RU2531043C1 - Laboratory analyser of gas density - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to facilities of analytical laboratory equipment, namely, to gas density analysers. A laboratory gas density analyser comprises a miniature turbulent narrowing device, the inlet of which is connected via a tee with a chamber for compression of analysed gas, made in the form of a spiral from a thin-walled metal tube, and the outlet of a measurement chamber of a pressure indicator, one of walls of which is made in the form of an elastic membrane, and its inlet is connected via a valve with a line of analysed gas. Also the analyser comprises a pneumatic tumbler connected to the outlet of the turbulent narrowing device, a syringe, the inlet channel of which is connected with the outlet channel of the chamber for compression of analysed gas, and the body is equipped with a nozzle, location of which is provided by the possibility to create a through chamber from the syringe as the piston is advanced to the maximum, a metre of time intervals with connecting and disconnecting inlets. At the same time the analyser additionally comprises a piezoresistive converter of force into an electric signal arising on an elastic membrane, electronic comparators of maximum and minimum signals of the piezoresistive converter and a reservoir with cooling liquid, where the chamber is located for compression of analysed gas. Besides, the outlet of the piezoresistive converter is connected with inlets of comparators, the outlet of the comparator of the maximum signal of the piezoresistive converter is connected to the connecting inlet of the metre of time intervals, and the outlet of the comparator of the minimum signal of the piezoresistive converter is connected to the disconnecting inlet of this metre.

EFFECT: increased accuracy of measurement of gas density.

1 dwg

Description

The invention relates to analytical laboratory equipment, in particular, to gas density analyzers.

A well-known laboratory gas density analyzer (Kirillin V.A., Sheindlin A.E. Studies of the thermodynamic properties of substances. M: Gosenergoizdat, 1963, p.176-178), which contains a pressure vessel filled with mercury and mounted vertically in a tripod on a certain height, a glass tube with an open lower end, in the upper part of which is installed a miniature turbulent narrowing device for the outflow of the analyzed gas. The lower part of the tube is located in a glass container with mercury, which serves as a barrier fluid. When the pressure vessel moves, the sample of the analyzed gas taken into the tube, due to the displacement of the level of mercury flowing from the pressure vessel to the container, begins to be displaced by the latter through the opening of the turbulent constricting device. During the outflow, the time is measured successively (using a stopwatch) when the mercury level reaches two electrical contacts located along the height of the tube, through which the signal electrical circuits are closed. The height distance between the two contacts is constant. This determines the constancy of the volume flowing out through the turbulent narrowing device of the sample of the analyzed gas. The expiration time of this sample of the analyzed gas is uniquely determined by its density.

The disadvantage of such an analyzer is the need to use mercury in it as a blocking fluid, which is undesirable from the standpoint of safety.

The closest in technical essence is a laboratory gas density analyzer (RU No. 44388, G01N 9/32, 2005 “Gas density analyzer”, LV Ilyasov, AV Buyanov) containing a miniature turbulent constriction device, the input of which connected through a tee to a chamber for compression of the analyzed gas, made in the form of a spiral from a thin-walled metal tube, and the output of the measuring chamber of the pressure indicator, one of the walls of which is made in the form of an elastic membrane, and its entrance is connected through the valve to the line of the analyzed gas, pneum a otumbler connected to the output of the turbulent constricting device, a syringe, the input channel of which is connected to the output channel of the chamber for compression of the analyzed gas, and the body is equipped with a fitting, the location of which is determined by the possibility of the formation of a flow chamber from the syringe with maximum piston extension, a time interval meter with on and off entrances.

Measurement of gas density by this analyzer is carried out by measuring the time interval for the expiration of a sample of the analyzed gas through a turbulent constriction device after it is taken and compressed with a piston in a closed container. In this case, the expiration time is defined as the difference in time points at which the maximum and minimum pressure values selected in advance are reached in the chamber for compressing the analyzed gas with a continuously changing pressure.

The disadvantage of this analyzer is the presence in its composition of an electromechanical device consisting of a metal membrane and two needle contacts, the closure of which determines the values of the two pressures mentioned above. The presence of an electromechanical device determines the low accuracy of measuring the gas density associated with the gradual oxidation of needle contacts, which leads to a change in transient electrical resistance.

The objective of the invention is the creation of a laboratory analyzer of gas density without electromechanical elements.

The technical result is an increase in the accuracy of measuring gas density.

The task and the specified technical result are achieved by the fact that the laboratory gas density analyzer contains a miniature turbulent constriction device, the input of which is connected through a tee to a chamber for compression of the analyzed gas, made in the form of a spiral from a thin-walled metal tube, and the output of the measuring chamber of the pressure indicator, one of the walls of which is made in the form of an elastic membrane, and its input is connected through a valve to the line of the analyzed gas, a pneumatic tumbler connected to the outlet of the turbulent a squeezing device, a syringe, the input channel of which is connected to the output channel of the chamber for compression of the analyzed gas, and the housing is equipped with a fitting, the location of which is determined by the possibility of forming a flow chamber from the syringe with maximum piston extension, a time interval meter with on and off inputs. According to the invention, the analyzer further comprises a piezoresistive transducer of force into an electrical signal arising on the elastic membrane, electronic comparators of the maximum and minimum signals of the piezoresistive transducer and a container with coolant in which the chamber for compression of the analyzed gas is placed, the output of the piezoresistive transducer connected to the inputs of the comparators, the output the comparator of the maximum signal of the piezoresistive transducer is connected to the switching input of Tell time slots, and the output minimum piezoresistive transducer signal disables the comparator is connected to the input of the meter.

This design allows you to measure the accepted maximum and minimum pressure values from the values of the electrical signal of the force transducer by determining the corresponding electrical signals using electronic comparators and an electronic meter of time intervals, i.e. provides all-electric measurement of the named pressure. The design also allows the use of high-precision, in particular piezoresistive, converters of force into an electrical signal for measurement, which determines the possibility of increasing the accuracy of measuring gas density.

Compared with the prototype of the claimed design has a distinctive feature in the combination of elements and their relative position.

A diagram of a laboratory gas density analyzer is shown in FIG.

The laboratory density analyzer contains a miniature turbulent constriction device 1 connected through a tee 2 with a chamber 3 for compression of the analyzed gas, made in the form of a spiral from a thin-walled metal tube, and the output of the measuring chamber 4, pressure indicator 5, one of the walls of which is made in the form of an elastic membrane 6. The inlet of the chamber 4 is connected through the valve 7 to the line 8 of the analyzed gas. The analyzer also contains a toggle switch 9 connected to the output of the turbulent constricting device 1, a syringe 10, the output channel 11 of which is connected to the input channel 12 of the chamber 3 for compression of the analyzed gas. The housing of the syringe 10 is equipped with a fitting 13, the location of which is determined by the possibility of forming a flow chamber from the syringe 10 with a maximum extension of the piston 14. The time meter 15 includes an input 16 and an input 17 off.

The analyzer also contains a piezoresistive transducer 18 of the force arising on the elastic membrane 6, into an electrical signal, electronic comparators 19 and 20 of the maximum and minimum signal of the piezoresistive transducer 18, and a reservoir 21 with a cooling liquid in which the chamber 3 for compression of the analyzed gas is placed. The output of the piezoresistive force transducer 18 is connected to the inputs of the comparators 19 and 20, the output of the comparator 19 of the maximum signal of the piezoresistive transducer 18 is connected to the switching input 16 of the meter 15 time intervals, and the output of the comparator 20 of the minimum signal of the piezoresistive transducer 18 is connected to the switching input 17 of the meter 15 time intervals. Comparators 19 and 20 are equipped, respectively, with devices for setting the response levels of maximum 22 and minimum 23 signal values of the piezoresistive force transducer 18.

Laboratory gas density analyzer operates as follows. After the piezoresistive transducer 18, comparators 19 and 20, devices 22 and 23, and time measuring devices 15 are turned on, the output of the turbulent constricting device 1 is connected to the atmosphere using the toggle switch 9. In this case, the piston 14 is set to the rightmost position shown in the drawing. After that, valve 7 is opened and the analyzed gas begins to enter the atmosphere, flowing through chambers 3, 4 and syringe 10, as well as through turbulent constriction device 1. Thus, turbulent constriction device 1, chambers 3, 4 and syringe 10 are flushed with the analyzed gas. Flushing lasts 1-1.5 minutes. Then, using the toggle switch 9, the turbulent constriction device 1 is disconnected from the atmosphere, and the excess of the analyzed gas flows into the atmosphere through the syringe 10 and the nozzle 13. This completes the operation mode of the “Preparation” analyzer. After moving the piston 14 of the syringe 10 to the left, at a predetermined position, the analyzed gas is compressed to a certain constant pressure and its temperature slightly increases. After a certain period of time, during which the gas temperature takes a certain constant value, for example, equal to the temperature of the coolant, a constant pressure is established in chambers 3 and 4. Then, using the toggle switch 9, the constriction device 1 communicates with the atmosphere, and the analyzed gas begins to flow through the constriction device 1 into the atmosphere (“Analysis” operating mode). In this case, the pressure in the chamber 1 begins to gradually decrease. Therefore, the electric signal arising at the output of the force transducer 18 also decreases, that is, the force arising on the membrane 6 under the action of pressure gradually decreases. This signal is fed simultaneously to the input of the comparators 19 and 20. When the signal at the output of the converter 18 reaches the adopted maximum value (specified by the comparator 19) corresponding to the received maximum pressure, a signal is generated at the output of the comparator 19, which, through input 16, turns on the measuring device 15 time intervals . The countdown begins. When, with a gradual decrease in the pressure in the chamber 4 and a decrease in the signal of the transducer 18, the latter reaches the adopted minimum value corresponding to the minimum pressure (set by the comparator 20), the comparator 20 generates a signal, which, through input 17, turns off the time counter carried out by the meter 15 time intervals. As a result, the value of - τ is measured _and the time interval of the outflow of the analyzed gas through the turbulent constricting device 1, which is usually 50-100 s. To increase the measurement accuracy, it is advisable to carry out a similar operation 3 times and determine the average value of time

.To determine the density of the analyzed gas, all the described operations must be repeated for the reference gas, which can be dried air, and the average time of air outflow is determined $${\overline{\tau }}_{\mathrm{at}}$$

.

The density of the analyzed gas is calculated by the formula

, $${\rho }_{\mathrm{but}}={\rho }_{\mathrm{at}}\cdot {\left(\frac{{\overline{\tau }}_{\mathrm{but}}}{{\overline{\tau }}_{\mathrm{at}}}\right)}^2$$

,

where ρ _in is the density of air under normal conditions.

Experimental studies of the model of a laboratory analyzer of gas density showed that when using high-precision modern converters of force into an electric signal, it is capable of measuring gas density with an error of ± 0.2%.

The advantages of the proposed technical solution:

- simplicity of design and the absence of electromechanical elements;

- high accuracy;

- low cost.

The proposed laboratory gas density analyzer can be implemented on the basis of a standard piezoresistive force transducer, a time interval meter and common electronic devices - electric signal comparators

Laboratory density analyzer can be widely used in the practice of factory and research laboratories of various enterprises of the gas, oil refining and petrochemical industries.

Claims (1)

A laboratory gas density analyzer containing a miniature turbulent constriction device, the input of which is connected through a tee to a chamber for compression of the analyzed gas, made in the form of a spiral from a thin-walled metal tube, and the output of the measuring chamber of the pressure indicator, one of the walls of which is made in the form of an elastic membrane, and its input is connected through the valve to the line of the analyzed gas, a pneumatic tumbler connected to the output of the turbulent constricting device, a syringe, the input channel of which is connected to the output channel chamber for compression of the analyzed gas, and the housing is equipped with a fitting, the location of which is determined by the possibility of forming a flow chamber from the syringe with maximum piston extension, a time interval meter with on and off inputs, characterized in that the analyzer further comprises a piezoresistive transducer of force into an electrical signal arising on an elastic membrane, electronic comparators of the maximum and minimum signals of the piezoresistive transducer and capacity with cooling the liquid in which the chamber for compression of the analyzed gas is located, the output of the piezoresistive transducer connected to the inputs of the comparators, the output of the comparator of the maximum signal of the piezoresistive transducer connected to the switching input of the time interval meter, and the output of the comparator of the minimum signal of the piezoresistive converter connected to the switching input of this meter.