Note: Descriptions are shown in the official language in which they were submitted.
.10~0'~'
Back~round of the Invention
In its broader applications, the field of the
present invention relates to means for verifying proper
operation of electrical computing circuitry employed for
pulse train manipulations or for establishing a comparative
relationship between plural pulse train generating means
exposed to similar inputs. The invention also relates to
the measurement of variable parameters. In a particular
application described herein, the present invention relates
to systems and methods for measuring the volume of fluid
flowing in a flowline, compensating for various factors
which affect the measurement, and verifying proper function-
ing of the compensating means.
The prior art is replete with systems for measuring
fluid flow in a flowline. Many of such systems are capable
of automatically compensating for changes in various para-
meters of the fluid, such as pressure and temperature, which
may affect the measurements. Such compensation provides a
corrected and standardized output value for the measured
fluid volume. Corrections are required because of errors
in the flow meter operation. Standardization is required
since the volume of liquids varies with changes in temperature
and the volume of gases varies with both temperature and
pressure. Standard U.S. volume measurements of petroleum
fluids are currently based on a temperature of 60F and
atmospheric pressure at sea level. As used herein, the
term fluid is intended to encompass both liquids and gases.
Certain of the prior art systems employ a
flowmeter to measure flow rate through the metered flowline
and transducers to measure the temperature of the fluid.
The flowmeters are generally of the type which generate a
series of pulses at a frequency which is representative of
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a measured volume of ~luid. An output device counts the
pulses to determine the volume. In one prior art system,
the temperature transducer output is employed to increase
or decrease the frequency of the pulses supplied to the
output device from the flowmeter. The output device counts
the number of resulting pulses to provide a temperature
standardized value for volume.
One prior art system compensates for temperature
effects by adding a burst of high frequency pulses to the
square wave pulse train being emitted from the flow meter.
The high frequency pulses are timed to occur in the period
between two adjacent square wave pulses. The output device
totals the high frequency pulses as well as the lower fre-
quency square wave pulses to obtain the compensated volume.
The required sensitivity of the output device to high
frequency signals makes the system susceptible to noise.
Efforts directed toward reducing noise distortion increase
the complexity and expense of the compensating circuitry.
Moreover, the requirement for inserting the high frequency
bursts into the interval between adjacent square wave pulse
places a practical upper limit on the square wave pulse rate.
If the pulse rate is too high, not enough time between
adjacent pulses is available for insertion of a relatively
large number of compensating spikes.
In the petroleum industry, accurate measurement
of petroleum fluids is of great economic importance which
explains the need for compensation devices. The loss or
addition of even a single pulse in a pulse train may affect
the output reading of the metering system by a substantial
amount. To ensure accurate measurement, the compensating
devices must be periodically tested. If the measuring
2 --
10~5~0~7
function of the system must be interrupted during testing,
important economic loss may result. Testing is also an
expensive requirement where sophisticated test equipment
and experienced technical personnel are required to perform
the tests. Conventional systems which insert a burst of
high frequency pulses between square wave pulses are
extremely difficult and expensive to test.
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SummarY of the Invention
According to the invention there is provided a system
for testing operation of a digital computing circuit of
the type in which input data in the form of an input pulse
train is supplied to the circuit input and pulses are
added to or removed from the input pulse train according
to a relationship characteristic of said digital computing
circuit so that the resulting output pulse train supplied
to the circuit output is representative of the application
of said characteristic relationship to the input data
comprising: a) first and second counters; b) electrical
circuit means providing the input pulse train to said
first counter and the output pulse train to said second
counter so that the count accumulated by the first counter
represents the number of pulses in the input pulse train
during the counting interval for the first counter and
the count accumulated by the second counter represents
the number of pulses in the output pulse train during the
counting interval for the second counter; c) gating means
actuatable for simultanèously starting the counting oper-
ation of said first and second counters; and d) display
means for displaying the accumulated counts in said first
and second counters.
All of the inputs to the system of the present inven-
tion, such as temperature and coefficient of expansion,
are converted into or supplied to the system in digital
form. The system itself is physcially arranged so that
discrete circuits perform a desired mathematical func-
tion. The combination of these circuits in the system
produces a series of mathematical functions which con-
vert the metered input value for flow to a temperature
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lO~S407
standardized, meter error corrected, value.
The provision of an all digital system with separate
circuits performing specific, known mathematical opera-
tions permits the system and its individual circuits to
be quickly and easily tested for proper operation by
unskilled personnel using simple calculators or manual
calculations. Additionally, the described design approach
permits the system to be easily tailored to suit special-
; ized applications. Thus, where the same fluid is always
flowing through the line, there is no need to correct fora variable coefficient of expansion and this circuit and
its function may be deleted without re-engineering the
; system. Other functions, such as pressure compensation,
may just as simply be added without need for extensive
design changes.
Verification of proper operation of the temperature
compensating means of the present invention is effected
by connecting an input prover or gross counter to the
input to the compensating means and an output prover or
net counter to its output. The two counters are inter-
connected to start and stop counting simultaneously and
to count independently. If the system is functioning
properly, the net count will differ from the gross count
by a factor having a value dependent upon the temperature
correction. Established tables may
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be consulted to provide the coefficient of expansion for
the fluid being metered. Given the temperature of the fluid
by either manual calculation or with the use of a simple
calculating device, the gross count is multiplied by the
coefficient of expansion. The result of this multiplication
will be equal to the count in the net counter if the compen-
sating circuit is functioning properly.
While the invention has been described for use
with a temperature compensation circuit, it will be
appreciated that it may also be used with other digital cal-
culating circuit means having known functional relationships
between the input and output signals.
The verification equipment of the invention monitors
the metering and compensating means without interrupting
normal metering operations. Thus, no shut-down time is
required to test the equipment.
In one form of the invention, the gross counter
may be employed to count the input signal applied to a
temperature multiplier unit, a coefficient of expansion
multiplier unit or a meter factor multiplier unit. The
second counter may be connected to monitor the output signals
generated by the temperature multiplier unit, the coefficient
of expansion multiplier unit, an Arithmetic Logic Unit or
the meter factor multiplier unit. The gross counter display
for a given period of time should be functionally related
to the net counter display by the mathematical operations
employed in the subcircuits or units included between the
two counters. Each multiplier unit may be checked individ-
ually, or the entire system may be checked.
An important feature of the present invention
is that the pulse stream supplied to the output device
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contains only square wave pulses. Since it is not necessary
to insert a compensating burst of high frequency pulses into
the pulse train as is necessary with certain of the prior
art designs, conventional high frequency noise filters may
be used in the system of the present invention so that noise
spikes may be prevented from producing faulty readings in
the output device. The use of a uniform square wave pulse
train without need for inserting signals between adjacent
pulses makes it possible to employ higher operating frequencies
with the system of the present invention.
In operation, the system of the invention modifies
the output pulse stream to form a compensating pulse stream
by continuously subtractiny square wave pulses from the
train to reflect the effect of variable parameters. This
compensating pulse stream is then combined with the original
gross output pulse train to provide a net pulse train which
is supplied to the end output device to show the standard- ^
ized corrected volume of fluid flowing through the flowline.
Because of the continuous nature of the compensation or
correction, a very large number of corrections or compensa-
tions may be included in the system without unduly increasing
the frequency of the pulse train supplied to the output
device and without altering the square wave form of the
signal.
The system of the present invention operates on
digital pulse trains using binary-coded-decimal (BCD) input
values so that the system is directly compatible with any
conventional digital computer without need for special
interfacing equipment. The signals in the system may also
be provided as BCD output signals for use with conventional
digital equipment. This is true with respect not only to
the output signal from the system but also with respect to
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the signal at the output of each individual subcircuit forming
the system. If desired, system input and output values may
- be communicated in digital form between the system and a
remotely located digital computer or other digital equipment
which even further enhances the flexibility of the system.
One of the important features of the present invention
is the provision of means for simultaneously gating the input
and output counters when a verification count is initiated and
stopping the counters simultaneously when the count is over.
This simple expedient ensures that the input and output count
are taken over the same time period. A gate delay circuit is
employed to form a clean gating pulse to the counters, free
of switch bounce or other mechanically induced noise.
Simultaneously, gating is effected by employing a common
gate delay circuit for both counters. By this means, the
discrepancies between capacitors, resistors and supply
voltages in two separate gate delay circuits are eliminated
so that the two counters are gated at precisely the same time.
It will be appreciated that this technique for verifying
operation of a digital circuit may be applied to any digital
circuit and is not limited to its described application for
verifying proper operation of the circuitry in a temperature
compensation system.
The gate delay circuit is also provided with circuit
means which provides a single, fixed duration square wave
pulse to the delay circuit ~henever the mechanical count-
initiate switch is depressed, regardless of the speed at
which the switch is opened and closed and regardless of whether
the switch is manually held in closed position for a prolonged
period of time. By this means, the gating of the two counters
is made independent of variations in the closure time of the
count-initiate switch.
Another important feature of the invention is
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that proper operation of the system or individual portions
of the system may also be verified ~uickly, without need
for shutting down the measuring function of the system
or diverting the fluid to a secondary metering system.
This is accomplished in part by digitizing all analog func-
tions, arranging the circuits so that their individual inputs
and outputs are connectable into the proving counters,
` providing for specific mathematical manipulations in each
circuit section and providing digital decimal displays for
the two counters and for ~T as well as for the inputs for
coefficient of expansion, meter factor and any other variable
parameters affecting the net count.
The temperature of the metered fluid is periodically
compared against a reference temperature to obtain a ~T value
which in turn is converted to BCD form and supplied to a
multiplying circuit in the compensation system. The BCD
signal which is applied to the multiplier is also supplied
to a digital display so that the values of ~T being used in
the multiplier is visually displayd and may be compared with
the value of ~T obtained by manual testing. Since the con-
verted multiplier value rather than the analog output value
of the temperature transducer is displayed, proper operation
of the BCD converting means is also verified during the
test.
Other features, objects and advantages of the
present invention will become more readily apparent from
the accompanying drawing, specification and claims.
Brief ~ n of the Drawing
The Figure illustrates a block diagram of the
compensating system of the present invention.
Description of the Illustrated Embodiment
Referring now to the drawing, the compensating
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totalizer system of the present invention is indicated
generally at 10. The system 10 is used for measuring the
volume of fluid flowing in a flowline ~1, standardizing the
measurement to a selected value of temperature and correcting
the abnormalities in the metering device. The system includes
a conventional flowmeter 12 which may be a turbine meter or
positive displacement meter or any other suitable ~etering
or measuring device capable of indicating the amount of
fluid moving through the pipeline. In the system of the
present invention, the flowmeter 12 is preferably of the type
which generates an electrical square wave pulse representative
of the passage of a known incremental volume of fluid through
the pipeline. These pulses from the flowmeter provide a
first digital signal which is supplied via conductor 12a to
an input amplifier 13 which amplifies the signals and elec-
trically isolates the rest of the system from the flowmeter.
The output of amplifier 13 is connected via conductor
13a to the input of a temperature multiplier unit 14. A test
point A is electrically connected to conductor 13a to provide
a means for monitoring the output of the amplifier 13. The
temperature multiplier 14 is also supplied with a binary-
coded-decimal (BCD) signal representative of a change in the
temperature (~T) of the fluid in the flowline as measured by
a conventional temperature transducer 15. The transducer 15,
which is disposed in the flowline 11, continuously measures
the fluid temperature and generates a representative analog
output signal. The analog signal is applied via conductor 15a
to a signal conditioner 16 which compares the analog signal
to a preselected signal representative of a standard tempera-
ture. Any suitable conventional means may be employed for theconditioner 16. In the illustrated embodiment, the reference
temperature is 60F which is the temperature used in the oil
industry as a standard for volume measurements.
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The signal conditioner 16 generates two output
signals, one of which is supplied to a conventional analog-
~ to-digital converter (ADC) 17 via conductor 16a. The signal
on line 16a is an analog signal, t~e amplitude of which is
representative of the magnitude of the change in temperature
(~T) from the reference temperature of 60F. The second output
from the signal conditioner 16, on a line 16b, is indicative
of the sign (plus or minus) of the temperature change from
the reference temperature.
The ADC 17 converts the analog ~T signal from the
signal conditioner 16 to a BCD ~T signal which is supplied
by a conductor 17a to the temperature multiplier unit 14 and
to a ~T temperature display unit 18 by conductor 17b. A line
17c provides the gross pulse signal to the ADC 17 so that the
signal on line 17a may be updated each time a selected number
of pulses in the gross pulse signal occurs, for example 1000
pulses.
The ~T temperature display unit 18 is conventional
and employs readout devices 18a to visually display the
change in fluid temperature with respect to the reference
temperature. By way of example, at 60F, the temperature
display 18a would indicate 0F,; at 125F, +65DF would be
displayed and at 0F, -60F would be displayed. The plus
and minus sign in the display device 18a is generated by the
signal conditioner 16 and supplied to the display unit 18
by the conductor 16b.
As previously mentioned, the BCD ~T output signal
from the ADC 17 on the line 17a is applied to the temperature
multiplier unit 14. The multiplier 14 is conventional and
functions such that the BCD ~T value is multiplied with the
flowmeter pulse train signal on line 13a. The resulting out-
put signal from the multiplier 14 is a digital, temperature-
compensated, square wave pulse train representative of the
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flowmeter signal value multiplied by the BCD ~T signal value.
The multiplier circuit 14 is similar to other multiplier cir-
cuits in the system 10 and functions to manipulate or alter
the pulse train supplied to its input according to a particular
mathematical equation. In the case of the circuit 14, the
equation is simply:
Pil~T ( . 01 )
where:
PO = the number of pulses in the output pulse
train over a selected interval;
Pi = the number of pulses in the input pulse
train over the same interval; and
QT = the absolute value of the temperature
difference between the actual fluid
temperature and the reference temperature.
Thus, it may be appreciated that, in general terms, the pulse
train Pi is continuously altered according to a specified
mathematical equation in an amount dependent upon the value`
of one or more variable mathematical factors (~T) employed
20 in the Equation. In operation, the variable factor values -
are provided as BCD inputs to the circuit performing the ~ -~
mathematical operation. Pulses in the input pulse train
are subtracted by the circuit over the given interval in ~ `
an amount dependent upon the particular mathematical opera-
tion being performed by the circuit. While the circuit 14
performs multiplication, other operations such as division,
subtraction or addition may also be performed.
Standardization of the volumP reading for the
system 10 requires that the coefficient of expansion for
the metered fluid be taken into consideration. This co-
efficient and the temperature of the fluid relative to the
selected standard temperature are employed in obtaining the
temperature standardized volume from the metered volume. A
second multiplier unit 19 is utilized to compensate for the
coefficient of expansion of the fluid being metered. The
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output signal from the multiplier 14 is applied by a conductor
14a to the unit 19. A test point B is electrically connected
to the output conductor 14a. The coefficient of expansion is
obtained from a reference table and manually entered by unit
20 as one input to the multiplier 19. The unit 20, which is
a conventional thumbwheel switch, displays the number entered
and converts the value to a BCD form for entry into the multi-
plier 19. The temperature compensated digital signal on the
line 14a provides the second input and the product of the two
inputs is formed on the line l9a. The unit 19, like the unit
14, may be any suitable conventional electronic multiplying
circuit which, when provided with digital inputs provides a
digital output pulse train representative of the product of
the inputs. This output generated by the unit 19 is a net
compensation signal which is supplied as one input to a con-
ventional arithmetic logic unit (ALU) 21 by a conductor l9a.
A test point C is electrically connected with the output line
l9a.
The ALU 21 also receives as inputs, the gross
flowmeter output signal from the amplifier 13 and the sign
(plus or minus) signal from the signal conditioner 16. When
the signal on the line 16b indicates a negative value for
~T, the ALU 21 algebraically adds the net compensation signal
to the gross flowmeter signal. When the signal on line 16b
indicates a positive value for ~T, the net compensation signal
is subtracted from the gross flow meter signal. The resulting
output from the ALU represents the net standardized volume for
the volume of fluid metered in the flowline.
The output of the ALU 21 is supplied to a meter
factor multiplier unit 22 by a conductor 21a. A test point D
is electrically connected to the line 21a. The meter factor
multiplier corrects for errors in the meter 12. In the system
10, the me'er factor is determined by dividing:
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(a) the number of pulses P(l) actually produced on the line
12a for a known volume of fluid traveling through the meter
- 12 into (b) the number of pulses P(2) which should have been
produced for such known volume according to the manufacturer's
specifications for the meter. This meter factor is manually
entered through the unit 23 as one input to the multiplier 22.
The unit 23 converts the meter factor value, in a conventional
manner, to a BCD signal on the line 23a. The multiplier 22,
like multipliers 14 and 19, multiplies the two signals together
and provides a digital output representative of the product.
This product, which is provided on the line 22a, is the
factored net output signal for the system in digital form.
A test point E is electrically connected to the line 22a.
The signal on line 22a is also provided to a conventional
scaler 22b which interfaces with a conventional output display
register 22c. The register 22c provides a visual display of
the temperature standardized volume of the metered fluid
corrected for meter abnormalities.
Since proper operation of the totalizer system lO
may be of great economic impoxtance, a verification circuit
24 is included in the system lO to provide a simple and quick
check of the system. The verification circuit 24 includes
an input or gross counter 25 and an output or net counter 26.
An input 25a to the gross counter may be selectively connected
to the test points A, B, and D by a selector switch 27a.
The net counter has an input 26a which is selectively connected
by selector switch 27b to the test points B, C, D, and E. In
the illustrated system, the switches 27a and 27b are ganged
for simultaneous movement. By moving the selector switches
to the appropriate position, the counters 25 and 26 will be
connected across the system lO or across one or more of the
multipliers in the system. Thus to check multiplier 14, the
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switches 27a, 27b are set to switch position 3; to checkmultiplier 19, they are set to position 4; to check multi-
pliers 14 and 19 and ALU 21, they are set to position 2; to
check multipliers 14, 19 and 22 and the ALU 21, they are set
to switch position 1.
The counters 25 and 26 are interconnected to gate
on and off simultaneously and to count independently. The
counters 25 and 26, which are conventional, include means for
resetting to zero and begin counting when they receive a first
electrical gate pulse G.P. The counters stop counting when
they receive a second gate pulse. The accumulated count in
each counter is presented as a visible, digital display. If
desired, the counters may be connected to be reset with the
first gate pulse or to be provided with other means for
starting or stopping the count operation. In the preferred
form of the invention, a gating circuit 30 is employed to
form a gate pulse which has a fixed amplitude and duration and
is free from noise and distortion. Direct mechanical switching
for starting and stopping the counters is preferably avoided
since the gate pulse generated from the closing (or opening)
of a mechanical switch may have a high frequency noise compon-
ent which may cause the counters to rapidly turn on and off.
Loss or addition of even a single pulse to the count in
either counter may be significant. While counters are cus-
tomarily provided with an electrical circuit for producing a
clean gate pulse following actuation of a mechanical switch,
the gate pulses in two different counters are not necessarily
identical. Differences in the timing circuit component values
or the supply voltages may cause identical counters to produce
gate pulses which are sufficiently dissimilar to cause the
two counters to start or stop at slightly different times even
though both are connected to the same switching means.
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One o~ the important features of the presentinvention is the provision of means for initiating or stopping
the count in counters 25 and 26 with the very same gate pulse.
Since the identical pulse is used to control operation of both
counters, the counts start and stop simultaneously.
In the Fig., a mechanical switch 31 is closed to
form the gate pulse G.P. A parallel RC timing circuit 32
cooperates with the charging capacitor 33 and resistor 34
to provide a momentary pull-down circuit. The pull down
circuit supplies a pulse to the gate circuit when the switch
31 is closed. The pulse width is dependent upon the component
values in the circuit 32 and is not affected by the length of
time that the switch is held in the closed position. If
desired, the circuit may be modified to produce the pulse
supplied to the circuit 30 when the switch 31 is opened
rather than when it is closed.
The procedure for checking a multiplier unit for
proper operation involves resetting both counters, setting
the selector switch 27a, 27b to the appropriate position
and depressing the switch 31 which allows the counters to
simultaneously start counting input and output pulses. At
any desired time, the switch 31 is closed again to stop both
counters simultaneously. At the end of the counting period,
the values displayed by the counters are compared. Where a
two input multiplier is being checked, the value in the net
counter divided by the gross counter value will be equal to
the multiplication factor entered in the second input to the
unit if the multiplier is working accurately. This test is
conducted while the normal metering function of the system
continues. Any suitable circuitry or devices capable of
performing the described functions for the various components ~ s
may be employed in the circuit 10. The meter multipliers,
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ALU unit, counters, scaler, register and other circuits and
devices described with reference to the present invention
are conventional and, per se, form no part of the invention
except as they are used in the described combination.
Theory and Examples of Operation
In the system 10, it is desirable to use digital
signals in the compensating circuitry in order to reduce
error and to make the system operation more comprehensible
to operators charged with the responsibility of verifying
the correctness of the system's operation. The meter output
is thus preferably digital in form and the temperature probe
output is converted to digital form. Where other type
transducers are employed to provide volume, or where addi-
tional parameters, such as pressure, are being monitored,
the outputs of such transducers are preferably digitized to
be compatible with the system.
The system 10 performs the temperature correction
by solving the following equation:
(1)NET = GROSS [1 + (60-T) (O.Ol) (C.E.)] (M.F.)
20 where:
T = the temperature in degrees Fahrenheit
of the fluid to be measured
C.E. = Coefficient of Expansion for the fluid,
expressed in percent per degree Fahrenheit
M.F. = the meter factor of the flow rate
transducer
NET = the standardized pulse signal corrected
for temperature and meter factor effects
GROSS = The Pulse signal obtained from the flow
transducer.
Equation (1) may be rewritten as follows:
(2) NET = M.F. [GROSS + GROSS(¦60-T¦) (O.Ol)(C.E.)]
for T<60F; and
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(3) NET = (M.F. ) (GROSS)
for T = 60F; and
(4) NET = M.F.[GROSS-GROSS(¦60-TI)(O.Ol)(C.E.)]
for T>60F.
Referring to the system functional diagram 10,
the fluid temperature is transmitted to the signal condit-
ioner 16 where it is linearized and subtracted from a 60F
reference. The output signal on line 16a is a voltage
proportional to ¦60-T¦. The signal conditioner also deter-
mines whether the temperature is greater or less than 60Fand provides an appropriate signal on the line 16b. Any
suitable conventional circuitry may be employed to provide
the function of the conditioner 16. The analog to digital
converter 17 accepts the absolute value of the temperature
difference from 60F (~T)and converts the voltage signal to
a three digit Binary Coded Decimal (BCD) number. The conver-
sion preferably occurs every 1000 gross input pulses. The
gross signal on the line 13a may be employed as a check for
the ADC 17. As an additional operational check and maintenance
~0 function, a 3-digit digital display 18a with sign, is provided
to monitor ~T. In this manner, the unit may be checked to
ensure that the proper temperature is being measured at all
times.
The temperature multiplier 14 accepts the gross
pulses from the amplifier 13 and multiplies by (~T)(.Ol)
in BCD form. Since this is a digital multiplication, the
product is represented by a serial pulse train. s
Example 1
As an example, consider ~T = +45.6F, and 1000
30 gross pulses. The value of ~T is multiplied by .Ol by shift-
ing the decimal point two places to the left therefore the
input to the temperature multiplier is 0.456. For 1000
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input pulses, 456 pulses are gated out of the multiplier 14
representing the product of (gross pulses ) (~T) (.Ol). An
operator attempting to verify that the system is operating
correctly may permit the input counter connected to point A
to count to 1000. Knowing that ~T is +45.6F (by simply
reading the display 18a), the operator may manually multiply
(1000)t45.6)t.Ol) to obtain 456. If the unit 14 is function-
ing correctly, the output counter should read 456. By taking
a manual temperature reading and calculating ~T, operation
of the temperature transducer 15 and the ADC converting
system 17 may be tested since the calculated value should
correspond with the value displayed at 18a if the components
are working correctly.
The coefficient of expansion multiplier 19 operates
in the same manner as the temperature multiplier 14. It
accepts the output of the temperature multiplier and multiplies
by the coefficient of expansion which is entered by thumbwheel
switches in the unit 20. The coefficient of expansion is
obtained, for example, from ASTM D 1250, Table 6, for the
fluid being measured and is entered in percent per F. The
output on line l9a of the coefficient of expansion multiplier
19 represents the "compensation flow" that must be added or
subtracted from the gross input on line 13a, depending on
the sign of ~T. The arithmetic logic unit 21 accepts the
gross flow and either adds or subtracts the compensation
flow as required. The meter factor multiplier accepts the
net flow output on line 21a from the ALU and multiplies
it by the number input on the meter factor thumbwheel switches
in the unit 23. The meter factor is derived by "proving"
the metering system. In the system 10, the meter factor
may vary from 0.0001 to 1.9999.
As an example of the complete system operation
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consider the following Examples:
C Example II
Assume: .
(a) 100 gross barrels flow through the flowline
and the flow meter 12 produces 1000 pulses/barrel or a total
of 100,000 gross pulses.
(b) The fluid is 40API:
(c) the fluid temperature is 50F; and
(d) the meter factor is 1.0026.
To calculate the net barrels measured, the formula used is:
(1) Net = GROSS[l + (l60-TI)(O.O1)(C.E.)](M.F.)
= 100[1 + (10~(0.01)(0.0472)]~1.0026)
(The C.E. figure of .0472 is obtained from the previously
referred to Table 6 of the ASTM).
NET = 100.7332 BBLS.
= 100,733.2 Pulses.
In the Temperature Compensating Totalizer, the following
values are used:
T = -10.0 (Equation 2 applies)
C.E. = 0.0472
M.F. = 1.0026
The output of the
temperature multiplier = (100,000) (10)(0.01) = 10,000 pulses
The output of the
C.E. Multiplier = 10,000 X .0472 = 472 pulses
The output of the ALU = 100,000 + 472 = 100,472 pulses
The output of the M.F. = 100,472 X 1.0026 = 100,733 pulses.
This value corresponds with the result obtained
from Equation 1. At each test point, a counter should show
the calculated values if the system is working correctly.
Example III
Assume:
(a) 100 gross barrels at 1000 pulses/barrel =
` 1007000 pulses;
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10ti5407
(b) 60 API Product at 70F
tQT = +10 and Equation 4 applies)
(c) Meter factor = 0.9987;
(d) C.E. = 0.0621.
Using Equation (4)
(4) Net = M.F. [GRoSS-GRoss(l6o-Tl)(.ol)(c.E.)]
= 0.9987 [1~0,000-100,000(10) (.01)(.0621)
= 99,249.807 Pulses.
Output of Temperature
Multiplier = (100,000) (10)(.01) = 10,000 pulses
Output of the C.E.
Multiplier = (10,000)(0.0621) = 621 pulses
Output of the ALU = 100,000 - 621 = 99,379 pulses
Output of the M.F.
Multiplier = (99,379)(0.9987) = 99,249 pulses
From the foregoina, it may be appreciated that the
system of the present invention permits technically unskilled
operators to quickly and easily test for proper operation of
one or more compensating devices in a measuring circuit using
only simple, inexpensive instruments and without having to
stop the measuring operation of the system. The system is
broken into discrete sections each of which provides a
customary mathematical function. Electrical access points
are provided to the input and output of each section so that
the pulses coming into and leaving each section can be
separately counted. The system is designed to employ digital
signals so that the input and output values of each section
may be directly entered into a mathematical equation without
need for conversion to a different notation.
The check for each section of the system requires
only that the digital values of the inputs and the output
be known over a given period of time. These values are used
in the known mathematical relationship relating the inputs
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~O~S4(~7
of the section to its out~ut to verify proper operation of
the section. In a two input multiplication section, the one
measured input would be manually multiplied by the known
second input to obtain the output value. This output value
must be the s~me as that shown on the output counter if the
section is functioning properly. Where more than one section
is being tested, the input showing on the input counter is
mathematically manipulated in a manner corresponding to the
mathematical functions performed by each included section
using the known input values to these sections. The result
achieved by the manual calculation must correspond with the
values shown on the output counters. Obviously, the figures
may be manipulated for verification against the input counter
value or the value of other inputs such as ~T, C.E. or M.F.
While the two-counter verification system has
been described in a method and as a part of a system for
verifying the proper operation of electrical circuits used
to correct and standardize a volume measurement, the invention
is of broader applicability. Generally speaking, the two-
counter system may be used to test operation of any digitalcomputing circuit of the type in which input data in the
form of an input pulse train is supplied to the circuit input
and pulses are added to or removed from the input pulse train
according to a known formula so that the resulting output pulse
train supplied to the circuit output is representative of the
application of the formula to the input data. To this end,
the input counter is connected to the circuit input and the
output counter is connected to the circuit output. The gating
system described previously ensures simultaneous starting and
stopping of both counters.
In yet another application, the two counters may
be connected to two independent sources of pulse train signals
- 21 -
10~54(~7to determine tl~e relationship between the two sources.
For example, one counter may be connected to a master flow
meter having a known relationship between the number of
pulses produced for a given volume of fluid flowing through
the meter and the second counter may be connected to a meter
which is to be tested against the master meter. If the same
volume of fluid is passed through both meters, both should
produce the same number of pulses. By simultaneously gating
the two counters as fluid flows through a pipeline into which
both meters are connected, the pulse output from each counter
may be determined for the same volume of fluid. The two
pulse counts may be used to obtain a comparative relationship,
or meter factor, for the second meter.
The foregoing disclosure and description of the
invention is illustrative and explanatory thereof, and
various changes in the steps as well as in the details of
the described construction and method may be made within
the scope of the appended claims without departing from the
spirit of the invention. By way of example rather than
limitation, the system components may be rearranged to suit
any requirement. Thus, the meter factor multiplier 22 may
be positioned between the input amplifier and the temperature
multiplier 14. Similarly, while a particular formula or
equation has been given for the circuit system 10, other
formulas may also be employed without departing from the
scope of the present invention. The system could, for example,
be designed to meter gas with the system output being compen-
sated for such things as pressure, temperature, coefficient
of expansion, caloric content and other parameters or varia-
bles. It will also be appreciated that one aspect of themethod and system of the present invention contemplates the
counting of the number of pulses into a given circuit over a
- 22 -
lO~S407selecte~ counting interval and the counting of the number of
pulses out of the same circuit during the same interval.
While two separate counters may be employed for this purpose,
it will be appreciated that the input and/or output signals
may be recorded so that a single counter may be employed
to count the two signals at different times. This may be
effected for example by counting the input while simultan-
eously recording the output and thereafter counting the
output from the recording. The important requirement is
that both counts be taken over the same interval.
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