Suitable for a wide range of Conductive liquids e.g. Sewage, Water, Acids, Alkalis, Milk, Beverages, Paper Stock, Detergents, Wine etc.
  Precise level detection with no deadband.
  Protection against dry running.
  Prevents pump overrun resulting in reduced operating costs.
  Ignores electrode fouling.
  Simple ‘Low Cost’ installation.
  Wide selection of electrodes and mounting accessories.
  Intrinsically Safe option (P7/IS).

Principle of Operation - Relies on the conducting properties of liquids to complete an electrical circuit between an electrode and the metal tank. For non-metal or coated tanks, the path may be through pump pipework. Alternatively, an earth electrode extending below the lowest active electrode may be fitted. Level sensing electrodes are normally mounted vertically and the controller switching action occurs as the liquid touches or leaves the electrode. Pressure tight electrodes are available for side entry if required. A low voltage A.C. signal is used on the electrodes to prevent electrolysis.

Sensitivity - The input switching point is adjustable between 100 & approx 18,000 ohms, which suits most applications, Higher values up to 500,000 ohms are also available for high purity water.

Switching Differential - Better than 5% of set sensitivity i.e. 50 ohms at 1000 ohms (5 ohms at 100 ohms sensitivity). This is necessary to avoid relay hold-on at the lower electrode caused by material clinging to the probe, electrode wetting, and viscous liquids such as sludge. This close switching differential also allows the high electrodes to ignore foam layers. (Fixed sensitivity controllers without a close switching differential are only suitable for clean water applications).

Fail Safe Feature - Set by a switch on the front panel. The control relay will revert to the alarm condition in the event of a power failure. L.E.D. status indication is provided. As a general rule emptying applications require a fail safe low (FSL) setting and filling applications a fail safe high (FSH) setting.

Mounting Details - The plug-in controller is designed for mounting into an international 11 pin DIN rail/surface mounting socket enabling ease of installation and servicing. The base of the plug-in enclosure has two plastic clips which enable the P4 unit to be securely locked into the Hawker supplied 11-pin base. (The P4 will however fit other bases but the clips may not secure it).

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