Design of a heat meter

Construction of a heat meter includes four mandatory elements:

Calculator
Flow sensor
Two temperature sensors

Single and modular construction

Single heat meter - this is a single device in which the calculator is inseparable from the flow sensor and temperature sensors. The complete set and primary calibration of single heat meters are carried out at the manufacturing plant, and such measuring devices are not subject to further re-equipment.

Modular heat meter - consists of separate modules (calculator, flow sensor, temperature sensor). Modular heat meters have flexible equipment and can be composed according to the most demanding requests, for example, to the depth of the calculator archive, the range of taken into account flows, and the length of the connecting wires.

Types of calculators

Calculator with autonomous power supply - equipped with a built-in power source. The advantages of a calculator with autonomous power supply include only the simplicity of installation. The disadvantages of such calculators are the short length of the connecting wires, which usually does not exceed 15 meters, and the short service life of the power source, which is from 6 to 12 years, which is less than the calculated resource of heat meters.

Calculator with external power supply - connected to an external power source with a voltage of 230V or 24V. Calculators of this type can be installed at a distance of up to 100 meters from heat carrier flow and temperature sensors, have an energy-independent memory, and in the absence of power, they stop accumulating data, while preserving the idle time.

Types of flow sensors

Heat meter with mechanical flow meter (mechanical heat meter) - is characterized by low cost, sensitivity to the quality of the heat carrier, and relatively high hydraulic resistance. The flow measurement principle is tachometric, and a paddlewheel rotor is installed in the flow section of the mechanical heat meters, which rotates and transmits the movement to the counting mechanism.

A mesh filter must be installed before the mechanical heat meter.

Heat meter with ultrasonic flow sensor - is characterized by high reliability and accuracy, as well as insensitivity to the quality of the water and creates insignificant hydraulic resistance.

The principle of operation of the ultrasonic flow sensor is based on the use of the dependence of the ultrasound velocity on the stationary and moving flows. Two sensors located in the flow section of the housing exchange ultrasonic signals, and the speed of the flow and, accordingly, the flow rate is estimated by the time it takes for the signal to travel from the transmitter to the receiver.

Heat meter with electromagnetic flow sensor - is characterized by minimal hydraulic resistance and the absence of protruding or moving parts in the flow section. Electromagnetic flow meters are insensitive to contaminants in the heat carrier that do not change the thermal conductivity of the liquid. Heat meters with electromagnetic flow sensors require highly qualified installation.

Thermal meter with resonance flowmeter - characterized by the absence of moving parts in the flow part and the property of self-cleaning from minor contaminants.

Types of temperature sensors

Together with heat meters, platinum temperature sensors of three types Pt100, Pt500, and Pt1000 are used. A platinum sensor is a resistor whose resistance varies depending on the temperature according to a known law. The letters Pt indicate that the sensitive element of the sensor is made of platinum, and the numbers 100, 500, and 1000 correspond to the resistance in Ohms of the sensors at a temperature of 0°C.