APPARATUS AND METHOD FOR MEASURING A DIVIDING PARTICLE SIZE OF A PARTICULATE SYSTEM

• US 3,557,352 A
• Filed: 11/01/1967
• Issued: 01/19/1971
• Est. Priority Date: 11/01/1967
• Status: Expired due to Term

• Current Assignee: Wallace H. Coulter, Walter R. Hogg
• Original Assignee: Wallace H. Coulter, Walter R. Hogg
• Inventors: Hogg, Walter R., Coulter, Wallace H.
• Application Number:
  US04/679,840
• Time in Patent Office: 1,175 Days
• US Class Current: 702/29
• CPC Class Codes: G01N 15/132 Circuits

Abstract

Apparatus which uses the Coulter particle analyzing system, converting the pulses obtained from said system into accumulated electrical quantities which may be compared to one another or to other quantities derived from the same system on the basis of which one can adjust the quantities relative to one another to achieve the size of a particle which divides the system into two fractional parts having a particular relationship to one another. A variation of this structure is one in which a particle size is obtained which establishes a point in the particulate system above or below which a predetermined fraction of the total mass exists. The preferred structure uses a threshold circuit responding to particle size and separating the electrical pulses produced by the particles being scanned in the Coulter apparatus through the use of such a threshold. The pulse trains are converted into current and these are compared, adjusting the threshold up and down until the desired relationship is reached in a comparison device. The level of the threshold being calibrated to particle size then represents the dividing size between the two fractions. One of the most useful pieces of information of this kind is the dividing size which is the mass median, in which the respective masses of particulate matter above and below the dividing size are equal to one another.

Claims

1. Apparatus for ascertaining that particle size, within a particulate system, above and below which size predetermined fractions of the total mass of the system are respectively included, said particle size being the dividing size between fractions, which comprises:

A. means having at least a range limit for deriving a first electrical effect proportional to the mass of particulate material of a firSt fraction, said first fraction having said dividing size as one of its range limits;

B. means for deriving a second electrical effect proportional to the mass of particulate material of a portion of said total mass, said portion including at least all of a second fraction and at most, both said fractions;

C. means for comparing said effects; and

D. at least one of said deriving means including;

i. means for moving at least a representative sample of said particulate system suspended in a fluid medium relative to sensing means responsive to movement of individual particles by producing electrical changes in said sensing means proportional, respectively, to the sizes of said particles; and

ii. means producing electrical pulses proportional to said respective changes.

2. Structure as claimed in claim 1 in which said range limit is adjustable and said comparing means comprise means for adjusting said range limit to establish a desired relationship between said first fraction and said portion and including means indicative of said adjustable range limit of the first fraction and adapted to be calibrated in terms of particle size.

3. Structure as claimed in claim 2 in which both of said deriving means comprise the structure of said one deriving means.

4. Structure as claimed in claim 2 in which said portion comprises only the second fraction.

5. Structure as claimed in claim 4 in which both fractions are equal.

6. Structure as claimed in claim 2 in which said portion comprises the total mass of said particulate system.

7. Structure as claimed in claim 6 in which said second deriving means comprise a gross particle measuring apparatus providing an electrical signal proportional to total particulate mass and said signal being said second electrical effect.

8. Structure as claimed in claim 6 in which said first fraction comprises total particulate mass of particles larger than said dividing size.

9. Structure as claimed in claim 6 in which said first fraction comprises total particulate mass of particles smaller than said dividing size.

10. Structure as claimed in claim 2 in which said first deriving means comprise a Coulter-type particle measuring apparatus;

said adjustable range limiting means including an adjustable threshold circuit arranged to be changed to adjust the range limit which defines said dividing size.

11. Structure as claimed in claim 2 in which said indicative means comprise a manually operable device

12. Structure as claimed in claim 11 in which said indicative means comprise an electrically operated readout having an output proportional to first fraction and said portion, respectively. 13 Structure as claimed in claim 11 in which said indicative means comprise electrical balancing means.

14. Structure as claimed in claim 2 in which said means for adjusting said adjustable range limit is an electrically operated threshold circuit and said indicative means is electrically operated.

15. Structure as claimed in claim 14 in which said indicative means comprise a voltmeter.

16. Structure as claimed in claim 2 in which said sensing means comprise at least two graduate sensitivity sensing zones of the Coulter type which establish a corresponding number of contiguous ranges of particle size, and means are provided for combining the outputs of these ranges to form said first fraction and said portion and for ascertaining the range in which the dividing size lies.

17. Structure as claimed in claim 2 in which said effects are digital.

18. Apparatus for ascertaining that particle size of a particulate system above and below which size predetermined fractions of the total mass of the system are respectively included, said particle size being the dividing size between fractions, which comprises:

A. signal producing means of the Coulter type including;

i. means for moving a representative sample of a particulate system suspended in a fluid medium relative to a sensiNg device responsive to movement of individual particles by producing electrical changes in said sensing means proportional to the respective sizes of particles; and

ii. means for producing electrical pulses as a result of such changes, and the respective electrical pulses being proportional in amplitude to the size of the respective particles producing the changes;

B. means for generating first representative electrical quantities respectively proportional to amplitudes of said electrical pulses;

C. means for separating said representative electrical quantities into two categories on the basis of the size of the particles respectively producing the same, the first category comprising all quantities greater than a measuring level, and the second category comprising all quantities less than said measuring level, said measuring level being calibrated to be proportional to particle size;

D. means for producing at least one signal representing the relationship between categories accumulated; and

E. means for adjusting the measuring level to produce a desired relationship between categories such that said at least one signal is indicative of said relationship and identifies said dividing size.

19. Apparatus as claimed in claim 18 in which said penultimate means comprise a plurality of accumulating devices producing visible phenomena indicating response and thereby enabling adjustment of the last-mentioned means.

20. Apparatus as claimed in claim 18 in which said penultimate means comprise a plurality of accumulating devices, having outputs connected to an electrical comparison device including a readout enabling adjustment of said last-mentioned means.

21. Apparatus as claimed in claim 18 in which the means for adjusting the measuring level is manually controlled and means are provided for weighting the quantities such that any desired relationship will result in a null comparison to be used while adjusting the measuring level.

22. Apparatus as claimed in claim 21 in which the weighting means are included with said comparing means.

23. Apparatus as claimed in claim 21 in which the weighting means are other than in said comparing means.

24. Apparatus as claimed in claim 18 in which the means for adjusting the measuring level comprise an integrating amplifier supplying a feedback to said separating means, means for comparing said separated quantities, said integrating amplifier being connected to said comparing means to receive the output thereof.

25. Apparatus as claimed in claim 24 in which means are provided for weighting the quantities such that any desired relationship will provide an equilibrium condition in said integrating amplifier with a resulting condition of measuring level.

26. Apparatus as claimed in claim 24 in which readout means are provided for measuring the feedback output of said integrating amplifier as a quantity proportional to measuring level.

27. Apparatus as claimed in claim 18 in which said quantities are equal whereby the relationship between quantities is one to one and the measuring level represents mass median.

28. Apparatus as claimed in claim 18 in which the separating means comprise a variable threshold circuit and the measuring level comprises the threshold level of said circuit.

29. Apparatus as claimed in claim 28 in which said apparatus has two channels connected to transmit said categories of pulses respectively to said generating means;

said first category comprising all pulses which exceed the threshold and said second category comprising all pulses which do not exceed said threshold.

30. Apparatus as claimed in claim 18 in which said categories of pulses are applied to said comparing means with opposite polarities and said comparing means combines said pulses algebraically.

31. Apparatus as claimed in claim 30 in which said comparing means includes an integrating amplifier and the means for adjusting the measuring level comprise a feedback circuit from said integRating amplifier to said separating means.

32. Apparatus as claimed in claim 31 in which readout means are provided to measure the output of said integrating amplifier to said feedback circuit, said output being proportional to measuring level.

33. Apparatus as claimed in claim 18 in which said separating means include a variable threshold device, precision pulse shaping means and switch control means, and in which said generating means comprise a pair of switches for providing electric current outputs, the said measuring level being the threshold of said threshold device;

said pulse shaping means receiving all electrical pulses and converting same into equal duration pulses of amplitudes equal respectively to the original pulses;

the threshold device being connected to said switch control means and operating to direct said equal duration pulses to one or the other of said switches depending upon whether its amplitude exceeds said threshold;

the pulses passing through each switch forming the first and second electrical quantities, respectively.

34. Apparatus as claimed in claim 33 in which means are provided to invert the phase of one of said quantities in which said comparing means include a summation network for adding the quantities algebraically.

35. Apparatus as claimed in claim 33 in which said pulse shaping means include a pulse stretcher and means for excising only a portion of each stretched pulse to provide said equal duration pulses.

36. Apparatus as claimed in claim 18 in which said separating means include a variable threshold device, precision pulse shaping means and switch control means;

and in which said generating and accumulating means comprise a pair of switches for providing electric current outputs;

the said measuring level being the threshold of said threshold device;

said pulse shaping means receiving all electrical pulses and converting same into equal duration pulse signals proportional respectively to the amplitudes of the original pulse signals;

the threshold device being connected to said switch control means and operating to direct said equal duration pulse signals to one or the other of said switches depending upon whether its amplitude exceeds said threshold;

the pulse signals passing through each switch forming the first and second electrical quantities, respectively.

37. Apparatus as claimed in claim 36 in which means are provided to invert the phase of one of said quantities and in which said comparing means include a summation network for adding said first and second electrical quantities algebraically.

38. Apparatus as claimed in claim 36 in which said pulse shaping means comprises a diode-capacitor pump circuit.

39. Apparatus as claimed in claim 18 in which there are a plurality of signal producing means, a plurality of range circuits, each connected to one said signal producing means and having individual separating means generating and accumulating means, and comparing means;

the summation means being common to all ranges and including all comparing means;

said adjusting means comprising an integrating amplifier connected with the summation means, said apparatus including programming means for connecting said integrating amplifier with the separating means one after another, if needed, and acting to vary said measuring level of the separating means with which it is connected while at the same time separating all pulses in all ranges of greater and lesser amplitude than said level into said two quantities for comparison;

the connection between integrating amplifier and a different separating means continuing to occur until a state of equilibrium is reached;

the output of said integrating amplifier being proportional to particle size.

40. Apparatus as claimed in claim 18 in which the means for adjusting the measuring level comprise an add-subtract register supplying a feedback to said separating means, said add-subtract register being connected to said comparing means to receive the output thereof.

41. Apparatus as claimed in claim 40 in which means are provided for weighting the quantities such that any desired relationship will provide an equilibrium condition in said add-subtract register with a resulting condition of measuring level.

42. Apparatus as claimed in claim 41 in which readout means are provided for measuring the feedback output of said add-subtract register as a quantity proportional to measuring level.

43. Apparatus as claimed in claim 18 in which the separating means comprise an analogue to digital converter and a digital comparator and the measuring level comprises a digitally coded number;

the digital coded number representing each particle-produced pulse amplitude being applied to a first input of said comparator and the digitally coded measuring level being applied to the second input of said comparator.

44. Apparatus as claimed in claim 43 in which the digitally coded numbers are binary coded.

45. Apparatus as claimed in claim 18 in which the separating means comprise an analogue to digital converter and a digital comparator;

the measuring level comprises a digitally coded number, and the means for accumulating and comparing the first and second electrical quantities respectively proportional to cumulative particle mass comprises an add-subtract digital register.

46. Apparatus as claimed in claim 45 in which said apparatus includes means for transmitting said categories to said add-subtract register in such a manner that digitally coded pulse amplitudes of the first category are added to and those of the second category are subtracted from the number stored in said register;

said first category comprising all digitally coded pulse amplitudes which exceed the measuring level and said second category comprising all digitally coded pulse amplitudes which do not exceed said measuring level.

47. Apparatus for ascertaining that particle size of particulate system above and below which size predetermined fractions of the total mass of the system are respectively included, said particle size being the dividing size between fractions, which comprises:

A. signal producing means of the Coulter type including;

i. means for moving a representative sample of a particulate system suspended in a fluid medium relative to a sensing device responsive to movement of individual particles by producing electrical changes in said sensing means proportional to the respective sizes of particles; and

ii. means for producing electrical pulses as a result of such changes, and the respective electrical pulses being proportional in amplitude to the size of the respective particles producing the changes;

B. means for generating first representative electrical quantities respectively proportional to amplitudes of said electrical pulses;

C. means for separating said representative electrical quantities into two categories on the basis of the size of the particles respectively producing the same, the first category comprising all quantities greater than a measuring level, and the second category comprising all quantities less than said measuring level;

said measuring level being calibrated to be proportional to particle size;

D. means for accumulating the separated representative electrical quantities of one category into a first accumulated electrical quantity proportional to cumulative particle mass;

E. means for measuring the total mass of the system to obtain a second representative electrical quantity proportional to a predetermined fraction of said total mass;

F. means for comparing said first accumulated electrical quantity and said second representative quantity one with the other; and

G. means for adjusting the measuring level to produce a desired relationship between quantities, the resulting measuring level thereby comprising the dividing size of particle representing the relationship between the fraction of total mass represented by said one category of particles and the said predeTermined fraction of mass represented by the second quantity.

48. Apparatus as claimed in claim 47 in which the means for measuring said second electrical quantity includes weighting means whereby said comparing means operates upon weighted electrical quantities.

49. Apparatus as claimed in claim 47 in which the means for adjusting the measuring level comprises an integrating amplifier supplying a feedback to said separating means, said integrating amplifier being connected to said comparing means to receive the output thereof.

50. Apparatus as claimed in claim 49 in which means are provided for weighting the quantities such that any desired relationship will provide an equilibrium condition in said integrating amplifier with a resulting condition of measuring level.

51. Apparatus as claimed in claim 47 in which said quantities are equal whereby the relationship between quantities is one to one and the measuring level represents the mass median.

52. Apparatus as claimed in claim 47 in which the means for measuring the entire mass of the system comprise Coulter apparatus.

53. The method of ascertaining the dividing particle size for any desired percentile mass of a particulate system which includes passing a sample of said system through a Coulter apparatus to obtain a string of electric pulses of amplitudes respectively proportional to said particles;

choosing a preliminary particle size of the system and dividing the pulses into two categories whose amplitudes are respectively above and below said preliminary particle size;

continuously accumulating the respective categories and converting same into electrical quantities and comparing continuously the accumulated quantities one with the other;

changing the particle size up or down until the compared quantities have a particular relationship representing the desired mass percentile;

the particle size resulting in such condition comprising the dividing particle size for such sample.

54. The method of ascertaining the dividing particle size for any desired mass percentile of a particulate system which includes passing a sample of said system through a Coulter apparatus to obtain a string of electric pulses of amplitudes respectively proportional to said particles;

subjecting said system to a signal related to the mass of the entire particulate system;

attenuating the last signal and converting same into a first electrical quantity proportional to the desired mass percentile;

choosing a preliminary particle size of the system and dividing the electric pulses into two categories whose amplitudes are respectively above and below said preliminary particle size;

continuously accumulating one category and converting the same into a second electrical quantity and continuously comparing the quantities one with the other;

changing the preliminary particle size up or down until the compared quantities have a particular relationship representing the desired mass percentile;

the particle size resulting in such condition comprising the dividing particle size for such sample.