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Regarding a piezo sensor like this one, if I want to read the output by an ADC does it require a buffer, a instrumentation amplifier or a type of interface?

I don't know the output impedance of it and cannot figure put how to condition before I hook it up to an ADC.

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2 Answers 2

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This is not a piezo sensor, it is a thin-film sensor. It is basically a pressure-sensitive resistor, so you just need to put it in a voltage divider with another resistor and measure the resulting voltage with your ADC. The pressure/resistance curve on page 2 of the data sheet should give you an idea of what value you need for the fixed resistor in the voltage divider.

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Comined with Elliot's information, the Specifications on the last page state:

  • Open resistance is >10MΩ
  • With a trigger force of 20g, the resistance is about 200kΩ
  • Max 6kg can be applied, and using the formula shown in the chart, this will result in a resistance of about:

$$y=153.18x^{-0.699}$$ $$y=153.18 \cdot 6000\text{g}^{-0.699}$$ $$y=153.18 \cdot 0.002285979$$ $$y=0.350166$$

Now this is not Ohms, this is the vertical scale of the chart. If the data is to be believed, a vertical value of near 7 equates to 20g actuation, so about 200kΩ. To scale this y value to Ohms then (assuming the vertical scale is linear):

$$\frac{200\text{k}}{7} = 28,571.42857 \text{Ohms/tick}$$ $$28,571.42857 \cdot 0.350166 = 10,004.74 \Omega$$

So the sensor is essentially "open" with less than 20g on it, and logarithmic from 20g to 6000g, with the lowest possible resistance being about 10kΩ.

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