# What type of signal conditioning is needed for this type of sensor?

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.

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.

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.