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### Topic: Measuring 3- Wire Strain Gauge (Read 7365 times)previous topic - next topic

#### dc42

#15
##### Sep 22, 2011, 09:01 am
*If* the strain gauges are of the sort where one element increases its resistance and the other decreases, then to use all 4 I would connect them like this. Let the 3 terminals of each one be called C (common), I (increase) and D (decrease). Connect them in a ring using the I pins and D pins so that each I pin is connected to another I pin and each D pin is connected to another D pin. Then use the four C pins as the bridge inputs and outputs.

What this gives you is a bridge in which one of the resistors is made up of two I elements in series, its two neigbours are each made up of two D elements in series, and the diagonally opposite resistor is also made up of two I elements in series.

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#### mechatronicaproject

#16
##### Mar 25, 2015, 05:07 pm
Hi,

We are working on the same problem for a mechanical engineering project.
Unfortunately, we can't seem to get it working properly.

Using a LM358 amp we have wired the wheatstone bridge, arduino and the amp properly, as instructed in the post. When hooking the arduino up to to our pc we get a steady stream of 2.5V.

However, when applying pressure on the strain gauges, no difference in voltage is noticed.
We have already varied the resistors to get different gains (x100, x1000) in the hope to notice a difference but that seemed not to change anything.

Is anybody willing to help us, any help would be much appreciated!