Auto Electronics

Melexis offers non-contact temperature measurement

Melexis Microelectronic Integrated Systems N.V. has introduced the MLX90614 family of non-contact thermometers, each consisting of an infrared sensor and a signal-conditioning chip packaged in a TO-can. The thermometers are AECQ100-qualified and suited for use in automotive air-conditioning systems among other applications, according to the company.

Melexis’ infrared business unit manager Victor Kassovski said that remote non-contact temperature measurement has been complicated and expensive due to the complex signal treatment and calibration involved. 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. The 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 chip’s EEPROM memory. The chip includes low noise amplifiers, a 17-bit A/D converter and a digital signal processor. Its operating temperature range is -40 °C to 125 °C, its extended object temperature range is -70 °C to 380 °C, and its temperature resolution is 0.01 °C. The standard MLX90614 has a high absolute accuracy of ±0.5 °C in the object temperature range of 0 to 50 °C and ±1 °C outside that range.

The digital output temperature is fully linearized and compensated for ambient temperature. The sensor transmits the result over an SMBus or by a continuous PWM signal. The system eliminates the design challenges of very small voltage signals, environmental effects and electromagnetic compatibility that can otherwise make infrared temperature measurements difficult and cumbersome, the company said.

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