GB1576274A

GB1576274A - Method and apparatus for determining or testing relationship between pulse trains

Info

Publication number: GB1576274A
Application number: GB473477A
Authority: GB
Original assignee: Mirdadian M K
Current assignee: Mirdadian M K
Priority date: 1977-02-04
Filing date: 1977-02-04
Publication date: 1980-10-08

Description

(54) METHOD AND APPARATUS FOR DETERMINING OR TESTING RELA TIONSHIP BETWEEN PULSE TRAINS (71) I, MOHAMMAD KIAN MIRDADIAN, a citizen of Iran, of 7015 Atwell, Houston, Harris County, Texas 77036, United States of America, do hereby declare the invention, for which I pray that a Patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to apparatus and methods for simultaneously obtaining pulse counts from first and second electrical pulse trains in order to determine or test a relationship existing between the two pulse trains. The invention has particular utility in connection with fluid flow rate measurements.

Many known systems for measuring fluid flow in a flowline are capable of automatically compensating for changes in various parameters 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 60 F and atmospheric pressure at sea level.

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 flow-meters are generally of the type which generate a series of pulses at a frequency which is representa tive of flow rate. An output device counts the pulses to determine the flow 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 flow-meter. The output device counts the number of resulting pulses to provide a temperature standardized value for s r A l

PATENTS ACT, 1949 SPECIFICATION NO. 1576274 The following corrections were allowed under Section 76 on 21 January 1981.

Page 2, line 24, for vaiable read variable Page 8, line 33, aster time delete and insert the Page 9, line 36, for relationsup read relationship Page 9, line 38, zlelete whole line insert NET = GROSS [I + (60-T) (. 01) (C. E.)] M. F. where: THE PATENT Bas 86'~'93J1 lao October 1981 (54) METHOD AND APPARATUS FOR DETERMINING OR TESTING RELA TIONSHIP BETWEEN PULSE TRAINS (71) I, MOHAMMAD KIAN MIRDADIAN, a citizen of Iran, of 7015 Atwell, Houston, Harris County, Texas 77036, United States of America, do hereby declare the invention, for which I pray that a Patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to apparatus and methods for simultaneously obtaining pulse counts from first and second electrical pulse trains in order to determine or test a relationship existing between the two pulse trains. The invention has particular utility in connection with fluid flow rate measurements.

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 flow-meters are generally of the type which generate a series of pulses at a frequency which is representative of flow rate. An output device counts the pulses to determine the flow 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 flow-meter. 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 frequenct 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 frequency 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 pulses 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 relative 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 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.

According to the present invention, there is provided apparatus for simultaneously obtain ing pulse counts from means producing first and second electrical pulse trains, comprising a circuit responsive to an input quantity to generate the first and second pulse trains with relative rates established by the said circuit, first and second counters arranged to count the pulses in the first and second pulse trains respectively, gating means actuatable at random and controlling both counters so as, in operation, to simultaneously start the counting operation of the first and second counters, and to simultaneously stop the counting operation of the first and second counters, and display means for displaying the accumulated counts in the first and second counters when the counting operations have been simultaneously stopped.

The apparatus may further comprise a pulse train source, and wherein the said circuit is a processing circuit operative on the pulse train from the source to perform a plurality of processing operations upon the pulse train, thereby to produce pulse trains having different rates at each of a plurality of at least three points in the processing circuit, and means for selectively connecting the input of each said counter to different selected ones of the said points.

The apparatus permits a 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 apparatus can be easily tailored to suit specialized applications.

In one embodiment, the pulse train source is a metering device providing pulses at a rate indicative of the rate of flow of a fluid and the processing circuit includes compensating means responsive to a measured parameter to modify the pulse rate in dependence upon the value of the parameter, the measured parameter being temperature, for example, or pressure.

Devices can be provided for setting in digital values, e. g. coefficient of thermal expansion, meter factor, the pulse rate being modifie in dependence upon the digital values. However, when the same fluid is always flowing through the line, there is no need to correct for a vaiable coefficient of expansion and this circuit and its function may be removed without reengineering the system. Other functions, such as pressure compensation, may just as simply be added without need for extensive design changes.

While the invention will be described below in conjunction with a temperature compensation circuit, it will be appreciated that it may also be used with other digital calculating circuits having known functional relationships between pulse trains.

The apparatus may also be used for determining the meter factor of a metering device, wherein the said circuit comprises the metering device and a standard measuring device, the first counter is arranged to count electrical pulses generated in response to the metering device functioning in a measuring operation and the second counter is arranged to count electrical pulses generated in response to the standard measuring device functioning in a measuring operation whereby the displayed counts are indicative of the meter factor.

The invention also provides a method of testing to obtain a meter factor for a meter device, which provides a pulse output, comprising the steps of using the meter device and a standard measuring means, to measure the same physical quantity, counting pulses from the meter device and the standard measuring means in first and second counters respectively, simultaneously gating the first and second counters to start them counting simultaneously and subsequently to stop them counting simultaneously and determining the ratio of the number of electrical pulses counted by the second counter to the number of electrical pulses counted by the first counter.

The invention still further provides a method of testing the 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 and pulses are added to or removed from the input pulse train, according to a relationship characteristic of the digital computing circuit, to form an output pulse train, comprising the steps of connecting a first electrical pulse counter to the circuit input and a second electrical pulse counter to the circuit output for respectively counting the pulses into and out of the circuit, starting and stopping the counting operations of the first and second counters simultaneously so that both counters count over the same interval, and comparing the count values in the first and second counters to determine whether or not they are consistent with the said characteristic relationship.

The apparatus can be used without interrupting normal metering operations. Thus, no shut-down time is required to test the equipment.

The pulse streams preferably contain 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 to suppress noise spikes. 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.

The processing circuit can include binary rate multipliers for modifying pulse frequencies.

Because of the continuous nature of the modification, a large number of binary rate multipliers may be included without unduly increasing the output frequency of the pulse train and without altering the square wave form of the signal.

An embodiment of the invention is illustrated in the block diagram constituting the sole Figure of the accompanying drawing and will now be described by way of example.

The illustrated apparatus 10 is used for measuring the volume of fluid flowing in a flowline 11, standardizing the measurement to a selected value of temperature and correcting for abnormalities in the metering device. The apparatus includes a conventional flowmeter 12 which may be a turbine meter or positive displacement meter or any other suitable metering 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 incremen- tal 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 electrically 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 temper- ature (AT) 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 standard temperature. Any suitable conventional means may be employed for the conditioner 16. In the illustrated embodiment, the reference temperature is 60 F which is the temperature used in the oil industry as a standard for volume measurements.

The signal condition 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, the amplitude of which is representative of the magnitude of the change in temperature (AT) from the reference temperature of 60 F. 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 AT signal from the signal conditioner 16 to a BCD AT signal which is supplied by a conductor 17a to the temperature multiplier unit 14 and to a AT 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 AT 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 60 F, the temperature display 18a would indicate 0 F, ; at 125 F, +65 F would be displayed and at 0 F,-60 F 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 AT 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 AT value is multiplied with the flowmeter pulse train signal on line 13a.

The resulting output signal from the multiplier 14 is a digital, temperature-compensated, square wave pulse train representative of the flowmeter signal value multiplied by the BCD AT signal value. The multiplier circuit 14 is similar to other multiplier circuits 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: Po = P, AT (0. 01) where: Po = the number of pulses in the output pulse train over a selected interval; P, = the number of pulses in the input pulse train over the same interval; and AT = 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 (AT) employed 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 operation 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 volume reading for the system 10 requires that the coefficient of I M. 3 t-, '-l,---±T) iiQ r-rNoff ; rii-nt in (i the temr) er- ature 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 adjust for the coefficient of expansion of the particular fluid being metered. The 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 multiplier 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 19a. 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 conventional arithmetic logic unit (ALU) 21 by a conductor 19a. A test point C is electrically connected with the output line 19a.

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 AT, 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 AT, 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 meter factor is determined by dividing: (a) the number of pulses P (1) actuall 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 registered 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 10 may be of great economic importance, a verification circuit 24 is included in the system 10 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 10 or across one or more of the multipliers in the system. Thus to check multiplier 14, the switches 27a, 27b are set to switch position 3; to check multiplier 19, they are set to position 4 ; to check multipliers 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. 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 avoided since the gate pulse generated from the closing (or opening) of a mechanical switch may have a high frequency noise component 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 customarily provided with an electrical circuit for producing a clean gate pulse following actuation of a mechanical switch, the gate pulses derived in this way 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.

In contrast to this, the described apparatus has means for initiating or stopping the count in counters 25 and 26 with the very same gate pulse, such that 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 may be employed in the circuit 10. The meter multipliers, ALU unit, counters, scaler, register and other circuits and devices described with reference to the present invention are conventional in themselves.

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 additional 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) (0.01) (C. E.) J (M. F.) 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|) (0.01) (C. E.)] for T < 60 F ; and (3) NET = (M. F.) (GROSS) for T = 60 F ; and (4) NET = M. F. [GROSS-GROSS (| 60-T|) (0.01) (C. E.)] for T > 60 F Referring to the system functional diagram 10, the fluid temperature is transmitted to the signal conditioner 16 where it is linearized and subtracted from a 60 F reference. The output signal on line 16a is a voltage proportional to l 60-Tl. The signal conditioner also determines whether the temperature is greater or less than 60 F and 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 60 F (AT) and converts the voltage signal to a three digit Binary Coded Decimal (BCD) number. The conversion 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 function, a 3-digit digital display 18a with sign, is provided to monitor AT. 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 (AT) (. 01) in BCD form. Since this is a digital multiplication, the product is represented by a serial pulse train. multiplied by. 01 by shifting the decimal point two places to the left therefore the input to the temperature multiplier is 0.456. For 1000 input pulses, 456 pulses are gated out of the multiplier 14 representing the product of (gross pulses) (AT) (. 01). An operator attempting to verify that the system is operating correctly may permit the input counter connected to point A to count to 1000. Knowingthat ATis +45.6 F (by simply reading the display 18a), the operator may manually multiply (1000) (45.6) (. 01) to obtain 456. If the unit 14 is functioning correctly, the output counter should read 456. By taking a manual temperature reading and calculating AT, 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 19a 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 AT. 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 consider the following Examples: Example 11 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 40 API ; (c) the fluid temperature is 50 F ; and (d) the meter factor is 1.0026.

To calculate the net barrels measured, the formula used is : (1) Net = GROSS [1 + (60-T|) (0.01) (C. E.)] (M. F.) = 100 [1 + (10) 0. 01) (). 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 Pules.

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 1000pulses/barrel = 100,000 pulses; (b) 60 API Product at 70 F (AT = +10 and Equation 4 applies) (c) Meter factor = 0.9987; (d) C. E. = 0.0621.

Using Equation (4) = 0. 9987 [100, 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 foregoing, it may be appreciated that the system of the present invention permits technically inskilled 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 known mathematical relationship relating the inputs of the section to its output 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 same 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 AT, 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 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 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 to determine the 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 '---''- < -'"tc : nt) ifftn !)'. nf the described construction

Claims

and method may be made within the scope of the appended claims. 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 formulae 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 compensated for such things as pressure, temperature, coefficient of expansion, caloric content and other parameters or variables.

WHAT I CLAIM IS :- 1. Apparatus for simultaneously obtaining pulse counts from means producing first and second electrical pulse trains, comprising a circuit responsive to an input quantity to generate the first and second pulse trains with relative rates established by the said circuit, first and second counters arranged to count the pulses in the first and second pulse trains respectively, gating means actuatable at random and controlling both counters so as, in operation, to simultaneously start the counting operation of the first and second counters, and to simultaneously stop the counting operation of the first and second counters, and display means for displaying the accumulated counts in the first and second counters when the counting operations have been simultaneously stopped.
2. Apparatus according to claim 1, wherein the first and second counters include means responsive to electrical gate pulses for starting their counting operation and the gating means includes a gate delay circuit which is actuatable to provide fixed length electrical gate pulses to the first and second counters.
3. Apparatus according to claim 2, wherein the gating means for simultaneously applying the same gate pulse to both the first and second counters for ensuring simultaneous starting of both counters.
4. Apparatus according to claim 2, wherein the first and second counters include means responsive to electrical gate pulses for stopping their counting operations and the gating means includes means for simultaneously applying the same gate pulse to both the first and second counters for ensuring simultaneous starting and stopping of both counters.
5. Apparatus according to any preceding claims, wherein the gating means includes a momentary pull-down circuit operable upon actuation of a mechanical switch, and independent of the length of time and switch remains actuated, for providing a fixed duration electrical pulse for activating the gating means.
6. Apparatus according to any of claims 1 to 5, further including reset means for resetting the counts in the counters to zero.
7. Apparatus according to any preceding claim, for determining the meter factor of a metering device, wherein the said circuit comprises the metering device and a standard measuring device, the'first counter is arranged to count electrical pulses generated in response to the metering device functioning in a measuring operation and the second counter is arranged to count electrical pulses generated in response to the standard measuring device functioning in a measuring operation whereby the displayed counts are indicative of the meter factor.
8. Apparatus according to claim 7, wherein the standard measuring device is a master meter calibrated to determine its meter factor.
9. Apparatus according to claim 7 or 8, wherein the metering device is a fluid flow meter installed on a pipeline for measuring fluid flow therethrough, and the standard measuring device is connected in series with the fluid flow meter on the pipeline for so determining the meter factor.
10. Apparatus according to claim 7 or 8, wherein said metering device is a fluid flow meter, installed on a pipeline for measuring fluid flow therethrough.
11. Apparatus according to any of claims 1 to 6, comprising a pulse train source, and wherein the said circuit is a processing circuit operative on the pulse train from the source to perform a plurality of processing operations upon the pulse train, thereby to produce pulse trains having different rates at each of a plurality of at least three points in the processing circuit, and means for selectively connecting the input of each said counter to different selected ones of the said points.
12. Apparatus according to claim 11, wherein the pulse train source is a metering device providing pulses at a rate indicative of the rate of flow of a fluid and the processing circuit includes compensating means responsive to a measured parameter to modify the pulse rate in dependence upon the value of the parameter.
13. Apparatus according to claim 12, wherein the compensating means is responsive to measured temperature of the fluid.
14. Apparatus according to claim 11, 12 or 13, wherein the processing circuit includes at least one device for setting in a digital value and means for modifying the pulse rate in denendence tir) the nr pnrh dicntn) vr)))) p
15. Apparatus according to claim 14, insofar as dependent on claim 12, wherein the or a said device is calibrated for setting in the coefficient of thermal expansion of the fluid.
16. Apparatus according to claim 14 or 15, wherein the or a said device is calibrated for setting in a meter scale factor.
17. Apparatus according to any of claims 1 to 6, wherein the said circuit comprises a digital computing circuit of the type in which pulses are added to or removed from an input pulse train, according to a relationship characteristic of the digital computing circuit, and wherein the first pulse train is the input pulse train to the digital computing circuit and the second pulse train is the output pulse train from the digital computing circuit.
18. Apparatus according to claim 17, wherein the computing circuit includes a plurality of individual subcircuits which perform individual operations, the apparatus comprising means for selectively connecting the input and output of individual subcircuits to the first and second counters.
19. Apparatus for measuring fluid volume, comprising apparatus according to claim 17 or 18 and metering means for forming the input electrical pulse train, in which the number of pulses in the signal is representative of the volume of fluid being measured.
20. Apparatus according to claim 19, wherein the computing circuit includes compensating input means for changing the said relationship in accordance with the value of one or more variables affecting the number of pulses in the input pulse train.
21. Apparatus according to claim 20, wherein the compensating input means includes binary coded decimal input means for supplying the variables to the computing circuit in BCD form.
22. Apparatus according to claim 20 or 21, including temperature measuring means for making a temperature measurement of the fluid being measured by the metering means and temperature conversion means for supplying the temperature measurement information to the computing circuit in binary coded decimal form as one of the variables.
23. Apparatus according to claim 22, further including a visual display device supplied with said BCD temperature information for forming a digital display of the value of the temperature measurement.
24. Apparatus according to claim 21,22 or 23, wherein the BCD input means includes means for supplying the coefficient of expansion of the fluid being measured by the meter means as one of the variables.
25. Apparatus according to claim 21,22,23 or 24, wherein the BCD input means includes means for supplying the meter factor value required to correct for meter error in the metering means as one of the variables.
26. Apparatus according to claim 25, wherein the characteristic relations up is representable as follows: NET = GROSS 1 + (60-T) (. 01) (C. E.) M. F. where: NET = the number of pulses in said second pulse train corrected for temperature and meter factor effects; GROSS = the number of pulses in said first pulse train obtained from said metering means; T = the temperature of the measured fluid in degrees Fahrenheit; C. E. = the coefficient of expansion for the measured fluid in percent per degree Fahrenheit; and M. F. = the meter factor of the metering means.
27. A method of testing to obtain a meter factor for a meter device, which provides a pulse output, comprising the steps of using the meter device and a standard measuring means to measure the same physical quantity, counting pulses from the meter device and the standard measuring means in first and second counters respectively, simultaneously gating the first and second counters to start them counting simultaneously and subsequently to stop them counting simultaneously, and determining the ratio of the number of electrical pulses counted by the second counter to the number of electrical pulses counted by the first counter.
28. A method according to claim 27, further comprising the step of multiplying the said ratio by the meter factor of the standard measuring means.
29. A method according to claim 27 or 28, wherein the meter device is a fluid flow meter installed to measure fluid flow along a pipeline, and the standard measuring means is a master meter installed in-line along the pipeline.
30. A method of testing the 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 and pulses are added to or removed from the input pulse train, according to a relationship characteristic of the digital computing circuit, to form an output pulse train, comprising the steps of connecting a first electrical pulse counter to the circuit input and a second electrical pulse counter to the circuit output for respectively counting the pulses into and out of the circuit, starting and stopping

1. 1"*----1----, 4 n thqt hoth coiinters count over the same interval, and comparing the count values in the first and second counters to determine whether or not they are consistent with the said characteristic relationship.
31. A method according to claim 30, wherein the same gate pulse is applied to the first and second counters for starting the counting operation of both counters and the same gate pulse is applied to the first and second counters for stopping the counting operation of both counters.
32. A method according to claim 30 or 31, wherein the circuit includes a plurality of individual sub-circuits which perform individual operations, including the steps of selectively connecting the input and output of individual sub-circuits to the first and second counters to count the pulses going into and coming out of such sub-circuits and employing the count values in said first and second counters for variable values to determine if the individual sub-circuits are operating according to the individual operations characteristic thereof.
33. Apparatus according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.