Field-Effect Sensors for Fluid Detection Applications

Technical Overview: How Field-Effect Works

Field-Effect sensors are digital, solid-state electronic devices that can detect conductive materials such as water or the human touch. The sensor’s cell design uses an integrated circuit (IC) that switches its output state when the conductive target is sensed.  A Field-Effect cell is comprised of three main elements, the IC, a unique sensing electrode geometry, and two tuning resistors.  Moreover, Field-Effect requires no moving parts, floats, software, or any other mechanism to operate.

When 5 VDC is supplied to the sensor, a low power, invisible field is created.  The field emanates directly through any protective dielectric barrier such as plastic or glass that may surround or cover the sensor. When a conductive object or material enters the field, the sensor detects the change and indicates an event has occurred with a corresponding output signal. The input stimulus to the field is typically water in most liquid level sensing applications, as is the case in TouchSensor’s™ LevelGuard Home Sump Pump Control product line.


Field-Effect Sensor by TouchSensor Technologies