Floatless Sensor

Floatless sensor or Floatless switch is the sensor to detect level of liquid which is detected through electrodes submerged in the liquid.

This sensor is usually widely used in chemical industry primarily to detect liquid level. As an illustration, the following image is an image of floatless sensor made by Omron:

PS-.S(R) Electrode
by Omron

61F-G Floatless Controller
by Omron

Like the others sensors, this sensor would consist of sensor head and controller or amplifier. The controller consist of circuit relay and transformer, which relay will be in the " ON status" when electrodes are connected by a liquid/fluid. The following image is an internal circuit of floatless controller:

61FG Floatless Sensor
by Omron

S0: O Volt or common supply for 110/220 Volt 
S1: 110 Volt supply, S2 : 220 Volt Supply
E3, E2, E1 : Electrode terminal
Here is the example of application of this sensor. Refer the application model that will be used to do with the choice of the controller. The following application is controlling the water supply. Pump ON-OFF will be determined by the level of the pump that is read by the controller through the electrode.

Automatic water supply control
Floatless 61F-G by Omron

The working principle of the circuit above can be explained as follows:

Working principle of Automatic
water supply control by Omron