CS VA 409 -Flow direction switch

CS Instrument

Thermal Flow Switch

Model VA 409

The thermal flow direction switch VA 409 with direction indication serves for determination of the flow direction of compressed air and gases especially in closed circular pipelines.


By means of VA 409 with flow direction indication the flow direction of the compressed air can be determined quickly and safely. Compared with the former mechanical paddle flow switches VA 409 is able to detect even the smallest changes in the flow direction quickly and without any mechanical movement.


The direction information in form of a potential-free contact (normally closed max. 60 VDC, 0.5 A) is transferred to the consumption sensors VA 500/ VA 520 or to a separate building management system (mbs). Two LEDs show the flow direction.


In connection with 2 consumption sensors VA 500/ VA 520 incoming and outflowing compressed air in closed circular pipelines can be measured precisely.

Special features of the flow direction switch VA 409

  • Detects smallest changes <0.1 m/s referred to 20°C and 1000 mbar
  • No mechanical wear parts
  • Easy installation under pressure



Detection range recognition flow direction
< 0.1 m/s referred to auf 20 °C and 1000 mbar
Measuring principle
calorimetric measurement
Sensor Pt 30/ Pt 700/ Pt 330
Measuring medium Air, gases
Operating temp.
0…50 °C probe tube
-20…70 °C housing
Operating pressure up to 16 bar
Power supply 24 VDC, 40 mA
Power input Max. 80 mA to 24 VDC
Protection class IP 54
EMV acc. to DIN EN 61326
2 x M12, 5-pole, plug A and
plug B
2 potential-free contacts
2 x U max. 60 VDC, l max 0,5 A (normally closed); on request: Normally open
Probe tube
stainless steel, 1,4301, length 160 mm, Ø 10 mm, safety ring Ø 11.5 mm, longer probes on request
Mounting thread G 1/2“
Diameter housing 65 mm
Flow direction 2 LEDs

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