A temperature sensor or thermal sensor is a device that, by mechanical or electrical means, transmits from one place (emitter) to another (receiver) the temperature of the emitter. That is, they are used for measuring the temperature and transmitting the signal to a remote control.
Mechanical Temperature Sensors
A mechanical temperature sensor consists of a bulb that contains a gas, which in contact with a hot body dilates; by means of a capillary tube, the increase in volume is transmitted to another bulb, in which an elastic membrane produces a pressure on the element that must be controlled by the temperature.
Electric Temperature Sensors
In this case, there are two types:
- Thermocouples (TC) that work according to the Seebeck effect. The heat of the body to be measured affects a thermocouple, consisting of two sheets of different metals, a device that is capable of generating an electric current, variable depending on the temperature to which it is heated, which the receiver receives. The sensor measures a certain voltage induced by a temperature difference in two joints of two joined metals.
- Thermoresistors (RTD). Also used as a temperature sensitive element is a material whose electrical resistance varies with the temperature (thermistor), the current that passes through it varies depending on it, so that by interconnecting it in an electrical circuit, the receiver receives the temperature of the emitter, measuring the current that reaches him.
Uses of the temperature sensors
It is used in thermal installations, both in buildings (heating, air conditioning) and in industry. It is also used in hostelry in kitchens.
An example of a mechanical probe would be when it was traditionally used in the kitchen to know the temperature of the roast. Currently more automated electric temperature sensors are used, with alarms for example.
In air conditioning, a temperature sensor is used to measure the temperature of the return air, which determines the temperature of the impulsion depending on it.
In the proportional regulation, two temperature sensors are used: one to measure the temperature of the outside (external sensor) and another to measure the temperature of the heat transfer to the outlet of the regulating valve (contact sensor); both data are sent to the switchboard that acts accordingly, according to the programming introduced.
For example, installations with a switchboard that starts the pump when the temperature sensor located at the outlet of the collectors indicates that the temperature is below 4 ° C. Then is ordered to reheat the collectors with the hot water accumulated, avoiding the danger of freezing.
The sensor incorporated in Tronic TE temperature controller
As an example, Tronic’s TE temperature controller incorporate a KTY-81 temperature sensor. Thanks to this we obtain the following benefits:
- Ventilation: When the sensor temperature is the same as the selected temperature, the fan will work at maximum speed
When the temperature goes down, the fan speed will decrease proportionally till the selected minimum speed.
- Heating: When the sensor temperature is the same as the selected temperature, the fan will work at minimum speed.
When the temperature goes down, the fan speed will increase proportionally till the maximum speed.