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Appendix D - Bridge Circuits

A bridge circuit generally outputs a small differential voltage. The LJTick-InAmp provides the amplification needed to acquire such a signal, converts the differential signal to single-ended, and provides a 2.5 volt reference voltage (VREF) that can be used for excitation.

A common example would be a Wheatstone bridge made of 350 ohm strain gauges. If VREF/GND is used to provide the excitation voltage for the bridge, it will draw about 2.5/350 = 7 mA, and the common mode voltage (Vcm) of the differential signal will be about 1.25 volts. The outputs would be connected to IN+ and IN-. If Voffset is set to 1.25 volts and the gain is set to 201, the allowable input range for the LJTIA is –0.00616 to +0.00622 volts (with 0-2.5 volt output).

2 comments

How about a diagram to show how this should be connected in this configuration? Thanks.

A diagram is a good idea.  In the meantime, see the diagram at Wikipedia.  Vref connects to "A" and GND connects to "C".  Then "B" and "D" connect to IN+ and IN-.

Forum topic #4376 has good information also.