Loss of Head Level Sensor

Sapcon’s Loss of Head level sensor is used to measure differential level (Loss of Head) in open channels , water canals and is also widely used in water treatment plants and filter stations. The MPLOH Series covers variants of LOH sensors that are based on RISC Processor. These utilize the principle of Quasi Differential Capacitance for continuous differential level measurement.

Key Features of Loss of Head Level Sensor

  • 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
  • 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

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The capacitance formed by the sensing probe and the water is measured which is directly proportional to the level of water known as ‘Head’. By measuring heads at two points called ‘High Head’ and ‘Low Head’, a difference can be calculated. This difference is ‘Loss of Head’. MPLOH measures the heads in mm and thus a calibration at site might be required. The two sensors digitally send their level values of head heights in digital format over the same set of wires, a shielded cable should be used to assure flawless operation.

  • Latest RISC core microcontroller technology
  • ‘Heads’ and ‘Difference’ are measured in mm from -400mm to 1500mm. -50.0% to +150.0% is also provided for 4-20mA associated Head / Difference
  • Two 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 purpose
Mechanical Specifications


  • W: Cast Aluminium weatherproof IP-67 Stoving enamel painted

Cable Entry

  • 3 X 1/2” BSP / NPT gland brass

Process Connection

  • Threaded Mounting: 1-1/2”, 2” BSP / NPT
  • Flange Mounting: As per specification

Extension (Probe Length)

  • Pipe SS (Still Well) extended up to 3000mm

Wetted Parts

  • S4: SS 304
  • S6: SS 316

Electronic Insert

  • LDC-117 / LCDM-111: (High Head and Low Head)

Power Supply

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

Measuring Frequency

  • 250Khz to 100Khz
  • Reverse Frequency Measurement

Operating Temperature

  • Ambient: 20C to +60C


  • 10 counts per PF


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

Input Power Supply

  • Universal Supply: 90-265 V AC, 50 Hz
  • 24 V DC


  • 03 SPDT Relay outputs
  • 0-100% Display
  • 4-20mA current output
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