Temperature measurement and designing control systems with thermocouple

Objective: In this study, the primary aim is to produce and characterize new thermocouples which are active temperature sensors by using two different metal sticks with spot welding. Our second goal is to design unique temperature measurement and control device based on ARDUINO by using a K and E type thermocouples, MAX6675, and INA114AP amplifiers. It is aimed at comparing the measurement performance of the developed device with other measurement devices by using statistical methods. Material and Methods: Temperature-voltage characterizations of the K type thermocouple which is used in this study were carried out with a Keithley-2182A Nanovoltmeter in a heated-cooled water bath. The K and J-type thermocouple sticks were removed, and a new E-type thermocouple was produced by using spot welding, and its temperature-voltage characterization was also performed in the same way. After that, two different ARDUINO-based temperature measurement and control systems which work with K and E type thermocouples, including i- MAX6675 module and ii- INA114AP amplifier, were designed and produced using Proteus software and turned into a device. The MAX6675 section of the device has internal compensation, while the "cold junction compensation" for the INA114AP section is designed through ARDUINO software. This uniquely developed device allows the user to manually adjust the desired temperature range for the operation of device which works with 230V and wanted to be controlled through menu. If temperature which is measured by the K-type thermocouple set exceeds the lower or upper temperature limit which is set by user, the power of device which is supposed to operate within the temperature range set by the user (230V AC) will cut off, and an alarm will be triggered. The temperature measurement accuracy of the developed device was compared with other measurement devices (Keithley-2182A Nanovoltmeter, RuoShui97 Digital Multimeter, and Fluke 17B+ Digital Multimeter) for heating and cooling experiment, and the success of our device was statistically analyzed with the reference of Keithley-2182A device. For comparison, the same heating-cooling water bath of thermocouple characterization experiment was used for measurements with all devices. Results: The heating-cooling characterizations of the E-type thermocouple which are produced by using spot welding and by K-type thermocouple were consistent with the characteristic values provided in the literature. It was observed that the INA114AP-based module of the temperature measurement and control device which is designed through Proteus software provides more accurate temperature measurements compared with the MAX6675-based module. Conclusion: It was concluded that the INA114AP-based section of the temperature measurement and control device designed for usage with the K and E type thermocouples provides more accurate measurements than the MAX6675-based design, and so, it can be successfully used for temperature control of devices operating with 23 0V AC. It was also concluded that, with further development of the system and proper implementation of the necessary "cold junction compensation", it would be possible to operate with other thermocouples as well.