SU1651114A1 - Method for temperature measurements - Google Patents

Abstract

The invention relates to thermometry, namely to means for measuring the temperature of gaseous media by the speed of sound propagation in a gas. The aim of the invention is to improve the accuracy of determining the temperature of gas media. Generate continuous periodic electrical signals at the source frequency (probe and reference), convert the electrical probe signal into acoustic oscillations emitted into the gaseous medium under study. After passing through a constant acoustic base, acoustic sounding oscillations are received and converted into electrical oscillations. The phase difference between the probe and reference oscillations is fixed. The oscillation frequency is changed to the value of the corresponding initial phase difference, and the temperature of the test medium is determined from the difference in the oscillation frequency after fixing the initial phase difference between the probe and reference oscillations. After this, the test medium is additionally heated with a heat source of known power. The frequency of the generated electrical signals is changed to the value at which the previously measured value of the phase difference between the probe and reference signals is restored, after which the value is recorded. The temperature of the medium T is determined from the results of measurements according to a known dependence. 1 il. (L with about ate

Description

The invention relates to thermometry, in particular to temperature measurements of predominantly gaseous media based on the speed of sound in a gas.

The purpose of the invention is to improve the accuracy of temperature determination.

The drawing shows a diagram of a device that implements the proposed method for determining the temperature of gaseous media.

The device contains a variable-frequency electric oscillator 1 with a digital frequency meter 2, a power amplifier 3 connected in series, an acoustic chamber 4 with an acoustic emitter 5, a receiver 6 and an electric heater 7, a voltage amplifier 8 and a phase meter 9 whose reference input is connected directly to the generator 1, regulated power supply 10 connected via a digital ammeter 11 to heater 7 of the acoustic chamber 4, which is thermally insulated from the environment and heated by a controlled source com 10 food.

The method for determining the temperature of gaseous media is carried out as follows.

Continuous electric oscillations are excited at the initial frequency f, which is measured by a digital frequency meter. Continuous oscillations of the frequency f are divided into probe and reference. They transform electrical oscillations into acoustic oscillations and emit them into an acoustic chamber with the gas medium under study and a constant acoustic base 06. Accepted acoustic oscillations are passed through the test medium and convert them into electrical oscillations. The phase meter is used to fix the phase difference between the probe and reference electrical oscillations.

   J5P (1)

JfR where a - is the coefficient determined by

I am the composition of the gas

on electric power dissipated by camera heater

DT KI2 R,

(3)

where R is the electrical resistance

chamber heater; K - coefficient taking into account the thermal connection between the heater and the gas environment of the chamber. Increase the frequency of probe and reference oscillations to obtain the initial phase difference

C-IP - Mr. GH ,,

Ja (T + AT)

where +

+ Af

- modified value

oscillation frequency.

The obtained value of the frequency fg is measured by a digital frequency meter.

Equating (4) and (1), get

(f, + D f) (X Ј (

t t r

(T + &) aT

(five)

After conversion, expressions (5) have

(

I

wed

- - relationship

specific heat capacity, R - universal gas constant, Hz - molecular weight of gas); T is the temperature of the investigated

environment.

First, they fix the phase difference C, corresponding to the measured temperature T. Then the acoustic chamber is additionally heated, passing an electric current through its heater. The magnitude of the current is chosen such that the reading of the phase meter decreases by 2-3% (two to three divisions with 100 divisions of the phase meter scale)

B- 2

About

-Ja (T + UT)

 (2

where DT - additional heating of the studied medium

The temperature of the additional heating of the test medium in the acoustic chamber is proportional to (f, + Af –Ј4LI + si

-four

& T

(6)

With the indicated overheating of the test medium (changing the phase meter reading by 2-3 divisions) & T "T and therefore

four

i & t. " 1 AT

1 + t 1 + 2T

(7)

Substituting (7) into (6) with regard to expression (3), receive

w. "t-f,.", | I-SiiSf.

(eight)

Having solved equation (8) with respect to temperature, one obtains

f KP-R

- Ј 2 fT - 2

(9)

From the obtained expression (9) it follows that the measured temperature does not depend on the composition of the mixture under study (y and | K) and the constancy of acoustics.

Also, errors due to the non-uniformity of the amplitude-frequency characteristics (AFC) of the emitters and receivers of acoustic j oscillations are excluded.

Determination of the coefficient of thermal coupling K included in the design formula (9) is carried out during the calibration of the acoustic chamber. For this, additional heating of the controlled medium is performed from condition (2) and the temperature of the medium T0 is measured. The heating is then compensated for by a corresponding change in the oscillation frequency15 and from the measured values of f, fЈ, In and Id determine the total thermal coefficient

KR

T

iSVLjyio Haas. (ten)

L a j

In the following, the thermal coefficient KR of the chamber chamber (% d-) is used

to determine the temperature of the test media.

The method of determining the temperature is implemented in the device as follows.

Generator 1, through power amplifier 3, excites in the emitter 5 undamped acoustic oscillations which pass through the test medium of chamber A and are perceived by acceptance 6 6. generator 1. Initially, the ammeter 11 is set to the zero value of the current of the heater 7 of the acoustic chamber A. The oscillation frequency of the generator 1 in the dipole 1-2 1-2 kHz is set such that the phase meter 9 gives zero reading. The value of this frequency f is measured by a digital frequency meter 2. Then a current is passed through the heater 7 from an adjustable source 10 of such magnitude to indicate that the phase meter 9 deviated by 2-3 divisions from zero. After obtaining a steady-state deviation of the phase meter, taking into account the thermal inertia of the chamber 4, the current is measured by an ammeter 11 and the oscillation frequency of the generator 1 is changed until the zero reading of the phase meter 9 is restored.

j

five

0

five

0

oh oh

five

14

The frequency f of generator 1 is measured by a frequency meter 2. From the measured values of the frequencies and f2 and the current value, the temperature of the medium under investigation is calculated using formula (9). The value of thermal temperature J7 is determined during the calibration of the acoustic chamber. To indicate the phase difference between the probe and reference oscillations, an electronic phase meter F2-16 is used, the oscillation frequency of the generator 1 is read by an electron-counting frequency meter 43-34 and an electric current by a digital ammeter L-564. A thermostatic chamber from an ultrasonic gas analyzer of the type UZG with a piezoceramic transmitter and receiver is used as the chamber 4. The chamber heater is disconnected from the thermostat and connected to an adjustable power source of type B8-27.

Carbon dioxide is used as the test medium (

 distribution at 20 ° C (258.3 m / s), the temperature of which varies from +25 to + 150 ° C. The measurement error does not exceed H), 1 ° C.

Using the proposed method is most effective for determining the temperature of aggressive and toxic gas mixtures, for example steam-gas mixtures of various halogens, used in the process of obtaining optical fibers.

Claims (1)

Invention Formula A method for determining the temperature, including generating two periodic electric signals of equal and predetermined frequency, converting the first electrical signal into acoustic oscillations measured in the medium under study, reverse converting acoustic oscillations into an electrical signal after passing a known distance in the medium under study and measuring the phase difference between the transformed and second generated electrical signals, characterized in that, in order to improve accuracy, after measuring the difference phases additionally heat the test medium with a heat source of known power, measure the newly established value of the phase difference between the transformed and the second generated electrical signals, change the frequency of the generated electrical signals until the newly established value of the phase difference becomes equal to the initially measured, and When this condition is met, the corresponding value of fh is recorded. Editor A. Kozoriz ; Compiled by E. R zantsev Tehred S. Migunova Order 1601 Circulation 389 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 Production and publishing complex Patent. Uzhgorod, st. Gagarin, 101 the frequencies of the generated oscillations, and the temperature T of the medium under study is determined by the formula t. ..Ј .. fi - h where W is the heating power; K is the thermal coefficient of the medium under study. Proofreader M. Samborska Subscription