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NNTP-Posting-Date: Mon, 07 Oct 2002 14:50:50 CDT
From: email@example.com (John Fields)
Subject: Re: Strain gauge measurement circuit design
Date: Mon, 07 Oct 2002 19:06:40 GMT
Organization: Austin Instruments, Inc.
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On Sun, 6 Oct 2002 21:31:34 +0000 (UTC), "Simon Price"
>I am trying to construct a circuit that will enable me to measure the output
>from a full bridge strain gauge (Configured as wheatstone bridge).
>The slightly unusual requirement for this design is that I need the system
>to be mobile and be able to re-calibrate itself automatically in a new
>position ( and orientation - within reason).
>I have built a circuit that uses a digital pot to initially 'balance' the
>bridge to give a zero output. The signal from the strain gauge is then fed
>into a high gain amplifier stage and sampled by the ADC on a PIC MCU. The
>PIC also controls the digital pot in order to balance the strain gauge. The
>problem that I have is that the digital POT only has 1024 tap off points
>(The highest I've been able to find) on it and this is causing me issues
>when I try and balance the output as the step size is too large and the
>output from the amplifier stage just swings from one extreme to the other.
>Anybody out there got any thoughts / ideas on possible solutions? Anybody
>tried to do this before?
Use two pots:
Professional circuit designer
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