FS Ex 10/11/15/20

Calorimetric flow switch for explosive atmospheres

I M1 Ex ia I Ma

II 1G Ex ia IIC T6 Ga

II 1D Ex ia IIIC T85°C Da

It is a device that monitors the flow of fluid based on calorimetry principle which can be used in potentially explosive atmospheres.

If the flow rate drops below a limit set by user, the status output is changed. The flow rate is displayed by ten LEDs and it is possible to select a boundary for contact making/breaking in the same graduation. The measuring cycle takes from 4 sec to 8 sec with the recommended measurement range 4÷150 cm/sec.

In case of an empty pipeline, the sensor behaves in the same way as with zero flow.

Made in four versions as follows:

  • FS 10Ex – 1× status output (depending on flow velocity)
  • FS 11Ex – 2× status output (depending on flow velocity)
  • FS 15Ex – 2× status output (1× depending on flow velocity and 1× on temperature)
  • FS 20Ex – 1× status output and 1× current output (depending on flow velocity)


  • design for use in explosive atmospheres
  • possibility to use another status output (version FS 15) for monitoring of temperature according to setting
  • for FS20 design, in addition to a closing contact also 4÷20 mA current output
  • 10 LEDs to display the current flow and adjusted switching limits
  • „self teaching“ system with an option to set Qmin and Qmax
  • possibility of setting the switching limits (insensitivity band preset)
  • electrical connection by means of M12, 4-pin connector
  • continuous control of the sensor for correct operation
  • full stainless construction


Flowswitch délka čidla 65mm


Flowswitch délka čidla 125mm


Power supply 24V±10%DC with polarity reversal protection
Input power 1,5/4 VA
Electrical connection connector M12x1 (4PIN)
Process connection according to DIN2353 with the M16×1,5 union nut through the 24° ring into the direct socket with pipe thread (G½”; G¼”; M14×1,5; NP¼”)
Sensor design compact, separated (standard 3 m cable)
Display 10× three-colour LED (flow velocity)
1× LED LED (temperature – for FS 15 only)
Output types relay relay (for FS 10 only), PNP, NPN, 4÷20 mA (for FS 20 only)
Contact rating 130 mA / 60 V / 500 mW
Response time * 1÷6 s
Velocity flow range 4÷400 cm/s
Accuracy ±2÷±8 cm/s
Hysteresis 2÷8 cm/s
Control 2× flush-mounted button
Temperature of liquid -10÷+80 °C
Ambient temperature -20÷+55 °C
Material in contact with medium stainless steel 1.4404
Maximum pressure 64 bar
Degree of protection IP67
Ambient humidity max. 90 %
Status contact SSR, passive, potential free, max. 350 V
AC/DC, 150 mA, 400 mW
Hmotnost 290 g
Weight (H×W×D) 91×74×60 mm (in case of the longer version, the height is 151 mm)


The flow switch point on LED scale can be implemented using two colours (red LED or amber LED), indicating at the same time which contact is normally closed or normally, open.

In case of FS15, the temperature switch point is indicated by the LED located between the control push buttons. If the temperature of media is above/below the set-point, the LED is red, indicating that PIN2 is open at the same time (the sensor supplied as standard is configured open at a temperature above the set limit with the LED turned ON).

If the logic of the normally open/normally closed point is changed by the user, the logic of both outputs is changed at the same time (applicable to FS 11 and FS15 versions).

first LED flashing the flow below the monitor range

first LED flashing the flow below the monitor range

last LED flashing the flow above the monitor range

last LED flashing the flow above the monitor range

rychlost proudění je v nastaveném rozsahu hlídače

rychlost proudění je v nastaveném rozsahu hlídače


The flow switch has two flush-type control buttons, making it possible:

  • the switching point/points for flow velocity (temperature in some case)
  • to change the logic of the N.O./N.C. output
  • to calibrate the minimum and maximum flow values of the monitoring device
  • to reset the original parameters from factory



In case when it is necessary to monitor the media flow in the pipe with a smaller DN than DN 25 (or the flow velocity is below the sensor range at the pipe diameter given), it is possible to use an adapter block with a corresponding flow velocity and ensure correct operation and keep the installation conditions in this way. The adapters are designed for a short version of the 65 mm sensor by using a direct neck with G½” pipe thread.

Individual designs:

  • FS adapter block DN20/G¾” for 1÷10 l/min. (size 150×50×40 mm)
  • FS adapter block DN15/G½” for 0,5÷5 l/min. (size 150×50×30 mm)
  • FS adapter block DN10/G¼” for 0,2÷2 l/min. (size 150×50×30 mm)
  • FS adapter block DN4,7/G¼” for 50÷500 ml/min. (size 70×50×30 mm)
  • FS adapter block DN2,7/G¼” for 2÷100 ml/min. (size 70×50×30 mm)


The flow switch is normally delivered for 24VDC±20% power supply. It must be fed from an intrinsically safe power supply with parameters compatible with our meter and with respect to the relevant classification according to the environment in which our meter will be used. The signal outputs of the flow switch may only be connected to devices that have the required degree of protection for use in potentially explosive atmospheres and their parameters correspond to relevant safety parameters for connection to our flow switch.

  Group I devices Group IIC and Group IIIC devices
Power supply Ui: 28,5 V Ui: 28,5 V
Ci: 0 Ii: max. 115 mA
Li: 0 Ci: 0
  Li: 0
Relay output passive Ui: max. 28,5 V Ui: max. 28,5 V
Ii: max. 115 mA Ii: max. 115 mA
Pi: max. 0,330 W Pi: max. 0,330 W
Ci: 0 Ci: 0
Li: 0 Li: 0
Relay output active Uo: max. Uo zdroje Uo: max. 28,5 V
Io: max. 115 mA Io: max. 115 mA
Co: * Co: *
Lo: * Lo: *
Current loop 4–20 mA active Uo: max. 10,8 V Uo: max. 10,8 V
Io: max. 196 mA Io: max. 196 mA
Po: max. 0,529 W Po: max. 0,529 W
Co: < 10 mF Co: < 1 mF
Lo: < 0,2 mH Lo: < 0,015 mH

* – the values are identical to those of the power supply