Model 591

SKU: 591

Pressure Transmitter, Cable Suspended, Integral Electronics

The Delta Controls Model 591 level transmitter incorporates both the sensor and the electronics unit in a single potted module. The module is protected by a Viton® sealed heavy stainless steel body. This lower body is sealed to an electrical cable, both of which are supported from the well head above. The sensor detects the pressure of the water surrounding it. This pressure is linearly proportional to the height of water above it. The sensor is connected to and referenced to atmospheric pressure by a vent tube in the cable. The sensor/electronics unit converts the pressure into a 4-20 mADC signal equivalent to the liquid level.

Unlike capacitance and admittance type devices, the Delta Controls Model 591 is unaffected by algae growth and sludge coating. Also, it’s calibration can be “bucket” checked or changed without the unit being installed in a well or pit. It is inexpensive to purchase and install. It is also virtually maintenance free which results in a low cost of ownership.

The Model 591 is also very useful for measuring levels in tanks. The flexible cable is easy to install, even when the head room above a tank is minimal. The small body diameter allows it to be installed through a small 3/4″ NPT hole. The optional TEF cable jacket and Hastelloy “C”® body are resistant to most corrosive agents.


  • 4-20 mADC signal, 2 wire loop
  • Small size is easy to install. Enters A 3/4" NPT (23 mm) hole and slides easily Into a 1" (27mm) pipe
  • Insensitive to down hole pumps
  • Ranges from 1 to 2500 feet (0.5 to 780 M) water
  • Support Cable: Up to 2500 feet (780m) long
  • Unaffected by algae and buildup
  • Spark and voltage surge protectors
  • Zero & span pots for field recalibration
  • Cable and sensor can be replaced in the field
  • Cable support clamp provided
  • Sludge nose optional for dirty liquids
  • Second vent tube in cable to check down hole sealing
  • Maintenance free operation


  • Technology: Silicon strain gage
  • Supply Power: 13 to 35 VDC 2 wire loop powered
  • Output Signal: 4-20 mADC, isolated, Intrinsically Safe
  • Loop Impedance: 550 ohms at 24 VDC,1100 ohms at 35 VDC
  • Adjustments: Span from 30% to 100% of range, zero to 30% is basic, non-interactive.
  • Vent Tube: Protected from moisture condensation by a desiccant filter or isolation bladder
  • Over Pressure: 2X Range (35 PSI / 2.5 Bar min) w/o damage; 3X Range (1000 PSI / 70 Bar min) w/o rupture
  • Temperature Range:
    • -20 to +180°F (-30 to 85°C) Operating
    • -40 to +220°F ( -40 to 105°C) Intermittent
    • 30 to +130°F Compensated (Higher Available)
  • Accuracy: ± 0.25% F.S. or better
  • Thermal Error: ± 0.02% F.S. / °F maximum
  • Barometric Effect: None
  • Weight:
    • Transmitter, less than 1 pound (0.5 KG)
    • Cable, 1 pound per 25 feet (0.5 KG/8 M)


Water wells, test wells, fuel oils, treatment chemical storage tanks, landfill leachate wells, reservoirs, storm water retention basins.

Optional Features

(in remote 4X housing)

  • Indicator: Large direct reading LCD
  • DC Power Supply: Integral VAC to 24 VDC
  • Alarm Module(s): Integral 5 amp SPDT
  • Pump Control: One or Two Pumps

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