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From: "Simon Price"
Subject: Strain gauge measurement circuit design
Date: Sun, 6 Oct 2002 21:31:34 +0000 (UTC)
Organization: BT Openworld
Reply-To: "Simon Price"
NNTP-Posting-Date: Sun, 6 Oct 2002 21:31:34 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
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?
Any help gratefully received
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