Temperature sensors for heating: purpose, types, installation instructions

When the heating devices required to control the degree of heating the coolant and indoor air. Remove and help to transfer information temperature sensors for heating, from which information can be read visually or immediately sent to the controller.

This device allows to process the information and, based on the control signal supplied.

The principle of operation of the thermal sensor

Heating control system can be a variety of methods, including:

• Automatic devices for timely The power supply;
• unit that monitors the security;
• mixing units.

For correct operation of all of these groups are required temperature sensors, feeding signals about the operation of the instrument. Observing the reading of these devices allow time to identify faults in the system and take corrective measures.

There are many types of devices used for removing heat. They can be immersed in the coolant, to be used indoors or located outside

The temperature sensor can be used as a separate device, for example, for monitoring the temperature of the room, or be integral part of a complex device such as a boiler.

The basis of such devices that are used in automatic control, the principle of converting electric signal into temperature readings. Due to this the measurement results can be transmitted across the network quickly in the form of a digital code, which guarantees high speed, sensitivity and accuracy of measurement.

At the same time various devices for measuring the heating step may have structural features, influencing a number of parameters (operation in a particular environment, the transmission method, and imaging method others).

Kinds of devices for removal temperature

Termopribor can be classified in a number of important criteria, including information transmission method, location and installation conditions as well as the algorithm readings.

By way of information transfer

According to the method used by the broadcast of information gauges are divided into two broad categories:

• wire devices;
• wireless sensors.

Initially, all similar devices equipped with wires, through which the temperature sensors were connected to the control unit by transmitting information to it. Although such devices are now pushed wireless counterparts, they are still often used in simple circuits. Furthermore, wired sensors are more accurate and reliable reading operation.

To ensure consistent operation wire sensor used in the composite device, it is desirable to combine it with the equipment, which is provided by the same manufacturer

At present, widely used wireless devices, which often transmit information using radio wave transmitter and receiver. Such devices can be installed virtually anywhere, including a separate room or outdoors. Important characteristics of such temperature sensors are:

• battery is installed;
• accuracy of measurements;
• distance signal transmission.

Wireless / wired device can completely replace each other, but their functioning have some peculiarities.

At the place and method of placement

At the place of mounting such devices are divided into the following varieties:

• invoices, attached to the heating circuit;
• submersible in contact with the coolant;
• room, inside a residential or office space;
• external, which are located outside.

Some units can be used several types of sensors to monitor the temperature.

On the mechanism of readings

By the method of demonstration equipment information may include:

• bimetal;
• alcohol.

In the first embodiment, it is assumed to use two plates made of various metals, as well as dial gauge. With increasing temperature an element deforms, creating pressure on arrow. Indications of such devices have good accuracy, but their biggest drawback is inertia.

Bimetal thermostats and alcohol are often set on a heating equipment such as boilers. They allow you to keep track of the heating, the excess of which can lead to fatal consequences

This shortcoming is almost completely devoid of sensors, which are based on the use of alcohol. In this case, hermetically sealed flask filled with alcohol-containing solution, expanding when heated. The design is quite elementary, reliable, but not very convenient for observation.

Various types of temperature sensors

To remove the temperature readings are used devices having different operating principle. Among the most popular are the following instruments.

Thermocouples: precise removal - the difficulty in interpretation

This device consists of two welded wires with each other, made of different metals. The difference in temperature occurring between the hot and cold end serves as a source of electrical current value of 40-60 mV (figure depends on the thermocouple material).

Most often the following combinations of metals and alloys used for the manufacture of thermocouples: chromium-aluminum, iron-kostantan, iron-nickel, nickel-chromium, and other

The thermocouple is considered a high-precision temperature sensor, however, to remove an accurate reading from it rather difficult. To do this, find an electromotive force (EMF) by using the device temperature difference. To obtain a correct, it is important to compensate for the cold junction temperature using, for example, a hardware method, in which the second thermocouple is placed in an environment previously known temperature.

Software compensation method involves placing a thermode another izokameru together with the cold junctions which allows to control the temperature with a predetermined accuracy.

Certain difficulties process is reading data from the thermocouple because of their nonlinearity. For the correctness of the testimony in the GOST R 8.585-2001 introduced polynomial coefficients, which allows to translate the EMF in temperature, as well as to perform inverse operations.

Another problem is that the readings are taken in microvolts for conversion which can not be used widely available digital devices. To use in the construction of thermocouple, you must provide accurate, multi-bit converters with minimal noise.

Thermistors: quickly and easily

Considerably easier to measure the temperature using thermistors, which are based on the principle of strength of materials depending on the ambient temperature. Such devices, for example, made of platinum, have such important advantages as high accuracy and linearity.

The main problem of such temperature sensors can be regarded as an extremely low temperature coefficient of resistance, however, to accurately measure its still easier than small catch voltage values ​​thermocouples

An important characteristic is the base resistor resistance at a certain temperature. According to GOST 21342.7-76, this index is measured at 0 ° C, it is recommended to use a series resistance (ohms), and the TCS - temperature coefficient, calculated by the formula:

TCS = (Re - R0c) / (Te - T0c) * 1 / R0c,

wherein Re - resistance at operating temperature, R0c - resistance at 0 ° C, Te - operating temperature, T0c - 0 degrees C.

The guests also shows the temperature coefficients, provided for the various measurement devices, made of copper, nickel, platinum, and identifies the coefficients used for calculating the temperature based on current performance resistance.

Thermistor sensors are widely distributed in electronic and mechanical engineering industry, thanks to the accuracy of readings, sensitivity and undemanding in operation

Measure the resistance can include the device in the power supply circuit and measuring the differential voltage. Prokonstrolirovat indicators by using integrated circuits, an analog output which is equal to the supply voltage. Thermal sensors such devices can be easily connected to the analog-to-digital converter digitizing it at eight or desyatibitnom ADC.

Digital sensor for simultaneous measurement

Widely used as digital temperature sensors, e.g., DS18B20 model, the operation of which is performed using the chip having three outputs. With this apparatus may take temperature readings simultaneously from multiple sensors operating in parallel, the error is only 0.5 °.

Popular model is a combined temperature / humidity sensor SHT1, which allows heat measurements with an accuracy of ± 2 °, and humidity with an accuracy of 5. However, the manufacturer claims that are more accurate and cost-effective instruments

Among other advantages of this device may be mentioned a wide range of operating temperatures (-55 + 125o). But the main disadvantage - slow operation: for the most accurate computing device requires a minimum of 750 ms.

Contactless irometry (imagers)

The action of these proximity sensors based on fixation of the thermal radiation emanating from the body. To characterize this phenomenon is used the amount of power allocated per unit time per unit area, which per unit of wave length range.

Such a criterion, which reflects the intensity of monochromatic radiation, called the spectral luminosity.

The following types of pyrometers:

• radiation;
• brightness (optical);
• color.

The first category enables measurements within 20-25000o C, but it is important to detect the temperature into account coefficient of the incompleteness of radiation, effective value of which depends on the physical state of the body, its chemical composition and other factors.

The picture you can see a schematic arrangement of the radiation pyrometer. Its main active components of the telescope is (+ eyepiece lens) and a battery, consisting of a series circuit of thermocouples

The brightness (optical) pyrometers are designed for temperature measurement 500-4000o C. They provide high precision measurements, however, can distort readings due to the possible absorption of radiation from the body of the intermediate medium through which observations are made.

Color pyrometer, whose action is based on determining the radiation intensity at the two wavelengths waves (preferably in the red or the blue segment of the spectrum), are used for measurements in the range 800 to 0 ° C. Their main advantage is that the radiation does not affect the incompleteness of the measurement error. In addition, the indicators do not depend on the distance to the object.

temperature transducers quartz (piezoelectric)

For readout of temperatures within -80 to +250 degrees can use quartz converters (piezo elements), the operating principle of which is based on the frequency dependence of Quartz by heating. In this case, the function of the inverter is influenced by the location of the cut-off of the crystal axes.

Piezoelectric (quartz) is most often the device is used during the research, since such devices are characterized by an extended measuring range, reliability, high accuracy

Piezoelectric sensors are fine sensitivity, high resolution, they can work reliably for a long period of time. Such devices are widely used in the manufacture of digital thermometers and is considered one of the most promising tools for future technologies.

Noise (acoustic) Temperature sensors

Operation of such devices is provided by removing the acoustic potential difference depending on the temperature of the resistor.

Acoustic methods allow you to take temperature readings in confined spaces and environments where direct measurement is impractical. Such devices have been used in medicine, in underwater research, as well as in industry

A method of measuring such sensors is rather simple: it is necessary to compare the two noise produced similar elements, one of which is at a known in advance, and the second - when determined temperature.

Acoustic temperature sensors suitable for measuring the interval -270 - + 1100C. In this process complexity is too low noise level: sounds amplifier, sometimes choke it.

Temperature sensors NQR

SUMMARY operation thermometers nuclear quadrupole resonance is the action of the field gradient which form crystal lattice points and a kernel - index caused by deviation from the symmetry of the charge sphere.

As a result of such a phenomenon occurs procession nuclei its frequency is dependent on the gradient field grating. The magnitude of this parameter also affects temperature: its ascent causes drop NQR frequency.

The main element of such sensors - ampoule with a substance that is placed in the coil inductor connected to the oscillator circuit. The advantage of the instrument is the unlimited duration of the measurements, reliability and stability. To the same disadvantage relates nonlinearity measurement that necessitates the use conversion function.

Devices for semiconductors

Category devices functioning on the basis of changes in the characteristics of p-n junction, caused by exposure to heat. The voltage across the transistor is always proportional to the temperature, which makes it easy to calculate this factor.

Advantages of such devices is the high data accuracy, low cost, the linearity characteristics for the entire measurement range. Installation of these devices can be done easily directly on the semiconductor substrate, so that they are perfectly suited for microelectronics.

Volumetric converters for removal temperature

The basis of these devices laid known principle of expansion and contraction of substances observed on heating or cooling. Such sensors are sufficiently practical. They can be used to determine the temperature within the boundaries of -60 - + 400 ° C.

To be able to visually monitor the temperature of the majority of temperature sensors on the premises, equipped with a display, which displays the current values

It is important to remember that the measurement of liquids such devices are limited to a temperature of boiling and freezing points, and gases - their transition to the liquid state. Caused by environmental influences measurement error for these devices is small enough: it varies within the limits of 1-5%.

Selection of the temperature sensors

such as the factors to consider when choosing such devices as:

• The temperature range in which the measurements are made.
• The need for and the possibility of immersing the sensor in the object or environment.
• Conditions of measurement: for readout in a hostile environment is better to choose a non-contact version of the model, or placed in a corrosion cabinet.
• The service life of the device prior to calibration or replacement. Some types of devices (eg, thermistors) quickly fail.
• Technical data: resolution, voltage, speed alarm, error.
• The magnitude of the output signal.

In some cases also important material of the body of the device, and the use of the premises - the size and design.

Recommendations for mounting their own hands

Such devices are widely used for various purposes: they are equipped with radiators, heating boilers and other appliances.

Before starting the installation, you should read the instructions carefully: it specifies not only the features of the installation (for example, Sizes for connection to the pipe), but also the rules of operation and temperature limits for which suitable measuring instrument. It is also necessary to consider the size of the liner, which can vary in the range of 120-160 mm.

The two most common case the temperature sensor installation.

Connecting the device to the heatsink

It is not necessary to equip the thermostat all the heaters. According to regulations, the sensors are mounted on battery if its total power exceeds 50% of the heat generation similar systems. If the room has two heaters, the thermostat will be set at only one having a greater power rating.

The temperature sensor is an integral part of temperature controllers, allowing to reduce or increase the heating of the radiators, floor heating and other heating devices

instrument valve is installed on the supply line in place of the radiator connection to the heating network. When it is impossible to tie it into the existing chain should be dismantled liner supply, which can cause some difficulties.

To carry out this manipulation is necessary to use the tool for cutting pipe, while the installation of the thermal head is easily performed without special equipment. Once the sensor will be mounted, combine sufficiently made marks on the body and the device, whereupon a smooth head is fixed by pressing the hand.

Mounting air thermode

Such a device is installed in the coldest room apartment draft-free (in the lobby, a kitchen or boiler installation it is undesirable because it can cause disturbances in the operation of the system).

When choosing a place you need to make sure that the unit does not fall sunshine, next should not be heating appliances (heaters, radiators, pipes).

For conventional heating system only one thermostat, whereas the collector circuit is desirable to use a plurality of sensors, whose number is equal to the number of rooms. This allows individual temperature control in separate spaces

Connecting device carried out according to the instructions that are found in the data sheet, wherein the terminals are used, or cable, which are supplied.

If necessary, a temperature monitoring system "warm floors" sensor may be located deep in concrete screed. In this case, the protection may be applied to a corrugated tube having one closed end and sloping bending (the latter feature allows you to extract the broken appliance, if necessary, replace it new).

Mounting of the device is as follows:

• In the wall of the recess is arranged for fixing the attachment device.
• With the front piece thermode is removed, after which the device is installed on the prepared site.
• Further to contacts connected heating cable, while the sensors - terminals.

The final stage - the connection of the supply cable and install the front panel into place.

If the device for which the functionality necessary internal connection sensor has a complicated structure, it is better to refer to specialists.

Useful videos on the topic

In the video below describes in detail how to carry out setting on the boiler Termopribor:

Is the installation of sensors on the flow and return pipes:

Temperature sensors are widely used in various fields of industry and for domestic purposes. Large assortment of such devices, which are based on different principles of operation, allows you to choose the best option to solve this or that problem. In houses and flats, such devices are often used to maintain a comfortable temperature in the rooms, as well as adjusting heating systems (cells, floor heating).