“A four-channel temperature datalogger for PT1000 probes measured by Atmega32U4 and logged on SD-card.
My intention was to develop a temperature measuring and datalogging device because I had none.
It should show the temperature measurement data on a display and at the same time store it on a SD card. That was the main requirement I set for myself. In addition, it should have batteries for wireless operation, so the whole system must be designed for low-power consumption.
The application is quite simple, you turn on the logger and start the operation. You can make various settings for the logger operation. In the video you can see the settings with two active channels and an automated measurement every 5sec.
The µC I chosen was the Atmega32U4 because it has a built-in USB interface and is easy to program via the Arduino IDE. Everything is powered by a linear voltage regulator (TPS782) with 3.3V, which is optimal for this application because it consumes only 500nA during operation. Three AAA batteries provide the power supply.The voltage at the PT1000 is amplified once by a differential amplifier and measured by the analog input of the Atmega. The measuring range is defined from -25°C to 120°C and corresponds to the voltage from 0V to 3.3V.The measurement data is displayed once on a 128x64 Oled and optionally stored on a FAT16 SD card. The time and date is provided by a real-time clock (RV3028C7), which only consumes 45nA in idle mode. Additionally, there are three user buttons for navigating in the menu and a reset button on the back.And two user leds and a USB interface. Almost all externally accessible parts are still equipped with ESD clamping diodes.”