Calibration
Dallas DS18B20 sensors can show small deviations from true temperature. Typical datasheet accuracy is about +/-0.5°C (from -10°C to 85°C).
Brautomat supports linear 2-point calibration.
2-point calibration with reference thermometer
Use a calibrated reference thermometer.
Heat a typical kettle volume to 40°C.
Enter the difference in
Offset 1 [40°C].Heat to 78°C.
Enter the difference in
Offset 2 [78°C].
Brautomat then applies this correction to future measurements.
During calibration, the sensor runs at 12-bit resolution (0.0625°C). Each calibration run records 60 samples (about 60 seconds), and the average is used.
In many setups, a 1-point calibration in an ice bath is already sufficient because DS18B20 offsets are often close to linear.
Calibration without reference thermometer
If no reference thermometer is available, use:
an ice bath (0°C)
boiling point at your local altitude
For the low point, prepare an ice bath with about 50% ice and 50% cold water and stir continuously.
For the high point, estimate local boiling point via altitude. At sea level (0 m, about 1.013 bar), boiling point is 100.0°C. Boiling point decreases by about 0.003354°C per meter altitude.
You can use tools such as: rechneronline boiling point calculator
For reliable results, keep boiling stable for at least one minute before starting the high-point calibration run.
Offset definitions:
Offset #1: difference between 0.0°C and first-run averageOffset #2: difference between local boiling point and second-run average
Calibration with clinical thermometer
A clinical thermometer can be used only in the lower range (up to about 40°C).
If using 40°C as upper calibration point:
Heat to 40°C.
Switch heating off.
Wait until temperature is stable for about 60 seconds.
Start calibration sample run.
Sensor calibration log file
A log file is written for each calibration. Example:
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