CA1102580A - Instrument for measuring sizes and quantity of particles in fluid medium - Google Patents
Instrument for measuring sizes and quantity of particles in fluid mediumInfo
- Publication number
- CA1102580A CA1102580A CA304,876A CA304876A CA1102580A CA 1102580 A CA1102580 A CA 1102580A CA 304876 A CA304876 A CA 304876A CA 1102580 A CA1102580 A CA 1102580A
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- light
- sensitive device
- particles
- instrument
- fluid medium
- Prior art date
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Abstract
INSTRUMENT FOR MEASURING SIZES AND QUANTITY OF
PARTICLES IN FLUID MEDIUM
ABSTRACT OF THE DISCLOSURE
According to the invention, the instrument for measu-ring the sizes and quantity of particles in a fluid medium comprises a light-sensitive device which converts light scattered by particles in a flow of a fluid medium which crosses a beam emitted by a light source, as well as some part of the light of that beam, arriving from an element whose purpose is to simulate a calibrated particle, to electric pulses. The light-sensitive device is connected via a divider, whose purpose is to distribute pulses according to the sizes of particles, to signal inputs of respective threshold devices whose outputs are con-nected to inputs of counters with indicators. The element which simulates a calibrated particle is adapted to perio-dically change, in the course of measurement, the bright-ness of light received by the light-sensitive device.
Interposed between the output of the light-sensitive device and reference inputs of the threshold devices is a circuit for converting output pulses of the light-sensi-tive device to direct-current voltage which adjusts the trigger levels of the threshold devices according to the amplitude of a pulse arriving from the element which simulates a calibrated particle.
PARTICLES IN FLUID MEDIUM
ABSTRACT OF THE DISCLOSURE
According to the invention, the instrument for measu-ring the sizes and quantity of particles in a fluid medium comprises a light-sensitive device which converts light scattered by particles in a flow of a fluid medium which crosses a beam emitted by a light source, as well as some part of the light of that beam, arriving from an element whose purpose is to simulate a calibrated particle, to electric pulses. The light-sensitive device is connected via a divider, whose purpose is to distribute pulses according to the sizes of particles, to signal inputs of respective threshold devices whose outputs are con-nected to inputs of counters with indicators. The element which simulates a calibrated particle is adapted to perio-dically change, in the course of measurement, the bright-ness of light received by the light-sensitive device.
Interposed between the output of the light-sensitive device and reference inputs of the threshold devices is a circuit for converting output pulses of the light-sensi-tive device to direct-current voltage which adjusts the trigger levels of the threshold devices according to the amplitude of a pulse arriving from the element which simulates a calibrated particle.
Description
o The present invention relates to instrument makina and, more particularly, to instruments ~or measuring the sizes and ~u~ntity of particles in a ~luid medium.
The most e~fective application o~ the instrument in accorda~ce with the invention is the control of air pol-lution in shops and o-ther production facilities.
The instru~ent of this invention can also be used to determine the degree o~ pollution o~ fluids in the chemical industry and at machine-building works.
~ he instrument according to the invention can further be used in medicine for analyzin~ the composition of blood and other fluids.
~ here are kno~n instruments for measuring the sizes and quantity of particles in a ~luid medium o~ the type th~t comprises a dark chamber, wherein a beam of light is emitted by a light source and shaped by a system o~ lenses. ~he chamber also accommodates a li~ht-sensitive device which receives light scattered by particles found aaross the path of the light beam. ~he particles are introduced into the chambor with ~ flow of a fluid m~di-um being investigated, v~hich i~ directed transversely to the light beam. The li~ht-sensitive device converts the flashes of lig~t, scattered by the particles, to eleotric pulses. ~he outpu~ of the light-sensitive device is connccted via a div~der, whose purpose is to distribute pulses accordi~g to the sizes of particles,
The most e~fective application o~ the instrument in accorda~ce with the invention is the control of air pol-lution in shops and o-ther production facilities.
The instru~ent of this invention can also be used to determine the degree o~ pollution o~ fluids in the chemical industry and at machine-building works.
~ he instrument according to the invention can further be used in medicine for analyzin~ the composition of blood and other fluids.
~ here are kno~n instruments for measuring the sizes and quantity of particles in a ~luid medium o~ the type th~t comprises a dark chamber, wherein a beam of light is emitted by a light source and shaped by a system o~ lenses. ~he chamber also accommodates a li~ht-sensitive device which receives light scattered by particles found aaross the path of the light beam. ~he particles are introduced into the chambor with ~ flow of a fluid m~di-um being investigated, v~hich i~ directed transversely to the light beam. The li~ht-sensitive device converts the flashes of lig~t, scattered by the particles, to eleotric pulses. ~he outpu~ of the light-sensitive device is connccted via a div~der, whose purpose is to distribute pulses accordi~g to the sizes of particles,
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to signal inputs of threshold devices. Outputs of the threshold devices are co~nccted to inputs of counters with indicators The accuracy o~ the instrument is checked with the aid of an element which si~ulates calibrated particles.
This ~lement comprises a movable member which is made to cross the light beam prior to measurement.
~ he accuracy of the instrumen-t is checked with the aid o~ an element which simulatcs calibrated particles.
This element comprises a movable member which is made to cross the light beam prior to measurement.
~ he instrument u~der review is checked onlg a short time before the measurement; it is adjusted by the ope-rator, which is an unnecessary complication in the use o~ the instrument~ In addition, the instrument under r3view does not make it possible to eliminate the ef~ects of such souroes of error as unstable volta~e of the power source, which may rapidly ~ar~ in the course of measure-ments.
It is an objocb o~ the present invention to provide an instrument ~or measuring the sizes and quantit~ of partioles in a ~luid medium, wherei~ the design of the olement simulating a calibrated partiole would make it possible to automatize the calibration of the instrument, while using the instrument to measure the sizes and quan-tities of particles.
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It is another object of the invention to improve the accuracy of measuring particle sizes.
It is still another object of the invention to facilitate the use of the instrument.
In accordance with an embodiment of the invention an instrument for measuring the sizes and quantity of particles in a fluid medium comprises a dark chamber, a light source accommodated in said dark chamber, means for shaping a light beam emitted by said light source, accommodated in said dark chamber, means for introducing the fluid medium into said chamber so that it crosses the light beam emitted by the light source: an element simulating a calibrated particle, accommodated in said chamber, a light-sensitive device installed in said chamber and intended to convert the light scattered by particles contained in the flow of the fluid medium which crosses the light beam emitted b~ said light source, as well a~ part of the light of that beam, arriving from said element, to electric pulses: said element for simulating a calibrated particle being adapted to periodically change, in the course of measurements, the brightness of the light received by said light-sensitive device;
a converter circuit for converting output electric pulses of said light-sensitive device to d.c. voltage, which circuit is connected with its input to an output of said light-sensitive device: a divider whose input is connected to the output of said light-sensitive device: threshold devices connected with their signal inputs to outputs of said divider which is intended to distribute electric pulses, arriving from said light-sensitive device, among said threshold devices according to particle sizes: an output of said converter circuit being connected to reference inputs of said threshold devices whose trigger levels are dependent upon d.c.
voltage at the output of said converter circuit: means for counting and displaying the quantity of pulses corresponding to that of particles in the flow of the fluid medium being investigated, which is done individually for each size group.
It is expedient that the element simulating a calibrated particle should be shaped as a rod adapted for reciprocating motion so as to periodically enter the light beam, for which purpose the rod is ooupled to an electro-magnet's armature.
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Such a design of the element simulating a calibrated particle is the simplest and accounts for a ma~imum accuracy of measurements.
The element simulating a calibrated particle may be designed as a light channel to transmit part of light of the beam emitted by the light source to the light-sensitive device, which channel accommodates a light chopper controlled by a drive.
The latter design makes it possible to adjust the brightness of light and, consequently, an equivalent calibrated particle size.
The instrument for measuring the sizes and quantity of particles in a fluid medium according to the invention is calibrated automatically in the course of measurements, which accounts for an excellent stability of the metrological characteristics of the instrument and a high accuracy of measure-ments.
Other objects and advantages of the present invention B
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will become more apparent from the following detailed description of a preferred embodime~t thereo~ to be read in conjunction with the accompanying drawin$s, wherein:
~ IG. 1 is a schematic diagram o~ an instrument for measuring the sizes and quan~ity o-~ particles in a ~luid medium, in accordance with the invention, includin~ a~
elevation view o~ an element for si~ulating a calibrated particle, which element is designed as a rod;
~ IG. 2 is a viow of a chamber with a system of mirrors, i~ accordance with the invention;
FIG. 3 is a schematic diagram o~ an instrument for measurin~ the sizes and quantity o~ particles in a fluid medium, according to the invention, wherei~ the element simulati~g a calibrated particle is designed as a system of prisms with a light chopper;
~ IG. 4 is a view o~ a chamber accomm~dating light guides.
~ he invention will be ~urther described in greater detail with re~erence to an instrument used to oontrol air pollution. ~he instrument comprises a daxk charnber 1 (~IG. 1) which accommodates a lamp 2 servi~ as a light sourae, and a system of lenses 3 intended ~or shaping a light beam. ~he chamber ~ further accommodates a light--se~sitive device 4 whose visual ray, shaped by a system . . .
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o~ lenses 5, extends at a perpendicular to the li~ht beam produced by the source 20 In order to introduce air to be checked for pollution into the chamber 1, the latter is provided with a nozzle (not shown) ins-talled so as to direct t~e air ~`low at the point of intersection of th~ above-mentioned beams.
An element 6 is intended to simulate a calibrated particle and is designed as a rod, also designated as 6, which is adapted to periodically change, in the course of measu-reme~ts, the brightness o~ light received by the light--sensitive device 4.
In order to vary the brightness o~ light, the rod 6 i~ made movable SQ as to be able to enter the beam emitted by the light source 2; ~or this purpose, the rod 6 is coupled to an armature 7 o~ an electroma~et 8 supplied by a generator 9 which is solely meant to energize the electromagnet 8. ~he rod 6 is arranged so that while in motion, it periodically gets into the beam emitted by the light source 2, scattering some light o~ that bearn in the direction o~ the light-sensitivo devico 4.
~ he light-sen~itive devioe 4 serve~ to convert li~ht it reaeives to clectric pulses. Its ~unatio~ may be per-iormed by an~ suitable li~ht-sensitive device, ~or example, a photoelectro~i¢ multiplier. An output of the li~ht-sen-giti~e deYioo 4 is conne¢ted to an input o~ a circuit 10 intended to convert output pulses o~ t-,he light-sensi~ive device 4 to d.c. voltage; the outpu-t o~ the device 4 is also connected to signal inputs o~ threshold devices 11, which connection is eflected via a divider 12 serving to di-stribute output pulses of the light-sensitive device 4 -amon~ the threshold devices 11 according to the sizes o~ particles contained in the air ~low~
An output of the converter circuit 10 is connected to re~erence inputs of the threshold devices ~1.
The circuit 10 ~or converting output pulses of the light-sensitive device 4 to d.c. voltage is an integra-ting cir¢uit aomprising a resistor 13, a diode 14 and a capacitor 15; the time constant o~ the integratin~
cir¢uit is selected to be much longer than the duration of the pulse produced at the output of the light-sensitive device 4 as it receives light s¢attered by particles ¢ontained in the air ~low; at the same time the time ¢onstant of the integrating circuit is less than the dura-tio~ o~ the pulse produced at the output o~ tb~ light--sensitive dcvioe 4 as it r~ceives light soattered by the rod 6 which serves to simulate a cal~brated particle. From the outputs o~ the threshold devices 11, pulses are applied to inputs of respe¢tive ¢ounters 16 with indicators in-tended to count and display the number o~ pulses corres-ponding to that o~ parti¢les o~ ea¢h size group contained in the air being investigated.
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. .. -, . . . . ~ , 2~0 The divider, threshold devices and counters ~ith indicators may cmploy any k~o~Yn circuitries suitable to perform their respective func-tions.
The element ~or simulating a calibrated ~re~uency may also be desi~ned as a light-tra~smitting channel 17 (FIG. 2) comprising a system o~ mirrors 17a and accommoda-ting a light chopper whose ~unction is per~ormed by a rod 6a coupled to the armature 7 of the electromaOnet 8 as described above. Part o~ lioht is removed ~rom the beam produced by the light source 2 (FIG. 1) by a diaphragm 18 put across the path of that beam.
~ he element simulating a calibrated frequency may ~urther be deæigned as a light-transmitting channel 19 (FIG. 3) comprising a system o~ pri s 20 and accommodating a light ohopper 21 controlled by an indepe~dent drive 22.
~he light chopper may be o~ any known type suitable for the purpose. Part of light is removed ~rom t~e beam emitted by the light source 2 b~ a diaphragm 23 arranged aoross the path o~ that boam.
~ he light-transmitting ohann~l 19 o~ FIG. 4 is aomposed o~ two light guides 24 and 25; in-terposed bet-ween the li~ht guides 24 and 25 is a light chopper 21 similar to tb~ one installed in the channel ~9 o~ FIG. 3.
Part o~ the beam's light i9 remoYed by a diaphragm 23 (FIG. 4).
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The instrument for measurin~ the sizes and qUantib~
of particles in a ~luid mediu~ operates as ~ollo~s.
~ he light source 2 (~ig~ 1) produces9 and the system of lenses ~ shapes, a sharply de~ined narrow beam o~
li~ht in the chamber 1. The ~lov~ o~ air to b~ ch~cked ~or pollution, and particles contained therein, are directed through the nozzle, arranged at a perpendicular to the plane of the attached drawin~s, so that the air flow crosses the light beam. As a particle is cau~ht in the light beam, it scatters a part of -the beam9s lnght i~ all directions; part o~ the light scattered b~ the particle gets into the visual ray o~ the light-sensitive device 4, shaped by the system o~ lenses 5O The light--sensitive device 4 converts the light it receives to electric pulses. ~he amplitudes of these pulses depend upon the brightness of light scattered by particles. ~rom the output o~ the light-sensitive device 4, the pulses are applied via the ohmic divider 12 to the signal inputs o~ the threshold devices 11 which are thus excited for a period o~ timo egual to the duration o~ the pulses. ~ho ~umber o~ threshold devices thus excited is determined by the pulso amplitude and, conseguently, by the size o~ the particle which causes a pulse to appear. ~he pulse produced by the top-order (with respect to the pulse amplitude) threshold device o~ the excited threshold - -, . . . . . . .
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devices is applied to the input o~ the respective counter 16 with indicators intended to count and display the qua-nti-ty of particles whose sizes are within the range o~ the given channel. Thus the size o~ a particle is derived ~rom the amplitude of the pulse at the ou-tput o~ the light-sensitive device 4. ~he amplitude o~ a pulse at the output of the light-sensitive device 4 is determined b~ the size o~ a particle, as well as by a number of ~ac-tors, including the brightness o~ the light source, the ¢o~version coe~ficient o~ the light-sensitive device ~, the sensitivity of the threshold devices 11, etc.
In ordcr to rule out tho ef~eots o~ these factors, the size o~ a particle is measured by comparing the amount o~ light scattered by the particle with the amount o~
light produced by the element which simulates a calibrated particle. A calibrated particle is simulated with the aid o~ the rod 6 which periodically gets into the light beam produced by the light source 2. ~he re~lecting sur-~ace o~ the rod 6 and the depth o~ its penetration into the light beam are ~eleoted 80 as bo ensure a oonstant in-tensity o~ the light scattered by the rod 6. The rod 6 is drive~ by the electromagnet 8 energized b~ the in-dependent generator 9. ~he oscillatio~ period o~ the generator 9 is bo ensure that the duration o~ the pulse produced at the output o~ the light-sensitive d~vice 4 by the light scattered b~ the rod 6 is much greater ~han ~ .
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the duration of the pulse caused to appear by a particle.
All the pulses produced at the output o~ the light-sensitive de~ice 4 are applied to the circuit 1~ for convertinD
output pulses o~ the light-sensitive device 4 to d.c.
voltage.
~ he duratio~ of pulses produced by particles con-tai~ed in the air flow is significantly shorter tha~ the time constant of the integrating circuit incorporated in the converter circuit 10; the number of particles producing pulses of great amplitudes is ne~ligible; as a result, the pulses produced by particles contained in the air ~low have no tangible e~ect upon the d.c. vol-tage across the output o~ the converter circuit 10. ~he duxation o~ a pulse produced by the rod 6 is enough to bri~g t~e charge o~ the capacitor 1~ to a level cor-responding to the ~ull amplitude of that pulse. As a result, at the output o~ the converter circuit 10 there is produc~d d.c. voltage whose level is equal to the am-plitude of the pulse produced by the ~lement simulating a calibrabed particle, ~rom the output o~ the converter circuit 10, d.c. volta~e is applied to the reference inputs o~ the threshold devices 11. 0~ all the threshold devices 11, onl~ that device is eæcited to whose signal inpu~ there is applied a pulse with an amplitude higher than the level of d.c. volta~c at its re~ere~ce i~put.
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~hus a change in the brightness of the light source 2,the conversio~ coef~icient o~ the light-sensitive devicé
4 and other ~actors which a~ect the amplitudes o~ pulses produced b~ particles contained in the air ~low is ac-companied by a change i~ the amplitudes of pulses pro-duced by particles contai~ed in the air ~low and in the level of d.c. voltage of the element which simulates a calibrated particle. o summarize, the sizes o~ particles contained in the air flow are measured by comparing these si~es with that of a ¢alibrated particle, which is done right i~ the course o~ measureme~t and accounts ~or a substantial improvement in the accuracy o~ measurements.
In ¢ases when the element simulati~ a calibrated particle is the light-tra~smittin~ channel 17 (Fig. 2) which tra~smits some light o~ the beam produced by the lig W source 2 to the light-sensitive device 4, a calibra-ted particle is simulated as ~ollows.
~ he light beam, e~itted by the light source 2 and shaped by the system o~ lenses 3, passes through the diaphragm 18 to reach the system compos~d o~ two mirrors 17a.
~ he light is re~racted by the mirrors 17a, and part of the beamt which passes through the diaphragm 18, is direoted at the light-sensitive device 4. Interposed bet-ween the mirrors 17a, across the path o~ the re~racted beam, ..
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is the rod 6a which periodically chops the beam. In all other respects, the instrument operates as in the c~se when the function of the element simulating a calibrated particle is performed by the rod 6 (Fig. 1).
When the ~lexible li~ht guides 24 a~d 25 (~IG. 4) .
are used to make up the light-transmittin~ channel 19, a calibrated particle is simulated as in the case o~
using the mirrors 17a and the system o~ prisms 20 in the light-transmitting channels 17 and 19. ~he function OL
the light chopper 21 is performed by hal~ o~ a disc rotated by t~o independent drivo 22.
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to signal inputs of threshold devices. Outputs of the threshold devices are co~nccted to inputs of counters with indicators The accuracy o~ the instrument is checked with the aid of an element which si~ulates calibrated particles.
This ~lement comprises a movable member which is made to cross the light beam prior to measurement.
~ he accuracy of the instrumen-t is checked with the aid o~ an element which simulatcs calibrated particles.
This element comprises a movable member which is made to cross the light beam prior to measurement.
~ he instrument u~der review is checked onlg a short time before the measurement; it is adjusted by the ope-rator, which is an unnecessary complication in the use o~ the instrument~ In addition, the instrument under r3view does not make it possible to eliminate the ef~ects of such souroes of error as unstable volta~e of the power source, which may rapidly ~ar~ in the course of measure-ments.
It is an objocb o~ the present invention to provide an instrument ~or measuring the sizes and quantit~ of partioles in a ~luid medium, wherei~ the design of the olement simulating a calibrated partiole would make it possible to automatize the calibration of the instrument, while using the instrument to measure the sizes and quan-tities of particles.
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. . . ~ , . . .
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It is another object of the invention to improve the accuracy of measuring particle sizes.
It is still another object of the invention to facilitate the use of the instrument.
In accordance with an embodiment of the invention an instrument for measuring the sizes and quantity of particles in a fluid medium comprises a dark chamber, a light source accommodated in said dark chamber, means for shaping a light beam emitted by said light source, accommodated in said dark chamber, means for introducing the fluid medium into said chamber so that it crosses the light beam emitted by the light source: an element simulating a calibrated particle, accommodated in said chamber, a light-sensitive device installed in said chamber and intended to convert the light scattered by particles contained in the flow of the fluid medium which crosses the light beam emitted b~ said light source, as well a~ part of the light of that beam, arriving from said element, to electric pulses: said element for simulating a calibrated particle being adapted to periodically change, in the course of measurements, the brightness of the light received by said light-sensitive device;
a converter circuit for converting output electric pulses of said light-sensitive device to d.c. voltage, which circuit is connected with its input to an output of said light-sensitive device: a divider whose input is connected to the output of said light-sensitive device: threshold devices connected with their signal inputs to outputs of said divider which is intended to distribute electric pulses, arriving from said light-sensitive device, among said threshold devices according to particle sizes: an output of said converter circuit being connected to reference inputs of said threshold devices whose trigger levels are dependent upon d.c.
voltage at the output of said converter circuit: means for counting and displaying the quantity of pulses corresponding to that of particles in the flow of the fluid medium being investigated, which is done individually for each size group.
It is expedient that the element simulating a calibrated particle should be shaped as a rod adapted for reciprocating motion so as to periodically enter the light beam, for which purpose the rod is ooupled to an electro-magnet's armature.
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Such a design of the element simulating a calibrated particle is the simplest and accounts for a ma~imum accuracy of measurements.
The element simulating a calibrated particle may be designed as a light channel to transmit part of light of the beam emitted by the light source to the light-sensitive device, which channel accommodates a light chopper controlled by a drive.
The latter design makes it possible to adjust the brightness of light and, consequently, an equivalent calibrated particle size.
The instrument for measuring the sizes and quantity of particles in a fluid medium according to the invention is calibrated automatically in the course of measurements, which accounts for an excellent stability of the metrological characteristics of the instrument and a high accuracy of measure-ments.
Other objects and advantages of the present invention B
.
.
.
5~
will become more apparent from the following detailed description of a preferred embodime~t thereo~ to be read in conjunction with the accompanying drawin$s, wherein:
~ IG. 1 is a schematic diagram o~ an instrument for measuring the sizes and quan~ity o-~ particles in a ~luid medium, in accordance with the invention, includin~ a~
elevation view o~ an element for si~ulating a calibrated particle, which element is designed as a rod;
~ IG. 2 is a viow of a chamber with a system of mirrors, i~ accordance with the invention;
FIG. 3 is a schematic diagram o~ an instrument for measurin~ the sizes and quantity o~ particles in a fluid medium, according to the invention, wherei~ the element simulati~g a calibrated particle is designed as a system of prisms with a light chopper;
~ IG. 4 is a view o~ a chamber accomm~dating light guides.
~ he invention will be ~urther described in greater detail with re~erence to an instrument used to oontrol air pollution. ~he instrument comprises a daxk charnber 1 (~IG. 1) which accommodates a lamp 2 servi~ as a light sourae, and a system of lenses 3 intended ~or shaping a light beam. ~he chamber ~ further accommodates a light--se~sitive device 4 whose visual ray, shaped by a system . . .
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o~ lenses 5, extends at a perpendicular to the li~ht beam produced by the source 20 In order to introduce air to be checked for pollution into the chamber 1, the latter is provided with a nozzle (not shown) ins-talled so as to direct t~e air ~`low at the point of intersection of th~ above-mentioned beams.
An element 6 is intended to simulate a calibrated particle and is designed as a rod, also designated as 6, which is adapted to periodically change, in the course of measu-reme~ts, the brightness o~ light received by the light--sensitive device 4.
In order to vary the brightness o~ light, the rod 6 i~ made movable SQ as to be able to enter the beam emitted by the light source 2; ~or this purpose, the rod 6 is coupled to an armature 7 o~ an electroma~et 8 supplied by a generator 9 which is solely meant to energize the electromagnet 8. ~he rod 6 is arranged so that while in motion, it periodically gets into the beam emitted by the light source 2, scattering some light o~ that bearn in the direction o~ the light-sensitivo devico 4.
~ he light-sen~itive devioe 4 serve~ to convert li~ht it reaeives to clectric pulses. Its ~unatio~ may be per-iormed by an~ suitable li~ht-sensitive device, ~or example, a photoelectro~i¢ multiplier. An output of the li~ht-sen-giti~e deYioo 4 is conne¢ted to an input o~ a circuit 10 intended to convert output pulses o~ t-,he light-sensi~ive device 4 to d.c. voltage; the outpu-t o~ the device 4 is also connected to signal inputs o~ threshold devices 11, which connection is eflected via a divider 12 serving to di-stribute output pulses of the light-sensitive device 4 -amon~ the threshold devices 11 according to the sizes o~ particles contained in the air ~low~
An output of the converter circuit 10 is connected to re~erence inputs of the threshold devices ~1.
The circuit 10 ~or converting output pulses of the light-sensitive device 4 to d.c. voltage is an integra-ting cir¢uit aomprising a resistor 13, a diode 14 and a capacitor 15; the time constant o~ the integratin~
cir¢uit is selected to be much longer than the duration of the pulse produced at the output of the light-sensitive device 4 as it receives light s¢attered by particles ¢ontained in the air ~low; at the same time the time ¢onstant of the integrating circuit is less than the dura-tio~ o~ the pulse produced at the output o~ tb~ light--sensitive dcvioe 4 as it r~ceives light soattered by the rod 6 which serves to simulate a cal~brated particle. From the outputs o~ the threshold devices 11, pulses are applied to inputs of respe¢tive ¢ounters 16 with indicators in-tended to count and display the number o~ pulses corres-ponding to that o~ parti¢les o~ ea¢h size group contained in the air being investigated.
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. .. -, . . . . ~ , 2~0 The divider, threshold devices and counters ~ith indicators may cmploy any k~o~Yn circuitries suitable to perform their respective func-tions.
The element ~or simulating a calibrated ~re~uency may also be desi~ned as a light-tra~smitting channel 17 (FIG. 2) comprising a system o~ mirrors 17a and accommoda-ting a light chopper whose ~unction is per~ormed by a rod 6a coupled to the armature 7 of the electromaOnet 8 as described above. Part o~ lioht is removed ~rom the beam produced by the light source 2 (FIG. 1) by a diaphragm 18 put across the path of that beam.
~ he element simulating a calibrated frequency may ~urther be deæigned as a light-transmitting channel 19 (FIG. 3) comprising a system o~ pri s 20 and accommodating a light ohopper 21 controlled by an indepe~dent drive 22.
~he light chopper may be o~ any known type suitable for the purpose. Part of light is removed ~rom t~e beam emitted by the light source 2 b~ a diaphragm 23 arranged aoross the path o~ that boam.
~ he light-transmitting ohann~l 19 o~ FIG. 4 is aomposed o~ two light guides 24 and 25; in-terposed bet-ween the li~ht guides 24 and 25 is a light chopper 21 similar to tb~ one installed in the channel ~9 o~ FIG. 3.
Part o~ the beam's light i9 remoYed by a diaphragm 23 (FIG. 4).
,;
,J
- - , .
. .
:.- ~ , . . . .
. . ~ . .
.: . : ~ - .
The instrument for measurin~ the sizes and qUantib~
of particles in a ~luid mediu~ operates as ~ollo~s.
~ he light source 2 (~ig~ 1) produces9 and the system of lenses ~ shapes, a sharply de~ined narrow beam o~
li~ht in the chamber 1. The ~lov~ o~ air to b~ ch~cked ~or pollution, and particles contained therein, are directed through the nozzle, arranged at a perpendicular to the plane of the attached drawin~s, so that the air flow crosses the light beam. As a particle is cau~ht in the light beam, it scatters a part of -the beam9s lnght i~ all directions; part o~ the light scattered b~ the particle gets into the visual ray o~ the light-sensitive device 4, shaped by the system o~ lenses 5O The light--sensitive device 4 converts the light it receives to electric pulses. ~he amplitudes of these pulses depend upon the brightness of light scattered by particles. ~rom the output o~ the light-sensitive device 4, the pulses are applied via the ohmic divider 12 to the signal inputs o~ the threshold devices 11 which are thus excited for a period o~ timo egual to the duration o~ the pulses. ~ho ~umber o~ threshold devices thus excited is determined by the pulso amplitude and, conseguently, by the size o~ the particle which causes a pulse to appear. ~he pulse produced by the top-order (with respect to the pulse amplitude) threshold device o~ the excited threshold - -, . . . . . . .
,., . ' :
... . . . . . . . . .
.. . .- . .- . -. - . . . . . .
- . . . . ..
., .
S8~
devices is applied to the input o~ the respective counter 16 with indicators intended to count and display the qua-nti-ty of particles whose sizes are within the range o~ the given channel. Thus the size o~ a particle is derived ~rom the amplitude of the pulse at the ou-tput o~ the light-sensitive device 4. ~he amplitude o~ a pulse at the output of the light-sensitive device 4 is determined b~ the size o~ a particle, as well as by a number of ~ac-tors, including the brightness o~ the light source, the ¢o~version coe~ficient o~ the light-sensitive device ~, the sensitivity of the threshold devices 11, etc.
In ordcr to rule out tho ef~eots o~ these factors, the size o~ a particle is measured by comparing the amount o~ light scattered by the particle with the amount o~
light produced by the element which simulates a calibrated particle. A calibrated particle is simulated with the aid o~ the rod 6 which periodically gets into the light beam produced by the light source 2. ~he re~lecting sur-~ace o~ the rod 6 and the depth o~ its penetration into the light beam are ~eleoted 80 as bo ensure a oonstant in-tensity o~ the light scattered by the rod 6. The rod 6 is drive~ by the electromagnet 8 energized b~ the in-dependent generator 9. ~he oscillatio~ period o~ the generator 9 is bo ensure that the duration o~ the pulse produced at the output o~ the light-sensitive d~vice 4 by the light scattered b~ the rod 6 is much greater ~han ~ .
-11- '~
' . . ~:; ' ~ ' :
. ~ ~ . . . - .
: ., . . ~
~ 5~
the duration of the pulse caused to appear by a particle.
All the pulses produced at the output o~ the light-sensitive de~ice 4 are applied to the circuit 1~ for convertinD
output pulses o~ the light-sensitive device 4 to d.c.
voltage.
~ he duratio~ of pulses produced by particles con-tai~ed in the air flow is significantly shorter tha~ the time constant of the integrating circuit incorporated in the converter circuit 10; the number of particles producing pulses of great amplitudes is ne~ligible; as a result, the pulses produced by particles contained in the air ~low have no tangible e~ect upon the d.c. vol-tage across the output o~ the converter circuit 10. ~he duxation o~ a pulse produced by the rod 6 is enough to bri~g t~e charge o~ the capacitor 1~ to a level cor-responding to the ~ull amplitude of that pulse. As a result, at the output o~ the converter circuit 10 there is produc~d d.c. voltage whose level is equal to the am-plitude of the pulse produced by the ~lement simulating a calibrabed particle, ~rom the output o~ the converter circuit 10, d.c. volta~e is applied to the reference inputs o~ the threshold devices 11. 0~ all the threshold devices 11, onl~ that device is eæcited to whose signal inpu~ there is applied a pulse with an amplitude higher than the level of d.c. volta~c at its re~ere~ce i~put.
. . . .: ' .
.
' ' ' ' ' ' ~ .
S.~
~hus a change in the brightness of the light source 2,the conversio~ coef~icient o~ the light-sensitive devicé
4 and other ~actors which a~ect the amplitudes o~ pulses produced b~ particles contained in the air ~low is ac-companied by a change i~ the amplitudes of pulses pro-duced by particles contai~ed in the air ~low and in the level of d.c. voltage of the element which simulates a calibrated particle. o summarize, the sizes o~ particles contained in the air flow are measured by comparing these si~es with that of a ¢alibrated particle, which is done right i~ the course o~ measureme~t and accounts ~or a substantial improvement in the accuracy o~ measurements.
In ¢ases when the element simulati~ a calibrated particle is the light-tra~smittin~ channel 17 (Fig. 2) which tra~smits some light o~ the beam produced by the lig W source 2 to the light-sensitive device 4, a calibra-ted particle is simulated as ~ollows.
~ he light beam, e~itted by the light source 2 and shaped by the system o~ lenses 3, passes through the diaphragm 18 to reach the system compos~d o~ two mirrors 17a.
~ he light is re~racted by the mirrors 17a, and part of the beamt which passes through the diaphragm 18, is direoted at the light-sensitive device 4. Interposed bet-ween the mirrors 17a, across the path o~ the re~racted beam, ..
-' ' .
.: -, .. . , . . ~ ." -.
, - . ' - ' ' ' ~.
S8~ ~
is the rod 6a which periodically chops the beam. In all other respects, the instrument operates as in the c~se when the function of the element simulating a calibrated particle is performed by the rod 6 (Fig. 1).
When the ~lexible li~ht guides 24 a~d 25 (~IG. 4) .
are used to make up the light-transmittin~ channel 19, a calibrated particle is simulated as in the case o~
using the mirrors 17a and the system o~ prisms 20 in the light-transmitting channels 17 and 19. ~he function OL
the light chopper 21 is performed by hal~ o~ a disc rotated by t~o independent drivo 22.
- -! ~ .
' ' ' ~`' . ' ~ .
~ " ~
Claims (3)
1. An instrument for measuring the sizes and quantity of particles in a fluid medium, comprising a dark chamber; a light source accommodated in said dark chamber; means for shaping a light beam emitted by said light source, accommodated in said dark chamber; means for introducing the fluid medium into said chamber so that it crosses the light beam emitted by the light source; an element simulating a calibrated particle, accommodated in said chamber; a light-sensitive device installed in said chamber and intended to convert the light scattered by particles contained in the flow of the fluid medium which crosses the light beam emitted by said light source, as well as part of the light of that beam, arriving from said element, to electric pulses; said element for simulating a calibrated particle being adapted to periodically change, in the course of measurements, the brightness of the light received by said light-sensitive device; a converter circuit for converting output electric pulses of said light-sensitive device to d.c.
voltage, which circuit is connected with its input to an output of said light-sensitive device; a divider whose input is connected to the output of said light-sensitive device; threshold devices connected with their signal inputs to outputs of said divider which is intended to distribute electric pulses, arriving from said light-sensitive device, among said threshold devices according to particle sizes; an output of said converter circuit being connected to reference inputs of said threshold devices whose trigger levels are dependent upon d.c. voltage at the output of said converter circuit;
means for counting and displaying the quantity of pulses corres-ponding to that of particles in the flow of the fluid medium being investigated, which is done individually for each size group.
voltage, which circuit is connected with its input to an output of said light-sensitive device; a divider whose input is connected to the output of said light-sensitive device; threshold devices connected with their signal inputs to outputs of said divider which is intended to distribute electric pulses, arriving from said light-sensitive device, among said threshold devices according to particle sizes; an output of said converter circuit being connected to reference inputs of said threshold devices whose trigger levels are dependent upon d.c. voltage at the output of said converter circuit;
means for counting and displaying the quantity of pulses corres-ponding to that of particles in the flow of the fluid medium being investigated, which is done individually for each size group.
2. An instrument as claimed in claim 1, wherein the element simulating a calibrated particle is a rod adapted for reciprocating motion so as to periodically enter the light beam, for which purpose said rod is coupled to an electromagnet's armature.
3. An instrument as claimed in claim 1, wherein the element simulating a calibrated particle is a channel which transmits a part of the beam's light to the light-sensitive device, which channel accommodates a light chopper controlled by an independent drive.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,876A CA1102580A (en) | 1978-06-06 | 1978-06-06 | Instrument for measuring sizes and quantity of particles in fluid medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,876A CA1102580A (en) | 1978-06-06 | 1978-06-06 | Instrument for measuring sizes and quantity of particles in fluid medium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102580A true CA1102580A (en) | 1981-06-09 |
Family
ID=4111631
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,876A Expired CA1102580A (en) | 1978-06-06 | 1978-06-06 | Instrument for measuring sizes and quantity of particles in fluid medium |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1102580A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5426501A (en) * | 1993-01-06 | 1995-06-20 | Laser Sensor Technology, Inc. | Apparatus and method for particle analysis |
-
1978
- 1978-06-06 CA CA304,876A patent/CA1102580A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5426501A (en) * | 1993-01-06 | 1995-06-20 | Laser Sensor Technology, Inc. | Apparatus and method for particle analysis |
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