AEA Amatrol's Sensor Logic Systems Practice Test

Capacitive sensing detects changes in capacitance caused by a nearby object's ability to store electric field energy, which depends on the material’s dielectric constant (relative permittivity). Materials with higher dielectric constants place more of the electric field within them, increasing capacitance for the same sensor geometry and making the object detectable from a greater distance. So, objects with higher dielectric constants are sensed at greater distances. Conductivity, magnetic properties, and thermal characteristics don’t determine sensing range in this basic capacitive model—conductivity can affect signal quality, magnetic properties relate to inductive sensing, and temperature effects don’t directly change the capacitive coupling. For example, water has a high dielectric constant and is detectable farther away than air, which has a very low dielectric constant.