Float Level Sensor Operating Principle

The FPI Sensors float level sensor operates with an internal magnetic reed switch and an external magnetic field mounted in the float. Inside the stem, there is an individual, hermetically sealed, electrically insulated, magnetically activated dry contact reed switch.

The reed switch is classified by its maximum power ratings and magnetic sensitivity. Because this is a dry contact, it stores no power. The reed switches are electrically isolated to pass a minimum 1.6KV Hipot (dielectric breakdown) test. The float on the outside of the stem provides the magnetic field (which is matched to the reed switch) to activate the internal reed switch.

FPI Sensors float level sensors are listed under UL File E324587. In addition, these sensors are designed to be compatible with intrinsically safe circuits for use in hazardous locations.

Maintenance of the float level sensor is suggested for applications where there is a potential for material buildup that would prevent the float from properly moving. To clean the sensor, remove from or access the float level sensor assembly in the tank and inspect for any foreign material build up.

If build up is present, select a cleaning solution that is compatible with the float level sensor’s float and stem material and clean appropriately. If the float needs to be removed, make sure the top of the float and the float stop locations are identified so insure the float goes back on to the stem with the proper orientation and the float stops are returned to there original location. To confirm the sensors operation, disconnect the wires from your control system.

Connect an ohm meter or continuity meter to the sensor wires. Move the float up and down to verify the switch opens and closes in the designed float location. The design dimensions of the sensor are typically measured from the face of the mounting fitting. See the specific drawing information for more detailed information.