Posted in | Gas Flow Sensors

FS2 Gas Flow Sensor - Detect Flow Speed and Direction

The Flow Sensor FS2 consists of four platinum thin film resistors. The low ohmic resistance with a small area is used as heater. Two high ohmic resistors on the left and right hand side of the heater are used to detect the flow speed and flow direction. A further resistance allows the measurement of the gas temperature.

The two resistors close to the heater can be connected in a bridge circuit. This leads in an output signal which is a function of flow speed and direction. In no flow condition, these two resistors are heated up equally. If flow appears, one of them is cooled more than the other, depending on flow direction.

The temperature difference can be measured and depends on flow speed and direction. Response and heating up time of this flow sensor is very short due to the small thermal mass. This kind of evaluation allows the measurement of very low flow speeds.

In order to detect higher flow velocities, the temperature sensor can be connected in a constant-temperature anemometer.

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  • Detection of flow direction
  • Small mass flows
  • Simple signal processing and calibration
  • No moved mechanical components
  • Excellent reproducibility
  • Excellent long-term stability
  • Easy adaptable for different applications or into housings
  • Best price-performance ratio


  • Differential pressure sensors
  • HVAC and building control solutions
  • Medical devices
  • Automotive industry
  • Device monitoring

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