Calorimetric air flow meter with dual flow switch and totaliser

Digital flow meter for measuring and monitoring small and medium air flows in pipes and hoses. It works on the calorimetric method, is maintenance-free and causes virtually no pressure loss. Wetted parts are made of stainless steel or polyphenylene sulphide; the instrument is offered as a compact unit, with display and sensor in one housing, or as a remote version, with the sensor connected to the display by cable.

Features

• Measuring ranges from 1…10 l/min up to 50…500 l/min of air
• Threaded connections from G ¼ to G ½
• Stainless steel fittings, polyphenylene sulphide housing
• Maximum pressure 10 bar, maximum temperature 50 °C
• Accuracy ±5 % of full scale
• LED indication of switching status (OUT 1 green, OUT 2 red)
• Two PNP open collector outputs and totaliser function

Operating principle

When power is applied, a thermistor built into the sensor is heated to a preset temperature above that of the medium. Air or gas flowing past the sensor removes heat in proportion to the flow velocity, lowering the thermistor's resistance; the velocity is derived from this resistance. A second sensor measures the medium temperature. The electronics compare the two resistances in a Wheatstone bridge and switch the output when the set value is exceeded or undershot.

Applications

Monitoring consumption and flow presence of compressed air or gas in small and medium-bore lines, including hoses.