SU1121621A1 - Method and device for hot-wire anemometer graduation - Google Patents

Abstract

1. The method of calibration of the hot-wire anemometer, which includes applying to the inputs of the sensitive element of a sinusoidal supply voltage, calibration speed signals at different temperatures of the gas flow, recording the amplitude of the output signal and determining the dependence of the amplitude of the output signal on the speed, that is, expanding the field of application and improving accuracy, additionally register phase shifts at the output of the electric circuit in relation to the supply voltage, determine the dependence phase of the output signal from the velocity and temperature of the gas stream, and when determining the calibration characteristics, the temperature and velocity dependencies on the phase and amplitude of the output signal are calculated by analytical calculation. 2. A device for calibrating a hot-wire anemometer, containing a unit for setting and controlling the velocity and temperature of a gas stream, a sensitive element included in one arm of a bridge electric circuit, a power supply voltage connected in one diagonal of a bridge circuit, and connected in series to the second diagonal of the amplifier , amplitude detector, computational unit and recorder, which is so that, in order to expand the scope of application and improve accuracy, it is additionally equipped with phase the detector, the reference input of which is connected to the power supply source, the measurement input a to the amplifier output, and the output to the second input of the computing unit.

Description

The invention relates to measuring equipment, namely, methods and devices for calibration of thermoanemometers.

There is a known method of x-calibration of an anemometer, which consists in establishing the dependence of the output signal of the thermo-anemometer on the speed at several gas flow temperatures. A device for implementing this method contains an electrical circuit with a hot-wire anemometer, setting the speed and temperature of the gas stream lj.

The disadvantage of this method is low graduation accuracy.

The closest to the proposed technical essence and the achieved result is the method consisting in supplying the inputs of the sensitive element of a sinusoidal signal with a graduated speed signal at different values of gas flow rate, recording the amplitudes of the output signal and determining the amplitude of the output the signal of the electrical circuit from the speed and temperature corrections L2j

A device for implementing this method contains a unit for setting and controlling the gas flow temperature; the sensitive element included in one shoulder of the bridge electrical circuit, the three different-1I arms of which are the adjustment unit, the source of the electrical signal included in one diagonal of the bridge circuit, the second diagonal of which is connected to a circuit of a series-connected amplifier, amplitude detector of the computing unit and the recorder 2j

A disadvantage of the known method and device is that they have a significant measurement error associated with a change in temperature of the gas stream being studied as well as a narrow field of application.

The purpose of the invention is to expand the scope and improve accuracy.

This goal is achieved by the fact that according to the method, which involves applying to the inputs of a sensitive element a sinusoidal supply voltage, velocity calibration signals at different values of the gas flow temperature, recording the amplitude of the output signal and. determining the dependence of the amplitude of the output signal on the speed, additionally register phase shifts on the electrical output of the electric circuit with respect to the supply voltage, determine the dependence of the phase of the output signal on the velocity and temperature of the gas flow, and determine the dependencies of temperature and velocity on phase and amplitude of the output signal.

A device for calibrating a hot-wire anemometer, containing a unit for setting and controlling the velocity and temperature of a gas stream, a sensitive element included in one arm of a bridge electric circuit, a power supply source connected to one diagonal of a bridge circuit, an amplitude detector connected to the second diagonal of the computing unit and the recorder are additionally equipped with a phase detector, the reference input of which is connected to the supply voltage source, the measurement input is connected to move the amplifier, and the output to the second input of the computing unit

FIG. 1 shows the change in the amplitude and phase of the output signal when a gas flow is applied to a hot-wire anemometer with a velocity V and a temperature T; in fig. 2 is a block diagram of a device for calibrating a hot-wire anemometer.

The essence of the method lies in the fact that the physical properties of the sensitive element of the hot-wire anemometer change under the action of a number of parameters. The output signals of the circuit are functions of these parameters:

A A (V, T); C |) cf (V, T)

where A is the amplitude of the output signal

thermo-anemometer;

tp is the phase shift at the output of the electric circuit with respect to the supply sinusoidal voltage.

The amplitude and phase of the output signal is different: it depends on both speed and temperature. The mathematical calibration characteristics gives the possibility to determine the dependence of the amplitude A and the phase tf of the recorded signal of the thermoanemometer on the measured parameters V and T.

The device contains a block 1:;. Tribute and control the speed and temperature of the gas flow, the sensitive element 2, included in the bridge cxc shoulder: 2) i, consisting of unregulated 3 and 4 and adjustable 5 (adjustment unit) element. The power supply voltage source 6 is included in one diagonal of the bridge. A second series amplifier 7 is connected to the second diagonal of the bridge, for example, an operational amplifier with a functional input, an amplitude detector 8 of the eight-detector unit 9 and a recorder 10. It is advisable to use a digital calculator consisting of input analog-digital converters, a synchronizer as a computing unit in the proposed device and the actual calculator. The phase detector t1 is connected by its reference input to the source 6 of the supply voltage, and the measuring input is connected to the output of the amplifier 7. The output of the phase detector 11 is connected to the second input of the digital unit 9. The phase detector can be implemented, for example, in the form of two voltage comparators.

united by their outputs in the coincidence circuit, the output of which is in the output of the phase detector.

The device works as follows.

The source of sinusoidal voltage 6 feeds the diagonal of the measuring bridge. The unit for setting and controlling the speed and temperature of the gas stream 1 creates a calibration effect that changes the parameters of the sensitive element 2. The amplitude and phase of this signal are functions of velocity V and temperature T. Amplifier 7 and amplitude detector 8 amplitude changes, and phase detector variations in the phase of the output voltage with respect to the supply voltage. The voltages from the outputs of the amplitude detector 8 and the phase detector 11 are fed to the input of the computing unit 9, where the processing according to the above algorithm is performed.

The proposed method and device for its implementation increases by 5-10 times the accuracy of the velocity measurement under the conditions of a change in the temperature of the gas stream, thereby expanding the field of application.

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Claims (2)

1. A method for calibrating a hot-wire anemometer, including applying a sinusoidal supply voltage to the inputs of a sensitive element, calibration speed signals at different values of the gas flow temperature, recording the amplitude of the output signal and determining the dependence of the amplitude of the output signal on speed, which is characterized by the fact that, in order to expand the region application and improve accuracy, additionally register phase shifts at the output of the electrical circuit with respect to the supply voltage, determine the phase dependence output signal from the velocity and temperature homo ka gas, and in determining the calibration characteristics computational and analytical means set depending on the temperature and velocity of F PS and output signal amplitude. 2. A device for calibrating a hot-wire anemometer, comprising a unit for setting and monitoring the gas flow velocity and temperature, a sensing element included in one arm of the bridge electrical circuit, a power supply source included in one diagonal of the bridge circuit, the second diagonal of which is connected to the amplifier in series, amplitude detector, computing unit and recorder, characterized in that, in order to expand the scope and improve accuracy, it is additionally equipped with a phase detector, op molecular input of which is connected to a supply voltage source, the input to the output of the measuring amplifier, and the output - to the second input of the computing unit.