### PT100 RTD Thermal Sensor Integration

The EasyPiezi (Rev 1.1.x and Rev 2.x.x) utilize an extra amp channel to allow the use of a PT100 RTD Thermal sensor with minimal additional components. The circuit is based on E3D's daughterboard designed for PT100 sensors.

![](../../assets/schematics/PT100-Schematic.jpg)

The circuit outputs a DC voltage that corresponds to the RTD's change in resistance, which in turn changes based on the temperature of the RTD. This output shares a common ground with other parts of the circuit, so only one additonal output pin is required to utilize it.

As this is a direct voltage reading, the usual TH# inputs on most controllers cannot be used (unless the user removes the pullup resistor attached to the input). Instead, the PT100 input must be attached to a bare analog input pin (any of the pins labeled A##, like A5 on Atmega controllers)