Water Flow Rate Sensor

Sapcon’s Rate of Flow level sensor is RISC Processor based continuous level indicator (level transmitter). The series of this sensor utilizes the principle of capacitance for level measurement. Apart from level indication, the built-in three point electronic level limit switch offers the switching functions for alarm annunciation and/or control application at the set point levels. The set points are independent of each other and are continuously configurable over the entire range.

Applications of Rate of Flow Level Sensor

The sensor is suitable for measuring the level of conductive or non conductive liquids, slurries and powdered or fine grained solids homogeneous composition having a stable dielectric constant.

Key Features

  • Selectable Display for ROF / Level / ROF% / Level%
  • Built-in equations along with custom Q=Kh^n for various weir types
  • Multi-purpose 5 digit Seven Segment LED display for best resolution and better viewing from distance

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In an application, the measuring electrode (sense probe) is provided with a stilling tube which forms a capacitor. The amount of capacitance of this capacitor is governed by the level of water between the two electrodes (sense probe & stilling tube). ROF measures the Change of Capacitance to measure the Change of Level of the water. This level is then converted to the Rate of Flow, depending on the weir type selected or K,n parameter entered for the equation for calculating Flow Rate.

  • Latest RISC core microcontroller technology
  • Selectable Display for ROF / Level / ROF% / Level%
  • Built-in “Time Aware” Totalizer function
  • Built-in equations along with custom Q=Kh^n for various weir types
  • Multi-purpose 5 digit Seven Segment LED display for best resolution and better viewing from distance
  • Two wire Pulse Coded Digital communication enabling two sensors to be connected on same pair of wires to the evaluation unit. Supporting as far as 1 KM distance between Sensor and Evaluation Unit with shielded two core cables
  • Three independent potential-free relays, providing flexibility of selecting six combinations of switching
  • Galvanically isolated true two wire 4-20mA proportional to 0.0% and 100.0% level is available for remote indication purposes
  • Two wire implementation solves the malfunction problems that occurs with various PLC 4-20 input interfaces and thus better suits for higher-end automation
  • 4-20mA loop can handle 700 Ohm loop resistance with internal isolated supply. The loop resistance can be 1K Ohm for external DC Supply of 24 Volts
Mechanical Specifications


  • Plastic potted with epoxy resin

Power Supply

  • 16VDC @ 5mA derived from Sensor Communication Interface of Evaluation Unit

Measuring Frequency

  • 250Khz to 20Khz
  • Reverse Frequency Measurement


  • 10 counts per PF


  • Digitally Encoded Current (8mA – 16mA) Pulse
Electrical Specifications

Power Supply

  • Universal Mains 90 to 265 V AC, 50/60 Hz and 24 V DC

Power Consumption

  • 3 Watts

Cable Specification

  • 2-Core
  • Resistance per core not to exceed 30 Ohms
  • Use of Shielded Twisted Pair Cables is recommended for long runs of cable
  • Cable Lengths of 1000 Meters are thus supported with Grounded Cable Shields

Zero% Range

  • 30pf to 250pf

100% Range

  • 10pf to 4500pf (Difference from Zero%)
  • Current: 4-20mA
  • RL max = 700 Ohm using internal isolated supply
  • RL max = 1K Ohm for external loop supply of 24 V DC


  • 3 potential-free relays with one set of potential-free change over contact per relay
  • Contact Ratings: 6 Amp @ 230 V AC 50/60 Hz for non-inductive loads

Switching Hysteresis

  • 1% in Single-point switching
  • 1 to 98% selectable in pump control
Applications Specifications
  • Measuring differential level In Open Channel
  • Water treatment plants
  • Effluent treatment plants
  • Filtration stations
  • CE mark
  • ROHS compliance
  • Weatherproof IP-67 protection
Switching Indication
  • Seven Segment Display
  • LED for 3 Relay Outputs
  • Continuous: -50% to 150% digitally on 1”2 Seven Segment Display
  • Switching: 5mm Red LEDs’ for Alarm Indication