Kofloc EX-250S Digital Mass Flow Controller

Digital mass flow device which is adopted the own developed both stable high speed thermal sensor and small proportional solenoid valve and is realized high accuracy and quick response with RS 485 communication in spite of compact.


In comparison with the conventional mechanical products, the mass flow measurement/control technology used in a mass flow meter and controller extracts electrical signals from the flow without significantly influencing the temperature or pressure, thus permitting sophisticated flow measurement and control.

The technology is widely used for manufacturing semiconductors, liquid crystal, optical fibers and other electronic devices, gas supply for fuel cells, and fuel gas control for burners, foods, biotechnology, as well as for experimental facilities and production/inspection systems in many other industries.




The natural environment is preserved through the balance of solids, liquids and gases that exist on the earth. However, human civilization has caused pollution that has greatly damaged our environment. The task of the present generation is to restore our environment to its natural healthy state. And this is also the greatest challenge for 21st century science and technology.

KOFLOC's corporate motto is "A Scientific Approach for Fluids." In other words, we create products that scientifically measure and control the balance of liquids and gases. We trust that through our work we are making a contribution to the regeneration of the environment and to the establishment of a prosperous society.


  • Lower cost but high accuracy measurment
  • High speed response and zero stability
  • 0-5VDC or 4-20mA Input/output signal and +/-15VDC or 24VDC power supply
  • Mediocrity D-sub 9pin
  • Gases registered in EX-250S are usable by rotary-switch
    *Calculate the flow rate with conversion factor based on N2 gas
  • RoHS compliance, CE marked


ModelMass flow controller EX-250SCMass flow meter EX-250SM
Sensor typeThermal sensor
Valve typeProportional solenoid valve (normally closed
Applicable gases*1N2, Air, H2, He, Ar, O2, CO2 (The other gases are N2 gas conversion)
Flow range*210SCCM-5SLM
Control Range2-100% (F.S.)
Response:Total flow rate control range ±1 sec (within ±2% F.S.)
L:50kPa-149kPa H:150kPa-300kPa
Accuracy *3 ±1.0%F.S.
Operating differential pressure *4 50-300kPa (Ar, CO2:100kPa-300kPa)
Inlet maximum pressure500kPa (G)
Proof pressure980kPa (G)
External leak rate *5≦ 1×10-8Pa·m3/sec
TemperatureWorking temp.5-50°C
Accuracy guaranteed temp.15-35°C
Allovwable storage temp.-10-60°C
Allowable operating humidity


10-90% RH (without dew condensation)
Materials of gas contact partSUS316, SUS316L, Magnetic stainless steel (*6), PTFE, FKM
Electrical connection


Dsub9 pin KFC Standard (SEMI standard)


Flow rate setting signal0-5VDC (Input impedance approx.1MΩ)

4-20mA (Input impedance approx.250Ω)


Flow rate output signal0-5VDC

or 4-20mA

Digital communicationRS485
Required power supply (DC)+15VDC (+/-5%) less than 100mA, -15VDC (+/-5%) less than 150mA Or +24VDC (+/-10%) less than 180mA (MFM: less than 100mA)
Joint *7 1/4SWL type (standard)
Mounting posture


Horizontal installation recommended.
Weight *8Approx. 500gApprox. 440g

(*1)The gases must be dry and clean, free of corrosive components and foreign matter such as dust and mist.

(*2)The flow rate calibration units SCCM and SLM indicate a mass flow rate converted to a volume flow rate in cc/min and L/min at 0°C and 1 atm.

(*3)Accuracy for calibration gas: N2, flow range (max. full scale).

(*4)The operating differential pressure may differ depending on specifications.

(*5)Mass flow meter does not contain magnetic stainless steel.

(*6)Contact us for any other joints.

(*7)Exclusive of weight of joint.

(*8)Pressure condition would be needed when you order.

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