Miniature Temperature Sensors

During the COVID19 pandemic, it became necessary to use quick and non-invasive techniques for assessing body temperature. Various locations that included airports, hospitals, schools, and shopping centers used non-contact thermometry. This essentially employs an infrared sensor for measuring the surface temperature but without any physical contact. Not only was this technique very popular, but it is now a typical way of taking body temperature. While providing quick and reliable readings, infrared thermometers are also non-invasive.

The accuracy of infrared thermometers largely depends on variables such as the nature of the surface it is measuring and its surroundings. However, Melexis Microelectronic Integrated Systems has now successfully resolved these problems. They have developed a miniature infrared temperature sensor that offers medical-grade accuracy and temperature compensation.

Melexis specializes in and offers several microelectronic ICs and sensors for various applications. Their sensors are applicable to consumer, automotive, digital health, energy management, and smart device industries. Samsung has deployed one of the Melexis products in their GWS smartwatch series. This is the medical-grade version of the MLX90632 temperature sensor, which operates on FIR or far-infrared technology. The enhanced accuracy of the MLX90632 temperature sensor along with its non-contact temperature measurement technique allows its use for menstrual-cycle tracking. A wide range of new and possible applications in health, sports, and other domains is now possible because of the reliable continuous temperature measuring capabilities of the sensor.

The MLX90632 FIR temperature sensor is an SMD or surface mount device that measures the infrared radiation from the object for reporting the temperature. As the sensor has a tiny SMD packaging, it is suitable for use in a variety of applications, especially in wearables, hearables or in-ear devices, and point-of-care clinical applications. All these applications require high accuracy for measuring the human body temperature.

In comparison to traditional contact methods of measuring temperature, the non-contact temperature measurement methods offer advantages, primarily as they enable sensing and measuring the temperature without directly touching the measured surface or object. This is helpful in specific circumstances where it is undesirable to make physical contact with the object, especially when the object may be fragile, under movement, or located in a hazardous area. When a quick response is necessary, or there is no guarantee of good thermal contact between the object and sensor, a non-contact temperature measurement technique is more accurate. It can also yield better and more reliable results as compared to what the contact temperature measurement techniques can.

The MLX90632 sensor is a minuscule device in a chip size of 3 x 3 x 1 mm QFN package. Within this tiny space, it incorporates the sensor element, the signal processing circuitry, digital interfacing circuitry, and optics. The small size enables quick and easy integration within a huge range of modern applications, typically with limited space.

Melexis calibrates its sensors in-house, thereby ensuring high accuracy. They compensate for harsh external thermal conditions with internal precautions for electrical and thermal operations. After amplifying and digitizing the voltage signal from the thermopile sensing element, the IC filters it digitally and stores the raw measurement data in its RAM. This is accessible via an I2C interface.