PHOTOELECTRIC DROP SORTING

A

ster

I.. F •

1968

M.G.

& ;

Oi. z.) I

J.

• a

a 1e

•

1 would so , B ..

and W .. B .. Earl~ I

SUMMI\RY

work of Abrahamson (1) has been continued in an

effort to develop an instrument to classify the

and solute of individual drops in a

two ... phase

a 1

(

)

)

method used (modulation

more

in use.

1

2

INTRODUCTION

The behaviour of the swarms of drops found in liquid•

liquid extraction processes is not at this

understood process. A large body of data is available on

the behaviour of single drops in well-defined fl9w situations

and some success has been achieved in understanding and

predicting the hydrodynamic and mass transfer behaviour of such

Very little progress has been made, however, in

using this knowledge to predict behaviour in complex systems

such as are in widespread industrial use. This is because of

unce:r:·tainty as to the basic mechanism of such

turbulence fields drop coalescence,

of s as re

phases~ and to which are

mod if by mass conditions

of .. To the single d:top to multidrop

it is nece to evaluate some o.r all of factors

which differentiate the complex situation from the simple ones

which are at present at least partially understood.

Abrahamson (1) points out that if simultaneous information

on drop diameters and mass transfer s in various places in

a available then some progress would be possible

towards applying single drop data to stirred tank systems.

Information on residence times and breakup a1'ld coalescence

could also be obtained if an experimental technique were

available for measuring simultaneously the size and solute

3

in all members of a dr'op population .. Tracer

techniques used in conjunction with this could yield much

useful data.,

This study a continuation of Abrahamson's work in an

effort to develop an instrument package that would give

simultaneous information on drop a.nd solute crn1centration ..

The method consists of withdrawing a stream of drops from a

stirred tank and diluting the stream sufficiently to ensure

that the drops will ss singl.)r through a narrow beam of light ..

drop causes a modulation of the beam» which

ss

by pulse width

a pulse width would sort

s; similarly, the solute is a function

of the pulse and a pulse amplitude discriminator

could sort the drops within each into concentration

.. For initial trials the liquids were kerosene

and water~ which are more suitable than and

system. used by Glen (2) because of their fairly high

index difference.

The initial aim of the work was to confirm the findings ,,

of Glen thai?, a turbulent breakup mechanism controlled the drop ..

distribution in the impeller of the mixer used.

4

(i)

The apparatus was basically the mixer used by Glen (2)

with a facility for the withdrawal of a small flow from the

impeller stream into a vertical viewing duct. The thdrawal

rate controlled by using a pump driven by a

controlled motor; in addition. a dilution flow tapwater

was added to increase the dispersion of ther swarm of drops

and lessen the probability drop coalescence withdrawal~

The dilution flow also that the ss

one

the

the light $ which by a 2mw

laser. A behind

a pulse

a pulse only drop fell within

limits. These pulses were then total

s. • 1 shows a photo of the

a layout • A led

follows.

(ii)

Abrahamson propo to sample a LL.IieU"i.UI of drops by

a sampling probe into the impel stream and

,..,

Q_

~ ~

w

CD

_J

<( ~

z w ~

-cr: w

0... X

w

.a

lL

0 0 0

TO SPEED CONTROLLED WITJ-DRAWAL PUMP

PHOTO I SENSoR I 0 I l1= I HE-NE LASER 0

PULSE- WIDTH

DISCRIMINATOR

000000 WINDOW COUNT

000000 TOTAL COUNT

ELECTRONIC SCALERS

. 0

0

0 I VIEWING DUCT 0

0

DILUTION FLOW

FROM MIXER

Fig. 2 SCHEMATIC OF APPARATUS

. - -

Fig. 3 SAMPLING S VIEWING ARRANGEMENT

5

matching the withdrawal velocity to the approach velocity of

the drops in the tank which could be estimated from the data

of Cutter (3) and other~. Such tests as he carried out

indicated that this method was not satisfactory • difficulties

caused by drop breakup on sampling were encountered and two

different-sized probes were required to cover the range of

drop sizes expected. The present writer of the opinion

that there would be some difficulty in determining the overall

distribution from these two fragmentary and to some extent

overlapping distributions.. A further disadvantage of

Abrahamson's system was that drops tended to coalesce on

upper

di

al (4)

the viewing

With this the

which would seriously

on was that of

s out a stream to

is

unconstrained as is no possibility that an excessively

bulky probe within the mixer will seriously distort the flow

• A vertical chute has the advantage that

drops do not coalesce on the walls, although the necessity to

put the drops through a af ling is a

drawback as this could cause breakup and/or coalescence.

alternative layouts were considered for the

viewing duct and since some first sight seem attractive

the reasons for their rejection are given in some detail.

A horizontal duct similar to that used by Abrahamson has the

6

advantage that the stream of drops need 110t turned through

a right-angle; however. it'was rejected on consideration of

vertical terminal velocities. For drops in the range

expected (up to 5 xnm) the data of Klee and Treybal (5)

indicate a spread of terminal velocities up to about 1 em/sec.

Using a sampling velocity of about 20 em/sec (l) and allowing

a maximum vertical deflection of about 1 or 2 mm (constraints

imposed by the necessity to avoid breakup and prevent drops

from coalescing on the upper surface of the duct respectively)

the drops would have to be to the light beam within

1/5 second sampling which would limit

chute to about 5 em, including

of dilution flow. With so

seems unl s~ II

will time s

the velocity drops

light beam would no longer a function of

length of th1!9

for

short a path~

dilution flow

through

only

because of random velocity fluctuations that would occur.

The use of a horizontal viewing chute on was also

considered; since such a chute could be made long enough to

eliminate the difficulties de above. However 11 the

wide spread of terminal velocities previously mentioned would

give to a differential migration effect, viz. the

distribution seen by the light pencil any particular place

in the duct would differ from the actual distribution because

of the varying rates of rise of drops in the duct. The top

1

of the duct would show too many drops and the bottom

too many small drops. This feet would accentuated as

the duct was longer ensure a smooth flow pattern in

the duct. (Because of the large number of drops withdrawn

it only possible to scan a small cross .... section of the duct

with the light beam if the drops are to give separate pul s.)

With these points in mind it was decided to withdraw a

stream from the mixer, take it through a gentle right .. angle

bend and dilute it at the entrance to the vertical viewing

the dilution flow to be just ficient to

that a of s was withdrawn from the tank.. This

(Glen

is in

an

swarms

in

lately work

unsuitable for technique with holdups as low as 5'%, .. )

The of the withdrawal tube was by two

constraints:

(a) it should be enough to sample .

... about 5 mm;

{b) it should not be so large that the withdrawal flow

appreciably distorts

the tank ..

circular symmetry of the flow in

From consideration of flows used by Glen. the impeller

to

pumping capacity as found by Holmes, Vonck.en and Dekker (6)

8

and the arbitrary restriction that the maximum

withdra:wal flow should not exceed S''h of the total impeller

flow. a withdrawal tube of 3/8 inch diameter was chosen.

Under most conditions the flow in the viewing tube would be

mainly dilution flow$ so the 5% represented a "worst

possible•• figure ..

The dilution flow wae introduced straight into the

viewing chute from two jets parallel to the actual withdrawal

tube ~ the use of grids to flatten the velocity profile across

the chute was tried» but these to cause breakup by

small .. turbulence .. section

of about 10 em the drops

s are fully 1 to ensure

swirls by dilution flow

the

of this

will through the beam 1 s

of the previously mentioned di in terminal velocities.

which will tend to narrow the distribution of pulse widths

obtained and lower the overall resolution of device;

~ if the withdrawal velocity is compared with

the natural

• 3

of rise, this problem will be minimised.

a photo of the sampling 11 viewing and

withdrawal arrangements.

(iii)

This is a driven by a DC with a

controller which will maintain the constant tp

within 1~ over a number of days.

scription of the circuitry •.

Abrahamson gives a full

( i v) L;Lght Sgurge

9

The requirement here was for a light source that would

1 of light about 1 em across and about 200

microns thick collimated over of

(about 8 rnm). to

30

or sensor,

are on the

of Glen and

lif

s were made to use a 12 volt

iodine with slits and col as described

by

count .. The smallest beam that could obtained had a

thickness of about 1 mm (or more) and attempts to diminish

this led to troubtes with, diffraction ; also the

intensity was too low • the beat photocurrent attainable ..

about 10 microampa. tests were out with

10

helium-neon laser, indicated

that a more powerful with an output of about 1 mw or

would probably meet all requirements. Further tests

with .a 1 mw "Laser:tronu ser borrowed from the Physics·

laser used had

university confirmed this, although the

too noisy an output to meet requirements

as.a suitable light source. This would be a problem with

any DC

a of 1\'11hite11 noise on the output

Further~ a·DC la is to an known as

(

, which causes random fluctu ...

2 "' 100

on (7 ). One other

it

a reasonably

i work.,

Accordingly, an AC multimode was acquired

1, TEMqmn).

ile

Multimode s have a flatter

mode ones, with a

high excitation frequency of

tube noise inte:rmodUlation are obviated.

A multimode tube also gives higher output (generally

about that a.n equivalent tube) • but has

disadvantage of beam divergence (5 milliradia:ns

as .4 ~illiradians). Unfortunately$ the exciter

11

at about 30 with the

which photodiode was capable of following, it was

nece build a high frequency oscil to

(this point is further discussed in

light sensor)"

description of the

A circuit diagram of the oscillator given in .. 4;

it is a Colpitts oscillator with voltage stabilization

running at a frequency of 500 an EL504

line output pentode a "Q ... lnductancen 234 coil

as a .. vo is

. about 5 kv on the to

ser was p so

at 1 em; was

a 1

l .. narrow

were blanked off with ma to light

the following au

horizontal 1 1/100 "'

vertical 1 1/40 ...

minL-num thickness ... ..2 mm

width 8mm

The of divergence was sfactory this

work .. (8) recommends the use of a converging light

field to avoid diffraction ts when backlit

drops; presumably the same ef could troub with

200- 6001/ IOOmA

\ I . Ol,uF 750V

6.3V X

~~ .oi~F 750V

earth

OA2

IOk lOw

.OIJ.IF T 60-60 750V Df

,,

_L .I }J F

680 5w

330pf

·a· 234

100

C>\ o<

I q eX,

I

'

~ ~ ~ c:>L,_.

H~---------.001 )JF

100 k

Fig 4 500 kHz oscillator

wall

one would •

500 oscil

could induced

this work.

(v)

~ so the ser wa<J

duct ra

2 mw

ll a

in the photodiode, which

l:ls his sensor a

sensor Y.Jhich, was an OAP12

..

12

on

as

the

100 s

was adequate for

of slow DC

was

use with

An

3v ampl

Its

A

by

ity

f

fo:t'

is

run at a much lower photocurrent ..

sensor \~as con which overcame the

s a

which

by

..

or by slow DC dr

This

slow

(see

output pulse of

the beam.,

ts in

ld provided

the photodiode.

prevent

circuitry and the level

lOOk

photo­diode

-6V

.22).JF

IOOpf

filtef .I ,.uF .047 }JF

OAPI2

+12V -r threshold

220

-t-12 v

.OI.AJ F

~ +II-= IOO)JF

8

.7

compardtor output 4

l lOOk

.OIJJF

~ -it:!: IOOJ.l F

.22}J

Fig 5 LIGHT SENSOR

VOLT AGE ACROSS LOAD RESISTOR

..........-PULSES CAUSED BY---

DROPS \

---J _________________________ ... _____________ _, __________ ..,_TH.FiE9blnL1~L(W_

OUTPUT WITH THRESHOLD (a)

_r 1 nL_____ OUTPUT WITH THRESHOLD (b)

____..JI I I I n.___

Fig. 6 EFFECT OF THRESHOLD

CONTROL ON LIGHT . SENSOR

has a small amount of hystere s built in so that slow•

or pulses from the diode will still give a

clean output .. The immunity to drift

AC coupling the diode to the level

achieved by

section .. this

not only eliminates DC drift problems but also means the

sensor will continue to function even if a sticks to

the walls of the chute' and obscures some of the light beam

13

(as was sometimes observed). To test the stability of the

unit the heatsink around the photodiode was until the

diode

about 100

current (normally less than 1 microamp) was

s ... 1 output was letely

..

e is an 2

• , of s, which across

100 kilohm " se

light incident on the diode ( as by a

pas through beam) will cause a in the diode

current a11.d hence a positive vo pulse will

across Rl~ which is coupled to the of transistor Tl ..

The coupling is via a two-section high pass filter with a

cutoff frequency of about 1 and a rolloff of 12 db/octave;

thus slow drifts in the diode current are f out,

while pulse amplitude information, if required, relatively

undistorted (the coupling is such that a 100 millisecond

square pulse at the diode would by about 10% .. the longest

.14

pulses are about 10 mseo and in shape).

Tl an fol the

output impedance of diode to the low., input

of comparator which follows.

The main active element in the circuit is a Fairchild

pA710C comparator; this is· a device whose output state

( .... Sv or +3.1v on pin 7) depends whether the input voltage

on pin 2 or less than a reference voltage applied

to pin 3, i.e. it

vo is lied

slightly by the

over

se

ld

to

two

llable by R4.

mentioned·,

inputs,.

12v

the

F

sensor

the 30 modulation initially

111 which was not

to remove the 30

, but would

about 5

information ..

rolloff was also

The reference

ly, and may

some

which

I>

"' 6. By

R4

capable of

on

a filter is likely to ring badly with single pulses

However~ since the diode response is 3 dB down at 50

with a fairly steep rolloff, the solution adopted was to

drive the laser at 500 kHzp a frequency well outside the

diode 0s sensitivity.

(vi) Pulst W~dtb D~sQ,~minato,

This device takes rectangular pulses of constant

litude and varying widths and gives a standard output

pulse when the incoming pulse falls within preset width

limits. From a terminal a pulse provided for

input pulse» thus is po both

number of

fraction

pulses from

amplitude of

width; this

• total

1

then

a

sensor are

1 to

s to two level

outputs will change state if their

a

input pulse

thresholds are

exceeded. These form a voltage window their outputs

are gated so that an output pulse produced only when

lls within the window. A complete description

gi·ven below• circuit diagrams of the various sections are

given in Figs 7, 8 and 9.

(a) Pulse

15

input pulse (po

10 10 Lisee wide)

from

lCl :. a J1L900

buf which inverts it and provides sufficient

drive for the following sections. The output of IC1 is a

negative going pulse +3.6v and zero (the normal

logic levels for this type of circuitry) which s to a

resistor string composed of a 1 ,kilohm and a 2.2 kilohm

resistor connected to the ... 6v· supply. This· shifts the

·voltage level so that the voltage at point A would if

unrestrained swing between +.Sv and -2v. The swing is,

however, limited to 1v (between zero and -1v) by the

clamping diodes Dl D2. The purpose of this is to

pulse for the integrator which follows.

this pulse are set by the

se the

16

up as

the te

lows:

ground Rl is adjusted to zero •

Then, using the one millisecond ~ a standard 1 milli-

second pulse is fed into the input from a pulse generator

and an oscilloscope connected place of the voltmeter;

R2 is then adju so that the maximum amplitude of the

is 4v.

The integrator (Al) is a pA702C operational amplif

with itive Three different feedback

capacitors (selected by a rotary switch) are provided:

.002 mfd& .02 mfd and .2 mfd corresponding to maximum"input

17

pulse widths 100 s,, 1 mil 10

milliseconds The output of

integrator is limited by the zener diode Z1 to about 5

volts, ... this to protect the following s. When the

trailing edge of the pulse is sensed the integrating

capacitor is discharged by transistors Tl and T2 (this is

described in more d,etail later) and the integrator is then

ready for another pulse. Diode D4 prevents latchup of the

the reference terminal on A2 from too high

a voltage applied (this could happen if the top of the

windo\4 were above top of the then in use).

A small (10 ohm) stor was placed in s with R3

(window bottom control) so that the window bottom cannot be

any lower than about 3'r.. of the ... this was found

nece to avoid spurious counts which were being caused

by drifts in the integrator output voltage in the

quie Since the still have ple:nty.of

overlap• this no drawback,.

(c)

are

is

s combinations

ld or both thresholds.

18

outputs from

one threshold~

from the

only in the first case, since this denotes

a pulse within the voltage window. It th$refore necessary

in the third situation the pulse from A2 should inhibit

or that from A3. However, the pulse from A2

is not po

pulse \~idth

pulse

(A

.. in

a pulse is

to other

pul

the pulse from A3» direct

has been where

in a buf memory which is

pulse a output

l

A

..

14 as

f s one e,s a

flip-flop is a inputs and two

this case the outputs are zero +3 .. 6v.

to one of input )

s reverse s until a pulse

only one

lied

("resetn) is

It the

f !' A NOR a with two output

are 1 low

no

and

output

output

a of ... if the

will high, but if one or xnore s high:.

19

In setup~ are the set•

flip ... flops making up the memory, 1C7 a three-

input NOR

IOS isconnected to A2 and hence "remembers" whether or

not the threshold on A2 has been exceeded .. Similarly 11 IC6

stores the history of A3. The outputs of ICS and IC6 are

connected to two of the inputs of IC7 .. In the "reset"

state, i.,e. with no pulses present, the output of ICS is at

zero and that of 106 is at +3.6v,. lf an input pulse

ld on A3, but not on A2 (i.e. it lls

within the vo window), the output of IC6 will fall

zero; will. also at zero

IC7 l

... a

same ..

se

normally

to this input

a po

Ic7. It fol

have

IC7 will

Af

pulse

(d)

IC1

the

Total pulse

To provide

diff

1

of this

pulse will

also from this

II

only IC6

to IC7 will be at zero

pulse (about 2 micro

be at the output

that or both

one input to

s

)

of

be no output pulse will produced,.

pulse memory, another

to memory ..

count~ re pulses

pUlses the initial input pulse from

by R8 and Cl to two

20

to and trailing s of the

input pulse ... diode D3 clips the from the leading

so that point E only a positive going spike

corresponding to the trailing of the pulse is present.

E is an input to IC2, a pL914 gate connected as two separate

D (the output corresponding to E) is

normally at +3.6v:~ but the positive go'ing at E drops D

to zero for about 2 microseconds. D is connected to the

third input of IC7 (the three input NOR

and

pulse

2

by IC3, a

pulse

buf

in the memory)

pulse is also

total pulse

so uses the

to

pulse

of

the

are

, then once

Tl across

on

comp

produced.

The output of 1C3 is also to IC4 11

11 however~ 6v than the

Thus the output of IC4 (at G) normally at

JlL900 buffer

usual 3.6v.

+6v. element is af1A710C comparator (A4) which

s one input lead connected to the output

other to the output of the integrator.

IC4 and the

the output

voltage of Al is limited to 5v by the zener diode Zl, the

voltage on pin 2 of A4 will normally be less than the 6v

21

on pin 3 the output of A4 will be at • liow when

the·2 micro pulse from 103 is applied to the input of

lCI+~ output of 104 (G) will fall to zero"' as will the

voltage on pin 3 (the reference input) of A4. Pin 2 on A4

to the integrator output, which at this stage '

will be between .Sv and .5v (i~e. at the top of the

ramp) ; since the vo on pin 3 of A4 is now less than

that on pin 2, the output of A4 will switch rapidly to +6v

and as a result two 2N3643 transistors Tl and T2 will be

The output of A4 also to the

which ho G at zero, i.e. the latches

on until the

reached

(the voltage on

pulse

, Tl ·and

SI!!IC:!OrllQ ~ Which

all cases ..

holds

completely

lied lC4. lf

would be turned on for

to

When this

voltage on pin 2 of A4 falls to zero

actually slightly above zero) and

the comparator output switches back to zero, turning off Tl

allowing the output of 1C4 to to 6v.. This

switching transient differentiated and applied to H (the

input to the second half of the buffer 1C2) and the resultant

output pulse is used to re the memory.

INPUT

+3.6V ----.----

uL900 <rc t>

PULSE SHAPER

A

2.2k

TO Cl

Rl - INTEGRATOR ZERO

R2- • SLEW RATE

R5- • RESET OVERSWOOT

COMPENSATION

Rg. 7 DISCRIMINATOR -

-sv

lk (R5)

+6V -.--

56k

PULSE SHAPER & INTEGRATOR

INTEGRATOR

AN lOll

(04)

-t-12V

OAZ202

270k

--sv

.oo2 uFwroo usl /'

22k

lk

TEST SOCKET

TO A3 S. A:2

220 ~ Ill 2N3643

TO f A4 PIN 2

(T2)

IOOpf

TO A4 PIN.7

OA91 (03)

(CI)

FROM ICI PIN 5

lk (R8)

+3.6V

1500pf (C3)

RESET

PULSE

+3.6V

READOUT

PULSE

+sy -----.--

iOOpf

lk5

TOTAL PULSE COUNT

FIG 8 DISCRIMINATOR- TIMING & CONTROL

FROM INTEGRATOR

OUTPUT

220

+12V

2

3

)JA710C

(A4)

-6V _

TOTI aT2

FROM INT!;:GRATOR I

OUTPUT (AIl •

220

220

I

ft, 1000 J.JF

100

100

I

220 (R4)

Fig 9

-+12V ---r-

7

~

60-1

250AJF

DLSCRIMINATOR-

1.5k

LSI< (IC6J

RESET

~ PULSE

12V AC

THRESHOLD

+3.6V --.-

+3.6V ----r-

READOUT

PULSE

DETECTION &

+3.6V

..ul914

GATING

I COUNT WITHIN

WIDTH WINDOW

10

7

Fig 10 --DISCRIMINATOR

CALIBRATION

WINDOW WIDTH

THRESHOLD

2 a 4 s e 1 a 9 10 11 12 13 MILLISEOS

thla calibrcation ia tor range 3 divide X-axis by 10 for range 2 & 100 for range 1

(e)

di

and linearity ..

model 114 pulse

device built and

22

reproducibility

A calibration chart obtained using a Tektronix

given in Fig. 10. The similar

scribed by Abrahamson had several defects,

window and threshold controls, slow recovery,

which system behaviour to be dependent on the frequency,

aa well as the width of incoming pulses and slow

which :restricted resolution available in the

These

)

both

window directly, which an

method of a constant

s were

one

to 10~000 or 100,000

the

for

within

alternative

window

23

Initially, the mixer was

at the top (similar to Glen's

up with the withdrawal tube

), no provision for

the introduction of a dilution flow; and the light source a

12~ quartz-iodine lamp (driven by a 12v lead accumulator to

eliminate 50 Hz modulation on the light). The. light sensor

was apparently satisfactory as it would give an output when a

wire was moved through the beam and problems of DC stability

had been overcome by AC coupling th• ph.otodiode, .Considerable

difficulties were with the light source. howe~er;

of dif s the was not sharply

and was not intensity

with no an

output even 1 it

to put down, which

sensor liable to spurious

pickup. Even if the de·vice were so well shielded this

could all eliminated, would be no of obtaining

an output with the modulation caused by the lest drops

(about 3%) .. Amplification the was also

considered, but this would amplify also, no

improvement,

difficulty was encountered with the sampling and

viewing setup where the

through a short tube then

was withdrawn from the mixer -.

into a flat viewing duct.

24

thought to conducive to obtaining a flat

velocity profi

conf that

velocity. Al

of

power inputs).

duct , studies

were large variations drop

• with no dilution flow. only a very re

conditions could (very low holdups and

The viewing duct was

in two small

light pancil;

to Abrahamson's

limits of

of the

succes

was

sum of all

the

fluctua

to

as

by

duct.

ser.

were in a one ...

was deduced

with

that if the

over full , the

was not equal to tal eount

of within a window

amounts.

of up f

s within

Also the

hundred -

di

to be

s was attributed

causing the

s to oscillate; to rectify this, suitable s of

were

a

output ... it was

output

~Jith no

shield the

500

its

osc

sensor

were connec

output

was

but this

sought..,

was

f

ItO

, but no was

VO across the

modulation on its

concluded was

photoelectric .. bypa to high

Unfortu11ately ~ it was

0 1 completely

as

~,;~a. s

was

to

was s was

s s .. s

about 1 O'Yo no:t"!nal

with s

s of a f

a difficult approach

by the

this the

II

not to

all

laser tuba

ss mo

~ -vJhich cau

1;

on

ser

is to

"

calibration­

method was

drops in was to

an o llo across of

26

sensor; as

would

pulse which it ..

both

While this \vas

one

drop and the

in principle~

reason

1 for two reasons: to drop it was

to use a f of light

for a short it was difficult to

drops, e ly in a flowing •

difficulties are probably not in but

it: was 11ot

an

some

ssible

to measure width or to

mo

sensor

f sen, which

success~' was

measure the pulse

sensor.

the drops also the distribution of

obtained matched with the distribution

program to

s is

s to

by photo ..

could

pulse widths.

distribution

27

CONOLU§IONS AND RECQMMENDAIIONS

With some modifications. this apparatus could be

satisfactory for measuring drop-size distributions. It is

felt~ however, that the original aim of producing a device

that would measure simultaneously the drop (from pulse

width) and tracer concentration (from pulse height) is not a

practical proposition. In the device developed. the light

sensor placed sufficiently far back for all forward

light to lost ~ this means that the drops

opaque to the light sensor. sensor was further

a function

po

a

A

re

s

1

so at the

as well as

as some was

This

• Thus

; however, it could u

pulse was produced by one

pulse would

smal s would

use a pulse

would not be

1 ones (though would

over•

problems) ..

with for a height discriminator

di is in 4.

Another problem

duct ... although

that of velocity variations in

is not too difficult to obtain a

velocity profile across

necessitY for a thin viewing section

of the duct

it hard to

a f

answer to

that all

by

the duct. Possibly the

in

s will entrained

they reach the light beam.

duct in

·the

avoid the troubles caused by 500

28

container should be built for the laser tube and oscillator.

lt should not be difficult enclose the whole assembly

11.0

which can

oscillator output.

could

cone

not

..

without

If neces

to about 200

should

is

se

too much

lat:or

without

this

or

29

a mono.stable multivibrator compo of

pt.914 ~ with a p.L900 driving an

• When the first flash f (by the camera) the

bur of light sensed by a photodiode, and

a variable delay time has elap is f

flash (connected across also

A in • 1 1

• 12 .. By in an

it is

100

Fig 12 --90 DELAY

80

70

60

50

40

30

20

10

DIAL SETTING

CALIBRATION '

2 4 s e 1 a a DELAY (Milli8EC)

.30

A circuit ol this is given in • 13.

Regulated supplies at +12v 11 +36.v, +6v, ... 6v, ... 12v- are

<il'Vailable 11 with 12v floating AC for the threshold

window settings on discriminator.

~ 230 v Oi c: ex, .. :J

12 ...

SO-l

SO-l

I 2500 pf

40V

s 220 H •oo,:,r ~I ~...,

OAZ 202

-l .. 25lpF 40V

1.51<

"'l" OJpF

1.811

ACI26

1.51<

Fig. 13 DISCRIMJNA TOR POWER

OC75

5 uF .211

OC74

SUPPLY

+12 v

L +.~6\fo

~O.AIF .J:,. 12V

+6V

~ -• IOO,AJF

12V

-6V

-12V

This

photograph•

output the l

resolution.

31

as input observed drop sizes from a

with the • as

distribution determined with

A listing given in Fig. 14 and le output in

Fig. 15.

FORTr<.A'\1 IV MDOEL 44 PS VERSION 2v LEVEl l

OIMENSIO~ DOROP(5000J,ODIA(8) ~EADl,SC~LE 9 DElT4

l FORHAT(2Fl0.51 2 FORMAl( 8F 10.41

I=O 63 ~EADLtDDIA

IF!DDIA(lll62,61,62 62 00 60 J=l 8 60 CDROP(J+Ii=DDIAlJI/SCALE

1=1+8 GO TO 63

61 '\IDRDP=I DMAX=DDR"":P ( U DO 36 I=l,ND~OP IF(OHAX-QDROP(lll34,36,36

34 GMAX=DDR~P(Il

DATE 68218

00.01 UC .. C•.2 0003 0004 JOCJ':> COOb 0007 :)003 0009 001v 0011 0012. 0013 0014 0015 OOlo 0017 0012 0019 C020

36 CONTir.UE L=lDMAX/DElTAI+l. 80UN2=0.J

6 FORMAT(/" LOWER LIMIT,MM',6X, 1 UPPER liHIT,MM 8 ,6X, 8 NO OF OROPS•,zx,

0021 002i on3 C024 002.S 0026 0027 ooze 0029 J03C• 0031 0032 0033 0034 0035 0036 0037 003~ 0039 (1040

FGRB.ll:-. II/

!'WINDOW PERCENT 1 ,2Xa 1 CUMULATIVE PERCENTS•) PRINT 6 r(BR=G DO 50 K=l,L NMBR=O i>.OUNl=BOuN2

BOUN2=B8UNl+DELTA CO 30 I=l,NOROP IF(BOUN2-UOROP(lll30,40,35

35 IF(00ROP!Il-BOUNll30,30,40 40 •;MBR=NMBR+l

KBR=KBR+l 30 CONTINUE

nPERC=IfLUAT!NMBRl/FLOATINDROPll*lOO.O CPERC=IFLOATIKBRl/FlOAT(NOROP))*100.0 eLT=BOUNl+.Ol*DELTA

50 PRINT5,BLT,BOUN2,NMBR,WPtRC,CPERt 5 FORM~T(/4X,f6.2 7 14X,F6.2,12X,I5,lOX,F6.2 7 lOX,F6.2)

r>~INll5 ,~DROP 15 FOKMATI/' TOTAL NO Of DROPS WAS',l5)

E:ND

MOuEL 44 PS VERSION 2, LEVEl 1 DATE 68218

TOTAL ~EMJ~Y REQUl~EMENTS ~053EO BYTES

CGMPILE~ HIGHEST SEI/E~ITY too= ~AS 0 II EXEC L~KEDTINOMAPI

Fig. 14 COMPUTER PROGRAM TO SORT

PAGE 0001

PAGE 0002

DROPS

ltH/ / )1•

~}N~~:•t 11'1111< llliilll ~I ~I VIlli IV W~';

Ill Will I I M II diM

o.on l\,(.)1)

u.lo ().,., DolO

(l, !U

U.l~

0,40

0,45

t). 1>0

OohO

0.&5

Uo70

0.75

o.no u.es Oo90

Oo95

loOO

lo05

1.10

lol5

lo 20

lo25

lo30

lo35

lo40

lo 45

lo50

1.55

lobO

lo65

lo70

lo75

loBO

lo85

lo90

lo9S

2o00

2o05

2ol0

2.15

2.20

2o 25

2.30

2. 35

2o40

2.45

2o50

2o55

Ill' I' I II I I Mil ,MM

\i, 10

,), 20

v.;~

\)I 3(J

u.,.o l)·'•5 II. 'jO

1),55

n.6o l)•biJ

o. 70 llo 75

(lo uo o.a5 0 o'/0

Oo95

looo 1.05

lolO

1.1~

lo20

1.25

1.30

lo35

1.40

1.45

1.50

1.55

1.&0

1.&5

lo 70

1.75

loOO

lo85

1.90

lo95

2.00

2o05

2.10

2.15

2.20

2.25

2.30

2o35 2o,,o 2o45

2o 50

2.55

lobO

2.60 2.65

2o65 2.70

2o70 2o75

}2TAL NO 8f DROPS WAS 27&0

II

Fig 15 SPECIMEN

IIIIII'I'V I.INKA .I I ill I

1~11 Ill 1111111'~ WINIJIJW l'tiH.Pll CUMIJI AI lVI I'IIICI 'II',

llr,

14•·

Hh

Zll

2'11

lh,

25;

111

201

81

15 7

IJ(>

4'.l

3'• 81

21

4r>

21

27.

l.J

IK

12

12

13

I (,

()

0

0

0

0

0

()

,)

[)

•)

')

n

o.o lt.'.JI

lj ,(J 1

I lo'll

HoOt 10.~11

'loll

, .. o~ 7,50

loOI

5.6'1

4o9J

lob)

4o4'1

lo27

2.91

Oo76

1.4'J

o.11>

o.ao o. 3b

o.&o; Oo43

Oo43

0.47

0.04

u.22

o.O'• 0.10

o,o7 o.o 0.07

o.o o.o4 o.o4 o.o 0.07

o.o4 o.o o,o7 o.o o.o o.o o.o o.o o.o o,o o.o o.o o.o o.o o.o 0,04

o.o1

PROGRAM

OoO

1 J.5~

il.'>h

'•2· 11•

/tf), l'J 1J1. 3fJ

61.311 6H .·an 'II. 811

77.51

112 .so ~4.ll

H6,b7.

U9,89

'12.86

93.62

95.07

95.81

'lbob"l

96.99

'17 ,64

98.08

98,51

'18.99

99.02

'19.24

99,28

99.46

99.53

Y9o53

99.60

99.60

99.64

99.67

99,67

99,7~

99o7ll

99.78

99.86

'19.86

99.86

99.86

99.8&

99.86

'19,86

99,81>

?9,86

?9.86

9'l,8n

99,86

99,86

99,89

qq,qt,

OUTPUT

32

A circuit is in • 16 for a pulse height

discriminator cornpatible with the preser&t width discriminator.

The ld detection section of the circuit is identical

with that in the width discriminator. but a logarithmic

lifier at the input avoids the need for several levels

of sensitivity. This is described in the Fairchild

Applications Handbook.

If litude discrimination were , a

lif would also

LOGARITHMIC

220

lOOk

'I

+12V

220

lOOk

220

<.:~

+12V

56 60-1

220~~--,-------------;

q·~~·

12V AC

Fig_ PULSE HEIGHT

RESET PULSE

+3.6V ----.--

II<

COUNT IN WlllTH WINDOW

+12V

470

DISCRIMINATOR

+3.6V

READOUT PULSE

pL914

COUNT IN HEIGHT

r·~·

COUNT IN BOTH

f"-

1,. J.. 11 "Development of a Photoelectric Method for

2.

4.

5.

7 ..

8 ..

Mea Drop... Distributions:.'' M.E. Thesis 11 University

of Canterbury (1967)

J .. B. Glen, ":Mass Di Systems", Ph.D ..

Univ. of Canterbury (1965)

L.A., Cutter~ Uflow and Turbulence in a

D.. .. The s, Columbia University ( 1960)

(u .. c. ilm 61, 246)

w ..

c ..

P .. E ..

J .. w ..

1,

41' 444 (1

J .. A ..

65/9 ..

, July 1 11 p ..

)

Tank" ,

the

1519 (1

130C

by

1

Liquid

1 ( 1

)