This reference design for the differential temperature measurement (DTM) subsystem of heat and cooling meters provides a fully digital alternative to thin-film platinum Resistance Temperature Detector (RTD) sensors. The Precision Temperature Sensor (PTS) achieves Class A RTD sensor accuracy from the –55° Celsius to 125° Celsius with zero calibration and Class AA accuracy with single-point calibration. The Digital RTD approach streamlines manufacturing processes by using integrated EEPROM memory to store user-defined parameters, eliminating the need to create and maintain accompanying documentation. The Digital RTD simplifies the analog signal processing by eliminating the offset and gain calibration steps of the analog to digital conversion required in traditional DTM systems. Electrostatic discharge (ESD) protection devices on the printed circuit board (PCB) protect against contact or air ESD strikes of up to 30 kV. The small size PCB fits into a 5.2-mm outer diameter metal sheath as commonly used with standard PT100/500/1000 sensors.
This digital RTD subsystem works with MSP430™ and SimpleLink™ microcontroller device families, using a four-wire digital interface.
- Fully digital precision temperature sensor as an alternative to platinum resistance temperature detectors; fits into standard 5.2mm sheath used in heat meters
- Eliminates precision reference resistor, RC-matched filters and impedance controlled signal traces used in two- or four-wire RTD configurations
- No calibration required to meet IEC/EN 60751-2008 Class A accuracy over -55 to 125°C; single-point calibration for Class AA accuracy
- Standard I2C interface to host microcontrollers (four-wire digital interface with I2C-bus + VDD + GND)
- Meets IEC61000-4-2 Level 4 ESD protection
- This subsystem is tested and includes firmware to interface with the MSP430FR6047 Ultrasonic Water Flow Meter Kit (EVM430-FR6047)