High sensitivity infrared thermometry for precise temperature control in domestic induction cooktops

A theoretical analysis and implementation of a high sensitivity infrared thermometry system for a precise real-time temperature control in domestic induction cooktops is presented. The temperature in the cookware constitutes the control variable of the closed-loop power control system implemented in a commercial induction cooktop. The system includes an InGaAs PIN photodiode and a differential preamplifier which detects the infrared radiation (IR) emitted from the bottom of the cookware and the glass-ceramic top. The analysis includes an algorithm to discount the contribution of the glassceramic material from the total signal. In an infrared thermography application where an IR sensor is used, measuring the object's surface emissivity is crucial because it significantly impacts the temperature measurement result. For a precise temperature control with a maximum temperature error of 5°C in all range of cooking temperatures (60°C to 250°C) a cookware emissivity measurement system is included. The accuracy and the validity of our model have been tested and confirmed with measurements performed with the proposed system. The experimental arrangement built to test the proposed system has validated the usefulness of the IR thermometry system applied to the cookware within the range of cooking temperatures from 60°C to 250°C, making it suitable for this application. It has been proved that the IR sensor and the associated electronic works properly in a high-temperature environment such as a real induction heating cooktop.