SU1281920A1 - Liquid filled-system thermometer and method of adjusting same - Google Patents

Abstract

The invention relates to thermometry and permits an increase in the accuracy of measurements when reconfiguring the measuring range. Inside the thermowell 1, an adjusting bellows 2 is installed with a threaded rod 3 and a running nut 7. As the temperature of the controlled medium 31 changes, the volume of the thermometric liquid 26 in the thermoelectric bottle 1 changes, which leads to

Description

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23

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moving along the remote capillary 4 in the housing 8 of the working pressure formation unit, causing the moving bottom to move behind the giving bellows 13 and springs 14. The working force of the upper bottom of the bellows 12 is transmitted to the lever system of the conversion unit 15, causing it to move through a certain angle. You running pressure causes in the bellows

1281920

27 feedback a new value of force compensation, preventing movement of the lever 16. When adjusting the thermometer, the deflecting bellows 13 and 24 with the springs 14 and 25 are pre-deformed by a magnitude that exceeds their deformation of the opposite sign due to a change in temperature of the controlled medium. 2 sp.f-ly, 1 ill.

, one . The invention relates to thermometry, in particular, to devices for measuring temperature in automatic counterbody systems and for controlling thermal conditions of technological processes in the chemical, petrochemical and other industrial sectors.

The purpose of the invention is to improve the measurement accuracy when reconfiguring the measurement range.

The drawing schematically shows the proposed device.

The manometric liquid thermoelectric thermometer contains a thermal cylinder I, an adjusting bellows 2, a threaded rod 3, a remote capillary 4, a groove 5, a pin 6, a running nut 7, a housing 8 of the unit for forming working pressures, a stud 9, a nut 10, a housing II thermo meter, measuring bellows 12, defining the bellows 13, specifying the spring 14, power conversion unit 15 to the output signal, lever 16, damper 17, complete 18, rotational support 19, measuring thermophone 20 bellows, forming unit housing 21 working pressure, mounting stud 22, nut 23, I give connecting bellows 24, setting spring 25, thermometric fluid 26, feedback bellows 27, pneumorel 28, corrector 29 zero, movable support 30.

The device works as follows.

The bulb 1 is placed on Wednesday 31, the temperature of which is to be measured. In steady state mode

The thermometer kinematic system is in balance.

When the temperature of the controlled medium 31 is changed, for example, when the thermal bottle 1 and the thermometric liquid inside it heats up, the volume of the liquid in the thermal bottle 1 increases. This excess fluid volume uV through the distance capillary 4 flows into the cavity of the housing 8, since the movement of the measuring bellows 12 is limited by the feedback system of the unit 15 (pneumatic compensation system), the change in the fluid volume uV in the housing 8 causes the moving bottom to move set bellows 13, and with it the upper end of the spring 14. This movement is determined by the expression

“. . ,

Sr.g.s.

where & g is the movement of the master bellows and the master spring; Sj J. - effective area of the setting bellows.

To move the driver bellows 13 and the driver spring 14 by the value of d X from the side of the thermometric fluid, a force equal to

Ft, (Z, .c + 2, ex), D,

etc.

FU elastic force of bellows

13 and springs 14; Z, is the rigidity of the driver

7 "C

bellows 13;

Z.PF stiffness of the setting spring 14.

In turn, from the side of the dowel - bellows 13 to the liquid act 31

em reaction R, the value of which is equal to the force of elasticity Hz

R.FJ.

The reaction R is the force with which the bellows 13, acting on the thermometric liquid, forms in it the pressure

R

Eph. Z.S.

This working pressure is set in the entire fluid volume of the measuring thermosystem and causes an operating force on the upper bottom of the measuring bellows 12.

p p with

f p 9 (f.U.C

where S, qj.y.c is the effective area of the measuring bellows. ; The working force P "is transmitted to; the lever system of the block 15 and causes this system to move at a certain angle, setting a smaller gap value in the nozzle-damper assembly and practicing the new output pressure Pg (, u, which, in turn, in the bellows 27 The communication unit 15 causes a new value of the force compensation, preventing the movement of the lever 16.

When operating a pressure gauge thermometer, if you do not take special measures when setting it up, there may be a violation of measurement accuracy when the ambient temperature changes in a wide alternating range. Alignment of fluid volumes in the outer part of the measuring thermosystem and in the compensatory thermosystem is a necessary, but insufficient, adjustment method. Even with the equality of the specified volumes of fluid in the thermal systems, it is possible that the output signal will go off scale. This phenomenon is explained by the following factors. The accuracy of adjustment and the stability of the technical characteristics of the thermometer are ensured by the equality of the rotating moments developed on the lever 16 of the block by 15 measuring bellows of 12 and 20 thermosystems. This equality must be maintained for any changes in ambient temperature.

With an increase in ambient temperature, the volumes of thermometryf5

20

25

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The fluid in the blocks 8 and 21 is increased, and the driver bellows 13 and 24 with the springs 14 and 25 are compressed. When the ambient temperature drops to 5, the volumes of the liquids in the housings 8 and 21 of the units decrease, and the driver bellows and springs expand. In this case, situations are possible (at certain values of the ambient temperature), when the reference bellows and SPRINGS are transferred from one deformation region to another (from the compression region to the extension region or vice versa).

If such a transition from a zone of compression to a zone of expansion (or vice versa) occurs asynchronously, then in the thermal system in which this transition occurs earlier, an abrupt change in pressure is observed, which causes an overshoot of the output signal.

The proposed method for adjusting a manometric thermometer exhausts the decrease in measurement accuracy and is carried out as follows. I

The bulb 1 is placed in a thermostat with a temperature equal to the average value of the limits of measurement. By rotating the 3Q nuts 23, the studs 22 shift the block body 21 upward, while the measuring bellows 20 is compressed. This deformation is transmitted to the driver sylph 24 and the spring 25, which at the same time BUT leads to an increase in the fluid pressure in the compensation thermosystem and to a decrease in the output signal of the thermometer. Then, by rotating the nuts 10 on the studs 9, the body 8 of the measuring thermosystem block moves upwards 40. In doing so, the measuring bellows 12 is compressed. This compression is transmitted through the fluid to the bellows 13 and the spring 14, causing an increase in the pressure of the liquid in the measuring thermosystem. The deformation (compression) of the master bellows 13 must exceed the total deformation of the opposite sign of this bellows caused by a decrease in the volume of the thermometric liquid in the measuring thermosystem when the temperature of the controlled medium decreases to the initial measurement limit and the ambient air temperature decreases to the minimum operating value. For example, if the thermometer has a measuring range from 80 to, and the adjustment is made at ambient temperature

20 ° C and a controlled temperature of 85 ° C (the output signal is fixed at this temperature), the precompression of the bellows 13 should be greater than the stretching of this pin, which would occur if the temperature of the controlled medium decreases to 80 ° C and the environment to - .

For temperature transducers that implement the proposed device and method, the preliminary deformation of the reference bellows and springs by 3.2 mm guarantees that the output signal will go off scale at any values of controlled and surrounding 1x temperatures.

Ф о рм ул а and 3 о, brct e and u

1, A pressure gauge thermometer containing measuring and compensating thermosystems with bhuks of forming working pressures containing elastic sensing elements and a unit for converting measurement results into an output signal, the measuring thermosystem containing also a measuring unit for setting limits and measuring temperature and thermoschons with a distance capillary that differs in order to

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increase accuracy when reconfiguring the measurement limits, a threaded rod with a running nut and an adjusting bellows, the fixed collar of which is hermetically connected to the thermoball cylinder housing, the movable shoulder with the remote capillary of the thermal balloon and the threaded rod, are inserted into the measurement limits tuning unit placed inside the thermal bulb; and the units for forming the working pressures of the thermal systems are equipped with housings, inside of which are enclosed sealed actuating bellows with springs, the fixed flanges of which are connected to the bottom t orats of blocks of blocks connected by upper ends with fixed collars of measuring bellows.

2, A method of setting a manometric liquid thermometer, concluding in the formation of working pressures of a thermometric liquid in thermal systems, is different from. By the fact that, in order to improve the accuracy in setting the measuring ranges, the elastic elements are pre-deformed by an amount exceeding their deformation of the opposite sign, due to the changed temperature of the controlled medium and the surrounding.

Claims (2)

Claim 1. A manometric liquid thermometer containing a measuring and compensation thermosystem with blocks for generating working pressures, 7 • containing elastic sensitive elements ^x and a unit for converting the measurement results into an output signal, and the measuring thermosystem also contains a unit for setting measurement limits and a thermoball with 3 remote capillaries, characterized in order to 0 6 to increase accuracy when reconfiguring the measurement limits, a threaded rod with a running nut and an adjusting bellows are introduced into the unit for setting the measurement limits, the fixed collar of which is hermetically connected to the body of the thermowell, the movable collar with a remote cap of the thermowell and a threaded rod, and blocks for forming the working pressures of the thermal systems are equipped with housings, inside of which are sealed master bellows with springs, the fixed shoulders of which are connected to the lower torus tsets of the cases of the blocks connected by the upper ends with motionless collars of measuring bellows. 2, A method for adjusting a manometric liquid thermometer, which consists in generating operating pressures of a thermometric liquid in thermosystems, characterized in that, in order to improve accuracy when setting measurement ranges, elastic sensitive elements are pre-deformed by an amount exceeding their opposite sign deformation due to a change in temperature controlled environment and ambient air.