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Semiconductors and thermistors

General

PTC and NTC thermistors and silicon-based sensors (KTY) are the proven choice for the thermal monitoring of electrical machines and their motor protection. Motor protection thermistors are particularly suitable for monitoring certain threshold temperatures. A reliable protection against overheating can be realized using these types of thermistors together with a matching trigger device. In many cases silicon sensors and NTC enable low-cost selective temperature measurement with sufficient accuracy.

Application

KTY, as well as PTC and NTC thermistors, are well suited as temperature sensors for many applications in the automation technology, in electronic components or in assemblies, in medical technology or in electrical machinery and equipment. Thanks to their compact size, they are ideally suited for installation in narrow copper windings of low voltage motors.

Functional principle

PTCs are ceramic resistors, which show a high conductivity at low temperature, whereas they have low conductivity at high temperature, so they have a positive temperature coefficient (PTC). They provide an alternative to metallic resistors (e.g. Pt100) and silicon sensors (KTY) for measuring temperatures, but are not linear with the temperature. There is a material-dependent critical temperature, at which a dramatic change occurs in the resistance value. The change in resistance can be used as a switch and enables the motor protector. Silicon sensors are inexpensive to produce by wafer processing, but face the disadvantage of being relatively imprecise in the application of linear temperature measurement. They must be linearized by calibration methods requiring electronic support. Hot carrier thermistors, usually made of semiconductor materials, conduct the electric current at high temperatures better than at low ones. They have a negative temperature coefficient (NTC).

Construction

As with Pt100 sensors EPHY-MESS provides PTC, NTC thermistors and KTY silicon sensors in many different designs and assemblies. The range includes versions with a simple base sensor connected to cable and insulation by heat-shrinkable tubes, as well as ceramic or metal sleeves. There are also offered with different heads as screw-in thermometers.

Available sensors

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