Water bath 8-channel calibrator using Android application as a test parameter interface and data storage system

The water bath is one of the laboratory equipment that serves to maintain the temperature of the water in the chamber. This chamber is used to soak reagents, incubate cells, and even melt substrates. Water heater calibration is a function feasibility test to determine whether the water bath is still suitable for use. Calibration is done by comparing the measuring instrument with the measuring material to be calibrated using national or international measuring standards. This article presents the research results on engineering a water bath calibrator using 8 channels whose measurement results can be displayed and saved to a CSV-type file via a smartphone application. The physical design is to place eight DS18B20 sensors at 8 different points in the water bath chamber to get the temperature value at each test point. The Atmega328P microprocessor processes the temperature detection results from the sensor and is then sent via the HC-05 Bluetooth module to the MIT App Inventor application, which is then displayed and stored in the android application. The measurement results of the calibrator prototype were compared with the measurement results of the national standard Multi-Channel Thermocouple Temperature Data Logger of the Madge-Tech brand. Analysis of the test results shows that the value of the test parameters at 8 points that appear through the smartphone application tends to increase with the same degree of increase as the value of the test results of the comparison tool. This fact proves that the thermodynamic phenomenon is in accordance with the working principle of this prototype and the working principle of data communication works well in this study.