SU1136083A1 - Hot-wire anemometer measuring system - Google Patents

Description

The invention relates to a measurement technique and can be used for technical and analytical measurements in gaseous media. Thermo-anemometric devices are known, which contain a sensitive element and a heater s in the form of an inductance coil with a cell communicated with the medium under study ij. The disadvantages of these devices are low accuracy and sensitivity of measurement, as well as the impossibility of measuring the composition of the test medium. Closest to the invention of the technical essence is a thermomemometric measuring system containing four thermometric sensing elements connected in an electrical circuit of a measuring bridge with a secondary device, a system for supplying the investigated medium with laminar and two tsgrbulent limiting drossel and a thermoelectric meter and a thermal sensor. made in the form of a chamber with end fittings, Nffl, in which the thermo-anemometric sensing element 2 is installed., To the disadvantages The devices relate to a large measurement inertia due to thermal transients, and low measurement accuracy. The purpose of the invention is to increase the accuracy and decrease the measurement inertia. To achieve this goal .termoanemometricheska measuring system comprising four sensitive hot-wire element connected velektricheskuyu measuring bridge circuit to the secondary device, inlet and outlet system of the investigated medium with two laminar and turbulent limiting choke and E Hot-film cell, hydrochloric vsholnen a chamber with the end Stutz ramie, in which the thermoelectric sensing element is installed, is supplied with three additional thermo-anemometric Cells, and two thermo-anemometric cells, sensitive elements of which are located in the opposite arms of the electric measuring bridge 3 are connected to the system for supplying the test medium through laminar limited chokes, and the other two thermo-anodematics cells are connected through turbulent limiting chokes. In addition, the inlet and outlet system of the test medium is equipped with pressure stabilizers installed at the inlet and outlet of the medium into the system. The drawing shows a diagram of the system. Thermoanem1: 1 measuring system contains a thermal anemometer of cell 1-4, made in the form of chambers 5-8 with end fittings 9-16. Sensitive elements 17-20 are placed inside each chamber, connected to the bridge measuring circuit provided with a secondary device 21, the supply system is analyzed the damage is done on the throttles x 22-25, and through the same type chokes. the medium is supplied to the cells, the sensitive elements of which are included in the opposite arms of the bridge measuring circuit. The system for supplying the analyzed medium is equipped with pressure stabilizers 26 and 27, respectively, at the inlet and outlet of the medium into the system. Thermoanemometric measuring system works in the following way. The medium being analyzed is through the pressure stabilizer 26 and the throttles 22–25 enters the hot-wire cells 1–4. The throttles 22-25 are selected in such a way that when the concentration of the analyzed medium corresponds to the beginning of the measurement range, the same amount of the analyzed medium flows through the thermo-anemometric cells 1-4, as a result of which the sensitive elements heated by the current passing through them are equally cooled their environment. At the same time, the temperature of sensitive elements, determined at constant heating by the thermophysical properties of the medium being analyzed and its speed in cells of the cells, is the same, their resistances are equal, and the electrical measuring bridge is balanced. When the concentration changes

i 1

of the analyzed medium, the gasdynamic resistances of different types of chokes vary with different gradients, and accordingly the flow rates of the analyzed medium flowing through the chokes also change as a result. Sensitive elements in the cell connected to different types of throttles are cooled differently, therefore their temperatures are taken different values and respectively

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resistances of sensitive elements vary. This is perceived by the electrical measuring circuit and the secondary device. Thus, each composition of the analyzed medium corresponds to a certain indication of the secondary device 21.

The thermo-anemometric measuring system provides higher measurement accuracy and lower measurement inertia.

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Claims (2)

(57; 1. THERMOANEMOMETRIC MEASURING SYSTEM, containing four hot-wire anemometric elements connected to the electrical circuit of the measuring bridge with a secondary device, a system for supplying and removing the test medium with two laminar and two turbulent limiting chokes and a hot-wire cell made in the form of chokes with end faces in which a hot-wire anemometer sensitive element is installed, characterized in that, in order to increase the accuracy and reduce the inertia of the measurement, it is equipped with for three additional hot-wire mesh, the two hot-wire cells sensitive elements are arranged in opposite arms of an electrical measuring bridge, are connected to the investigated medium supply system through laminar restrictive vayuschie throttles, and the other two are connected via a hot-wire Acheyki turbulent limiting chokes. 2. The system according to claim 1, characterized in that the system for supplying and discharging the test medium is equipped with pressure stabilizers / installed at the inlet and outlet of the medium into the system.