SLW Series – Conductivity Level Switch

SLW conductivity level switch is based on the principle of measuring level through the electrical properties of the process material. As the name suggests, conductivity based level switches and sensors sense the level of water or other conductive liquids that have free ions.

These switches are successfully used in processing plants for conductive liquids of conductivity not less than 25μ Siemens.

Applications of SLW Conductivity Level Switch

  • To avoid overflow
  • For maintaining a constant level to avoid material wastage
  • For switching off pumps when running dry and indicating an empty tank to avoid  wear and tear and production stoppage

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A low AC voltage is applied between the probe electrode and the tank wall (or reference electrode in case of insulated tank). When the liquid comes in contact with the electrode tip, a conductive path is established between the sense electrode and the tank wall / reference electrode. This current is sensed, amplified and made to operate a relay whose contacts in turn can be used for annunciation / control.

Mechanical Specifications


  • Cast aluminium, weatherproof Stoving enamel painted suitable for back panel / wall mounting

Cable Entries

  • 3 Nos. of 1/2″ BSP


  • 1 1/2″ BSP screwed / Flanged 2″ ANSI, 10 mm thick
  • Others (as per size and rating specification)

Probe Type

  • Rod Probe
  • Rope Probe


  • MS: MS (Electroplated)
  • S4: SS 304
  • S6: SS 316
  • SL: SS 316 L
  • PV: PVC
  • PT – PTFE (Total Teflon)
  • HD – Hast Alloy C
  • PC – PTFE Coated (Anti-corrosive)
Electrical Specifications


  • 110 or 230 V AC (15 to +10%) 50 Hz (as specified in the order)

Relay Output

  • One Relay / Two sets / Three Sets of potential-free change over contacts rated at 6A 230 V AC, 50Hz for non-inductive load

 Power Consumption

  • 5 VA approx.

Fail-safe Mode

  • High and Low Field  selectable

Response Time

  • 0.5 second

Switching Delay

  • 0.5 to 20 seconds for probe covered and uncovered condition (on request) High or       Low Field selectable

 Maximum Sensitivity

  • 25μ Siemens




  • 12 V AC (across probe & tank wall / grounding electrode)


  • < 4 mA (between probe & tank wall / grounding electrode through liquid)
Application Specifications


Operating Temperature

  • 20°C to +60°C


  • 10 Bars
  • Flameproof Housing for IIA and IIB Gas group as per IS 2148
Switching Indication
  • 2 LED’s
  • Red: Alarm, Green: Normal