The PT100 RTD Evaluation Board demonstrates how to bias a Resistive Temperature Detector (RTD) and accurately measure temperature. Up to two RTDs can be connected. The RTDs are biased using constant current source and the output voltage is scaled using a difference amplifier. In addition to the difference amplifier, a multiple input channel Programmable Gain Amplifier (PGA) MCP6S26 is used to digitally switch between RTDs and increase the scale up to 32 times.
The output of the difference amplifier is connected to a 12-bit differential Analog-to-Digital Converter (ADC) MCP3301. The ADC outputs serial data to the PIC18F2550 using a Serial Peripheral Interface (SPI). The data is transmitted to a PC using a USB interface.
A Graphical User Interface (GUI) is used to acquire the data. The acquired data is graphed as a real-time stripchart display. In addition, the user can select input channels, acquisition interval, and stripchart display buffer size.