Melexis unveils the MLX90617, an infrared thermometer for non-contact temperature measurements in induction hob applications. This sensor uses optical filtering to measure the temperature of the cooking vessel’s base through the ceramic hob surface, improving cooking control, safety, and end-user experience.
Due to existing technology limitations, the temperature control in a typical induction hob is based on the backside temperature of the ceramic glass plate used in induction hobs. With the MLX90617, Melexis has developed an advanced but cost-effective solution capable of “looking through the glass” to provide the real-time temperature at the base of a cooking vessel.
In Operation
The MLX90617 is designed to be used alongside another non-contacting temperature sensor (such as the MLX90614 or MLX90632), which is also mounted below the ceramic surface of the hob. Optionally, an in situ emissivity measurement using an LED and a light sensor can be considered for best-in-class accuracy.
To ascertain the temperature of the cooking vessel, the MLX90617 measures the emitted radiation from the pot or pan’s base, with the second sensor measuring the radiation emitted by the ceramic glass plate and the sensor. The accompanying LED and light sensor are used to measure the reflectivity of the pot and therefore calculate its emissivity. Through relatively simple real-time processing, it is then possible to determine just the temperature of the cooking vessel’s base, ignoring the radiation from the ceramic surface and sensors.
Enhancing Induction Hob Design
As the temperature of the pot or pan’s base is monitored by the sensor, rather than the glass, the hob’s control electronics have a closer insight into the temperature of food. It can also contribute to an increase in the system’s safety by detecting out-of-range temperatures, as well as enabling the development of more advanced automated cooking systems.
The MLX90617 features a factory-calibrated wide temperature range of -0°C to 125°C for the sensor operating temperature and is designed to measure cookware temperatures ranging from 70°C to 250°C. It is available in industry-standard TO39 packaging with a 5V supply voltage. The SMBus digital interface can be easily integrated into induction hob designs.
The T039 packaging encompasses the integration of both the IR-sensitive thermopile detector chip and the signal conditioning ASSP, accompanied by a built-in low-noise amplifier, a 17-bit ADC, and a powerful DSP unit.
Extensive Development
“Our customers’ requests initially sparked the development of the MLX90617. However, the challenges of working with relatively small signals of infrared at short wavelengths made us question its feasibility,” admitted Joris Roels, Marketing Manager at Melexis. “Through extensive development and application testing, we’ve not only overcome these hurdles but also delivered a cost-effective, user-friendly solution that truly meets our customers’ needs.”