electronica – Sensor technologies for next-generation temperature measurement

Melexis has announced two new sensing technologies for simplified integration of temperature measurement into applications that look to improve levels of safety, efficiency and convenience.

The MLX90640 infrared (IR) sensor combines high resolution with the ability to operate reliably in harsh environments, and offers a less expensive alternative to more expensive high-end thermal cameras.

This 32 x 24 pixel device is suited to safety and convenience applications that include fire prevention systems, smart buildings, intelligent lighting, IP/surveillance cameras, HVAC equipment and vehicle seat occupancy detection. It has a -40°C to 85°C operational temperature range and can measure object temperatures between -40°C and 300°C.

Maintaining high levels of precision across its full measurement scale, it is able to deliver a typical target object temperature accuracy of ±1°C. It also exhibits superior noise performance, with a noise equivalent temperature difference (NETD) of just 0.1K RMS at a 1Hz refresh rate.

Unlike microbolometer alternatives, the sensor does not need frequent re-calibration, thus ensuring continuous monitoring and lowering system cost. Field-of-view (FoV) options comprise the standard 55° x 35° version and a 110° x 75° wide-angle version. The MLX90640 is supplied in a compact, 4-pin TO39 package incorporating the requisite optics. An I2C-compatible digital interface simplifies integration.

Melexis has also unveiled the MLX90342, a high-performance quadruple thermocouple interface that provides rapid response and very high levels of accuracy when measuring extreme temperatures. It has been specifically designed to allow automotive designers to address the need for more stringent engine and exhaust thermal management and control. This need is being driven by the higher temperatures associated with new, smaller, more efficient engine designs.

Target applications include turbo charger temperature control, exhaust gas recirculation (EGR), selective catalytic reduction (SCR), diesel oxidation catalyst (DOC) and diesel/gasoline particle filtering systems. Drawing on nearly three decades of automotive engineering experience, the MLX90342 supports a -40°C to 1300°C thermocouple temperature range and has an operating temperature specification spanning -40°C to 155°C. Sophisticated on-board cold junction compensation and linearization, plus factory calibration, guarantee an intrinsic accuracy of ±5°C (at 1100°C).

The sensor interface is housed in a miniature, 26-pin 6mm x 4mm QFN package and has a rapid refresh rate of 50Hz that aligns with manufacturer expectations for high-speed response. Temperature data can be transmitted via a SENT Revision 3 digital interface, while extensive diagnostic capabilities monitor the health of the sensor and interface, identifying operational problems without the need for additional components. As a result, signal path integrity of data between the sensor and the engine management software is completely assured. Comprehensive integrated fault detection mechanisms also help sensor designs to conform to the latest vehicle exhaust regulations.

Author
Neil Tyler