It is a calorimetric flow switch so it is designed for monitoring of thermally conductive liquids. The big advantage of this type of flow switch is the fact that it is usable also in explosive atmosphere.

Key technical properties

Flow switch FS Ex 10/11/15/20 flow switch is certified for use in the following areas with explosive atmosphere:

I M1 Ex ia I Ma

II 1G Ex ia IIC T4..T6 Ga

II 1D Ex ia IIIC Txx°C Da


The flow switch for liquids is made in four versions. These are 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)


The operational status is displayed using 10 LEDs. If the flow rate drops below the user specified limit (after exceeding in some case), the status output will be changed. The flow rate is indicated by ten LEDs within the measurement range and you can select the boundary for making/breaking the contact in the same graduation. The measuring cycle takes from 4sec to 8sec with recommended measurement range 4 ÷ 150 cm/sec (for default setting, the measurement range is 4 ÷ 400cm/sec). If the piping is empty, the sensor behaves identically as in the case of zero flow rate.

We offer two standard lengths of the bar type sensor according to piping ID at the installation site. The customer may select a bar type sensor 65 mm or 125 mm in length as needed. If the flow rate of medium is to be monitored in a pipe smaller than DN25 (or the flow velocity is below the sensor range for the given pipe diameter), it is advantageous to use an adapter block with the corresponding flow velocity and thereby ensure proper functioning and maintain the installation conditions. The adapters are designed for the short version of 65mm sensor with the use of direct neck with G½“ pipe thread. Individual designs of adapter blocks are as follows:

  • FS adapter block DN20/G3/4“ pro 5 ÷ 100 l/min. (rozměr 150×50×40 mm)
  • FS adapter block DN15/G1/2“ pro 2 ÷ 40 l/min. (rozměr 150×50×30 mm)
  • FS adapter block DN10/G1/4“ pro 0,4 ÷ 20 l/min. (rozměr 150×50×30 mm)
  • FS adapter block DN4,5/G1/4“ pro 0,1 ÷ 5 l/min. (rozměr 70×50×30 mm)
  • FS adapter block DN2,7/G1/4“ pro 0,075 ÷ 2 l/min. (rozměr 70×50×30 mm)


The designation of a switching point on the LED scale can be implemented in two colours (red and amber LEDs) that indicate simultaneously if the switching contact is closed or open:

In the case of FS15, the LED in the middle between the control buttons is used for temperature switching point indication. If the temperature of medium is above/below the set-point, the LED glows red and simultaneously indicates the open PIN2 (sensor delivered as a standard is set to be opened at a temperature above the set limit with the LED on).

When logics of the making/breaking points is changed by user, the logics of both outputs is changed at the same time (applies to versions FS 11 and FS 15).


Flow Switch 10/11/15/20 od společnosti Comac Cal s.r.o.


Hlídač průtoku FLOW SWITCH od Spolčnosti Comac CAL s.r.o


Hlídač průtoku FLOW SWITCH od společnosti Comac CAL s.r.o


The flow switch contains two flush-buttons by which means it is possible to set:

  • sswitching point/points for flow velocity (or temperature in some case)
  • To calibrate minimum and maximum flow rate for the sensor
  • To reset default parameters from the manufacturer




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 sensor and with regard to applicable classification according to the environment in which it will be used. Signal outputs of the flow switch can only be connected to devices with necessary protection degree for use in explosive atmospheres and their parameters correspond to applicable safety parameters for connection to our flow switch.


Group I devices Group IIC and IIIC devices
Power 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

* – values are identical to those of the power supply


Application of the flow switch in industry


Flow switch applicable to explosive atmosphere are used in all sorts of industries such as mining, petrochemical, chemical, etc. Due to absence of moving parts, it is an ideal substitution of mechanical flow switches with short service life. Conversely, flow velocity electrical evaluation is a guaranty of long time stability of all parameters. It is used with advantage, e.g. in cooling systems or building applications. Another possible employment is, e.g. in the technology complex where it provides information on operation of the entire technology, or conversely, as a safety element protecting against empty piping, low flow quantity, etc.

Flow switch FSEx 10/11/15/20 calorimetric flow switch and its main advantages

  • Designed for use in explosive atmosphere
  • Possibility to use another status output (version FS 15) for monitoring of temperature according to setting
  • For FS 20 design, in addition to the making contact also 4 ÷ 20 mA current output
  • 10 LEDs to display the current flow and adjusted switching limits
  • „Self-teaching“ system with the possibility of Qmin and Qmax settings
  • Possibility to set switching limits (pre-set neutral zone)
  • Electrical connection through M12 (4-pin) connector
  • Continuous control of the sensor for correct operation
  • Full corrosion-proof construction
Product photgalery

Technical parameters