load cell

D. Abram

I have a load cell I'm trying to read with a BS2.· The cell has a four wire lead, two for a 10 VDC excitation voltage and 2 for output.· The output is rated at 2mv/V.··So I believe that at 100% capacity the cell will output 20 mv (10V x .002).· Total range of the output is 0mv to 20mv

After great deal of research I think I should be able to use an op-amp to scale the voltage up to the 0 -5v range that I could use the LTC1289 ADC to read the voltage and·translate the voltage reading to·the weight on the cell.· I have the details of the ADC but I need some direction on the op-amp portion of the circuit.

Any suggestions or pointers to reference material would be greatly appreciated.
·

Martin Hebel

What you really want is a good Instrumentation Amplifier.· We work with load cells in our classes.· The inst. amp amplifies the $%^& out of the actual signal·while cancelling out the noise (high CMRR).

The AD524 is a good, simple one with adjustable gains of 10, 100,·1000.· Do a search at www.digikey.com, and 'fairly cheap' at $16.· You can build an amp yourself with 3 op-amps, and·it's discussed in Parallax's "Process Control" text, but a good packaged one ensures very high precision resistances for good noise cancellation.

-Martin



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StampPlot - GUI and Plotting, and XBee Wireless Adapters
Southern Illinois University Carbondale, Electronic Systems Technologies

Mohamed Refky

The AD7730 is a complete bridge transducer ADC connected directly to the load cell and outputs a serial word and easy interface to BS2.

Search the forum for AD7730 you will find example code.