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Publication numberUS3603875 A
Publication typeGrant
Publication dateSep 7, 1971
Filing dateMay 12, 1969
Priority dateMay 12, 1969
Also published asDE2022878A1, DE2022878B2, DE2022878C3
Publication numberUS 3603875 A, US 3603875A, US-A-3603875, US3603875 A, US3603875A
InventorsCoulter Wallace H, Hogg Walter R
Original AssigneeCoulter Electronics
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Particle analyzing method and apparatus employing multiple apertures and multiple channels per aperture
US 3603875 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent Wallace H. Coulter Miami Springs;

Walter R. Hogg, Miami Lakes, both oi, Fla. 823,743

May 1 2, l 969 Sept. 7, 1971 Coulter Electronics, Inc.

Hialeah, Fla.

Continuation-impart of application Ser. No. 527,146, Feb. 14, 1966, now Patent No. 3,444,463, dated May 13, 1969.

[72] Inventors [2i Appl No. [22] Filed [45] Patented [73] Assignee {54] PARTICLE ANALYZING METHOD AND APPARATUS EMPLOYING MULTIPLE APERTURES AND MULTIPLE CHANNELS PER 235/92 PC; ass/35,40, 102, 20s

Primary Examiner-Michael J. Lynch Attorney-Silverman & Cass ABSTRACT: Disclosed is an improved method and apparatus for analyzing particles by the Coulter principle of employing an impedance responsive detecting aperture through which pass particles in suspension. Employed herein are a plurality of logically parallel detecting apertures, preferably of different microscopic sizes, each aperture feeding circuitry which is subdivided into a plurality of channels, each responsive to a difi'erent narrow subrange of particle size. By time and volume related elements, there is generated an output voltage which is proportional to particle volume per unit time over the entire particle system; hence, statistically valid data is available at all times during an analysis run, even in the event of a malfunctioning blockage of an aperture.

SHEET 2 0F 3 PATENTED SEP 7 IHTI PATENTED SEP 7 I97! SHEEI 3 UF 3 .PARTICLEANAIJYZING METHOD AND APPARATUS EMPLOYING MULTIPLE APERTUIRES AND MULTIPLE CHANNELS PER APERTURE CROSS-REFERENCE TO RELATED APPLICATIONS This is a Continuation-in-part of our copending application Ser. No. 527,146, filed Feb. 14, 1966, entitled Particle Analyzing Apparatus and Method Utilizing Multiple Apertures," now U.S. Pat. No. 3,444,463 issued on May 13, 1969 and hereinafter referred to as the firs-t" copending applica tion.

Cited hereinafter as the second" copending application is Ser. No. 410,882, filed Nov. 13, I964, and entitled Automatic Particle Size Data Converting Apparatus."

This and the cited two copending applications are assigned to Coulter Electronics, Inc. manufacturers of apparatus, including particle analyzers, known throughout the world by the trademark Coulter Counter." Such apparatus and methods for utilizing the Coulter principle are discussed herein with reference to the Coulter apparatus and Coulter method.

BACKGROUND OF THE INVENTION This invention relates generally to particle analyzing apparatus and method especially the type which use the Coulter principle described in U.S. Pat. No. 2,656,508, and more particularly is concerned with apparatus and method which utilize a plurality of apertures, each aperture having a plurality of channels for obtaining information.

The cited first copending application describes and claims apparatus and a method operating in accordance with the basic principles used in the apparatus of this invention. A fluid suspension of particles is passed through a plurality of apertures simultaneously or consecutively or in consecutive groups, each aperture having its own aperture current supply and its own detector to provide one channel for the signals produced by the respective aperture. Certain advantages are gained by the use of multiple apertures, such as savings of time, better statistical data, etc. Such advantages are inherent in this invention as well. Likewise, the apparatus of the first copending application includes a vote circuit which identifies and can reject automatically, information derived from a channel which is erroneous because of blockage of the aperture producing the signals-of that channel. The disclosed embodiment of this invention uses such vote circuits, but, as will be seen, a feature of the invention substantially decreases, if not completely eliminates the need for such circuits.

The structure of this invention is of the special kind that uses apertures of different size to give statistical information of the distribution of particles in a system having particles of widely different sizes. Since this is a special case of the basic concept, a discussion of the problems involved in obtaining distribution data for this kind of a system will be in order, although to some small extent repetitious of the discussion in the first copending application.

The second copending application describes means for reducing particle count information gathered from a plurality of channels, all coupled to the single aperture of the apparatus. The characteristics of an ordinary so-called industrial system of particles are fairly well known. These systems would include slurries,'dusts, powders, emulsions, and the like of a vast gamut of materials. These characteristics are generally as follows:

1. Most importantly, the dynamic range of particle size is very great, compared, for example with ordinary blood cells or biological particles. The smaller particles, not uncommonly, may be thousands of times smaller than the larger particles.

2. The occurrence of the particles, that is their distribution sizewise in the sample follows a general pattern in which there are an exceedingly larger number of smaller particles than larger particles For example, there may be tens of millions of particles of the order of several microns in diameter compared to a few hundreds of particles of the order of several hundred microns in diameter.

3. Notwithstanding the second characteristic described above, the greater volume or mass of particulate material in most types of sample will occur somewhere near the center of the range of particle sizes, i.e., is contributed by the middle sized particles.

In the classical methods of particle study, Stokesian methods involving sedimentation were used to obtain the data of size distribution and mass. These methods may be categorized as gross in concept because large quantities are weighed, settled, dropped, sieved and/or spun to give the, required data. As opposed to such methods, the Coulter apparatus has permitted the electronic counting of particles one by one, accomplished by passing the suspension at a high speed through a microscopic aperture. The Coulter apparatus has become widely used in many particle categories formerly handled by Stokesian methods.

There is no need to explain the Coulter principle at length, other than to state that where an aperture is provided in an insulating wall, and a fluid suspension of particles is flowed through the aperture from a fluid body on one side of the wall to a second fluid body on the other side, each time a particle passes through the aperture it will displace its own volume of fluid and thereby change the impedance of the fluid contained in the aperture as measured between the electrodes used to make connection to it. This presumes that the current-carrying capabilities of the fluid and the particulate matter are different. If there is an electric current also passing through the aperture, one may generate electric signals as a result of the concomitant changes in impedance, and by coupling a suitable detector commonly as a simple amplifier to the respective bodies of fluid, normally through the same electrodes that provide the connection to the aperture current source, one may obtain substantial electric pulses, each representing a passage of a particle. The duration of each pulse is equal to the duration of the particles stay in the aperture, and if operating conditions are properly chosen, the amplitude is proportional to the total volume of the particle, substantially irrespective of its shape.

This should be contrasted with optical scanning which responds to maximum cross sectional area of the particle perpendicular to the direction of light, which varies widely for irregularly shaped particles due to their unpredictable orientation.

Counting and sizing by Stokesian methods have resulted in characteristic curves which describe a particle system, and although the Coulter apparatus has capabilities far exceeding those of the Stokesian apparatus, the data gathered from such apparatus for the most part are required to be converted or reduced into information in the classical form. Persons working in the particle field have become accustomed to such form and base their actions on interpretations thereof.

Two characteristic curves are used to express particle distribution in the classical form. One curve, called the differential curve consists of a plot of the distribution of particulate material in the various ranges, the horizontal axis being particle size and the vertical axis being, volume of particulate material existing in any given range of particle sizes. The second curve, called the integral curve, gives percentage of particulate material above a stated size. The horizontal axis of the integral curve is also particle size, but the vertical axis is volume or percent of the total mass of particulate material above any size. The differential curve is usually somewhat bell-shaped, while the integral curve is a reverse S. Obviously, the percent point at the top of the integral curve will represent the smallest particle, and the 0 percent point of the same curve will represent the largest particle. In both cases, since the size range of particles is great the horizontal axis is usually logarithmic. One curve may also be converted into the other.

The Coulter Counter has gone a long way in providing information to be used in producing these curves which are so important to the understanding of those working in this field, but

its capabilities and potential have only been partially utilized.

The invention contemplates a vastly increased use of the capabilities of an apparatus which operates on the Coulter principle as a result of which many advantages are achieved not capable of achievement heretofore.

Prior counting and sizing apparatus of the Coulter type utilized a single aperture for obtaining the information needed to describe a particle system. It was desired to extend the range of particle sizes covered by the aperture to derive as much information as possible from the aperture. Various techniques attended such attempts, all of which were directed toward the obtaining of the best quality and the maximum amount of information.

The use of a single aperture of a compromise diameter decreased sensitivity of the aperture to the smaller particles and increased coincidence loss for a given particle concentration. It also introduced an error in linear response to particles greater than or percent of the aperture diameter. It usually required multiple dilutions to get the best results, including scalping or decanting to prevent large particle blockages. Dividing the sample runs into two ranges with different apertures alleviated some of the problems arising because of the very wide range of particle sizes, but prior art has taught that the use of more than one aperture is a last resort, and the maximum span of each aperture was usually demanded.

SUMMARY OF THE INVENTION The invention herein does the opposite of what has been attempted in prior applications of the Coulter apparatus. Instead of extending the range of any single aperture, this invention is based on the use of only the smallest feasible range capability of an aperture.

Among the objects of this invention are: obtaining a saving of time in running a sample; eliminating the problems involved in scalping or diluting; making unnecessary prior knowledge of the distribution and population of the type of particle system being studied; obtaining a vast increase in accuracy and in'the quantity of data which may be obtained on a given sample run; improving the reliability of the apparatus and in addition decreasing the likelihood of blockage; making possible the acquisition of valid data even when a blockage occurs; and in general improving greatly the overall quality and statistics in practically every respect of the information obtained.

In using the Coulter apparatus, one device described in said second copending application provided structure for reducing the data before presentation, so that the output of the device enabled the construction of the integral and differential curves of the particle system directly from the readouts. A plotter suitably connected could draw the curves. This apparatus used a single aperture to make a sample run, the spectrum of particle sizes being divided into a plurality of consecutive ranges each providing the signals to a separate channel by means of suitable threshold circuits. The ranges were chosen to have a progressive relationship in accordance with a known function, such as, for example, a two-to-one relationship between contiguous ranges based upon the average size of the particles in the respective ranges. An equal volume of suspension was scanned for each range in any given sample run. The resulting counts were operatedupon before deriving the final data, in accordance with a progressive function equal to that used to divide the spectrum into ranges. The values in the resulting series were directly proportional to the total volume of particulate material in each respective range.

Thus, the data for constructing the ultimate integral and differential curves were available, albeit with the attendant disadvantages of using a single aperture. This included the loss of any usable data upon blockage of the single aperture. Use of more than one aperture required two dilutions, and two independent runs, but this gave rise to added blockage problems. Scalping could not'be avoided.

The invention has as another object the provision of apparatus intowhich one may readily construct the principles of the data reduction structure described above, without unduly complicating the apparatus.

In using a plurality of apertures, it should beunderstood that in the lower ranges it is not essential that the same amount of suspension pass through the apertures for a good statistical sample as in the case of the upper ranges. One may therefore decrease quite substantially the chances of .bloekage by scanning only a minute sample in an aperture of high sensitivity, and obtain excellent results. The apparatus of the invention enables this to be done automatically and with proper relationship to the other data being gathered by the device.

The invention provides output information for each channel in the form of a voltage which is proportional to volume per unit time, representing volume of particulate material in that channel or of that size particle, but considering the entire particle system. Thus the points of the integral curve are obtained directly. Since this information is being produced at all times, even when blockage occurs, the information obtained up to that time on any group of channels produced by the aperture which just blocked is still valid, albeit statistically representative only of the amount of sample scanned.

The structure of the invention accomplishes the above by using two elements in each channel controlled from the same voltage reference source. One element furnishes volume information and the other time. The volume information is provided by integrators that are slowly accumulating charge through capacitive pump circuits driven by the particle pulses. A scale factor is applied to the pump circuits by the voltage reference source and size of pump capacitors. The time information is obtained from an integrator which runs continuously and accumulates charge from the same reference voltage source. Signals from both integrators of each channel are applied to a multiplier, but the time integrator signal is first operated upon by a reciprocal computer so that the multiplier output is of voltage representing particle volume relative to time. Since the flow rate through each aperture is known, the multiplier output may be calibrated in terms of number of particles per unit volume of sample suspension which is the required form.

Many advantages and objects which are not set forth above will become more apparent as a description of a preferred embodiment of the invention is set forth in detail, in connection with which there is illustrated in block diagram form a portion of a typical particle analyzing apparatus constructed in accordance with the invention, to enable an understanding thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A and FIG. 1B are the left and right halves, respectively, of a block diagram of a portion of a particle analyzing apparatus constructed in accordance with the invention, the portion illustrated relating only to the channels of one of a plurality of apertures included in the apparatus.

FIG. 2 is a placement diagram showing the relationship between FIGS. 1A and 1B.

FIG. 3 is a front elevational view of a structure which may be used to provide the scanning system for the entire apparatus, including means for functionally supporting six apertures.

FIG. 4 is a sectional view taken through the structure of FIG. 3 along the line 4-4 and generally in the indicated direction.

FIG. 5 is a diagram of a typical pump circuit of thetype used in the apparatus.

FIG. 6 is an enlarged sectional view along the line 6-6 of FIG. 4.

DESCRIPTION OF A PREFERRED EMBODIMENT The apparatus of the invention utilizes a plurality of apertures, each of which is chosen according to a sequence designed to use a high degree of the capabilities of the aperture, considering sensitivity, coincidence, flow rate and the probability of clogging. The apertures may be mounted in a plurality of aperture tubes of the type known and all tubes immersed in a container of the sample for a static determination, or these apertures may be located in a conduit or pipe through which there is flowing a continuous stream of the sample suspension. In either case, the structures may take many dif ferent forms. One such form is shown in FIGS. 3 and 4.

Each aperture is connected into the system in a manner to provide independent flow-including means to permit the sample to be carried through the apertures consecutively or simultaneously or in consecutive groups. Means may be provided to trigger the operation of one flow inducing means upon the completion of operation of the preceding one. Each aperture has an independent current source and an independent detector, such that care must be taken electrically to isolate the downstream ends of the apertures to prevent interaction between them. There will be an electrode in the downstream fluid for each aperture and a single common electrode in the upstream body of fluid, usually at ground potential.

In an apparatus which is intended to provide an output representing numbers related to the amount of particulate volume in the respective ranges of a particle system, the device described in the second copending application identified above which used a single aperture was somewhat limited. Although data reduction was accomplished, it is apparent that the same volume of sample passes through the aperture for any sample run to give information for all ranges. The amount of material in each size range varies considerably, as pointed out, and it is not necessary to pass the same volume of suspension through the aperture for a good statistical count in heavily populated ranges as in sparsely populated ranges.

In the apparatus of this invention, the flow time in heavily populated ranges may be decreased by any suitable factor to give a count which may be then multiplied by the factor to give the total relative count. This decreases the chance of clogging by the same percentage. Furthermore, since there is to be an operation made upon the count to provide the desired data reduction, such operation could as easily be fonned by means of changing the time for the sample flow, either alone or in combination with some other means.

The apparatus, through the use of multiple apertures, may utilize rate of flow, size of aperture, and in addition, variation of constants of the circuits to achieve the desired operation upon count, and hence in this respect alone, is a substantial improvement upon the prior single aperture apparatus. In addition, the need for scalping and redilution is eliminated.

The particular apparatus which is discussed herein is one in which there is a plurality of channels for each aperture, so that the range represented by the chosen limits for any aperture may in turn be divided into what may be called subranges, each of which produces signals passing through a single electrical channel. Furthermore, means are included in the apparatus for taking only as much data as absolutely necessary including means for arriving at a correct measurement even if an aperture clogs, the latter event being less likely to occur in this apparatus than in previous devices.

In the practical structure, only a portion of which is illustrated in the figure, there are 25 channels of information, one for each size range of particles. This number has been chosen in order to accommodate a large and yet practical majority of particle systems which are known to be measurable by the Coulter method. The operation of the apparatus is arranged to be based upon differences between channel sizes consisting of successive factors of two, as explained in connection with the structure of said second copending application, so that starting with the smallest channel, the average particle size in the next channel will be two times as large, in the next channel four times as large as the smallest, in the next eight times as large as the smallest and so on. Of course, any desired factor may be used within the above design criteria, or any other method of choosing levels, even without the use of some function of interrelation, but in the latter case, of course there would be no partial reduction of data.

The choice of aperture sizes and particle size ranges described above results in an important, unexpected, and previously overlooked benefit, namely, the ability to accept, without further adjustment or manipulation, particulate systems of any nature, whether broad or narrow, consisting mostly of large or small particles, that is, whether the bellshaped curve is broad or narrow at the center, whether the peak occurs right or left of center, and so on. Suitable analog clock means are used to permit the apertures to pass fluid suspension for only the minimum time that it is almost certain a good sampling will be obtained while clogging is unlikely, considering that particular size of aperture. The data reduction is performed in part by this decrease in sample as the particle size decreases. Even if clogging does occur, data which is taken may be divided by the elapsed time to make it usable, but perhaps with less statistical reliability.

In the drawings, the FIGS. 1A and 13 actually comprise parts of a single illustration. This is intended to show a single range, defined by an aperture, and three subranges or channels within the principal range. As will be seen, from the numbering of the components, it is understood that this in turn is a small part of a large apparatus, but the components of the ap' paratus are repetitious in nature, the whole being designed to give a thorough statistical analysis of a particle system.

The block it) which is identified as A4! is one of six apertures, for example, which are used by the apparatus. Accordingly there are other blocks which would be displayed above the portion shown which represent the larger apertures, and which would be identified as Al, A2 and A3. Likewise, the portion below the illustrated portion would have blocks representing the smaller apertures identified as A5 and A6. In order to illustrate the nature of the device, the sizes of the six apertures might be chosen as A1 560 microns in diameter A2 280 microns in diameter A3 microns in diameter A4 70 microns in diameter A5 30 microns in diameter A6 20 microns in diameter These apertures each represent a range of particle sizes, and were chosen to afford the best statistical information in the ranges which will be covered by each. The largest aperture, which would be A1 might be divided by suitable threshold circuits into nine subranges and thus provide information on nine channels; the next four ranges might each have three channels, and the smallest range might have four channels. The channels for the extremes of size range typically include a very small percentage of the total particulate material and hence do not justify the accuracy obtained by having only three sized subranges per aperture. Thus, there would be a total of 25 channels provided by six apertures.

For the purpose of conforming to the relative sizes of the channels, which will be providing a partial reduction of data, it will be noted that the apertures are chosen so that the diameters decrease from aperture to aperture by very nearly a factor of two.

The amount of sample which will be moved through the respective apertures, according to the said first copending application which is mentioned above, will be equal in simple apparatus, but for best results should vary in accordance with the size of the particles studied. Thus, since the smaller apertures will be primarily used for obtaining the signals from small par ticles, which are typically extremely numerous, only a fraction of the amount of sample taken in the larger apertures will be driven through the smaller. A structure for accomplishing this could be a micrometer head syringe operated by a constant speed synchronous motor. The motor is clutched to the syringe by a high speed magnetic or other type of clutch, and a suitable timing device, such as a light interrupter disc with light source and photocell may give a digital or analog measurement of the amount of movement of the syringe, to be related in other parts of the-circuit with other components of the apparatus.

This fluid driving device whether operated by pump or suction may be the same for several apertures, those with greater sampling time and requiring passage of greater amounts of sampling fluid being associated with other fluid moving devices.

In FIGS. 1A and 1B, the fluid moving device is the block 11, called a suction device 04. Each aperture will have its own suction device. The practical structure of FIGS. 3 and 4 does not illustrate fluid moving means. Some fluid moving means are illustrated in U.S. Pat. Nos. 2,869,078 and 3,015,775.

Since the components described will be duplicated, only the one series associated with the aperture A4 will be described. The aperture A4 like the others, has its own aperture current supply source identified by the designation R4 and the block 12. The signal from the aperture A4 is amplified to a useful level by the amplifier 135 shown in block 13. Output from the amplifier B5 is applied by way of the connections 14, 15, 16 and 17 to the blocks 18, 19, 20 and 21, respectively, these blocks being identified by the labels C16, C17, C18 and C19, respectively; and threshold levels are built into the blocks in such a manner that there is a factor of two between each threshold level all through the apparatus. The threshold circuits between contiguous aperture groups have the identical level. Thus, the next threshold circuit above C16, which is the smallest in the group served by the aperture A3 and is shown in the drawings, is C15, identical in level to C16. Likewise the first threshold circuit C20 of the next smaller group, is identical in level to the level of the threshold circuit C19. Between each threshold circuit, therefore, there is a subrange of particles whose average volume changes from channel to channel by a factor of two.

Two types of Coulter electronic counting and sizing apparatus in use have different kinds of threshold circuits, one of which has a single voltage level to pass only pulses which exceed that level, and the other of which has two voltage levels, so that only pulses whose amplitudes fall within the defined window will be passed. The first type of threshold circuit is an integral type, and the second is a differential type. A differential type typically comprises two integral types interconnected by veto logic circuitry. These kinds of threshold are both useful in accumulating and reducing data obtained by Coulter Counters as the Coulter apparatus is known. In the drawings, the threshold circuits identified as C are of the integral type, hence there is one more threshold in each range than the number of eventual channels to define size limits. Ob viously differential threshold circuits could be used.

The threshold circuits throughout the apparatus are connected in pairs to veto logic circuits designated D. The threshold circuits C16 and C17 are connected to the veto logic circuit D13. The threshold circuits C17 and C18 are connected to the veto logic circuit D14. The threshold circuits C18 and C19 are connected to the veto logic circuit D15. The veto logic circuits are designated by reference characters 22, 23 and 24. The veto logic circuits define the limits of channels by preventing any pulses whose amplitudes do not fall between the levels established by the two thresholds feeding each veto logic circuit from eliciting an output from a veto circuit. Thus, each pair of threshold circuits and their connected veto logic circuit form a differential threshold circuit defining a window.

The outputs from the veto logic circuits appear at 25, 26 and 27 and must pass through the AND gates E13, E14 and E in order to affect the pump circuits F13, F14 and F15, respectively. The AND gates are numbered 28, 29 and 30 while the corresponding pump circuits are numbered 31, 32 and 33. The AND gates are opened and closed at various times by the signals appearing at the control line 34, and thus determine the times that pulses will be fed through the pump circuits to integrator circuits where they are accumulated. Integrator circuits are identified by the letter G and the blocks are numbered 35, 36 and 37. During a count, a voltage exists on the line 34 so that signals from the veto circuits D13, D14 and D15 will pass through the gates.

For any given aperture such as the aperture A4, particles of different sizes are counted, sorted according to their appropriate size levels or ranges and fed to the corresponding integrators for a measurable length of time. Pump circuits F13, F14 and F15 pass charges to the following integrators at rates determined by the DC reference to which their pump condensers charge, this reference being supplied at the line 49 from the DC reference K (FIG. 13). T 7

As previously explained the pump circuits identified by the letter F receive pulses from the AND circuits and transmit charges to the integrators G13, G14 and G15 where they are accumulated. Now each pump circuit includes a capacitor which is to be charged upon the arrival of pulse via path 57, 58 or 59 to the voltage impressed on path 49 by DC reference 74 of FIG. 1B, the charge being pumped to the integrator connected to that pump circuit. The amount of charge that any given pump circuit will transmit to its integrator for a given pulse is determined by the reference voltage derived from the line 49 and the capacitance of the capacitor. Reference may be had to FIG. 5 for an example of pump circuit. The incoming pulses appear via the path 57, having been transmitted from one of the AND gates E13, E14 or E15. Pulses operate a switch 181, which has the effect of connecting the capacitor 182 alternately between the reference voltage supply means K and ground. Each time the switch 181 connects capacitor 182 to the reference voltage K, it charges up to this voltage due to current flowing through diode 184. When the switch reverts to its normal position, the diode 184 blocks flow of current to ground and the diode 183 passes substantially all the charge to the integrator. The switch 181 may be a transistorized circuit in which transistors are switched between conducting and nonconducting conditions upon receiving pulses from the AND circuit preceding.

It will be seen that if the reference voltage from the DC Reference K at 74 is increased, it will require fewer pulses to cause any given voltage level to be reached by the integrator into which the pump is transmitting charge. Assuming a constant rate of arrival of pulses, and a given reference voltage, the integrator will reach any predetermined level after a given time has passed. By increasing the reference voltage that time can be decreased.

It should be recalled that the integrators G13, G14 and G15 are each accumulating information which represents volume of particulate matter for each channel.

The current supply R4 at 12 and the fluid moving device Q4 at 11 have connections to a control binary circuit P9 which is shown at 39 on the left-hand side of FIG. 1A. This latter circuit is usually in the form of a set-reset flip-flop (or RS flipfiop) whose purpose is to start and stop the counting of the entire range defined by the channels of A4. There is a start" line 40 and a stop" line 41 and a connection from the control binary P9 at 42 through a delay circuit 44 labeled S3 and a line 43 to another control binary P3 shown in block 45. This same circuitry is duplicated for each aperture.

In this apparatus, counting in the several ranges may be done simultaneously for all apertures, consecutively, or in groups. If simultaneously, the line 40 originates in a suitable common control for all control binaries connected to the apertures, which may manually or electrically furnish a start signal to all aperture scanning systems. If consecutive, either individually or in groups, the signal may come as a result of some prior event. In this embodiment, the start signal comes from the completion of counting in the previous contiguous range. The control binary P2 shown as block 62 at the bottom of FIG. 1A is equivalent to the binary P3. When counting is completed in the prior range, a stop signal on line 63 will change the state of the binary 62 causing it to remove a voltage existing on the line 64. This line 64 connects with the line 40 through a trailing edge detector 66 which connects with the control binary P9 so that the state of this binary is changed. The scanning is started by this change of state of the binary P9 and likewise it produces a signal output 42 passing through the delay circuit S3 at 44 and the line 43 to the control binary P3,

changing its state. The delay circuit P3 is to obviate switching transients caused by starting the scanning operation. The change of state of the control binary P3 places a signal on the line 3d and its extensions, thereby providing one input to the AND gates E13, E14, E15 and E23 at 77 in FIG. 113, so that these gates are receptive to signals. Otherwise, no signals can pass these gates. The voltage on the line 34 does not affect the control binary P at 101 of the next range until it is removed by control binary P3, at which time the trailing edge detector 103 applies the necessary trigger to initiate the same cycle of events in the next range.

When the counting in the aperture A4 has been completed, there will be a signal at 65 as well as at 41. The signal at 65 changes the state of binary control circuit P3, removing the voltage on the line 34 and its extensions and blocking the AND gates 28, 29 and 30. It also changes the state of the control binary P10, shown in block 101 and this starts the counting in the next channel.

The count in the channels of aperture A4 will continue until some predetermined number of particles is counted on one of the channels of the aperture Ad, unless halted prematurely by approaching saturation of any integrator by OR gate J10 and threshold circuit C40 or at a predetermined time as set by threshold C io, or upon the arrival of a pulse via line 67 indicating a pluggage. This number of particles is controlled by the threshold circuit C33 shown in FIG. 18 at 46. This' threshold circuit, when operated by reaching the proper number which has been set into its circuit, that is voltage, produces a trigger signal at 47 that is applied to the OR gate J4. The outputs from this gate are 65 and 41. Output 65 triggers binary P3 as explained above. Output d1 triggers control binary circuit P9 which stops the operation of scanning.

Since the net effect of the quantity of sample scanned, the size of the integrator capacitors and the size of the pump capacitors in the pump circuits F13, F14 and F are adjusted to be proportional to the volumes of the particles represented by each channel, the information stored in the integrators G13, G14 and G15 is proportional to the volume of material in that size range. This information is continually passed to readout circuits, as will be described, by suitable connections 83, 84 and 85.

It is desired to stop the counting when a given number has been reached. In order to specify the desired statistical accuracy, or coefficient of variation, it is necessary to take the relative size information from the three channels of the aperture Ad by the use of simple DC amplifiers or voltage dividers H6 and H7 shown at 50 and 51 which multiply or divide by 2 or for the inside and outside channels, respectively. Note that the integrator 615 has its output 52 connected to the OR gate J33, the integrator G14 has one output 53 connected through the voltage divider H7 to the line 5% which leads to the input of the OR gate J33 and the integrator G13 has its output 55 going through the voltage divider 1-16 to the line 56 which is another input ofthe OR gate J33. This latter is numbered 60.

While the circuits J10 and J33 at 97 and 60, respectively, designated as OR gates comprise as many diodes as they have inputs and have the same circuit diagram as OR gates, their function is somewhat different from the function generally delegated to OR gates. These circuits make use of the fact that the output voltage of an OR gate will equal the largest input voltage. It is thus an analog as well as a logical element. Accordingly, any one of the channels in the range may raise the voltage at 61 to a value which will reach or exceed the threshold level in the circuit C33. When this occurs the count is shut off in the manner described through the OR gate J4. J4 performs a logical function only. Note that any of the inputs to the OR gate J ll will shut off the count. Besides the input 47, there is one at 67 which comes from a debris alarm T45 shown at as driven in some manner by the output of the amplifier. For example, the debris alarm T4 may detect low frequency components caused by the presence of debris to give an audible or visual warning and a signal which shuts off the counting. Such a device is described in Us. Pat. No. 3,259,891 issued Ill July 5, 1966 to the applicant herein. Likewise, the threshold circuit C40 at 69 may be adjusted to some level which represents a condition just short of saturation of the circuit components connected to the inputs 70, 71 and 72 of the OR gate J10 and which will serve to stop the counting. The path 73 to the OR gate M is provided with the separate, adjustable threshold circuit C46 at 99 in order to give the operator control over the counting time.

The threshold circuit C33 like all of the other threshold circuits in the apparatus is variable over a substantial range, such as for example 8] to l, which provides a 9 to 1 choice ofsigma which could be selectable by a suitable control on the threshold circuit.

At the same time that information is being gathered related to the volume of particulate matter in each channel, a simulated timing device is being operated. In the particular circuit this timing device is in the form of a simple integrator or clock integrator G28, shown in FIG. 113 at 76. This integrator accumulates charge only from one source, namely the DC reference K by way of the line 75 and the switch E23, shown at 77. Since the switch E23 and the AND gates E13, E14 and E15 are all operated by the same control binary P3 via path 34, they all operate for the identical time interval and hence the voltage to which the clock integrator G28 charges is a measure of the time during which range particulate volume accumulations are made in the integrators G13, GM, and G15.

The DC reference K serves all of the pump circuits and clock integrators of the apparatus through lines 49 and 75. The voltage from the clock integrator G23 is transmitted through a reciprocal computer L I shown at 79 to each of the multipliers M13, M14 and M15 designated by the characters 80, 81 and 82. Since the volume information from the integrators G13, G14 and G15 is also being transmitted to the multipliers by the lines 83, 5M and 85, respectively, the operation performed in each multiplier is to combine the voltage representing volume for a particular channel and the reciprocal of time. The result is volume per unit time. Since the flow rate through each aperture is known, this is directly convertible to particulate volume per size range per unit volume of suspension. This output at 89, 911 and 91 is the desired information which is always valid, irrespective of how much sample has passed through the aperture and for how long. Accordingly, stopping the pulses from the aperture A l at any time before the desired count is reached will not affect the information gathered up to that time. The only question will be the statistical quality.

The control exerted upon the integrators G13, GM and G15 was described above in connection with the pump circuits F13, F1 1 and F15. By having the same voltage reference source control the clock integrator G28, the output information of volume relative to time is obtained. The voltage of the DC reference could be fixed, of course, to produce the results described. Greater flexibility is achieved, however, by making the voltage of the reference K variable. Referring to FIG. 5, variation can be seen to increase or decrease the number of pulses required to cause the integrators G13, G14 and G15 to reach any predetermined level. The same variation affects the clock integrator G23. Although it is independent of the number of pulses arriving, it depends upon the value of the reference voltage for its charge. Decreasing the reference voltage increases the time for the clock integrator G23 to charge. The reciprocal of this charge when multiplied by the value of the volume integrators will therefore always give the same value of volume with respect to time.

The voltage of the source could be variable from a low valuesay 12.5 volts to 200 volts and this could be related to values of sigma. Low voltages would establish small unit charges and cause the volume integrators to accumulate charge at a slow speed thereby permitting the storage of many times more unit charges than if the reference voltage were high, before saturating. The clock integrator would also be slowed down. As indicated, the relationship would not change,

but the amount of sample measured would increase with greater resulting accuracy. If the aperture clogged before the end of the run, the measurement would stop and the full statistical accuracy not obtained. it would still preserve the same relationship.

if the voltage of the reference K were raised, tee reverse would take place. The result could be a saving of diluent and increased freedom from clogging at the expense of lesser statistical accuracy.

This adjustment is a great tool for flexibility and is quite simple in concept.

The reciprocal computer L4 at 79 transmits the signal from the clock integrator to all multipliers 80, 81 and 82. The multipliers are accordingly performing the operation particle count multiplied by relative cubic volume divided by time.

This quantity is fed by the read-outs N13, N14 and N15, shown respectively at 86, 87 and 88. It may be described as the mean particle volume multiplied by the particle count in each channel per unit time. Since time is proportional to the amount of sample volume passed, this yields as an expression which may be written k(pv) (pc)/sample volume total particle volume per channel/sample volume where k is some constant, pv, is the means particle volume of the channel in question and pc is the particle count per channel. The voltage output at 89, 90 and 91 represent these quantities. These quantities may be fed by suitable lines to a summing matrix 92 along with the other values from the other channels, the output used to draw a curve in a suitable plotter 93 giving directly percent above stated size, or any other curve representing the values.

To conclude relative to the nature of the voltage output, since each line at 89, 90 and 91 carries a voltage which is proportional to the volume of material in the window represented by that channel or subrange of the range encompassed by the aperture A4, the information which has been achieved is the ultimate desired by the particle worker to use in the construction of his classical curves. The apparatus has weighted everything in accordance with the time run, size, and so on, having performed all of the data reduction required to give volume of particulate material for the particular size of particles in that range.

The components of the apparatus described are capable of being constructed through the use of well-known electronic techniques. It is believed that the identification and described functions should be sufficient for those skilled in this art.

With respect to the scanning system, one form of multiple aperture apparatus using six apertures is shown in FIGS. 3 and 4. The apparatus is designated generally 120 and is shown as apparatus for use with a static sample, but it should be understood that it is capable of being used with a flow-through or on-stream sample. There is a vessel 121 which has a generally circular sidewall 122 with a rear wall 123 and a relatively thick front wall 124. The vessel is preferably made of glass or other insulating material, and the purpose for making the front wall relatively thick is so that conical sockets may be accurately formed therein as by grinding. Such a socket is shown at 125. A female fitting 126 is mounted on the sidewall 122 in the bottom thereof for drainage, there being a suitable stopcock 127 engaged therein for obvious purposes.

As stated above, there are six apertures in connection with this apparatus, only one of which is seen in FIG. 4. This aperture is designated 128, and it is formed in a wafer 129 set into the bottom wall of a hollow, generally frustoconical fitting 130 that includes an outer cover glass 131 held in place by spring 132, and upper integral inlet conduit 133 and a lower outlet conduit 134. On its interior there is a foil electrode 135 electrically connected to a terminal band 136 to which there is electrically engaged lead 137.

As shown in FIG. 3, this structure described in connection with the fitting 130 is duplicated in each of the other fittings 140, 141, 142, 143 and 144. The-purpose of the inlet conduit equivalent to the conduit 133 shown in H6. 4 is to enable fluid to be introduced into the interior chamber of each of the fittings. This chamber is designated 145 in the fitting 130, and it is in contact with the electrode 135. Likewise all of the chambers have this same arrangement.

The purpose of the outlet conduit 134 and its equivalent in each of the other fittings is to permit flushing and removal of air. Accordingly, the large body of fluid 146 will be feeding into six independent systems. Each fitting has its own electrode equivalent to the electrode 135 and its own hot electrical lead. These are designated 147, 137, 148, 149, 150 and 151. The common electrode 152 in the vessel 121 has an electrical lead 153 common to all the other electrical leads.

The construction using the disclike cover glasses, as shown in 131, enables the inner chambers to be cleaned and enables the ready installation, repair, etc., of the electrode system. It also enables illumination and viewing of the apertures, as by elements 154 and 156.

Apparatus which utilizes more than three or four apertures would most likely be used in distribution studies so that the aperture sizes would be different. in such an arrangement it would be preferable that some advantage be taken of the tendency of the larger particles to settle. Statistically, this would not to any great extent change the nature of the distribution data if settlement were not permitted to take place over a substantial period of time. Accordingly, it would be preferred that the aperture of the fitting 144 be the smallest and the aperture of the fitting 140 be the largest with the intermediate graduated. The order of increasing size would be in accordance with the level of the aperture and would be 144, 142, 130, 143, 141, 140.

A large drain at the bottom of the vessel could permit large and heavy particles to drop into the fitting 126 where they could remain despite efforts to stir the suspension, and upset the true size distribution. Conveniently a poppet valve is seated in the seat 171 formed in the vessel when the stopcock is closed (FIG. 6). The plug 172 has a groove 173 which cooperates with the valve stem 174 to permit the valve 170 to drop into seated condition when the stopcock is closed. When the plug 172 is rotated to open condition the valve is raised.

The illustrated apparatus and description omit any reference to a voting circuit which could act to stop the operation of that portion of the apparatus which includes an aperture that clogs. if desired, this could be connected using contiguous channels in different ranges as the comparison basis. Since these channels are preferably of the same range of size, the result is common ranges in different apertures which may be used in connection with differential amplifiers to produce signals when different, indicating an abnormality in at least one of the apertures.

In many other respects considerable variation can be made without departing from the spirit or scope of the invention as defined in the appended claims.

What it is desired to secure by Letters Patent of the United States is:

1. A method for analyzing a particulate system by the use of at least one passageway through which a sample portion of the particulate system passes and is detected, said method comprising the steps of:

producing output signals each proportional to the volume of each detected particle of said system,

passing said output signals to a plurality of logically parallel channels, separating said channels to be selectively responsive to said output signals in channels according to an incrementation based upon the amplitude of each said output signal,

accumulating separately and progressively the output signals for each said channel over a determinable period of time,

generating a signal proportional to the reciprocal of said period of time, and

producing for each channel an electric signal quantity equal to the mathematic product of said accumulated output signal and said reciprocal time signal at any specific time to obtain an electric signal quantity proportional to the total particulate volume per unit time based upon said specific time for each channel.

2. A method according to claim 1 comprising the further step of dividing the volume of said sample portion by said specific time,

said step of producing thereby yielding the ratio of total particulate volume per channel to volume of said sample portion.

3. A method according to claim 2 comprising the further step of maintaining the ratio between sample portion volume and specific time constant.

i. A method according to claim 3 comprising the further steps of terminating the accumulating step upon the accumulation of a preset signal amplitude in one of said channels.

5. A method according to claim 3 comprising the further step of terminating the duration of said specific time in response to improper detection of said particles.

6. A method according to claim 3, comprising the further step of terminating the duration of said specific time in response to an accumulation of said output signals upon attaining signal capacity of any one channel.

'7. A method according to claim 3 comprising the further step of terminating the duration of said specific time in response to a fixed time measurement.

8. A method according to claim 1, including sending the output signals through a plurality of the passageways arranged logically parallel, each passageway arranged to pass the separated output signals through its interrelated channels, and

arranging the incrementation of all said separated output signals in a regular progression based upon particle volume.

9. A method according to claim 8 comprising the further step of enabling said accumulating step for the separated output signals for any one of said plurality of channels in relationship to the same accumulating enabling of the other of said plurality of channels.

Ml. A method according to claim 8 comprising the further step of regulating the rate of flow of said sample portion through said passageways so that such rate is different for each passageway.

Ill. A method according to claim 10 in which said regulating is accomplished by sizing said passageways according to a mathematic progression.

12. A method according to claim ti comprising the further step of arranging the passing of the output signals through the passageways such that a narrow amplitude range is sent through each passageway.

13. A method according to claim d comprising the further step of summing progressively said product in each channel for all said channels.

14. Apparatus for analyzing particles suspended in a fluid medium which comprises:

particle suspension holding means,

a plurality of apertures in fluid communication with said suspension holding means, each aperture being a different size,

means for moving the fluid medium through the apertures,

transducer means associated with each aperture to produce signals as particles pass therethrough, said signals being respectively proportional to particle volume,

lid

threshold circuit means dividing each transducer output into a plurality of size channels, each channel having means for accumulating charge proportional to total particulate volume and deriving a first signal proportional to said accumulated charge,

means for deriving a second signal proportional to the volume of the fluid medium which passed through the aperture of the said transducer means during the period of time that said charge was accumulated, and

means for dividing the first signal by the second signal to achieve a third signal proportional to the particulate volume concentration.

15. Apparatus according to claim 14 in which means are provided to render said fluid moving means operative for each aperture consecutively.

16. Apparatus according to claim M in which means are provided to disable all of the channels associated with any aperture after a predetermined length of time so that the duration of signal transducing associated with each aperture varies directly as the size of the aperture.

t7. Apparatus according to claim 14 in which disabling circuits are provided for disabling the operation of any given group of channels associated with an aperture when the aperture has passed a number of particles which produce charge accumulation to :a predetermined signal level in any one ofa plurality of circuits, including at least said charge accumulating means.

1%. Apparatus according to claim M in which the aperture sizes vary from aperture to aperture by a factor, and

the size ranges of the channels associated with each aperture also vary by the same factor.

19. Apparatus according to claim 18 in which said factor is two to one, and

the channel size ranges progress from aperture to aperture.

210. Apparatus according to claim M in which said aperture sizes differ by a factor which causes the percentage of coincident passage of particles of the smallest size measured by each aperture to be substantially the same for all apertures, such that the same particle concentration can be effectively scanned by all apertures, substantially irrespective of the breadth and average size of the particle system.

2H. Apparatus according to claim 24) in which said factor is substantially two to one in diameter, and

the size ranges of the channels associated with each aperture vary by a factor of substantially two to one by particle volume.

22. Apparatus according to claim M in which a pump circuit is provided in each channel for driving its charge accumulating means,

an inverse time signal accumulating circuit comprises said second signal deriving means,

a reference voltage is connected to said pump circuit and said time signal accumulating circuit so that the rate of charge accumulating and time signal accumulating are always inversely proportional to each other, and

multiplying means connects each charge accumulating means with said time signal accumulating circuit to define said dividing means and provides an output signal representative of particle volume per unit concentration irrespective of the amount of time that the aperture is passing fluid medium.

23. in an apparatus for analyzing a particulate system by the use of at least one passageway through which a portion of the particulate system passes and is detected in a manner which produces output signals each proportional to the volume of each detected particle of said system, the improvement which comprises:

a plurality of logically parallel electrical channels selectively responsive to receive said output signals according to an incrementation based upon the amplitude of each output signal,

means for progressively accumulating separately the output signals for each said channel over a determinable period of time,

means for generating a reciprocal of said period of time, and

means for producing for each channel the mathematic product of said accumulated output signal and said time period reciprocal at any specific time to obtain the total particulate volume per unit time based upon said specific time for each channel.

24. Apparatus according to claim 23 further comprising means for dividing the volume of said sample portion by said specific time, thereby yielding the ratio of total particulate volume per channel to volume of said sample portion.

25. Apparatus according to claim 24 further comprising a reference signal source coupled to said accumulating means and said generating means for maintaining the relationship between sample portion volume and specific time constant.

26. Apparatus according to claim 25 further comprising means for terminating the duration of said specific time in response to a preset signal amplitude in one of said channels.

27. Apparatus according to claim 25 further comprising means for terminating the duration of said specific time in response to improper detection of said particles.

28. Apparatus according to claim 25 further comprising means for terminating the duration of said specific time in response to an accumulation of said input signals upon at taining signal capacity of any one channel.

29. Apparatus according to claim 25 further comprising means for terminating the duration of said specific time in response to a fixed time measurement.

30. Apparatus according to claim 23 in which a plurality of the passageways are arranged logically parallel, each having its interrelated channels, and

the incrementation of said channels is interrelated in a regular progression base upon particle volume.

31. Apparatus according to claim 30 further comprising means for enabling said accumulating means for said plurality of channels of any one passageway in times relationship to the enabling of said accumulating means for said plurality of channels of at least one other of said passageways.

32. Apparatus according to claim 30 further comprising means for regulating the rate of flow of said said sample portion through said passageways so that such rate is different for each passageway.

33. Apparatus according to claim 32 in which said regulating means are the passageways themselves which have their diameters arranged according to a mathematic progression.

34. Apparatus according to claim 33 in which there is provided a sufficient plurality of passageways and channels per passageway for causing each passageway to respond to an especially narrow range of different volumes.

35. Apparatus according to claim 30 further comprising means for summing progressively said product in each channel for all said channels.

zg ggg UNITEII STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,603,875 p d Sept. 7, 1971 Inventor(s) WALLACE H. COULTER, et a1.

It is certified that errer appears in the above-identified patent and that said Letters Patent are hereby cerrected as shown below:

Column 11, line 6, change "tee" to --the-'-, line 16 change "by" to "to", line 25 change "means" to --mean--; Column 12, line 65, delete "channels to be selectively responsive to said"; Column 13, line 44, after "in" insert --timed--; Column 16, line 7, change "base" to --based--, line 10 change "times" to --timed--, line 26, after different" insert --partic1e--.

Signed and sealed this 9th day 01" May 1972.

(SEAL) A 1*; Lest:

DWARD M.FLJ:TCHI:3R,JR. ROBERT GOTTSCHALK 1i tte sting Officer Commissioner of Patents

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
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US3345502 *Aug 14, 1964Oct 3, 1967Berg Robert HPulse analyzer computer
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3768084 *Jul 14, 1972Oct 23, 1973Becton Dickinson CoParticle counter having a clog and bubble alarm
US3810011 *Apr 18, 1973May 7, 1974Coulter ElectronicsApparatus and method for analyzing the particle volume distribution for a plurality of particles of different size in a quantity of liquid
US3863056 *Jun 29, 1973Jan 28, 1975Coulter ElectronicsMethod and apparatus for multichannel voting
US4075462 *Jan 8, 1975Feb 21, 1978William Guy RoweParticle analyzer apparatus employing light-sensitive electronic detector array
US4418313 *Sep 8, 1981Nov 29, 1983Medicor MuvekProcess and circuit arrangement for the determination in a diluted blood sample of the number of red blood corpuscles, the mean cell volume, the value of haematocrit and other blood parameters
US4535284 *Jul 10, 1981Aug 13, 1985Coulter Electronics, Inc.High and low frequency analysis of osmotic stress of cells
US6175227Jul 1, 1998Jan 16, 2001Coulter International Corp.Potential-sensing method and apparatus for sensing and characterizing particles by the Coulter principle
US7034549 *Mar 31, 2004Apr 25, 2006The United States Of America As Represented By The Secretary Of The NavyDevice to detect and measure the concentration and characterization of airborne conductive or dielectric particles
WO2010124202A1 *Apr 23, 2010Oct 28, 2010Beckman Coulter, Inc.Method of characterizing particles
Classifications
U.S. Classification324/71.1
International ClassificationG01N15/10, G01N15/12, G01N33/49
Cooperative ClassificationG01N15/1245
European ClassificationG01N15/12C