ASK Corporation. Hydraulic, Coolant Accessories and Measuring Instruments.

  • Measuring Instruments
  • Digital flow sensor

A single unit offers three functions: Flow Switch, Flow Sight, and Flow Meter.


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  • This sensor has a seven-segment LED digital display to make you read flow rate value easily.
  • You can select one of two different kinds of output types: PNP output or NPN output.
  • This sensor is used with a connector (M12×4-pin).
  • You can use the digital flow sensor with an input power supply of from 12 to 24 V DC (permissible voltage fluctuation ±10 %).
  • The amplifier protection structure conforms to IP67 equivalent.
  • You can set the lower limit of the flow rate. If the flow rate falls below this limit, the red LED lamp (NG) turns on, and contact signal output is given to notify the operator of the critical situation.
  • In the case of low pressure specifications, you can check the flow of fluid by observing the rotor rotation.
  • You can use the sensor at the desired installation position (horizontal, vertical, or tilted position) and in the desired inflow direction.
  • Rotor can be cleaned by air removing the cap from the front of the main body.
  • Cable is an option.


DFS - 2 - O - *
num num num num
num Model Digital flow sensor
num Screw diameter
(for both sides)
1 : Rc1/8
2 : Rc1/4
3 : Rc3/8
6 : Rc3/4
8 : Rc1
num Applicable fluid O : Hydraulic oil, lubrication oil (DFS-1: Only O type)
W :Water, water soluble cutting oil
num Custom specification Please ask us.

Example of use

  • Seizure can be avoided by flow control of lubricating oil for the spindles and bearings of machine tools, printing machines, presses and speed reducers.
  • Tool damage and fire can be prevented by control of coolant flow to machine tools.
  • This sensor is used to check if the filter is clogged or not.
  • Coolant flow control.


☻ Body and overall Specifications
Type DFS-1 DFS-2 DFS-3 DFS-6 DFS-8
Connection diameter Rc1/8 Rc1/4 Rc3/8 Rc3/4 Rc1
Maximum Flow Rate ( ℓ/min) 1 10 20 50 100
Measurement Range ( ℓ/min) 0.2∼1 1∼10 2∼20 5∼50 10∼100
Maximum Pressure (MPa) 3 3 (if a metal/plastic cap is installed)
25 (if an all-metal cap is installed)
Flow Sight Function Available Available (if a metal/plastic cap is installed)
Not available (if an all-metal cap is installed) ※1
Accuracy (ℓ/min) ±0.1 ±0.5 ±1.0 ±2.5 ±5.0
Applicable Fluid ※2 Hydraulic oil,
Lubrication oil
Hydraulic oil, Lubrication oil
Water, Water-soluble cutting oil
Pressure loss ※3 > 0.03MPa > 0.025MPa
Temperature 0~80 ℃ (Fluid)     0~50 ℃ (Ambient temperature)
Material (Fluid contact part) C3604 (Ni Plating),Nd-Fe-B,POM,PC,NBR (DFS-1: C3604→SUS304)

☻ Amplifier specifications
Power source DC12~24 V (permissible voltage fluctuation ±10 %)
Current Consumption Maximum 100 mA
Output NPN open collector (factory setting) /PNP open collector.
Maximum load 100 mA
Connection M12X1-4-pin connector (DC)
Degree of Protection IP67 equivalent
Material (outside) ABS, NBR, PA, and POLYESTER
Display ※4 Seven-segment LED (Green/Red)
Output state ※5 More than adjusted value : LED (Green) ON / LED (Red) OFF
Less than adjusted value : LED (Green) OFF / LED (Red) ON
Connector ※6
※1:You can not see fluid if the metal cap (for high pressure) is installed.
※2:We adjust each type of sensors at our factory in accordance with fluid type. Please specify the type of fluid you intend to use the sensor with when you place your order.
※3:Value for Max. Flow rate at viscosity 32 cSt.
※4:You can select the non-display mode.
※5:You can configure alarm flow rate optionally. See the DFS instruction manual on how to configure.
※6:We also sell a single article of sensor cable. Please ask us, for details.

Principle of actuation

The detection part of digital flow sensor utilizes rotation of the rotor (turbine) installed in the passage. The measuring part detects, by means of the external magnetic sensor, the rotational speed of the permanent magnet mounted on the circumference of the rotor.
You can select NPN output or PNP output optionally.


Hydraulic oil: 32 cSt/0 specification Water: ------/W specification

The test at our factory is performed in the condition above. About accuracy, confirm specifications of each digital flow sensor unit.

Digital Flow Sensor Selection Chart

Caution of use

  • Do not use this sensor in the place to be sprayed with coolant liquid directly to amplifier.
  • Amplifier case is made of ABS. Do not use the ingredients of coolant influencing ABS.
  • Be sure to use this sensor within the maximum service flow rate.
  • Do not install this sensor near a machine generating magnetic field (motor for example) to avoid malfunction.
  • For accuracy, provide straight piping of more than 10 times the inner diameter of the pipe on the upper side, and more than 4 times on the lower side. Do not install curved, confluence, or branch piping (,that is, elbow, tee, throttle valve), near the outlet.
    Model No Upper Flow Passage Lower Flow Passage
    DFS-1 > 100mm > 40mm
    DFS-2 > 140mm > 60mm
    DFS-3 > 170mm > 70mm
    DFS-6 > 270mm > 110mm
    DFS-8 > 340mm > 140mm
  • The rotor incorporates a magnet. For hydraulic oil and lubricant oil, install a filter of 5 to 20 microns; for water and coolant, a filter of 20 to 50 microns.

* Contact our sales staff, for use of a NC lathe for general purpose or grinding machine with coolant containing much cut dust.
* If cut dust sticking to the rotor prevents it from rotating, remove the front cap of the main body and perform air blow to eliminate the cut dust.
* O specification could "change a measurement value" and "consume components in a short time" from the influence of fluid viscosity.
Please use fluid viscosity within the range of 32cSt±50%.

Drawing data download

Product nameType No.Download
Oil 0.2~1ℓ/minDFS-1-OPDF
Oil 1~10ℓ/minDFS-2-OPDF
Water and water soluble coolant 1~10ℓ/minDFS-2-WPDF
Oil 2~20ℓ/minDFS-3-OPDF
Water and water soluble coolant 2~20ℓ/minDFS-3-WPDF
Oil 5~50ℓ/minDFS-6-OPDF
Water and water soluble coolant 5~50ℓ/minDFS-6-WPDF
Oil 10〜100ℓ/minDFS-8-OPDF
Water and water soluble coolant 10〜100ℓ/minDFS-8-WPDF

* Please confirm "Terms of Use" about the use of PDF data.