Projects / Measurements, sensors and data acquisition
Autonomous high-accuracy PT1000 temperature sensor up to 260 C: 24-bit measurement path, Li-ion power, solar charging, 433 MHz radio and calibration.
The task was to develop a wireless high-accuracy sensor for a high-temperature zone. It had to operate autonomously, measure temperature with an external PT1000 and transmit data to a monitoring system without constant maintenance.
An autonomous high-accuracy temperature sensor was prepared. The external PT1000 is placed in the process zone, while the electronic module digitizes the signal with a 24-bit ADC, monitors power state and transmits temperature and diagnostic parameters over the radio channel.
Project materials
Engineering context
The temperature-sensitive element can be located in a zone up to 260 C, while the electronics must be placed separately.
Autonomous operation requires strict power control for the ADC, dividers, radio module and boost converter.
PT1000 measurement requires a stable measurement path and calibration.
Along with temperature, the system has to transmit battery state, solar-panel state and error flags.
Work done
Circuit design based on STM32L151 and ADS1220.
Support for PT1000 in 2-wire and 3-wire configurations.
Li-ion battery power.
Solar-panel input and charging circuit.
Power control for measurement and RF nodes.
Firmware with RTC wake-up.
Temperature calculation and storage of calibration coefficients.
Short radio protocol and diagnostic flags.
Details
The high temperature belongs to the measured zone, not to the PCB. The external PT1000 is connected to the electronic module through a connector, while the board remains in milder conditions.
The ADS1220 with excitation current sources and an external reference makes it possible to build an accurate PT1000 channel. Calibration and error checks were added for practical operation.
The sensor wakes up on schedule, performs measurement, transmits a short packet and returns to sleep. Solar charging and battery monitoring help use the device in hard-to-access points.
Contact
Contact us by email. We discuss custom electronics and automation tasks remotely with companies, labs, small businesses and individual customers worldwide.
