Contact sensors are security devices typically installed on doors and windows. They can notify you and your system in the event a door, window, or gate opens, or send an alert during an intrusion. A contact sensor is a two-part device comprised of 1) a reed switch, a simple electrical switch controlled by a magnetic field and 2) a magnet. A contact sensor serves as the basic building block to any security system. These sensors are most often used to add security to the doors and windows of your home. When a door or window is closed, the sensor itself aligns with a magnet.
Thermocouples. This type of contact sensor is extremely useful and versatile. Thermistors. The word thermistor is a combination of the words thermal and resistor. Liquid-in-glass Thermometers. Resistance Temperature Detectors (RTDs) .Bimetallic Thermometers. Phase Change Devices. “Differential transformer” method ⇒ Method using a magnetic coil “Scale” method ⇒ Method using an internal scale (ruler). Contact Temperature Sensors are temperature sensors which are required to be in physical contact with the object being sensed and use conduction to monitor changes in temperature. They can be used to detect solids, liquids or gases over a wide range of temperatures.
As shown in Figure 1, there are typically four main components in a sensor node [1], i.e., a sensing unit, a processing unit, a communication unit, and power supply. A sensor is a device that detects and responds to some type of input from the physical environment. The input can be light, heat, motion, moisture, pressure or any number of other environmental phenomena.
