The infrared thermometer revolutionized the design of the induction hob

     Melexis has introduced the MLX90617, an infrared thermometer for non-contact temperature measurement in induction hob applications. This ground-breaking sensor uses optical filtering to measure the temperature of a cooking container base through a ceramic hob surface, enhancing cooking control, safety and end-user experience.

     Due to the limitations of the prior art, the temperature control of the typical induction hob is based on the back temperature of the ceramic glass plate used by the induction hob. With this new device, the company has developed an advanced and cost-effective solution that provides real-time temperatures at the bottom of cooking containers "through the glass."

     Through optical filtering technology that precisely tuns the ceramic glass used in the induction hob, the device can capture the radiation emitted from the lower part of the cooking pot as it is transmitted through the ceramic glass plate. An advanced algorithm is used to consider the energy generated by the ceramic glass plate itself.

     The device is designed to be used with another non-contact temperature sensor, such as the MLX90614 or MLX90632, which is also mounted below the hob ceramic surface. In-situ emissivity measurements using leds and light sensors can be considered first-class accuracy.

     To determine the temperature of the cooking container, the device measures the radiation emitted by the pot or pot base, and a second sensor measures the radiation emitted by the ceramic glass plate and the sensor. The included LED and light sensor are used to measure the reflectivity of the pot and thus calculate its emissivity. With relatively simple real-time processing, it is possible to determine the temperature at the bottom of the cooking container, ignoring the radiation from the ceramic surface and sensors.

     In contrast to the standard induction hob setup, which measures the temperature of ceramic glass (Tglass) through advanced optical filtering, the device provides a real-time output of the bottom of the cooking container (measured Tpot) through the glass. When the results were compared, the measurements provided by the MLX90617 were significantly closer to the actual temperature of the cooking pot and pot (Tpot measurements).

     By integrating this device, induction hob manufacturers can create a solution that improves the precision of their products, thereby benefiting the end user's cooking experience.

     Since the temperature at the bottom of the pot or pan is monitored by a sensor rather than glass, the control electronics of the hob give a deeper insight into the temperature of the food. This is especially beneficial for cooking operations that require precise thermal regulation over a small temperature range. It can also improve the safety of the system by detecting temperatures that are out of range and allow the development of more advanced automated cooking systems.

     The device features factory-calibrated sensor operating temperatures in a wide temperature range from -0 ° C to 125 ° C and is designed to measure cookware temperatures from 70 ° C to 250 ° C. It comes in an industry-standard TO39 package with a supply voltage of 5V. The SMBus digital interface can be easily integrated into induction hob designs.

     The T039 package integrates an infrared sensitive thermopile detector chip and signal conditioning ASSP with a built-in low noise amplifier, 17-bit ADC and powerful DSP unit. "Our customer's request initially triggered the development of MLX90617. However, the challenge of processing relatively small short-wave infrared signals made us question its feasibility, "admits Joris Roels, marketing manager at Melexis. "Through extensive development and application testing, we have not only overcome these obstacles, but also provided a cost-effective and user-friendly solution that truly meets the needs of our customers."