Non-Contact Temperature Measurement Made Simple and Inexpensive

Temperature is the most often measured physical parameter. However, remote non-contact temperature measurement has previously been complicated and expensive due to the complex signal treatment and calibration involved. In response to this problem, Melexis announces the availability of the MLX90614 infrared thermometer family. This small and cost effective non-contact thermometer delivers a fully calibrated, digital temperature reading of a remote object. It achieves this feat by integrating an infrared sensor and a custom signal conditioning chip in one TO-can package. Due to the built-in intelligence, high accuracy and wide temperature operating range of the MLX90614, OEM manufacturers can easily integrate non-contact temperature measurement in car air conditioning, room heaters, home appliances, handhelds and medical equipment.

The sensing element in the MLX90614 is an automotive grade silicon chip with a thin, micro-machined membrane heated by the infrared radiation of a distant object. This heating is detected by on chip thermocouples. The custom built signal conditioning chip amplifies and digitizes the minute thermocouple voltage and calculates the object temperature using factory set calibration parameters stored in the EEPROM memory of the chip. The digital output temperature is fully linearized and compensated for ambient temperature. The sensor transmits the result to the user‘s application either over an SMBus or by a continuous PWM signal. The whole thermometer system is enclosed in a TO-can. To the OEM manufacturer these properties offer the advantage of easy integration of the sensor on the application’s PCB without the need for expensive external components. This self contained system eliminates the design challenges of very small voltage signals, environmental effects and electromagnetic compatibility which otherwise make infrared temperature measurements difficult and cumbersome. The high level of integration makes the MLX90614 very cost effective compared to other infrared solutions currently on the market.

The MLX90614 applies advanced low noise amplifiers, a 17-bit ADC, and powerful DSP unit in its signal conditioning chip allowing a wide operating temperature range of -40°C to 125°C and an extended object temperature range of -70°C to 380°C while maintaining a temperature resolution of 0.01°C. The standard MLX90614 has a high absolute accuracy of ±0.5°C in the object temperature range of 0°C to 50°C and ±1°C outside that range. These qualities make the sensor suitable off the shelf for a wide range of uses. A version with the increased accuracy needed for medical applications is also available upon request.

There are 2 variants of the MLX90614 available, one for 3 Volt and the other for 5 Volt power supply operation. With its less then 1mA current consumption, the 3 Volt option is targeted at handheld, battery operated devices. For this reason the sensor also has a power saving “sleep” mode in which the current consumption can be as low as 2µA. For power directly supplied from a 12V car battery, the 5 Volt model contains electronics to operate it at higher voltage with a few external components.

Victor Kassovski, infrared business unit manager at Melexis, comments: “We have condensed Melexis’ decade long experience with non-contact thermometer manufacturing in the MLX90614 and made sure that this thermometer will be an easy to use, cost effective solution for OEM manufacturers in a wide range of applications.”

The MLX90614 is qualified in accordance to AECQ100 and is ROHS compatible. It can be soldered up to 260°C according to JEDEC 020C.

Samples of the integrated thermometer are available now and production quantities can be ordered with a lead time of 20 weeks. Estimated pricing for the MLX90614 will be 4.55 Euros at 1,000 pieces quantity.