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Smart, ultra-small infrared thermometer

21st February 2013


The most prominent application for infrared thermometers is measuring body temperature to check for fever and illness.

There are three main types of IR fever thermometers: ear thermometers, forehead thermometers and non-contact, distance-read thermometers. Measurement accuracy depends on a) the calibration accuracy of the thermometer and b) how accurately the temperature measured on the patient’s exterior can be translated into an internal body temperature. For most medical applications, a measurement accuracy of ±0.2°C or better is required.

Melexis now announces the availability of the MLX90615. This is the world’s first intelligent infrared thermometer integrated into the ultra small TO-46 package commonly used in the manufacture of ear thermometers. This ultra-small and cost effective non-contact thermometer delivers a fully calibrated digital temperature reading achieved by integrating an infrared sensor with a custom signal conditioning chip in a TO-46 package.

The sensing element in the MLX90615 is a silicon chip with a thin, micro-machined membrane heated by the infrared radiation of the object. This proven Melexis technology has been applied to industrial and automotive temperature measurement challenges for many years. A custom built signal conditioning chip amplifies and digitizes the minute voltages generated by the thermocouples on the sensor membrane and calculates the object temperature using factory set calibration parameters stored in the memory of the chip. The digitised temperature is fully linearised and compensates for ambient temperature. The high level of integration makes the MLX90615 very cost effective compared with previous infrared solutions.

The MLX90615 applies advanced low noise amplifiers, a 16-bit ADC, and powerful DSP unit in its signal conditioning chip. This allows a wide operating temperature range of -40°C to 85°C and an extended object temperature range of -40°C to 115°C while maintaining a temperature resolution of 0.02°C. The MLX90615 has a high absolute accuracy of ±0.1°C in the critical temperature range of 36°C to 39°C.

The MLX90615 uses a 3 Volt supply voltage and consumes less then 1 mA in normal operation. The sensor includes a power saving ‘sleep’ mode during which the current consumption can be as low as 2µA. The MLX90615 is qualified in accordance with AECQ100 and is RoHS compliant. It can be soldered up to 260°C according to JEDEC 020C.

Luc Buydens, product marketing manager for Melexis’ infrared products said, “This new intelligent infrared thermometer enables our customers to easily and efficiently produce ear thermometers and other medical equipment with the required accuracy. It is especially ideal in applications such as self monitoring and mobile electronic devices where the small sensor size and low power consumption are premium assets.”

MLX90615






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