Thermistor and Optic Sensors SP-M/SP-IO

Liquid Level Sensors For Storage Tanks and Other Fixed Applications

Featuring Dynacheck® – Automatic and Continuous Self-Checking Circuitry


The Scully SP-M (thermistor) and SP-IO (optic) models are single point liquid level sensors for use with Scully ST-15 self-checking control monitors. They are used in storage tanks, double containment piping trenches, and double wall storage tank interstitial space monitoring. These reliable sensors have no moving parts and thus are virtually maintenance free.

The SP-M and SP-IO style sensors have a 3/8″ NPT mounting thread and are generally used in conjunction with an SP-O or SP-H style holder. The sensors can be easily extended to the desired installation depth using standard 3/8″ IPS pipe and a pipe coupling. The SP-O elbow holder is generally used when a single sensing point is needed. It can accommodate either an SP-M or SP-IO sensor and mounts into a 3/4” NPT opening in the tank. The SP-H holder allows for up to 3 SP-M and/or SP-IO sensors to be conveniently installed into a single 2″ NPT tank opening. SP-H holders are commonly used to implement multiple high-level and low-level warning points. Both sensor holders are threaded to accept a 1/2″ NPT conduit fitting.


  • Maximum safety with Dynacheck– Automatic and continuous self-checking circuitry when used with Scully monitoring systems.
  • Field-proven, level-sensing technology.
  • Reliable components with no moving parts.
  • Functions within a wide range of temperatures and in a variety of liquid products.
  • Years of dependable, virtually maintenance-free operation.
  • Easy Installation.
  • Custom sensing level adjustment at installation.
  • FM and CSA approved

NOTE: Scully Thermistor Sensors are available in three temperature ranges. (See reverse side for details). Consult Scully for more information.

Liquid Level Sensors For Storage Tanks and Other Fixed Applications


  • Temperature Range: Standard; 0Љ to +140ЉF (-18Љ to +60ЉC)
    • Low; -40Љ to +122ЉF (-40Љ to +50ЉC)
    • High; 0Љ to +200ЉF (-18Љ to +93ЉC)
  • Product Range: Gasoline through #6 oil, and most low viscosity petro – chemical liquids
  • Level Responsibility: +/- 1⁄16″ (1.6mm)
  • Size: Refer to diagrams
  • Response Time: 0.5 second maximum, refer to the controller specications
  • Exposed Materials: Sensors: Aluminum body, Boroscilicate glass sensing element
  • Holders: Aluminum housings, Viton® seals (SP-H only)
  • Electrical Connections: Optic sensors have two-5’ leads. Low temp and Standard Thermistors have two-15’ leads. High temp Thermistors have three-15’ leads.
  • Compatible Rack Controls: Scully ST-15 Series and other stationary thermistor control units. Consult Technical Data Sheets #67036, #60629, #60633

NOTE: The SP-H is designed to withstand pressures up to 400 psi.




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