We have for a long time wanted a temperature logger and this has resulted in this project. We choose to interface the thermometer through USB as this is todays best standard. When the thermometer is connected to the PC you operate it through my brothers program written in Realbasic.
Update: On request from Andre in Russia we have updated the pic program to enable it to use a DS18B20 thermometer chip with 0.1 C resolution. The Windows software is updated accordingly.
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This is the USB thermometer pcb with all components mounted. We use a either a 18F2550 or a 18F2553 PIC to interface the USB, a DS1307 I2C as real time clock and a 24LC1025 I2C serial EEPROM to store the measurements. You can connect either a DS18S20 or a DS18B20 as a temperature sensor.