level,it takes roughly 40 to 50 sec to stabilize (Please refer the attachment).

Could it be because of the internal capacitance of the board,if so how can it be reduced or avoided.

Thanks in advance

enter image description here

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  • \$\begingroup\$ What happens when you blow cold or hot air over the whole setup? \$\endgroup\$
    – maxy
    Commented Mar 19, 2014 at 6:41
  • \$\begingroup\$ The entire setup was kept under AC and was also kept at open environment both has the same result \$\endgroup\$
    – TSDCR
    Commented Mar 19, 2014 at 6:44
  • \$\begingroup\$ How about a circuit diagram? \$\endgroup\$
    – Andy aka
    Commented Mar 19, 2014 at 8:44

1 Answer 1

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A board capacitance * metallized strain resistance time constant is likely to be in the millisecond range. However the self-heating from I^2R thermal effects and temperature coefficient of the material is more-likely to have a time constant of a minute, if I imagine your design correctly.

Try lowering the bias and/or drive voltage to prevent self heating and increase the filtering of the noise to improve the signal to noise ratio at higher gain needed to achieve the same sensitivity.

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  • \$\begingroup\$ the charging time got reduced \$\endgroup\$
    – TSDCR
    Commented Mar 21, 2014 at 12:04

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