SU1700389A1 - Liquid maximum thermometer - Google Patents

Abstract

The invention relates to a measurement and control technique and can be used in medicine, veterinary medicine, meteorology, hydrology, etc. The purpose of the invention is to simplify the design. The thermometer contains a thermal cylinder 1, a measuring capillary p 2, equipped with a rotary scale 3, and a sealed chamber 4, partially filled with liquid 5. In the internal cavity 6 of the thermal balloon there is a device 7 in the form of a piston pair 8, E with a screw drive 10 and limiters 111 and 12 the stroke of the piston. The handle 13 of the screw 10 is led outside the casing of the thermowell 1. In addition to the device 7, inside the thermobag 1 there is a nipple 14 rigidly connected through the adapter 15 to the end of the measuring capillary 2. g; and its free end 17, made constricted, is inserted into the chamber 4. The turning scale 3 is made in the form of an endless belt 18, put on rollers 19, which are fixed on the support post 20. 4 Il.

Description

The invention relates to a measuring and control technology, namely, devices designed to accurately measure and record maximum values of measured temperatures in various fields of science and technology, including in medical practice for measuring human body temperature.

The purpose of the invention is to simplify the design.

Figure 1 shows the thermometer, front view; figure 2 is the same, side view; fig. 3 - the same side view (embodiment); figure 4 - the same view

front (option design).

The thermometer (FIGS. 1 and 2) consists of a thermal bulb 1, a measuring capillary 2, equipped with a swivel scale 3, and a sealed chamber 4, partially filled with indicator liquid 5.

In the internal cavity 6 of the thermal bulb 1 there is a device 7, made in the form of a cylindrical sleeve 8, inside of which a packed piston 9 is placed, equipped with a screw drive 10 for moving it inside the sleeve 8. The stroke of the piston 9 is limited by rigid stops 11 and 12.

3

ABOUT

s

00

h

The handle 13 of the screw 10 is brought out of the body of the bulb 1,

The device 7 is intended to remove tracer liquid from the measuring capillary 2.

In addition to the device 7 inside the cavity 6 of the thermal bulb 1, there is a nozzle 14 rigidly connected through an adapter 15 to the end of the measuring capillary 2. The other end 16 of the nozzle 14 remains open inside the cavity 6. The nozzle 14 and adapter 15 are designed to prevent air (gas) from entering inside the cavity 6 with a decrease in ambient temperature below 20 ° C and at the same time avoid ruptures of the thermometric liquid.

The sleeve 8 of the device 7 and the nozzle 14, like the bulb 1 itself, are made of a material with high thermal conductivity and at the same time serve as longitudinal partitions designed to reduce the thermal inertia of the thermometer.

The measuring capillary, made, for example, from plastic, is bent at an angle of 180 °. Its free end 17, made constricted, is inserted into the sealed chamber 4 with indicator liquid and lowered into the liquid to a depth that ensures that the end 17 exits the liquid when the thermometer is turned at an angle close to 180 °. This is necessary to communicate the measuring capillary with the gas cavity above the liquid in the indicator chamber 4 in order to reliably remove the indicator liquid from it.

The turning scale 3 is made in the form of a flexible endless belt 18, mounted on rollers 19 with a handle fixed on the axis of one of them, which are fixed on support column 20 rigidly connected to thermal balloon 1. The upper part of thermal balloon is covered by protective cover 21, which made removable and made of transparent material.

In the embodiment of the thermometer shown in FIGS. 3 and 4, the housing of the thermowell 1 is made in the form of a cylindrical chamber 22, inside which is the device 7 and the socket 14, intended for the same purpose as in the first version of the thermometer shown in FIG. 1 and 2. In this embodiment, the scale 3 is made circular as well as the chamber 4 with indicator liquid, and the measuring capillary p 2 is bent into a spiral 23 having two screws in order to increase the measurement scale. The rest of the thermometer design is similar to the design in the first embodiment (Figures 1, 2).

The thermometer works as follows

The thermometer bulb 1 of the thermometer is placed in the socket of the instrument or another place whose temperature is to be measured (for example, a person's armpit when using the thermometer as a medical thermometer).

At the same time, the thermometric liquid in its cavity 6 will begin to expand and will rise along the measuring capillary 2 until the temperature of the thermal bulb 1 becomes equal to the temperature at the measurement site (in this case, the human body). At the same time, when the thermometric liquid rises in the measuring capillary, the gas (air) in its channel will begin to bubble through the opening in the narrowed end 17 of the capillary introduced into the indicator liquid below the level in chamber 4. The process of leaving the gas bubbles from the capillary also will occur until the level of the thermometric liquid in the capillary 2 ceases to change.

When the temperature of the thermowell decreases (after the thermometer is removed from the measurement site), the thermometric liquid will begin to return to its original position. As a result of the part of the air that has left the capillary 2, the indicator liquid 5 will be sucked into it. Based on the law of continuity, the volumetric amount of indicator liquid drawn into the measuring capillary will be close to the volume of air that has come out of it, since that the compressibility of air at its small volumes and small values of pressure (vacuum) occurring in this case can be almost neglected.

Turning the scale 3 using the knob around the rollers 19 until the scale zero is set at the level boundary of the thermometric liquid in the measuring capillary 2, and at the same time it reads the scale, which falls on the level limit of the indicator liquid drawn into the measuring capillary p, we will get the value of the maximum temperature that the bulb had at the time of its removal from the measurement site, and hence the temperature of the object at the measurement site (in our case, the human body).

It should be noted that the digitization of the rotary scale, produced, for example, directly in degrees of temperature, must be reversed, i.e. the smallest distance between the levels of liquids (thermometric and indicator) in the measuring capillary will correspond to the upper limit of the scale of measured temperatures, and the largest, on the contrary, the lower limit, the measured value of the maximum temperature will be as long as it is necessary.

To bring the thermometer to the initial state (for new measurements), it is necessary to remove indicator liquid 5 from measuring capillary 2. To this end, it is necessary to unmute the thermometer in a vertical plane at an angle of 180 ° so that end 17 of measuring capillary 2 goes out from the indicator liquid inside the chamber 4, Then using the device 7, turning the knob 13 of the screw 10, move the piston 9 until all indicator liquid comes out again into the chamber 4. After that, return the piston 9 to its original position until it stops 11, wherein the track to ensure that the capillary was not hit indicator fluid. The presence of the lower stop 11 prevents a change in the established zero position of the level of the thermometric liquid in the measuring capillary, and therefore eliminates the possibility of a systematic error in thermometer performance due to this factor. It should be noted that, as an indicator liquid in a thermometer, the same thermometric liquid can be successfully used, which is filled with a thermal bottle 1 (for example, transformer oil). The only limitation is the need to eliminate the possibility of their interconnection, which is served by the top stop 12. The effect of the thermometer in the circular version shown in FIG. 3 and 4, is not different from the one described above.

In order to assess the accuracy of measurements carried out with the help of a thermometer, we consider the main factors affecting its error. As shown by the analysis, the main factor is the factor characterized by the ratio of the volume of air bubbles emerging from the narrowed end of the measuring capillary and the volume of indicator liquid sufficient to visually assess the amount of displacement of its level in the measuring capillary. These volumes are expressed by the following simple dependencies:

DC

l d2

(2)

where A U1, A 1) 2 are the volumes of the indicator liquid and the air bubble, respectively;

di, d2 are the channel diameters of the measuring capillary and the hole in its narrowed end;

AI is the length of the measuring capillary characterizing the resolution of the observer’s eye and equal to half the price of the smallest scale division,

In order to ensure the required measurement accuracy, it is necessary and sufficient that the volume of gas bubbles (air) leaving the end of the measuring capillary is always less or at least equal to the volume of indicator liquid in the section of length D |, i.e. to make the following inequality:

Alb D lhili

10 15 20 25 30 35 40 45 50 55 tgsby3 oM

-D |

(3)

6 4

Calculations have shown that to provide a maximum temperature measurement, for example, to use a thermometer as a medical maximum thermometer with an error of ± 0.1 ° C in the temperature range 32-42 ° C with a diameter of the di channel in the measuring capillary equal to 0.1 cm (1 mm), it is necessary that the diameter d2 of the hole in its narrowed end should not exceed 62–0.8 mm. As for such influencing factors as a possible change in ambient temperature during the measurement process and the compressibility of gas (air) mentioned above, the analysis showed that the errors due to these factors will be an order of magnitude smaller than the first one. Since the air is in closed cavities above the thermometric liquid in the measuring capillary 2 and above the indicator liquid in chamber 4, the pressures in them will always be the same, and therefore no undesirable displacements of the level of indicator liquid will not occur.

As for the effect of the compressibility of gas (air), which will occur only for the first version of the thermometer, since only in this version there is a vertical portion of the measuring capillary, on which the force of the weight of the indicator liquid, which is drawn inside the measuring capillary, acts with small lengths of this area (no more than 100-120 mm), the magnitude of the non-linearity of the scale due to this factor, as shown

the calculations will not exceed -1%. It should be noted that this value can be reduced by creating an increased initial gas (air) pressure inside the indicator chamber 4 and in the gas cavity above the thermometric liquid in the measuring capillary 2,

Claims (1)

The formula of measurement is the Maximum liquid thermometer containing a capillary with a scale placed in a transparent case, connected at one end to a reservoir filled with a thermometric liquid, characterized in that, in order to simplify the design, two rollers are inserted into it. five Two handles, a chamber mounted on a tank and partially filled with indicator liquid, and connected to a reservoir of piston steam with piston stroke limiters and a screw drive, one end of which is fixed to the piston, and the first handle is mounted on the other end. p is bent 180 ° with a pointed second end placed in the indicator liquid, and the scale is in the form of a flexible endless belt placed with tension on the rollers, mounted rotatably on the axes fixed in the case, t rec one of which is mounted thereon with the second handle removed from the housing. Fig / 2 13  f 3 UCL, tfrss7 SS77JSSSSS X. yy V Yu 17 Fi.Z 23 23