LA-UR- 99-2191

Approved forpublic release;distribution is unlimited.

Title: L’I’SGRAIXOMETERSBASED-ON SUPERCONDUCTINGIMAGING SURFACE DESIGN

Author(s):A. N. MATLACHOVR. H. KFWUSM. A. ESPY

Submittedto: ISEC ’99 COW.BERKELEY, CA06/21-25/99

RECEIVI?%DSWfl71999

LN!3TI

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ABSTRACT

The electromagnetic flowmeter is obstructionless and insensitive to the metered stuff’s

constitutive properties. For low zero-point drift, EM flowmeters employ a low frequency

alternating induction, usually with square waveshape. With conventional signal conditioning,

high frequency induction leads to excessive zero-point drift for the instrument. The conventional

instrument is useable with electrically conductive fluids, where there is no triboelectric noise.

Nonconductive fluids have substantial triboelectric noise, with spectral density experimentally

measured to be f ‘2-6. Here we use an electromagnet and signal conditioner that allows high

frequency induction, where the noise is low, but eliminates the heretofore excessive drift — such

that the EM flowmeter can be used to meter any stuff, whether conductive or insulating, that can

be pumped, blown or extruded through a pipe.

Designs and test hardware are shown. An injury occurred, with slow recovery: the principal

investigator could not do all the flow test stand work desired. As an option, the flow testing has

been simulated on a computer. Using characteristics of transformer oil as the metered fluid, the

new signal conditioner has produced*: (1) signal/noise/drift behavior experienced in prior

published work, and (2) signal – without noise and drift – with performance of today’s

commercial EM flowmeters.

1. FUNDAMENTALS

The EM flowmeter is the fundamental flowmeter. Its basis is a Lorentz transformation: a

magnetic induction B in a stationary frame of reference is observed in the moving frame to have

the same value of B — but one also observes an electric field E equal to u x B, where u is the

velocity. The electric field E, which is the basis of the EM flowmeter, exists solely because of

motion. It involves no constitutive parameters: no material properties, such as sound speed,

electrical conductivity or perrnittivity, viscosity, or other.

Since the EM flowmeter does not depend on any constitutive property of the metered

material (meterand)**, in principle it can meter any stuff that can be blown, pumped or

extruded through a pipe.

The instrument has no moving parts. It is obstructionless, nonintrusive. It is linear — thus

* by varying operating parameters

*~rovided the meterand’s properties do not distort the flowmeter’s magnetic field.

CUSHING ASSOCIATES 1

it correctly meters the average of pulsating flow. It

meters flow in either direction. Present state of the art

limits the instrument to conductive liquids; it has found

wide application in the process industries, sewage treat- ELECTRODES

ment plants and aqueducts.

For conducting fluids, a technical discussion of the 1

EM flowmeter can be found in Shercliff’s monograph. \ AV = uBd

Spurious signals — to be rejected by a signal conditioner ~wre 10 Volhge AV, fluid moving

— are discussed in Section 3. with velocity u through induction B.The EM flowmeter was first operated with insulating

liquids in the 1960s (ref 1). Signal voltage is the same as that produced in standard EM

flowmeters (typically 1 millivolt per meter/see).

Because of electrode-chemistry voltage drifts (Section 3.1), the EM flowmeter must use an

alternating magnetic induction in order to have a stable zero-point. For conductive meterands,

where there is no triboelectric noise, the induction frequency is low and the zero-point drift

(Section 3.4) is low. Further, use of a square wave alternating induction, and signal sampling

techniques, eliminates zero-point drift.

Application of the instrument to insulating liquids has not

heretofore been commercially usefhl, because the required high

1/

F

frequency magnetic induction gives fise to excessive zero-point Bdrift. q

The EM flowmeter performs fundamentally as a volumetric\

u

flowmeter. However, by making use of the Clausius-Mossotti F =qux Brelationship (for nonpolar fluids) or the Debye relationship (for E = F\ q = u x B

polar fluids), it optionally operates as a mass flowmeter. Figure 2. Magnetic force on

a moving charge q.2. THE FLOW SIGNAL

The simple configuration of the electromagnetic flowmeter is shown in figure 1. It shows

the directions of induction B, velocity u and induced electric field E. Figure 2 is more

rudimentary: it shows the force F on a charge q that is moving with velocity u through an

induction B. The induced electric field E is defined as F/q.

Figures 3a and 3b show that ions, which exist in a conducting medium, have forces as

indicated. Conductive EM flowmeters have an insulating pipe wall, the ions pile up and

CUSHING ASSOCIATES 2

generate a counter electric field, as shown figure 3c. A pair of electrodes, which penetrate the

insulating boundary, sense a potential difference owing to the flow.

There are no ions if the meterand is an insulator. Rather, the charges are confined to their

respective molecule. Each molecule polarizes, as shown in figure 3d. Again we need an

alternating induction B: the alternating polarization is sensed as a polarization current —

capacitively, by electrodes on the exterior of the insulating boundary.

E =u)(BMAGNETIC$ B

INDUCTION

m\ u

4i’uk&&ELomFLOWCONDUIT INTO PLANE

()OF FIGURE

a

P‘Ii!if!!e~pgg+-++: * gic ---+(y:+

: comR+ EIECTRIC~

: CiiARGE

+, FIELD-_ ACCUMULATION

- AT BOUNDARY+ +- - -~

()c

-—,.-T?T=7. ., .-.. , . ....< ,. .,.,,’.?,.. . ., .. ,,.<,. ..-..-, ... ... ,5T-I- .. ,$. -,,. L,:. .,....>..%,.----,.:.’ .,..-,2..-<,$’k’s.b,.wT.z?77m---+:~:~. :-. . .~-: ;?-, ,.;- ,:. -; L ,

PosmIONS NEGATIVE

)%

IONS

w

H

L BOUNDARY

(b)

(d)

Figure 3. (a) Electric field fiduced by motion through a magnetic field. (b) Ion motion in

conducting liquid. (c) Counter-field produced by boundary constraint. (d) Molecule

polarization in insulating liquid.

CUSHING ASSOCIATES 3

The flow signal in commercial EM flowmeters is about 1 mV per m/see. The selected

magnet induction level is a compromise among S/N ratio, response time (instrument bandwidth)

and power operating costs. It follows that — for a given flowmeter shape or configuration —

the magnitude of magnetic induction B scales inversely with the pipe diameter; and the magnetic

stored (reactive) energy each cycle scales as the square of pipe diameter.

A steady magnetic induction cannot be used since electrochemical voltages (and their history

dependent variation) at the two detection electrodes overwhelm the DC flow-generated voltage.

Also, to eliminate spurious power-mains voltages, modem EM flowmeters operate at a

submultiple of 60/50 Hz. Magnet frequency of 7.5 or 3.75 Hz is typical in the US. Since we

use a conservative (low loss) system with electromagnet and storing capacitors, the stored energy

alternates between %L12 and %CV2.

3. SPURIOUS SIGNALS

3.1 Electrode Electrochemical Effects

In conventional flowmeters the electrodes are in direct contact with the metered liquid. If

the two electrodes are of different material, then we have the basis of an electrochemical cell— which produces an EMF large enough to swamp the flow-generated voltage. Identical

electrode materials should solve the problem; but they don’t, because no two electrodes can be

made with aady the same electrochemical properties, such that the cell EMFs are negligible

compared with flowmeter EMFs. Further, electrochemical properties of an electrode drift —

with temperature, pressure, ageing, . . . — and so variable EMFs swamp the flowmeter voltages.

Since the middle 1930s alternating induction has been used.

3.2 Preamplifier Input-equivalent Noise

The EM flowmeter produces an analog voltage, which is sensed by an analog amplifier. The

noise level (whether noise voltage or noise current) of the first stage determines the noise level.

Whether OP-amps or FETS are used for the first stage, noise spectral density is about f‘1 for

frequencies above 100 Hz.

3.3 Power Mains Interference

Many instruments are vulnerable to 60/50 Hz power mains voltages that somehow leak into

the system. Their elimination is handled by a signal conditioner that is synchronous with the

power mains. Basically, the signal conditioner must average the flow signal over a period that

CUSHING ASSOCIATES 4

is exactly one period of the power cycle — such that the time integral is exactly zero.

3.4 B-dot Pulse; B-dot Aftereffect: Zero-Point Drift

The EM flowmeter is a circuit. loop —

partly hardwire, partly diffuse through the

metered fluid, as shown in figure 4. The

transformer effect* is -d#/dt, where ~ is

the flux threading the loop — or A“dB/dt

(A”B-dot), where B is the flux density and

A is the area of the threaded loop, as

shown in figure 4. It is theoretically pos-

sible to set up the circuit such that the net

flux threading the loop is zero — shown in

figure 4(b), simply eliminating the hum.

Or if imperfectly done, one neutralizes the

hum by superposing the negative of the

hum. The problem is that neutralization

consists of the difference of two fairly

sizeable quantities.

Figure 4(al) shows a positive loop area

and the B-dot pulse has the same sign as

the flow signal, shown in figure 4(a2).

The large B-dot pulse at the start of each

half cycle is owing to the changing large

current in the magnet coil. The small

(exponentially decaying) B-dot aftereffect

DIFFUSE CIRCUIT CURRENTS

/f

CENTROIDOF DIFFUSECIRCUIT CURRENTS

RETURN CIRCUIT WIRE(OVER TOP OF PIPE)

FLOW SIGNAL

w

TIME*(a2)

PULSE

FFECT

& TIME*

(C2)

Figure 4. Magnitude and sign of B-dot aftereffect

is proportional to circuit loop’s area: (a) positive,

(b) zero, (c) negative.

for the remainder of each half cycle is owing to the decaying eddy currents in the magnet

core**.

Figure 4(c1) shows a negative loop area and the B-dot pulse’s sign is opposite to that of the

*labelled hum by Warshawskyg since it is the same frequency as the flow signal.

**and somewhat owing to: (1) loss factors in the flowpipe’s dielectric materials;and, (2) eddy currents in the flowmeter’s conductive housing.

CUSHING ASSOCIATES 5

-—.— .-— --- -. . m.

flow signal, as shown in figure 4(c2).

Figures show thezero chcuitloop a=, mdno B-dot pulse ortiereffut.

Cementing the return circuit wire such that the loop area is zero is difficult. More seriously,

the loop’s geometry changes with temperature, pressure, ageing, . . . , the loop area cannot be

maintained at zero, and antihum neutralization is not viable.

Figure 5 shows an electrical method to effect a zero loop area. But non-RETURN

stability of loop area requires that the B-dot aftereffect be sensed con-

tinuously and discriminated against.

Hum or B-dot aftereffect is the most serious problem when operating at

high frequency. If a sinusoidal magnetic induction were used, the flow

signal is in phase with the induction B. The hum is in quadrature.

However, loss factors in the magnet and in the flowpipe cause a phase shift

in the dB/dt voltage such that a bit of it gets in-phase with the flow signal.

Variation of loss factors gives a variable amount of phase-shifted hum – ie, Fi@re 5SEl~tri-

variable amount of spurious flow signal. cal scheme to

With a square wave magnetic induction, dB/dt is (ideally) a pulse*, and minimize B-dot

one need sample the flow voltage after the pulse has finished. However, the looP area.

above-described loss factors produce an aflereflect of the dB/dt pulse: the dB/dt aftereffect is an

exponential (or higher order) voltage decay after the pulse. In conventional low frequency

flowmeters the dB/dt aftereffect has fully decayed before the flow signal is sampled.

With a high frequency square wave of induction, the decay is only partially completed before

onset of the next dB/dt pulse and its consequent decay. One can’t wait for full decay. Rather,

one must sample the signal plus decaying hum with enough sample points to calculate both (1)

the constant flow signal voltage, and (2) the decaying spurious hum voltage.

3.5 Triboelectric Noise

Triboelectric noise occurs in turbulently flowing dielectric fluids. Practical fluids contain

particles or inhomogeneities: dirt particle, air bubble, . . . — which have a specific gravity

different from the fluid. Hence the particle does not follow the fluid’s turbulently accelerating

streamlines; rather the particle “rubs” its way through the fluid. It is analogous to the classic

rubbing of “cat’s fur on amber”, producing static electricity.

with time integral AB.

CUSHING ASSOCIATES 6

The rubbing friction produces charge sepa-

ration or ions (perhaps mislabeled: ions in a

dielectric fluid don’t migrate through the jluid

much); the equilibrium population of ions depends

on: (1) rate of ion production, (2) mobility of the

ion, and (3) the force of attraction between op-

positely charged ions. The first depends on the

flow Reynolds number. The third is perhaps most

important: the recombination force of attraction is

proportional to the fluid’s specific permittivity

(dielectric constant K), and the equilibrium con-

centration of ions is proportional to #. For water

(K= 81) ions sustain in large concentrations

while in hydrocarbons (K = 2) the concentration

is very low and electrical conductivity is very low.

Early effort to “salt” a hydrocarbon — to make it

conductive enough for the EM flowmeter —

failed.

uC/l

Ez

\! nlr I I I II. i

FREQUENCY, HzThe spectral density of triboelectric noise

Figure 6. Spectral distribution of noisevoltage is shown in figure 65. Experimental

2“6fall-off. Atvoltage with transformer oil in a 32 mm

evidence indicates it follows an fdiameter flowmeter. Parameter is mean

high frequency the measured spectral density fallsflow velocity Tin m/s (after ref 5).

to an asymptote appropriate to the input-equivalent

noise of the measuring instrument — an f-l fall-off.

Figure 6 shows the spectral density, in the frequency domain, of triboelectric noise voltage.

Figure 7 shows a typical trace of tribolelectric noise voltage in the time domain.

The noise is autocorrelated (a

time series): it is continuous in

time. When voltage samples are

taken At apart, the dz~erenceAV in

noise voltage is small if At is

small; and AV approaches zero as

At approaches zero.

CUSHING ASSOCIATES

ROW WIOCZIK 1.13 mh2“

e 1“~ 0’‘1*W”nV “’ “i~~)j- udm~-’”i Y A>.1. r v ‘d

%=AV”’W’’’”W*W*b

-2-0 s 10 15 20

llM& SECONDS

Figure 7. Triboelectric noise voltage in 35 mm flowmeter.

7

However, at any time t the noise voltage maybe quite large. During work described in ref-

erence 1, the voltages were (autocorrelated) random with mean value zero — and over a long

time appeared on the oscilloscope to be about a volt peak-to-peak — as shown in figure 7.

Figure 8 shows EM flow

zero-point drift was about

4. EXPERIMENTAL DATA

signal data using transformer oil as the measurand (Ref 1). The

&5

percent of full scale. The instru-

ment used a square wave magnetic

induction. On each half cycle, one

voltage sample was made — as late

as possible before the next dB/dt

pulse, to give maximum time for ~’

the aftereffect spurious VO@e to F@re 8. F1OW signal for 1971 experimental deCtrOma&

decay. netic flowmetering of transformer oil in 3.5 mm pipe.

Then state-of-the-art OP amps

amplified noise pulses. The OP amps output voltage slewing rate was unsymmetric: rising slew

rate was much greater than falling rate, as shown in

figure 9. Hence, a noise pulse was followed faithfully

during its rise; but the rapid fall of the noise pulse was

not accommodated. Consequently, the integrated volt-

seconds under the noise pulse was greatly amplified by

the OP amp, as shown. During such noise overload, the

amplifier could not pass the (coherent) signal voltage, and

the instrument’s phase sensitive detector produced a

dropout in detected voltage.

5. TRANSDUCER

5.1 Configuration

Figure 1 showed the scheme of the EM flowmeter.

wog

~e2

E20 v TIME +

Figure 9. Asymmetric slew rate of

1970’s Op-amps.

Figure 10 shows this effort’s actual

design; it is similar to that used in reference 1. The metered fluid passes on the interior of the

dielectric liner, as shown in figure 10a.

Two electrodes (electrode manifolds) are emplaced on the outside surface of the liner.

CUSHING ASSOCIATES 8

MAGWTIC

FLUV C@DUITlWnJcTIm

jWJw~ DIELECTRIC LIkJER

i

0-

(b) (c)

Figure 10. (a) Cross section of electromagnetic flowmeter for conductive as well as insulating

liquids. Flow is into plane of figure. (b,c) Electrode manifold unrolled, showing electrode,

guard and common manifolds.

Figures 10b and 10c show that each electrode is curvilinear — matching the liner’s contour —

and of length L. They are “wide area” electrodes — to provide an adequate value of capcitive

coupling through the liner to the flow generated voltage. Electrode manifold is guarded on all

sides — except through the liner to the metered fluid.

5.2 Eddy Currents

The wide area electrode plates shown in figure 10 must have good conductivity. If made of

a continuous sheet or foil, the eddy current losses are prohibitive with the high frequency

alternating induction. Reference 1 used conductive carbon paint to cover the entire surface of

CUSHING ASSOCIATES 9

-— —----

the electrode; then superposed stripes of highly conducting silver paint in order to have good

comection.

The present design uses printed circuit photo-etching technique to make the entirety of highly

conductive fdm – but in a gridwork, as shown in figure 11.

Conductive carbon paint is superposed — especially on the guard

— to make sure direct capacitance between electrode and

common is negligible.

6. THEORY

Reference 1 discussed the EM flowmeter with and without theFigure 11. Photo-etched

dielectric liner shown in figure 12. The theory used the pa-mylar sheet used for wide

rameter rarea electrodes shown in

figure 10.r = a/b, (1)

equal to one

1, the flow-

p&matca‘w<,CONDUIT

KIK

where a and b — as shown in figure 12 — are respectively the interior and exterior radii of the

liner.

The fimdamental analysis is done with the parameter r

— ie, when there is no liner. As described in reference

meter’s equivalent circuit is then as shown in figure 13a*

The writer has derivedl the analytical expressions for:

(1) CO, the direct empty-pipe capacitance between flowmeter electrodes;

(2) Vg, the flow-induced voltage; and,

(3) RO, the flowmeter’s internal resistance.

In today’s commercial EM flowmeters RO, which is inversely

proportional to fluid conductivity, is small; and the two capacitances,

(K-l)CO and CO, have negligible effect. However, as the fluid conduc-

tivity is lowered, the two capacitances come into play. In an insulating fluid, such as petroleum,

ROis effectively infinite. Then the two capacitances forma voltage divider; the terminal voltage

V depends on the fluid’s specific permittivity (dielectric constant) K.

Figure 12. a and b:

interior and exterior

radii of flowmeter’s

liner.

● For simplicity we show a single-sided equivalent circuit. In practice a balanced arrangement isused.

CUSHING ASSOCIATES 10

COshunts the flowmeter voltage Vg. Figure 13b shows the trouble: i. is a current loss from

the flowmeter’s terminal node. Figure 13c shows the needed correction: injection of current i.

into the input of the preamplifier via neutralizing capacitor CO.

The preamplifier with a gain of 1 is essentially an impedance changer. The amplifier with

a gain of 2 produces at its output a voltage of 2V; exactly twice the fiowmeter’s terminal

voltage. With this done, the flowmeter’s terminal voltage no longer depends on the fluid’s

specific permittivity; the terminal voltage V is the same as the flowmeter generator voltage Vg.

With this artifice the EM flowmeter is insensitive to any constitutive characteristic of the

measurand. The only requirement is that the measurand consist of some substantive stuff (but,

as the stuff’s density approaches that of vacuum, we might expect trouble, described below.)

Figure 13c shows another cap-

acitance Cg, the guard capacitance.

With insulating fluids the flow-

meter generator’s internal im-

pedance is very high. Any spur-

ious capacitance to ground would

be just as injurious, in practice

more injurious, as the shunt capaci-

tance CO. Figure 10 showed the

sensing electrodes to be capacitor

plates on the exterior of a dielectric

liner. State of the art technique

calls for fill guarding of these

capacitor plates so that there can be

no signal current loss by way of

spurious capacitance to ground.

Cg is the direct capacitance

(b)

!●

(c)

A (d)

Figure 13. (a) Equivalent circuit for EM flowmeter. (b)

Signal current loss io. (c) Neutralizing capacitor Co. (e)

Volumetric/ Massmetric mode toggle switch.

between the sensing electrode and its guard. The unity gain amplifier in figure 13c assures that

there is no voltage difference across Cg and hence no loss of signal current.

Figure 13d shows a toggle switch that enables the EM flowmeter to be a volumetric flow-

meter; or, optionally, a mass flowmeter for many fluids as discussed in reference 1.

CUSHING ASSOCIATES 11

6.1 Management of Triboelectric Noise

The foregoing art is well proven. The remaining step is the management of triboelectric

noise — the object of this effort.

Figure 10 displayed the electrode design for the laboratory EM flowmeter which worked with

insulating fluids. Se&on 6 describes the details of figure 13c’s unity-gain preamplifier. CO,

mentioned earlier, is the dir,ect capacitance, through the empty pipe, between the two wide area

electrodes.

The preamplifier is essentially an impedance changer, whose low-impedance analog output

voltage can be accessed with today’s state-of-the-art voltage samplers and thereafter processed

with microprocessor-controlled digital technique.

6.2 Input-Equivalent Noise Regeneration

Analysis — for r = 1 — shows that in the volumetric mode, our impedance changer’s

regeneration scheme effectively multiplies the flowmeter’s terminal voltage by K/(K- 1), and so

neutralizes the transducer’s inherent (K-1)/K voltage divider. In the massmetric mode the

changer effectively multiplies by (K+2)/(K-1).

The impedance changer’s active input element (usually a low noise FET) has an in-

put-equivalent noise en. The changer’s regeneration scheme inherently multiples en by K/(K-l)

when in the volumetric mode, and by (K+2)/(K- 1) in the massmetric mode. As measurand

density approaches zero, so also does (K-l). We may say, if we like, that our impedance

changing artifice sustains the correct flow signal even as a measurand approaches vacuum

density; but if we insist on that viewpoint, we must observe that concomitantly our input-

-equivalent noise increases without bound as we approach vacuum.

7. EXPERIMENTAL SETUT

7.1 Timing Strobes

Figure 14 shows the timing strobes for the instrument. The key strobe is C60, Which is

locked to the power mains (50/60 Hz) so that we may have synchronous rejection of any

spurious power mains interference.

The magnet frequency is in the neighborhood of 1 Khz – we choose the 16th harmonic of

60 Hz: Cl @ 960 Hz*

●For magnet frequency of 1920 or 3940 Hz we replace figure 14’s C60 by C60a or C60b.

CUSHING ASSOCIATES 12

In each magnet half cycle there

are 32 strobes available. As a

detailed example, figure 14 shows

the strobes that are the last eight in

each half cycle. We label these

sampling strobes S00, S1O, S20 . . .

for the first half magnet cycl~ and

S01, S11, S21 . . . for the second

half cycle.

The last strobes – S70 and S71— we use to reset the preamplifier,

as discussed below. In reference 1

only one sample was used each half

cycle; the last possible sampling

moment was used, strobes S70 and

S71. No reset was done then.

The strobe CS’S duration is

regulated such that the Magnet high

voltagepower supply is switched to

sustaining voltage power supply

when magnet current has achieved

its set value. The circuitry for

doing this is shown in figure 15.

7.2 Magnet Drive

Figure 15 is a schematic of the

magnet drive. QD 1 . . . QD4 form

a bridge. When figure 14’s Cl is

RESET ~

960 Hz cl~120 Hz C2~60 Hz C60~

C60a~C60b~

60 tiz C60~

Figure 14. Timing strobes.

CL+8

C0+8

COO*C13COOKC17C01*C13col~c17C02*C13C02XC17C03*C13C03*C17C04*C13C04*C17C05*C13cos~c17C06XC 13C06XC17co7~c13C07*C17S70 OR S71

C1+8C1+16C1+32C 1+64

C60+8C60+64

true, current flows one way through the magnet coils; when Cl is false, current flows the

opposite direction. QD1 through QD5 are IGBTs (insulated-gate-bipolar-transistor). Logic

strobe power cannot directly provide adequate gate-to-source voltage: their source voltages vary

widely. Floating (at source voltage) gate drivers, with floating DC/DC converters drive the

gates directly — as shown in figure 15.

CUSHING ASSOCIATES 13

. . ------ --..-,. -.

PSI is the magnet drive’s steady current sustainer power supply. Its steady magnitude is

adjusted such that the Current Control Voltage VCCis held to a preset constant v~et.

A)

()aTO

~615 %lNSULATXDGATE

\~ > < -

+~ =C2 g

3

SXS850

TO lGST SOURCS‘ 1+~ =C4

‘5414

cl

rl+12V Ov -12V

DC/DC (b)CONVSRT2R

CM 212D6NFR

& +5

Figure 15. Brief schematic of magnet drive: (a) Basic; (b) Gate driver.

PS2 is the magnet drive’s switching power supply. It is gated by QD5; it is ON when strobe

CS is true. A comparator with Schmidt trigger keeps CS true as long as VCCis less than the

v set”

7.3 Square Wave

Figures 16c and d show practical square waves for the magnetic induction. To achieve this

a large switching voltage is applied for the duration of the strobe CS (see figure 14); thereafter

a small sustaining voltage satisfies the magnet coil’s IR drop during the steady current remainder

of the square wave.

CUSHING ASSOCIATES 14

8 PREAMPLIFIER

8.1 B1ock Diagram

Figure 17 is a block diagram of thepre-

amplifier. It isessentially aunitygainim-

pedance changer – plus regeneration to neu-

tralize the flowmeter’s inherent internal

capacitance CO (refer figure 13).

The regeneration gain is shown as 1.5,

coupled with a regeneration capacitor 4Co —

as a compromise to lower the peak-to-peak

noise voltage excursions at the output of the

regeneration amplifier*.

Even the differentially sensed noise vol-

tages are sizeable (see figure 7), and show up

at the output of the diffamp. However, The

diffamp’s output voltage differences – meas-

B

dB/dtI4 ), I

INTEGRALOF EACH/dB/dt PULSE Eii AB

SAMPLINGTIKESY 1

B \ \ r

/ / /

dB/dt

INTEGRALOF EACHL -dB/dt PUISE IS AS

L

(a)

(b)

(c)

(d)

= - (&uonCJ1m dI’oti

Figure 16. (a) Ideal square wave. (b) (Impra-

ctical) Dirac pulse for dB/dt. (c) Practical

“square” wave. (d) Practical dB/dt pulse.

ured a small time At apart — are small (see figures 6 and 7). These small excursions are all that

show up after the temporal dz~erentialstage shown in figure 17. The RESET strobe zeroes the

signal voltage just before the magnet reverses phase. Hence, the voltage showing a~er the

magnet completes phase reversal is thefillpeak-to-peak signal voltage. And the signal sampling

system and conditioner need accommodate only the dynamic range of the flow signal — plus the

random small tribolelectric noise voltage dzfierences appropriate to sampling % millisecond

apart.

The common mode amplifier senses the full tribolelectric noise voltage. Normally it is small

enough to be accommodated by the signal conditioner. However, should there occur a rogue

voltage spike — owing to a dirt particle or other foreign material — which exceeds a preset

tolerance, a flag tells the signal processor to ignore that datum and continue using the prior,

valid datum.

For experimental work the sampling modules and data processing are handled by National

Instruments DAQ (data acquisition) board installed in PC. The temporal differential unit

presents a small dynamic range to be accommodated by the samplers; the absolute value of the

●Tolerance-wise, optimal is gain of 2.0, with regeneration capacitor of 2C0.

CUSHING ASSOCIATES 15

KARL%’ —B-en (.W

So4slhifLECISilE Rcm?qCIRCUIT Vr.ts

IUCKTICDlwcrllm

;“@______,F~re 17. Block Diagram of preamplifier and signal processor.

:$11 {urnlml/wl_llZ8V:n1/8vm,,ou

VRI 20NC)TRINPOTw 20NnTR1WOT‘f% l~TR114POT

C,1OOOPF,SOVp;y;:fi

4pF air capacitor

QJQI 2N6907 (DUM *ET)

DI 1N4615u 1N4003h IN4615Ib 1N4003Ul, U2, U3, wOP-27

● WIITi T?A GROIJND~

Figure 18. Schematic of% of differential preamplifier.

triboelectric noise voltage has been removed by the temporal differential unit.

8.2 Schematic

Figure 18 show the schematic of the preamplifier. ~ and Rll maintain the QI gate at

ground (common) potential. C4 and Rll assure that ~ is fully guarded at the flowmeter’s 960

Hz repetition rate.

Let G4 be the gain of the regeneration amplifier U4. Let CObe the flowmeter’s empty pipe

capacitance (see figure 13), then potentiometer VR3 is adjusted such that

CUSHING ASSOCIATES 16

(G4 - l)CR = 4C0 (2)

When this is done for both halves of the differential preamplifier, it neutralizes theintemal

capacitance Co. The sensed flow generated voltage is then independent of the metered fluid’s

constitutive properties.

9 DATA PROCESSING

Data processing is discussed in comection with figures 14 and 19. For simplicity in this

example, we take data flowmeter voltage samples during the last quarter of each half cycle of

the magnet. Referring to

figure 14, during the fist

half cycle of the magnet

we have available sampling

strobes S00, S1O, . . .

S70*; second half cycle,

Sol,sll, . . . S71*. S70

and S71 are used for

RESET (see figures 14 and

19) – so that would leave

up to seven +/- sampling

pairs during the last quar-

ters of the magnet half

cycles**.

9.1 Power Mains Noise

Rejection

As indicated in

figures 14 and 19, sixteen

magnet cycles cover one

980 Hz cl ~

‘34&’’og=upg ~

LAST 8 STROBES IN d,,, L,,JSACHMAGNSTHAWCVCLE ~~1 $4 01 11S31 1 41$S16 71

N I 14V56 01 II 1 1V41 V6WI

TEMPORALDIFFEREIWIALFOR Z8ROTH MAGNETCTCLE

U06 = V60 - V61

*,1TBMPORALDIFFSREtWIALFOR nTH NAGNETCTCLE

Un6 = V60 - V61 n =Oto F

U-NEW TRANSFBRRSDTO REGISTER O OHOLDUNLESS EXCESS NOISE FLAG 1S TRUE @

+

8SANPIZSPSR1ST HALF 0 1 2 3 567POWER NAR4S CTCLS IU061U161U261U361 U:61U561U661U761

+U-HOLD TRANSFERREDTO REGISTBR 8 814flD

UNLESS EXCESS NOISB FLAG 1S TRUE

~m

8SAMPLESPER2ND HALF 8 9 A B c D E FPOWSR NAINS CYCLB tU86 [U96 [UA6iUB6 IUC6! UD6iUE6 IUF6 i

W$ : :60 + U61

W& s U60 + U61 n= Oto7

& = (1/E)&

complete cycle of the 60 Fi~re 19. Data reduction scheme.

* and similar strobes within C1O through C17.

** Or more if we use all the strobes available.

CUSHING ASSOCIATES 17

-.. ——-— n——-- ---

Hertz power mains.

Hence for each temporal difference pair (eg, difference of voltage samples taken at

strobes S50 and S51) we must average the pairs over sixteen sample pairs — such that the 60-Hz

noise component averages to zero, exactly.

The sample pairs are held in registers, as shown in figure 19. At each magnet cycle,

after the sample pair has been formed, registers F through O are right-shifted.

The data in register 7 is not immediately shifted into register 8; rather it is held

provisionally in the 8HOLD register. Similarly, the newest data has been held provisionally in

the OHOLD register. If the excess noise J?ag (see figure 17) remains FALSE, the data in

register OHOLD is shifted into register O; and data in register 8HOLD is shifted into register 8.

The sixteen registers are then averaged and data reduction proceeds, as described below.

Optionally, the 60-hertz average may be low-pass filtered (to, say, a 1-, 3- or 10-second

response time) before data reduction proceeds.

9.2 Data Reduction

We describe here the data reduction for a flowmeter having a f~st-order (exponential)

decay in its spurious dB/dt aftereffect. It involves three parameters and in principle requires

three data points each half cycIe to ascertain the flow steady voltage and the decaying zero-offset

aftereffect (hum) voltage.

Figure 19 shows the expression for VPm (voltage averaged over a power mains cycle)

(3)

when strobes S60 and S61 are used. Note that for each n, W6n is the sum of two samples which

were taken 180° apart with respect to the 60-hertz power mains cycle. Hence, the power mains

spurious signal cancels out for each W6n.

The data reduction system can, in the present design, handle up to 31“ data points and

in the extreme one would use numerical methods to solve for a 3l-parameter empirical best

* As shown in figure 14,

CUSHING ASSOCIATES

strobe 32 is used for RESET.

18

fit* for the spurious aftereffect offset voltage.

For the first order system the sensed voltage is of the form

V = Vf + V~e-d? (4)

where V is the sensed voltage; Vf is the steady signal of the flow voltage and V~ and ~ are

parameters describing the spurious exponential decay.

Reduction is eased if the samples are taken at equal intervals ~. For the simplest method,

we take three samples (there is no loss in generality by Setting$ = 0):

The solution for the steady flow parameter Vf is:

Vf = (v; - v~v3)/(2v~ - VI - V$

(5a)

(5b)

(5C)

(6)

Warshawskyg solves the system of equation 5 by using 4 or more samples. The Basic program

shown in the Appendix follows Warshawsky’s approach.

Table I shows the data obtained with the EM Flowmeter simulation, using the Basic code

shown in the Appendix. The Basic code uses dimensionless variables for ordinate and abscissa

(amplitude and time).

Following are the parameters used:

Flow signal 1000 amplitude units ,

Unit of Time 1 strobe duration

Magnet alternation period 64 strobes

Power Mains period (for 60 Hz) 1024 strobes --16 magnet alternations

If applied to the (approx) 1 Khz square wave flowmeter used in reference one, 1 strobe

duration equals about 16 psec. As noted earlier, the magnet frequency selected was the 16th

harmonic of the power mains 60 Hz frequency; ie, the Power Mains period is 1024 strobes.

* Or fit a 31 degree power series best approximation.

CUSHING ASSOCIATES 19

Table I

CUSHING ASSOCIATES 20

In Table I the flowmeter signal AMPO is maintained at 1000 amplitude units. One

sees that computing precision is important. Rows 29 through 40 show that Basic’s double

precision pays off. Further, extending the samples back as far as possible is advantageous.

The magnet’s half period is 32 strobes. We should allow 8 strobes for the magnet

coils’ transition voltage duration (8 strobes = 1 CS strobe in figure 14) to complete its effect

before sampling. Hence, in Table I we want the product of columns E and F to be not greater

than 24.

Using the dB/dt amplitude BDOT at 3000 units is extreme. But it shows the power

of the scheme to reject dB/dt aftereffect. In reference 1 the observed zero-point drift was about

*5 percent of Ml scale. Table I would indicate that, with double precision, the drift can be 270

percent and still have the multi-sampled flow signal accurate to 0.1 percent of full scale. That

exaggerates; but the system has wide margin to reduce the already achieved *5 percent to *O. 1

percent.

Triboelectric noise was not implemented in the Appendix’s Basic code. Rather,

we rely on figure 6’s noise data.

The scheme’s power depends on knowing which is the correct aftereff=t function

of time. Eddy currents in the magnet core indicate first order decay. But decaying eddy

currents provide second order decay. And so forth.

Experiment is imperative: to ascertain the applicable aftereffect decay function.

A frost approximation might use the first 31 terms of the power series for the exponential; then

perturb the series’ coefficients to accommodate almost exponential decay — eg, to account for

second and higher order decay of the spurious aftereffect voltage.

It is perhaps not surprising that the present data reduction scheme — tailored to

first order decay – performs well when the aftereffect input to the simulation is exactly first

order decay.

Column G shows results with a single sample each half cycle — as was done in

reference 1. Column H show results with multi-samples each half cycle.

The Basic program that provided the data is in the Appendix. The program

includes an input parameter LOWPASS — not listed in Table I, since its value was kept at unity

throughout the calculations. LOWPASS is the number of 60-hertz cycles to average over —

useful if more smoothing is required, as it would be if we included triboelectric noise in the

calculation. The program is arranged such that Results are computed after the 60-hertz noise

has been averaged out — ie, after the input data has been smoothed over 16 magnet cycles. If

CUSHING ASSOCIATES 21

- —-— ..- .——.-

NSAMPLE is 60 then the Results are additionally smoothed over one second.

If amount of memory is no consideration, one could rearrange the program such

that Results are computed after the input data has been smoothed for the overall one second —

ie, after the input data has been smoothed over 960 magnet cycles.

CUSHING ASSOCIATES 22

10 TEST FACILITY

Figures 20 and 21 are photographs of the flow test stand.

- SIANDPIPE

RESERVOIR(55 GALLONOIL DRUM’)

VARIABLE

CUSHING ASSOCIATES

SPEEDCENIWUGALPUMP

TURBINEMETER(REFERENCE)

Figure 20. Flow test stand.

23

~ TURBINE METER(REFERENCQ

Figure 21. Flow test stand.

CUSHING ASSOCIATES 24

REFERENCES

1. Cushing, Vincent, “Electromagnetic Flowmeter, ” l?LOW(Proc. of May 1971 Flow

Symposium) (Roger B. Dowdell, cd.) Vol. 1, Part 2, ISA, Pitts., (1974).

2. ---- , U.S. PatentNo. 4,159,645, “Electromagnetic Fluid flowmeter with Tolerance

to Spurious Signals. ” (1979)

3. ---- , U.S. Patent No. 4,458,542, “Electromagnetic Flowmeter with Wideband

Preamplifier. ” (1984)

4. Giles, A, and A. Paiste, “Report on Effects of W-5 Fuel Characteristics on

Capacitance Fuel Quantity Gages (Temperature Range +38°F to -36°F,

Aeronautical Instruments Laboratory, U.S. Naval Air Development Center,

Johnsville, PA, Report No. NADC-AI-5770, Oct. 23, 1957.

5.

6.

7.

8.

9.

EIentschel, Rainer, ‘tuber Inductive Durchilussmessung Mischleitender und Iso-

lierender Flussigkeiten, ” Eng. D. dissertation, Technical University at Hanover

(1973).

Shercliff, J. A., l%e Theory of ElectromagneticFlow Measurement (Cambridge

University Press, New York, 1962).

Smythe, Charles Phelps, Dielectric Behavior and Structure (McGrawHill, New

York, 1955, Ch. I).

Stewart, John W, J. C7zem.Phys, 40, 11, 3297 (1964). (1962).

Warshawsky, Isidore, Foundationsof Measurementand Instrumentation (NASA

Reference Publication 1222 (1990), pp87-89).

CUSHING ASSOCIATES 25

.,...,,-=-,.-?7- ,., . ., . ,. , . .. ,, . . ,-, ..,.. , . ... . ‘,.,“,>,.”,.,./,.,.V’m., k,,.,. . . . . . . . .. . >,, ..,..,, .. . . . . ..- .+. ,,, .,’. —.. -

CUSHING ASSOCIATES

Appendix

Basic Program:

ALLMETER.~E

26

“i20 ‘ ALLMETER. JBE -- FOR EM ALLMETER FLOWMETER SIMULATION30 “ COPY OF THIS SOURCE CODE CAN BE OBTAINED BY EMAILING VINCENT@CUSHINGS.COM40 ‘ DEFINT I-N : DEFSTR S: OPTION BASE 160 : DEFDBL A-Z: DEFINT I-N : DEFSTR S: OPTION BASE 180 FF$ = CHR$(12): QUOTE$ = CHR$(34): CR$ = CHR$(13): PI = 4 * ATNfl): NTAB = 8100120130140150160180200220240260280300320340360380400420440

DEF FNIO (N) =INT(2 A (N-i))”.. . .,

DEF FNNC (M, N) = ((M AND FNIO(N)) = FNIO(N)) ‘ FNNC(N)=-1 (TRUE) IF BIT # N (1,...,N,...,16) IS ON; FNNC(M,O) TRUE8 FOR ALL MDEF FNNT (M, N) = -(N>O) * (M OR FNIO(N)) - (N C O) * (MAND NOT FNIO(-N)) ‘ +N TURNS ON BIT N IN M; -N TURNS OFF# BIT NNDELAY = 2 ‘ REM: 2 SECOND TIME DELAYKEY ON: KEY 7,’’SAVE’’+QUOTE$+“L.L’’+QUOTE$+’’,+CR$:R$: KEY 9, “SYSTEM’’+CR$: KEY 8, “LPRINT FF$’’+CR$DIM NPARAMS(10) ‘ STORE 7 INPUT AND 3 OUTPUT VARIABLES AS INTEGERSDIM SPARAMS(10) ‘ STORE 7 INPUT AND 3 OUTPUT VARIABLE NAMES AS STRINGSDIM STITLES( 2) ‘ STORE 2 TITLES AS STRINGSREM: DSP(160,1MULT,IMAG): 160 -- 2 60Hz 1/2 CYCLES; IMULT -- 8 60Hz 1/2 CYCLE; 32 POSSIBLE SAMPLE PAIRSDIM 11$(2) ‘ INSTRUCTION FLAG: PRINT TO PRINTER AND PRINT TO FILEDIM DsP(2,8,32)DIM T(32), Y(32), DY(32) ‘ FOR WARSHAWSKY’S DATA REDUCTIONDIM AV(32) ‘ TO CALCULATE A, B AND TAU IN SIG = A + B*EXP(-T/TAU)PRINT “STROBE 1 <--> INTERVAL 31; 2 <--> 30; 3 <--> 29; ...?cPRINT “NSAMPLES = QUANTITY OF STROBES; NDN = SEPARATION BETWEEN STROBEs”GOSUB 10000GOSUB 11000GOSUB 6000

100010201040106010801100112011402000202020402060208021002120214021602180220022202240

8 CONVERT NPARAMS( ) TO RECOGNIZED VARIABLESAMPO = NPARAMS (1)BDOT = NPARAMs(2jTAU = NPARAMS (3)

NSAMPLES = NPARAMS(4)NDN = NPARAMS (5)PMO = NPARAMS (6)

NLOWPASS = NPARAMS(7)* . .

DETECT PAIRSFOR 164 = 1 TO NLOWPASSFOR 160 = 1 TO 2 ‘ FOR EACH HALF OF 60 HZ CYCLEFOR IMULT = 1 TO 8 ‘ MAG FREQUENCY IS 16TH HARMONIC OF 60 HZ; IMULT IS WHICH OF 8 IN EACH 60 HZ HALF CYCLEFOR IMAG = 1 TO NSAMPLESTOTAL = OFOR IHALF = 1 TO 2 ‘ WHICH HALF OF MAGNET CYCLEGOSUB 5000TOTAL =ToTAL+ (3- 2*IHALF )*( FS + DBDT + PM )NEXT IHALFDSP(160, 1MULT,IMAG) = ToTAL/2NEXT IMAGNEXT IMULT

CASHING ASSOCIATES Al

22603000302030403060308031003120314031603180320032203240326032803300332033404000401040204040406040804100412041404160418042004220424042604280430043204340436043804400442050005020504050605080

NEXT 160I AVERAGE OF IMULT OVER BOTH POWER MAINS SINUSOIDAL HALF CYCLESFOR IMAG = 1 TO NSAMPLES ‘ FOR EACH STROBE POSITIONAV8 = oFOR IMULT = 1 TO 8 ‘ FOR EACH OF THE 8 IN EACH HALF OF THE POWER MAINS SINUSOIDSAV60 = oFOR 160 = 1 TO 2 ‘ FOR EACH HALF OF THE POWER MAINS SINUSOIDAV60 = AV60 + DSP(160,1MULT,IMAG)NEXT 160AV60 = AV60/2AV8 = AV8 + AV60NEXT IMULTAV = AV8/8AV(IMAG) = AVAV64 = AV64 + AVNEXT IMAGAV64(IMAG) = AV64/NLOWPASSNEXT 164PRINTt CALCULATE FLOW SIGNAL. cf Isidore Warshawsky, “Foundations of Measurement and Instrumen-t tationt”‘ NASA Reference Publication 1222, p87 et seq (1990)FOR N = 1 TO NSAMPLEST(N) = ( N - 1 )*NDNY(N) = AV(N)NEXT NNCALC = NSAMPLES - 1B1 = O: B2 =O:co=FORN=lDY(N) = YB1 = B1 +B2=B2+co = co +c1 = c1 +DO = DO +NEXT N

o: cl =O:DO=OTO NCALCN+l) - Y(NY(N+l) - Y N)DY(N)”2Y(N)Y(N)*DY(N)Y(N)’2

D = NCALC*B2 - B1”2P = (B1*CO - NCALC*Cl)/DFS = (B2*C0 - Bl*Cl)/DNPARAMS(10) = -1/LOG(l - l/P): NPARAMS(8) = Y(NSAMPLESGOTO 7000ENDr GENERATE SIGNALS: GOSUB 5200 ‘ GENERATE TIME: GOSUB 5400 ‘ GENERATE FLOW SUGNAL: GOSUB 5600 ‘ GENERATE DB/DT SPURIOUS SIGNAL (NOISE): GOSUB 5800 ‘ GENERATE 60”HERTZ SPURIOUS SIGNAL (NOISE)

CASHING ASSOCIATES A2

.

: NPARAMS 9) = FS

51005200522052405400542054405600562056405660580058205840586060006020604060606080610061206140615061606170618061906200621062206240700070207040706070807100712071407500752080008020804080608080

1

#

RETURN# GENERATE TIME Tr = (160 - 1)*512 + (IMTJLT- 1)*64 + IMAG(IMAG) + (IHALF - 1)*32RETURN8 GENERATE FLOW SIGNALFS = (3 - 2*IHALF)*AMpoRETURN

GENERATE DBDT COHERENT NOISE VOLTAGE;B = (T -1) MOD 32DBDT = (3 - 2*IHALF)*BDOT*EXP (-TB/TAU)RETURN# GENERATE 60 HZ POWER-MAINS COHERENT NOISE VOLTAGEPMO = NPARAMS(6)PM = PMO*SIN( 2*PI*T/1024 )RETURN8 DEFAULT INPUT DATA; USER CHANGES PARAMETERS IN 22000NPARAMS( 1) = 1000: SPARAMS( 1) = “ AMPO “ ‘ AMPo, FLOW SIGNAL SQUARE WAVE AMPLITUDENPARAMS~ 2j = 3000:NPARAMS( 3) = 300:NPARAMS( 4) = 4:NPARAMS( 5) = 1:NPARAMS( 6) = 1000:NPARAMS( 7) = 1:8

SPARAMS~ 2j = IIBDOT “ ‘ BDOT, AFTEREFFECT AMPLITUDE -- IE, HUM AMPLITUDESPARAMS( 3) = “ TAU “ ‘ TAU, AFTEREFFECT DECAY TIME CONSTANTSPARAMS( 4) = “SAMPLES” ‘ SAMPLES, TOTAL NUMBER OF SAMPLES PER MAGNET HALF CYCLEsPARAMS( 5) = “ DN “ ‘ DN, SEPARATION BETWEEN SAMPLESSPARAMS( 6) = “ PMO “ ‘ PMO, POWER MAINS NOISE PEAK AMPLITUDESPARAMS( 7) = “LOWPASS” ‘ LOWPASS, NUMBER OF 60-Hz CYCLES TO AVERAGE; LOWPASS

OVER 1 SECOND.SPARAMS( 8) = “FSINGLE” ‘ CALCULATED FLOW SIGNAL USING SINGLE DATA POINT PER

CYCLESPARAMS( 9) = “FMULTI “ ‘CALCULATED FLOW SIGNAL USING MULTI DATA POINTS PER

CYCLE .SPARAMS(10) = “TAU/DN “ ‘CALCULATED TAU/DN USING MULTI DATA POINTS PER

CYCLE .STITLES( 1) = “ EX I ST I NG PARAMETERS 11

STITLES( 2) = “ INPUTS RE, CHANGE INPUT DATA; SETUP COLUMN HEADINGSIF FNNC(11,2) THEN GOSUB 8600IF FNNC(I1,l) THEN GOSUB 8300GOSUB 8000GOSUB 9000FOR I = 1 TO NPARAMS(4)IMAG(I) = 31 - (NPARAMS(4) - I)*NPARAMS(5)NEXT It COMMENCE CALCULATIONGOTO 1000# PRINT TO MONITOR: TITLES, COLUMN HEADINGS AND DATACLSPRINT STITLES(l + IDONE1)FOR I = 1 TO 7 + 3*IDONE1PRINT TAB((I-l)*NTAB) SPARAMS(I);

CUSHING ASSOCIATES A3

= 60 AVERAGES

MAGNET HALF

MAGNET HALF

MAGNET HALF

SULTS”

81008120814081608180820082208240830083208340836083808400842084408460848085008520854086008620864086608680870087208740876087808800882088409000902090409060908091009120914091609180

NEXT IPRINTFOR I = 1 TO 7 + 3*IDONE1PRINT TAB((I-l)*NTAB) NPARAMS(I);NEXT IPRINTIDONE1 = 1RETURN? PRINT TO PRINTERIF IDONE1 = 1 THEN GOTO 8460LPRINT STITLES(2)FOR I =1TO1OLPRINT TAB((I-l)*NTAB) SPARAMS(I);NEXT I‘ LPRINTIF IDONE2 = O THEN GOTO 8520FORI=1TO1OLPRINT TAB((I-l)*NTAB) NPARAMS(I);NEXT IIF (NOT FNNC(11,2)) THEN IDONE2 = 1RETURN# PRINT TO FILEIF IFILE = O THEN OPEN “O”, 1, “DATA.I”: IFILE = 1IF IDONE1 = 1 THEN GOTO 8760PRINT #l, STITLES(2)FOR I = 1 TO 10PRINT #1, TAB((I-l)*NTAB) SPARAMSINEXT IIF IDONE2 = O THEN GOTO 8840FOR I = 1 TO 10PRINT #l, TAB((I-l)*NTAB) NPARAMSNEXT I

I);

I);

IF (NOT FNNC(I1,l) ) THEN IDONE2 = 1RETURN? MAKE CHANGESPRINT: PRINT: PRINT: PRINT: PRINT “MAXE CHANGES; RETURN IF NO CHANGE; ‘E’ EXITS TO SYSTEM”FORI=1T07PRINT SPARAMS(I) + “ = “;: INPUT; ““, sPRINTIFS= ~,E,~THEN cLOsE: sYSTEM

IF S = ““ THEN GOTO 9160NPARAMS(I) = VAL(S)NEXT IRETURN

10000 ‘ TIME DELAY10020 TX = O: TTO = TIMER10040 WHILE TX < TTO + NDELAY: TX = TIMER: WEND

CASHING ASSOCIATES A4

10060 RETURN10080 END

:-. 11000 ‘ SET INSTRUCTION FLAGS11020 CLS: PRINT: N = 5 ‘ 1111040 11$(1) = “ALSO PRINT TO PRINTER” ‘

!0000 0000 0001

11060 11$(2) = “ALSO PRINT TO FILE ‘DATA.l’l’ ‘ 0000 0000 001011080 PRINT TAB(19+N); “11 CONTROL SETTINGS”

. 11100 PRINT11120 FOR I = 1 TO 2: IF 11$(1) = ““ THEN 11140 ELSE PRINT TAB(15+N); RIGHT$(STR$(I), 2) + “11140 NEXT I

“ + 11$(1)*;E 11160 PRINT TAB(5+N); “INSTRUCTION NUMBERS; LEAVE SPACE IF TWO NUMBERS 11; : LINE INPUT ; S

11180 S1 = LEFT$(S, 1).. 11200 IF (S1 = ““) OR (S1 = “O”) THEN 11 = O: GOTO 11340;, 11220 L = INSTR(S, “ “)T

11240 IF L = O THEN 11 = FNNT(I1, VAL(S)): GOTO 11340,>11260 S1 = LEFT$(S, L - 1)

~, 11280 11 = FNNT(I1, VAL(S1))b 11300 S = MID$(S, L + 1)r: 11320 GOTO 11220

11340 PRINT,/ 12000 RETURN

;,:;.,,

.

;:

/,2,,,,,.,

..

1

I.

CASHING ASSOCIATES A5