Rusovská 7, Bratislava, Slovakia, tel: +421-905-469130, mail: firstname.lastname@example.org, web: www.loxtechnologies.com
Beawer PT-1 is prototype for compact device enabling precision testing and operation of MEMS (micro-electro-mechanical system) heater devices. It is designed to deliver up-to 5W into a platinum-based microsystem heater, while obtaining information about heating element resistance by 4-wire sensing interface. Beawer involves double DC-DC conversion circuitry with 3V..6V inputs, which generates constant internal 3.3V and 5V supplies and variable heater voltage up to 25V. Linear heater current controller enables currents up to 1A with minimal power dissipation due to variable supply voltage. The heater resistance is derived differentially by superposing sinusoidal AC current of variable frequency in 1Hz to 100Hz range into the DC current value and measuring the corresponding AC part of the heater voltage by performing synchronous detection at selected carrier frequency. Analog signal conditioning circuitry involves differential stages for heater current and voltage measurements and subsequent low-pass pre-filtration to 400Hz in 3-pole Butterworth linear filters. After 14-bit ADC conversion, the DC and AC voltage and current values are processed in dsPIC33FJ128GP804 digital signal controller. Internal digital interface to the Beawer controller includes USB, SPI and RS485 physical layers. For power outputs of 2W and less, Beawer can be operated and supplied directly from PC USB interface.