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  1. M

    load cell to AD620 op amp, circuit not working, is chip dead?

    I wrote the wrong value for the gain resistor in the first drawing, I've updated that and added more information. Odd anomaly: if I wire it up as shown, with the excite  voltage (4V as tested when not connected to anything) taken from the bias network, it then reads 0.41V... Mystified as to why...
  2. M

    load cell to AD620 op amp, circuit not working, is chip dead?

    Just a thought: if the reference voltage is 3V, the +supply is 6V, then isn't the negative supply then equal to -3V, relative to the reference voltage? Or am I missing something? (Probably.) Richard B
  3. M

    load cell to AD620 op amp, circuit not working, is chip dead?

    Okay, I think... If I increase the excite voltage to 4V so the sense voltages are approx. 2V, would that work? Not sure at all how I'd make a negative supply. 15 years ago, when I last used any electronic knowledge, I'd have known, but it's amazing how much gets forgotten if you don't use it...
  4. M

    load cell to AD620 op amp, circuit not working, is chip dead?

    Thanks, Hero999, I tested the outputs from the load cell, with a 3V supply voltage, the sense outputs are both 1.5V, with a maximum change of 1mV under physical load.(Which is all as expected from a wheatstone bridge) Obviously the sense voltage is below the figure of 1.9V for chip input, but...
  5. M

    load cell to AD620 op amp, circuit not working, is chip dead?

    A couple more relevant bits of datasheet... Richard B
  6. M

    load cell to AD620 op amp, circuit not working, is chip dead?

    Hi, I'm building a machine that will utilise a load sensor from a digital weighing scale. The load sensor has a built in wheatstone bridge, and I'm using an AD620 op amp to get the signal up to a readable level. The first circuit is for this. There is a resistor network to provide a 3V...
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