Testing a calibration method for temperature sensors in different working fluids

Temperature is one of the crucial parameters in every aspect of life; therefore, it is essential to be able to measure it accurately. Temperature data acquisition utilizing a K-type thermocouple and MAX6675 module as cold junction compensation is being increasingly used by researchers because of its availability and relative ease of use. Ktype thermocouple and MAX6675 can be used as valid data acquisition if the sensors are properly calibrated. This research proposes a calibration method for K-type thermocouple and MAX6675 sensors based on Arduino microprocessor with DS18B20 thermistor as the reference, which has been previously calibrated with the ASTM-117C thermometer. Calibration was performed at ambient conditions utilizing the energy from the environment where four K-type thermocouple and MAX6675 sensors were calibrated alongside two DS18B20 sensors in ambient water for 24 hours. To increase the accuracy of the K-type thermocouple and MAX6675 sensors, simple mathematical methods were used in Arduino coding, thereby providing automatically calibrated values. After calibration using the proposed method, the sensors then were used in reading temperatures of ambient air and water. The result of this study is simple methods to improve the accuracy of K-type thermocouples and MAX6675 sensors to be used for reading temperature values in different working fluids using Arduino Microprocessor. The error value before calibration was 4.9% compared to 0.42% and 0.61% after calibration in ambient-water and ambient-air respectively.