Note: Descriptions are shown in the official language in which they were submitted.
~6~
The present invention is directed to spectrophoto-
metric analysis, and more particularly to methods and apparatus
for electro-optical analysis of emulsions and suspensions. Yet
more specifically, the invention is directed to me~hods and
apparatus for infrared anal~sis of percentage by weight of fat,
protein and lactose in milk.
An object of the present invention is to provide a
spectrophotometric analyzer for analysis of emulsions and sus-
pensions which is economical in manufacture, and which is reli-
able and accurate over extended periods of operation. A further
and more specific object of the invention is to provide a com-
pact electro-optical analyzer possessing a reduced number of
optical elements and a shortened beam path length as compared
with prior art analyzers of similar type.
A further object of the invention is to provide an
improved sample cell for spectrophotometric analysis of fluids.
Yet another object of the invention is to provide an improved
system and method for directing fluid to be analyzed to the
sample cell.
In furtherance of the above, another object of the in-
vention is to provide an improved homogenizer for use in optical
analysis of emulsions and suspension such as milk.
Accordingly, the present invention provides a sample
cell for use in optically analyzing fluids comprising a pair of
flat parallel op~ical windows and means spacing said windows
from each other to provide a ~enerally planar sample zone,
fluid inlet and outlet ports including openin~s extending
through one of said windows and spaced from each other such that
fluid enteriny said inlet port traverses said zone between
said windows before exitin~ said outlet port, a fluid passage
extending past said inlet port and connectiny with said inlet
port through an openlng in a side wall of said passage, and a
-- 1 --
6~
filter medium carried against said passage side wall across
said opening such that fluid which enters said zone through said
inlet port is filtered by said filter medium while fluid passing
through said passage past said inlet port tends to wash said
filter medium.
The invention, together with additional. objects,
features and advanta~es thereof, will be best understood from
the following description, the appended claims
- la -
6~
and the accompanying drawings in which:
FIG. 1 is a top plan view of the optical
portion of a presently preferred embodiment of the
electro-optical analy~er provided in accordance with
the invention;
FIG. 2 is a schematic diagram of a system
for directing fluid to be analyzed to the sample cell in
accordance with the presently preferred embodiment of
the invention;
FIG. 3 is a functional block diagram of
analysis e:Lectronics in accordance with the invention;
FIG. 4 is a flo~ chart illustrating operation
of the invention;
FIG. 5 is a side elevational view of the optical
filter drum and coding disc assembly illustrated in
FIG. l;
FIG. 6 is a side elevational view of the chopper
disc and drive motor illustrated in FIG. l;
FIG. 7 is a sectional view of the homogenizer
in accordance with the invention and illustrated
schematically in FIG. 2;
FIG. 8 is an exploded perspective view of a
presently preferred embodiment of the sample cell in
accordance with the invention,
FIGS. 9, 10 and 11 are respective plan, side
elevational and front elevational views of the sample
cell illustrated in FIG. 1 and scherr~tically in FIC,. 2;
FIGS. 12 and 13 are sectional views taken
along the respective lines 12-12 in FIG. 10 and 13-13
in FIG. 11; and
6a~
FIGS. 14a-14c together comprise an electrical
schematic diagram of the memory, correction and scaling
circuitry illustrated in block form in FIG. 3, FIGS. 14a
and 14b being interconnected along the lines a~b in each
5 FIG., and FIGS. 14b and 14c being interconnected along
the lines b-c in each FIG.
The principles of invention will be described
in detail in connection with a presently preferred
application thereof to infrared spectrophotometric
analysis of milk for percentage by weight of fat,
protein, lactose and water or solids therein. However,
it must be recognized that such principles are equally
applicable to analysis of other dairy products, to
non-dairy food products such as meat and grain, and to
non-food products such as paints, pharmaceuticals or
chemical and gas compositions.
Referring to FIG. l, the optical section or
portion of the electro-optical milk analyzer provided
by the invention comprises a ceramic infrared energy
source 20 enclosed within its own cooling chamber 22.
An interference filter 24 having a preferred pass band
in the range of three to ten microns is disposed in one
wall of chamber 22 and transmits infrared energy from
source 20 to a pair of plane mirrors 26,28 which operate
to split the filtered infrared energy into diverging
baams 30,36 illustrated in phantom lines in FIG. l.
The first or reference beam 30 i5 reflected by plane
mirror 26 onto the surface of a spherical mirror 32
from whence reference beam 30 is focused onto an optical
axis 34. The second or measurement beam 36 is reflected
by plane mirror 28 onto the surface of a second spherical
-- 3 --
mirror 38 from whence the measurement beam is directed
to intersect the reference b am from a direction orthogonal
to beam axis 34. A sample cell generally indicated at
66 and to be described in greater detail hereinafter
in connection with FIGS. 8-13 is disposed at the focus
of reference beam 30 on beam axis 34~ An ellipsoidal
mirror 68 has a first focus at sample cell 66 and a
second focus at a detector 70 for directing and con-
centrating the optical energy transmitted through sample
cell 66 onto detector 70. Preferably, mirrors 26,28
32,38, 100 and 68 are of glass with highly reflecting
surfaces of aluminum or gold.
An upstanding vane or shutter 40 is disposed
in the path of measurement or reference beam 36 or 30
(drawing shows vane in measurement beam), and is rotatably
coupled to a motor 42 for a pucpose to be described
hereinafter. A drive gear 44 is coupled to the shaft
46 of a servomotor 48 through a slipping clutch mechanism
(FIG. 1 and schematically in FIG. 3) and through the idler
gear 50 to a gear section 52 mounted to pivot in the
plane of FIG. 1 about the pin 54~ An arm 56 is rigidly
coupled to gear section 52 and has a comb or shutter 58
(FIGS. 1 and 3) carried on the pivot-remote end thereof
for adjustable placement within the path of reference
beam 30 between mirror 32 and sample cell 66 as controlled
by servomotor 48. Co~b 58 is arcuate in cross section
with a radius centered on the axis`of pivot pin 54 and,
as best seen in FIG. 3, possesses a plurality of trans-
versely spaced longitudinal slots 60 each having a width
which varies linearly with arcuate comb length. ~hus,
~6~
reference beam 30 is selectively attenuated as a linear
function of the degree or extent to which comb 58 is
inserted into the beam. Com~ 58 is preferably coated
with material which absorbs infrared energy. A coil
spring 62 (FIG. 1) extends between arm 56 and a fixed
stanchion 64 for resiliently biasing gear drive chain
or transmission 44,53,52 so as to achieve substantially
zero backlash. Coupled to gear 50 is an accurately
linear potentiometer arranged to provide a voltage to
measuring circuits which is proportional to the percentage
transmission (%T) of the sample. A second potentiometer
coupled to the same spindle within the same potentiometer
housing provides velocity feedback for the servomotor
drive circuit.
A filter wheel 72 shown in FIGS. 1 and 5
comprises a drum co~pled by the gears 74,76 to a drive
motor 78 to rotate about a fixecl axis 79 (FIG. 5)
orthogonal to reference beam axis 34. Drum 72 includes
segmented circumferential rim portions 80 w~ich intersect
reference beam 30 between comb 58 and cell 66 as drum
72 is rotated, and an axially facing aisc portion 82
which intersects measurement beam 36~ First and second
series of optical absorption-type filters are respectively
disposed in rim portion 80 and disc portion 82 of drum
72, and are grouped in coordinated pairs on corresponding
radii from the axis of rotation 79 such that one filter
in each filter pair simultaneously intersects associated
ones of the reference and measurement beams 30,36.
More particularly, four circumferentially spaced reerence
filters 84,86,88,90 are mounted in associated segments
of drum rim portion 80 sequentlally to intersect reference
-- 5 --
6~
beam 30 as drum 72 is rotated in the counterclockwise
direction as viewed in FIG. 5. In analysis for fat,
protein, lactose and water concentrations in milk,
reference filters 84-90 preferably possess nominal peak
transmission wavelengths of 3.47, 6.68, 7.67 and 5.55
microns respectively. A series of circumferentially
spaced measurement filters 92,94,96 and 98 are disposed
on the planar disc portion 82 of drum 72 in radially
aligned association with respective reference filters
84,86,88 and gO as best seen in FIG. 5. For analysis
of fat, protein, lactose and water in milk, filters
92,94,96 and 98 preferably possess nominal peak trans-
mission wavelengths of 3.418, 6~46, 9.6 and 4.7 microns
respectively. Preferably, at least fat measurement
filter 84 is tiltably mounted (by means not shown) so
as to facilitate factory fine-tuning of the peak trans-
mission wavelength to the value~; indicat~d.
A detent locking arrangement 118 is provided
for holding drum 72 in ~ixed rotational position with a
filter pair in the associated beam paths. Detent 118
comprises a series of five V-shaped notches 120,122,124,
126 and 128 (FIG. 5~ disposed about the periphery of
drum disc portion 82. Notches 120,122,124 an~ 126 are
respectively diametrically opposed to filter pairs 84,92;
86,94;88,96; and 90,98. Notch 128 is for holain~ drum
72 in a rest positionc A roller bearing 130 is rotatably
mounted in the plane of a drum axis 79 on a spring-biased
pivot arm 132 ~or resiliently engaging the respective
detents as drum 72 is rotated. Thus, in the position
illustrated in FIG. 5, bearing 130 resiliently engages
64
notch 120 to hold fat reference and measurement filters
84,92 in reference and measurement beams 30,36 (FIG. 1).
When drum 72 is rotated to the next position wherein
bearing 130 engages notch 122, protein reference and
measurement filters 86,94 are held in the beam paths.
Notch 124 operates in conjunction with lactose reference
and measurement filters 88,96, and notch 126 operates
in conjunction with water reference and measùrement
filters 90,98 in a similar manner.
10A program or code disc 112 (FIGS. 1 and 5)
is mounted on gear 76 and is thereby rotatably coupled
to filter drum 72 such that a peripheral portion of disc
112 passes through the optical sensor generally indicated
at 114 in FIG. 1 as a function of drum rotation. Optical
15sensor 114 is responsive to peripheral apertures 116
(FIG. 5 and schematically in FIC;. 3) in disc 112 for
controlling system electronics ~FIG. 3) to stop rotation
of d~m 72 when a selected filter pair is disposed in
the corresp~n~ing beams, to control the electronics for
measurement of the particular constituent with which
the filter pair is associated and to switch the pump
motor on at the correct point in the operation cycle.
Provision of interference filter 24 adjacent infrared
source 20 ~FIG. 1) f~r pass`ing only a portion (three to
ten microns) of the infrared spectr~m of interest to
the absorption-type reference and measurement filters
reduces heating of the latter and improves accuracy of
the overall apparatus.
~ chopper shutter or disc 100 (FIGS. 1 and 6)
is positioned at the zone of intersection between reference
beam 30 and measurement beam 36 at an orientation of 45
-- 7
8~4
with respect to both beam axes. As best seen in FIG. 1,
disc 100 is angled to nest within the angle formed by
drum rim and disc portions 80,82. Disc 100 comprises
a semicircular aperture 102 (FIG. 6) and a semicircular
reflective portion 104 alternately positioned in the
paths of beams 30,36 at the point of intersection there-
between as disc 100 is rotated by the motor 106 coupled
to the disc drive shaft 108 by the belt and pulley
arrangement generally indicated at 110 in ~IG. 1.
Thus, disc 100 nested within the rim and disc portions
of drum 72 is operative alternately to direct the
measurement and reference beams through sample cell 66
onto detector 70. More specifically, when aperture 102
of disc 100 intersects the optical beams, reference
beam 30 is transmitted on beam axis 34 through aperture
102 and sample cell 66 to detector 70 while measurement
beam 36 passes through the aperture away from the sample
cell. When reflective disc portion 104 intersects the
respective beams, measurement beam 36 is folded thereby
to focus at sample cell 66 confocally with reference
beam 30, and thus is transmitted to detector 70 by
ellipsoidal mirror 68. At the same time, reference
beam 30 is reflected by the rear surface of disc portion
104 away from the sample ce h.
~5 Thus, rotation of disc 100 at the preferred
frequency of 12.5 hertz ~50 hertz ~inus frequency) or
15 hertz (60 hertz minus frequency) operates to transmit
to detector 70 a composite beam which alternates in
intensity as a function of the difference in percentage
transmission of a sample in cell 66 at the particular
wavelengths transmitted by whichever reference and measurement
-- 8 --
filters are in the beam paths. Detector 70 produces a
signal which is amplified and conditioned by amplifier
111 and associated circuitry (FIG. 3~ to drive servomGtor
48 (FIGS. 1 and 3). This positions comb 5~ within beam
30 so as to minimize this intensity aifferential. In
this manner, the ultimate position of the servomotor
4B, and the potentiometer coupled to it, for ~ny filter
pair, is proportional ~o the change in transmission of
the sample situated in cell 66 at the wavelengths
transmitted by that filter pair.
FIG. 2 illustrates a presently preferred
embodiment 140 of the fluid drive system for placing
test fluid in the sample cell generally indicated at
66 in FIG. 1, System 140 comprises a diaphragm-type
homogenizer 142 (FIGS. 2 and 7) operatively coupled to
an hydraulic pump 144 (FIG. 2) and having an inlet 146
to draw a fluid milk sample from the vessel 149. Pump
144 includes ~ reciprocable piston 147 for driving
hydraulic fluid under pressure to homogenizer lA2
through the conauit 148. A code disc illustrated
schematically at 150 in FIG. 2 ls coupled to the piston
drive mechanism ~not shown) ~or cyclically operating pump
144 in a manner to be described. A pressure relief valve
151, including a valve stem 152 and a coil spring 154
is coupled internally of pump 144 to conduit 148. In
one working embodiment of the invention, pump 144 co~prises
a Series (1) Actuator Pump marketed by Dia-meter Pumps
Ltd. of Station ~oad, Liss. Hampshire England.
~eferring to FIGS. 2 and 7, ho~ogenizer 142
includes a resilient diaphragm 160 having an annùlar
lip 161 captured between body blocks 162,164. The
g _
~.6~
central portion of diaphragm is disposed within a
diaphragm pump chamber 166. On one side of diaphragm
160, chamber 166 is coupled by passage 168 extending
axially through a ~itting 169 to a nipple 170 threadably
received in fitting 169 for receiving hydraulic pump
fluid through conduit 148 (FIG. 2). The other end 167
of fitting 169 acts as a diaphragm stop on the decompression
stroke of the pump cycle. Fitting 169 is rigidly attached
to block 164 and lip 171 takes the axial load imparted
on the compression stroke. An annular lip 165 in
block 162 insures accurate location of the diaphragm
stop 167 in relation to the diaphragm 160. High tensile
bolts 163 are used to fasten together blocks 162,164.
A second passage 172 extends axially in block 162 from
chamber 166 through a gasket 174 and an orifice 176 to
a first homogenizing valve generally indicated at 178.
Valve 178 comprises a sapphire ball 180 normally biased
by a coil spring 182 against a ceramic valve seat 184
restricting fluid communication from diaphragm chamber
166. Valve 178 opens to a second homogenizing valve 186
comprising a sapphire ball 190 biased by a coil spring
192 against a stainless steel valve seat 194. Valve
186 opens to a nipple 1960 Nipple 196 is ce~ented into
a fitting 195 which encloses spring 192 and balll90, and
which in turn is threadably received into a larger fitting
193. Fitting 193 encloses orifice 176 and valve seats
184,194, all of which are held rigidly therein under
compression by fitting 195 in cooperation with a sleeve
191 surrounding ball 180 and spring 1820 Fitting 193
is threadably received in block 162 and captures gasket
174 in sealing engagement around the diaphragm-remote end
-- 10 --
of passage 172.
A passage 198 extends laterally of passage
172 to a gravity and pressure operated check valve 200
comprising a ball 202 normally biased by gravity down-
wardly against a valve seat 204. A passage 206 extends
from valve seat 204 to a nipple 205 for receiving a fluid
sample through conduit 146 (FIG. 2). Nipple 205 is
cemented into a fitting 203 which, in turn, captures
valve seat 204, ball 202 and a ball-guide sleeve 201
within an outer fitting 199 by being threadably received
in the latter. Fitting 199 is threadably received within
block 162 in axial alignment with lateral passage 198
and captures a sealing gasket 197 therearound. Upward
motion of ball 202 during suction of diaphragm 160 is
limited by a pin 208 press fittecl in and extending across
sleeve 201.
Orifice 176 passes through a removable disc
of stainless steel and is included in the homogenizer
head merely as a means of enabling the pa~ts to be
disassembled. The valve seats, balls and springs may
be removed from the separated ho~ogenizer unit by first
unscrewing fitting l9S from fitting 193, and then
pressing a rod against the disc containlng the smaller
orifice 176 in a direction f~om right to left as shown
~5 in FIG. 7~
In operation, pump 144 alternates between a
negative or suction pressure with reference to homogenizer
142 wherein diaphragm 160 is withdrawn to the position
illustrated in FIGSo 2 and 7, and fluid to be homogeniæed
~0 and tested is drawn by negative pressure through conduit
146 and check valve 200 (FIG. 7) into chamber 166. On
-
the next succeeding pressurization stroke, the diaphragm
160 is displaced to the left in FIGS~ 2 and 7 forcing
the sample fluid drawn during the suction portion of
the pump cycle through orifice 176 and valves 178,186
to outlet nipple 196. Preferably, the stroke of piston
147 (FIG. 2) is slightly greater than the volume of
diaphragm chamber 166 such that pressure relief valve
151 (FIG. 2) is actuated on each stroke for deaerating
the pump hydraulic fluid. Valve 151 preferably is set
at 3800 psi. In the homogenizer illustrated in FIGS.
2 and 7, a pump pressure in the range of 3000 to 5000
pounds per square inch, typically 3500 psi, is contemplated.
High pressure operation in this range and the two-staye
homogenizing valve arrangement 178,186, has been found
to reduce the particle size of the larger globules in
whole milk to about two microns.
Sample cell 66 is illustrated schematically
in FIG. 2 and in greater detail in FIGS. 8-13. Cell 66
comprises a pair of flat parallel optical windows 210,212
spaced from each other in asserr,bly by a shim 214 of con-
trolled thickness and having an oval center opening for
proviaing a planar sample zone 216 between windows 210,212.
In the preferred err~bodiment of the invention for measuring
fat, protein, lactose and water concentrations in milk,
shim 214 and, therefore, planar sample zone 216 possess
a thickness of thirty-seven microns. One of the windows
210,212 is constructed of calcium Eluoride material
having a cut-off at approximately 11 microns while the
other window is of barium fluoride material having a
cut-of at 12~5 to 13 microns. As best seen in FIGS.
8 and 13, window 212 has a pair of circular openings
-- 12 --
218,220 extending therethrough transversely of oval
sample zone 216 and spaced from each other lengthwise
of the sample zone such that fluid entering opening
218, which is an inlet opening, traverses the sample
zone in the upward direction in FIG. 13 and then exits
opening 220, which is the outlet op2ning. Second openings
222,224 extend through outer window 210 in respective
alignment with inlet opening 218 and outlet opening 220,
and communicate with a circular groove or channel 226
of semicircular section having a preferred diameter of
0,3 mm formed on the face of a stainless steel plate
228 cemented to window 210, such that a portion of the
fluid entering inlet 218 will flow through opening 222,
channel 226, opening 224 and then exit outlet 220
thereby to bypass sample zone 216. Plate 228 has an
oval center opening 230 for admitting infrared radiation
therethrough to windows 210,212.
Windows 210,212, shim 214 and plate 228 are
placed in ~acing engagement as described, Ps best
appreciated with reference to FIGS, 8 and 13, this
sandwiched assembly is then located together with a
centrally apertured ring 236 within the machined central
bore 235 of a cylindrical block 234. A pair of plates
232,233 having central openings of smaller aperture
than bore 235 are then placed over the axial faces of
cell bloclc 234 and fastened thereto by the pan head screws
231 and flat head screws 239 to hold the sandwiched asse~bly
within the cell block. Holes in 233 are counterbored to take
spr~ngs 237 under the heads of screws 231. Springs 237
serve to spring-load parts 236, 228, 210, 214 and 212
together between plates 233 and 232 to give eq~lal
surface loading on all parts. Holes in plate 233 are
- 13 -
~6~
large enough to allow heads of screws 238 to pass
therethrough and bed against the surface of block 234,
Plate 232 has openings 229 which align with openings
218,220 in window 212 and which receive sealing rings
227. The entire cell block assembly is then fastened
to a port block 240 by the bolts 238.
Port block 240 includes inlet and outlet
passages 242,244 (FIGS. 8, 10, 12 and 13) respectively
communicating with openings 218,220 in window 212
through plate openings ~29. Outlet passage 244 in
block 240 communicates through a tubular nipple 246
(FIGS. 9-11) and a conduit 248 (FIG. 2) with a pressure
valve 250 comprising a ball 252 biased by coil spring
254 to retard flow through conduit 248 tand therefore
through cell 66). Valve 250, when openedr feeds
~luid in conduit 248 to waste through a drain 256.
inlet assembly 258 (FIGS. 9-12) comprises a fitting
260 threadably received into a side opening in block 240
and a hollow tu~ular ~ilter 262 extenaing axially ~rom
fitting 260 into a cylindrical flow passage 264 in
block 240. A passage 266 (FIGS. 11 and 12) communicates
transversely with passage 264 axially spaced from filter
262, and extends through bloc~ 240 to a second outlet
nipple 268 (FIGS. 9-11). Outlet nipplè 26g is connected
by a conauit 270 ~FIG. 2) to a valve 272 controlled by
disc 150 in pump 144~ Nipples 246,268 are screwed and
cemented into associated openin~s in port block 240.
As best seen in FIG. 12~ inlet passage 242 in block 240
communicates with passage 264 at right angle5 approximately
centrally of ~ilter 262 such that fluid entering passage
242 passes through the filter side wall and is ~iltered
- 14 -
thereby, A nipple 259 is a running fit into fitting 260
for connection to conduit 197 (FIG. 2) from homogenizer
142.
Thus, it will be evident that, with pressure
valve 250 (FIG. 2) normally closed and control valve
272 held normally open, fluid fed to sample cell inlet
258 by homogenizer 142 normally flows through the hollow
central opening in filter 262, through passages 264,266,
nipple 268 (FIGS. 11 and 12), conduit 270 (FIG. 2) and
valve 272 to waste, whereby filter 262 is self-cleaning.
On the other hand, when valve 272 is closed, fluid
pulses from homogenizer 142 are routed through the
side wall of filter 262 into passage 242 (FIGS. 2, 10
and 12-13) in block 240. ~ portion of this fluid passes
through sample zone 216 while the remainder bypasses
the sample space through channel 226 (FIG. 13) in plate
228 as previously described. Disc 150 (FIG. 2) controls
pump 144 such that ~ach sampling cycl~e comprises a
plurality of between five and fifteen, preferably
twelve, pulsations of homogenizer 142, On the first
eleven pulsations in the preferred mode of operation,
valve 272 is held open such that the homogenized milk
effectively purges homogenizer 142, conduit 197 and
inlet assembly 258. In particular, it will k~ appreciated
that the purging fluid tends to wash tubular filter 262.
Prior to the twelfth pulsation of homogenizer 142, valve
272 (FIG 2) is closed. Thus, the pressure of the twelfth
pulsation is effective to open pressure valve 250 such
that fluid is then routed through the side wall of tubular
filter 262 and -through sample zone 216 as previously
-- 15 -
- ~;
described. After the twelfth pulsation, operation of
pump 144 is automatically terminated by disc 150 (FIG. 2)
and optical characteristics of the sample in sample zone
216 may be measured.
Preferably, each pulsation of homogenizer 242
provides approximately 0.6 milliliters of homogenized
fluid. The sample zone 216 itself holds approximately
0.005 milliliters of fluid. Thus, it will be appreciated
that the total volume of fluid provided by homogenizer
142 during each purging and cell-refill cycle, and
also during the twelfth pulsation through the sample
zone itself, is substantially in excess of that required
for obtaining a measurement sample. However, the additional
wastage offers the significant aavantage previously
described of automatically purging all flow lines
including the cell. Preferably, conduits 197,270
and 248 (FIG. 2) are constructed of xesilient material
such as tubular PVC or elastically absorbing transient
pressures caused by the pulsating fluid flow thereby
to prevent flexure of optical windows 210,212.
Plates 228, 233, 232, cell block 234~ ring
236 and port block 240 (FIG. 8~ are preferably constructed
of corrosion resistant material such as stainless steel.
Heating resistors 274,276 arè mounted on the cell-remote
side of block 240 and are connected to appropriate
control circuits 278 (FIG. 3) for heating block 240 and
thereby maintaining the temperature of sample cell
assembly 66 at a selected temperature above instrument
temperature. For analysis of milk, a cell temperature
of ~0 ~ 0.2C is preferred. Temperature control circuit
278 may comprise a suitable bridge circuit or the like
responsive to a thermistor 280 (FIG. ~) mounted on the
port block assemhly 240. Similar temperature control
structure is preferred in connection with homogenizer
142 but is not illustrated in FIG. 7. Preferably,
homogenizer 142 is physically located closely adjacent
to cell 66 but external to the optics unit, and test
measurements are performed a short time after fluid
sample is placed in the cell so that the homogenized
fat particles in the milk do not have an opportunity
to form aggregates.
Instrument measuring and control circuits are
illustrated in functional bloek form in FIG. 3 and
include decoding cireuitry 282 responsive to coded
apertures 116 in program disc 112 through optieal
sensor 114 for inaicating whieh of the filter pair on
drum 72 is in the beam paths, and thereby controlling
the remainder of the circuits ~or measurement of fat,
protein, lactose and water/solids concentrations.
Deteetor 70 is connected through the normally closed
contacts of a run/calibrate switch 284 to the input of
amplifier 111, which is a.e. eoupled and tuned to 12.5
+ 3 Hz (for 50 hertz line freq~lency) or to 15 + 3 Hz
(for 60 hertz line frequency). Connection of detector
70 to amplifier 111 is through one of four variable
resistors 450-456 (selected through switches 460-466
by photoposition decoaing circuitry 282 for fat, protein,
lactose and water/solids respectively) which determines the
servo amplifier voltage gain and hence sensitivity to the
detector signal voltage for each component being measured.
The amplifier OUtpllt drives servomotor 48 which controls
the comb position.
- 17 -
A voltage derived from the potentiometer 468
coupled to the comb mechanism provides velocity feedback
to amplifier 111 insuring a controlled rate of co~ move-
mentO Also coupled to the comb mechanism is the precision
potentiometer 290~ Thus, a voltage directly proportional
to comb position is provided to an input of amplifier 470
Summed to this amplifier is a voltage derived from one
of four preset adjustable resistors 472-478 selected
through switches 480-486 by photoposition decoding
circuitry 282 for fat, protein, lactose and water/solids
respectively. This provides a bias to the co~b position
voltage prior to logging by log amplifier 292. Adjustment
of the bias allows the output of the log amplifier 292
to be linear for equal increments of %T of the component
being measured in the cell in accordance with Beer's law.
Beer's law is: D = ln 1 for V equals optical density,
T
T e~uals percent transmission and ln indicates the
taking of the natural logarithm (base e).
The sequential concentration signals from
log amplifier 292 are fed by slope control resistors
294-300 through switches 302-308 controlled by disc
decode circuitry 282 to a four-channel memory, correction
and scaling circuit 310 which will be described in
greater detail in connection with FIG. 14. Circuit 310
provides at its output a series of uncorrected signals
Fo~Po~Lo and WO for fat, protein, lactose and water
respectively, and a second series of signals F, P, L
and W/S which have been cross-corrected for effects
due to absorption of infrared energy at the particular
test wavelengths selected for the others. The outputs
of circuit 310 are connected through a four-pole double-
~!~8~9L
throw switch generally indicated at 312 for selectingeither corrected or uncorrected signals, and through a
four-channel a/d converter 314 to digital readouts
316,318,320 and 322 for indicating concentration in
percentage by weight of fat, protein, lactose and water
or solids respectively. Displays 316-322 preferably
comprise decimal displays.
The decoded outputs of circuit 282 are
additionally connected to an optical zero adjustment
circuit 324 which controls the position of vane 40
(FIG. 1) by means of motor 42. Zero adjust circuit 324
receives second control inputs from the manually adjustable
resistors 326,328,330 and 332 for placing vane 40 (FIG. 1)
in the desired zero adjust~ent position for fat, protei~,
lactose and water respectively. Calibration of zero
adjustmen~ circuit 324 and of memory, correction and
scaling circuit 310 will be discussed in greater detail
hereinafter. It will be appreciated, of course, that
the various resistors illustratea in FIG. 3 (and in
FIG. 14 yet to be described) are to be connected to
appropriate biasiny voltages such as ~12 volts, -12
volts and zero volts or ground.
Referring now to FIGS. 14a-14c, memory correction
and scaling circuitry 310 illustrated ~herein basically
comprises four circuit channels 340,346,348 and 350
~FIGS. 14a-14b) respectively labeled for providing
corrected and uncorrected indications of fat, protein,
lactose and water concentrations, and a fifth channel
432 (FIG. 14ci for deriving an indication of non-fat
solid concentration or total solid concentration from
- 19
signals available in the other four channels. Fat
channel 340 receives an input signal from adjustable
scaling resistor 294 (FIGS. 3 and 14a) through switch
302, which preferably comprises an FET switch controlled
by disc decode electronics 282 as previously described.
The switched input signal is fed and stored on a capacitor
342 across the input of a high impedance input current
amplifier 344 which provides at its output the uncalibrated
fat signal Fo~ Similarly, protein, lactose and water
channels 346,348 and 350 each include a corresponding
storage capacitor 352,354 and 356 connected across the
input of the high impedance input amplifiers 358,360
and 362 for providing uncorrected protein, lactose
and water signals Po,Lo and WO respectively.
- l9a -
8~
The output of fat input amplifier 344 is
connected in fat channel 340 through an adjustable
resistor 364 to a summing junction 366 at the input of
second stage amplifier 368. The output of amplifier 344
is also connected through the adjustable resistors 370
and 372 to the summing junctions 376 and 378 at the
inputs of second stage arnplifiers 382 and 384 in
protein and lactose channels 346 and 348, and through
the adjustable resistor 374 to one input of the second
stage amplifier 386 in water channel 350. The output
of protein input amplifier 358 is connected through an
adjustable resistor 388 to protein summing junction 376,
through a second adjustable resistor 390 to fat summing
junction 366, and through a third adjustable resistor
392 to lactose summing junction 378. The output of
lactose input amplifier 360 is connected through a first
adjustable resistor 394 to lactose summing junction 378,
through a second adjustable resistor 396 to protein
:: summing junction 376, and through a third adjustable
resistor 398 to fat summing junction 366. The output
of water input amplifier 350 is fed to a summing junction
380 at a second input of second stage amplifier 386,
the output o~ which is connected to fat summing junction
366 through the adjustable resistor 400, to protein
summing junction 376 through adjustable resistor 402
and to lactose summing junction 378 throuyh the adjustable
resistor 404. Summing junctions 366,376,378 and 380
are additionally connected to the adjustable resistors
406,408,410 and 41~ respectîvely.
- 20 -
Seccnd stage amplifier 368 in fat channel
340 is connected through an output amplifier 414 for
providing an analog signal (voltage) F as a linear
function of fat concentration and corrected for cross-
absorption effects as previously described. Similarly,protein an~ lactose second stage amplifiers 382 and
384 are connected through corresponding output amplifiers
416 and 418 for providing corrected analog protein and
lactose signal (voltages) P and L. The output of amplifier
386 in water channel 350 is connected through an output
amplifier 420 to one selectable contact of a switch 422
which selects either water concentration W or one of
the solid concentrations TS (total solids) or SNF
(solids non-fat) for display on digital readout 322
(FIG. 3). The output of second stage amplifier 368 in
fat channel 340 is additionally connected to solid
~6~869~
channel 432 through the adjustable resistors 426 and
428 to the two selectable contacts of a switch ~30
for choosing TS or S~F for display. The common contact
of switch 430 is connected to a summing junction 434
at the input of an amplifier 436. The output of second
stage amplifier 382 in protein channel 346 is.connected
through an adjustable resistor 438 to solid sum~ing
junction 434. The output of lactose second stage
amplifier 384 is connected through the adjustable
resistor 440 to junction 434, and the output of water
second stage amplifier 386 is connected through an
adjustable resistor 442 (FIG. 14b) to summing junction
434. An adjustable resistor 444 provides an offset
volta~e to compensate in the solids and solids non-fat
readout for the average value of mineral matter in milk.
The wipers of adjustable resistors 370,372 and 374 in
fat channel 340,390 and 392 in protein channel 346,396
and 398 in lactose channel 348, and 400,402,442 and 404
in water channel 350 have normally open switches connected
thereacross to ground for short circuiting the respective
adjustable resistors during the calibration operation to
be described.
Corrected signals for fat F, protein P,
lactose L, water W, total solias TS and solids non-fat
SNF are given by the following equations:
F = aF0 + bPo + cLo + dW + e
P fFo + gPO + hLo + iW -t j
L = kFo + mP0 + nL0 + oW ~ p
W = W0 ~ qF0 + r
TS = sF -~ tP + uL + xW -~ v
SNF = wF + tP + uL + xW + v
- 22 -
~1~6~8~
wherein the coefficients a-x are predetermined empirically
and are adjusted by the variable resistors in FIGS. 14a-14c.
coefficient calibrated by
variable resistor
a 364
b 390
c 398
d 400
e 406
f 370
g 3~8
h 396
i 402
i 408
k 372
m 392
n 394
o 404
p 410
q 37~
r 412
s 428
t 438
u 440
v 4~4
w 426
x 442
The values of coefficients a-x depend upon the characteristics
of the filters and vary a great deal fro~ one ~ilter batch
to anothex.
- 23 -
Before discussing overall operation of the
invenkion, the method of calibration will be briefly
described. First, referring to FIGS. 1-3, pump 144
is operated to draw water, preferably distilled water,
into homoyenizer 142 and pulse water through the fluid
system to purge the homogenizer, the various conduits
and sample cell 66. A "sample" of water is left in
the sample cell. Servomotor 48 is turned on and
switch 312 (FIG. 3) is in the uncorrected position.
Filter drum 72 (FIG. 1) is then operated sequentially
to place the fat, protein, lactose ana water filter
pairs in the respective optical beams. With the fat
filters in the beams, ~or example, and chopper 100
energized such that radiation is incident on detector
70 as an alternating function of the intensity of the
sample and reference beam passing through the sample
cell, resistor 326 (FIG. 3) is adjusted until the
arcuate comb 58 is in an arbitrary '`zero" position
which yields a "zero" reading at display 316~ AS
resistor 326 is adjusted, vane 40 (FIG. 1 ) is correspondingly
adjusted to selectively attenuate measurement beam 36
so that the measurement and reference beams at 3~418
and 3.47 micron wavelength respectively are equal in
intensity at'detector 70. l~is procedure is then repeated
for protein, lactose and water successively, such that
resistors 328,330 and 332 (FIG~ 3) are adjusted to
correspond to zero positions for each of these measurements
respectively. Thereafter during measurement operations,
optical zero adjust circuitry 324 ~FIG~ 3) will automatically
rotate vane 40 by rneans of ~notor 42 to the adjusted zero
- 24 -
36~
position depending upon the constituent to be measured.
With switches 430 and 422 (FIG. 14c~ in the
TS or total solids position, servomotor 48 (FIG. 3) is
disconnected (by switch means not shown) and resistor 444
(FIG. 14c) is adjusted until the reading on display
322 (FIG. 3) is equal to the sum of displays 316,318
and 320. With servo 48 off, filter drum 72 is then
rotated to the fat position and resistor 294 (FIGS. 3
and 14a) is adjusted while switch 312 is sequentially
switched back and forth between corrected and uncorrected
positions until the corrected and uncorrected fat signals
indicated at readout 316 are identical. The same
procedure is then repeated for protein, lactose and
water such that adjustable resistors 294-300 are in their
calibrated positions.
Dru~ 72 is then again returned to the fat
position and switch 284 (FIG. 3) is placed in the calibrate
position wherein servo amplifier 286 is connected to
adjustable resistor 28B. Servomotor 48 is re-energi2ed
-and resistor 288 is adjusted until digital display 316
reads "10.00" with switch 312 in the uncorrected position.
The switches across adjustable resistors 370,372 (FIG. 14a)
are open and the remaining switches across the various
adjustable resistors in FIG. 14 are closed~ Resistors
~5 364,370 and 372 are then adjusted while switch 312
(FIG. 3) is alternately switched between corrected and
uncorrected positions until the corrected fat siynal
equals lOa, i.e. aFO, the corrected pr~tein signal equals
the uncorrected P signal (Pv) plus lOf and the corrected
lactose signal equals the uncorrected signal Lo plus lOk.
- 25 -
~6~8~
Filter drum 72 ~FIG. 1) is then moved to the protein
position and resistor 288 is adjusted to yield an unc~rrected
signal PO on display 318 of "10.00". The switches across
adjustable resistors 390,392 (FIG. 14a) are c,pened and
the remaining resistor-bridying switches in FIG, 14
are closed. Resistors 388,390 and 392 are then adjusted
w~ile switch 312 (FIG. 3) is alternately switched between
corrected and uncorrected positions until the corrected
protein signal on display 318 is equal to lOg, i.e~
gPO, the corrected fat signal at display 316 is equal
to the display at the uncorrected position of switch
312 plus lOb and the corrected lactose signal at display
320 is equal to the signal in the uncorrected position
of switch 312 plus lOm. Drum 72 is then rotated to the
lS lartose position and resistor 288 is adjusted to yield
an uncorrected lactose signal at display 320 of "10.00".
The switches bridging resistors 396 and 398 tFIG~ 14b)
are opened and the remaining resistor-bridging switches
in FIG. 14 are closed. Resistors 394,396 and 398 are
then adjusted while switch 312 (FIG. 3) is alternately
switched between corrected and uncorrected positions
until the corrected lactose si~nal at display 320
is equal to lOn, the corrected fat signal at display
316 is equal to the signal when switch 312 is in the
! 25 uncorrected position plus lOc and the corrected protein
signal at display 318 is equal to the signal when switch
312 is in the uncorrected position plus lOh. Servomotor
48 is then turned off. All resistor-bridging switches
in FIG. 14 are closed and switch 312 is placed in the
uncorrected position. Resistor 444 (FIG. 14c) is then
re-adjusted until the display at 322 is equal -to the sum
- 26 -
o~ the displays at 316-320 plus the required correction
constant v.
For normal application to the analysis of whole
milk ~or fat, protein, lactose and solids or solids non-fat,
circuits 340,346,348 and 432 will normally be used. Up
to now it has not been found necessary to apply water
corrections to the fat, protein, or lactose channels.
At the time of determining the design features of the
invention described herein, it was visualized that the
water channel could be employed in the following ways.
(1) As an extra means of applyiny cross
corrections to fat, protein, lactose channels an~ thus
indirectly to solid channel for variation in mineral
matter. This has not proven to be worthwhile, presumably
lS because the mineral matter being of high specific gravity,
or small bulk, displaces little water and therefore
shows little sensitivity to change in content of
mineral matter. The means for applying these corrections
are still available and the coefficients are adjusted
in the same way as described for fat, protein and
lactose but using resistors 400,402,404,442.
(2) As a direct means of determining total
solids or solids non-fat. This is effected by measuring
at the water wa~elengths the ~isplacement of water by
other components and relating this directly to results
obtained from standard methods (e.g. gravimetric and
hydrometer). Results compared by these two methods
~instrument v. either standard) have given standard
deviations of 0.1%. However, standard deviations as low
as 0.07 - 0~08% are easily achieved using the summation
method and, to date, this latter method has been
preferred. Note: when this direct method is used for
solids non-fat, the effect of fat is offset by switching
into use resistors 374 in the fat channel 340~
(3) As a means of applying total corrections
to individual components. Each component can be corrected
for effects of all other components by using water-only
corrections, e.g. equally accura~e results have been
achieved for fat using water correction as with the
protein and lactose corrections applied separately.
An instrument user requiring fat-only readout
could therefore obtain a faster rate of sampling using
the fat/water correction combination. Also, in cases
where fat and solids non-fat or fat and total solids
results are required by the user who is able to tolerate
slightly less accurate solids measurements, this method
would be preferred. It should be explained that in order
to obtain corrections for displacement rather than
absorption effects, the infrared filters are reversed
in the optical system, i.e. the water absorption filter
is placed in the reference beam and the reference filter
is placed in the measuring beam~ There is no doubt that
for some milk product analysis applications the water
channel will be used to good effect.
Constants e, j, p and r are not required
when t~e instrument is set up for analysis of whole milk.
It is~ however, visualized that for certain applications
to milk product analysis, it may be necessary to include
an intercept adjustment. In such cases this can be
eEEected in fat, protein, lactose and water channels ~y
- 28 -
adjustments to resistors 406,40~,410 and 412. The
value of these constants or intercepts will be indicated
by the calibration data for the appropriate component.
With all adjustments made, the embodiment of
the invention hereinabove described is now ready for
operation. Referring to FIGS. 1-4, a specimen of milk
to be sampled as in cup 149 in FIG. 2 is located beneath
homogenizer inlet tube 146. Pump 144 is then activated
to provide eleven pulses of milk from specimen 500
through homogenizer 142 to purge the sample cell 66
and the lines connecting the homogenizer to the sample
cell, After the twelfth pulse from homogenizer 142,
which places a specimen to be tested wit-hin the sample
cell, pump operation is automatically terminated.
Filter drum 72 is then activated sequentially to stop
at the fat, protein, lactose and water positions. In
the fat position, reference and measurement beams are
alternately directed throu~h the sample cell 66 onto
the detector 70 which, in turn, operates servomot~r
48 to position co~b 60 within re~erence beam 30 (FIG.-l)
until the reference and measurement ~eams seen by the
photocell are equal in intensity. The signal on
resistor 290 (FIG. 3) indicative of fat concentration
is then stored on capacitor 342 (FIG~ 14a)~ This process
is repeated in the protein, lactose and water positions
of filter dru~ 72. Corrected fat, protein and lactose
concentrations in percent are t~en displayed at 316-320.
If water display is desired, switch 422 ~FIG. 14c) is
placed in the position indicated and percent water
concentration is displayed at 322~ If total solids or
- 29 -
solids non-fat are desired, switch 422 is placed in
the desired position such that percentage of total
solids or solids non-fat is automatically provided
at display ~22. The specimen at 149 may then be changed
and the cycle repeated as desired.
The invention claimed is:
- 30 -
