Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
  • G01D3/028—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure
  • G01D3/032—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure affecting incoming signal, e.g. by averaging; gating undesired signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D18/00—Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
  • G06F2218/02—Preprocessing

Definitions

• This invention relates to metrology, and, in particular, to general purpose measuring devices for measuring variable values, and more specifically, to a measuring apparatus, system, method, and program that perform digital calculation or data processing in order to reduce measurement errors.
• the invention can be used to make reference measurements of any measurable quantity.
• a known device for determining the value of a measurement that changes over time is described in certificate of authorship SU 1649460 Al, 5/15/91, G 01 R 19/00, and contains two approximate measurement modules that can give an output signal for the value of the measurement and for three previously set parameters of the same type as the measurement.
• the device can indicate the relationship between the true value of a measurement and the measured value for each of the approximate measurement modules, as well as between the true value of the parameter and the measured value of the parameter for each of the approximate measurement modules in the form of linear relationship with undetermined constant coefficients.
• the device can detect unambiguously determined relationships between the true value of the measurement and the measured value as measured by the approximate measurement modules, by selecting the values of these coefficients.
• the device can also determine the true value of a measurement based on this unambiguously determined relationship.
• the principal disadvantages of the foregoing device are the inadequate precision of the measurements, such that the representation of the relationship between the true and measured values is limited by the linear function, as well as the inadequate universality and undesired complexity of the use of the device, since data on the true values of the parameter (a sample measure), measured with reference-level precision, are required in order to take measurements. A need exists, therefore, to provide a device for reducing measurement errors that does not suffer from the foregoing disadvantages.
• the system comprises plural sensing stations.
• At least a first sensing station comprises a sensor and an indirect measurement module, and detects a measurable physical quantity or phenomenon, such as, e.g., voltage, current, a quantity of liquid flow, or some other measurable physical quantity.
• the station produces a corresponding uncompensated measurement signal representing the detection, varied at least somewhat by an error introduced by the indirect measurement module.
• the system also includes at least a second sensing station that includes an approximate measurement module and another sensor, for preferably measuring either the same type of physical quantity (or parameter) as that measured by the first sensing station or another type of physical quantity that is related to the physical quantity measured by the first sensing station through a predetermined relationship.
• the second sensing station outputs a corresponding uncompensated measurement signal that includes an error resulting from the approximate measurement module.
• a relative error rate of the indirect measurement module preferably is less than a relative error rate of the approximate measurement module.
• the system also comprises a measurement error correction module, having a first input coupled to an output of the approximate measurement module, and a second input coupled to an output of the indirect measurement module.
• the measurement error correction module performs calculations employing one or more mathematical formulas based on a relationship between a variable representing a substantial approximation of the "true" or actual value of the physical quantity being measured and physical measurements made over a predetermined time period.
• the module determines a substantial approximation of the actual, or true, value of a measurement (for at least two instances in time) in accordance with signals received through its first and second inputs.
• the error includes at least a systematic error component A syst and a random error component A rauß d , each of which is determined according to this invention.
• the measurement value module then compensates for error in at least one uncompensated measurement signal outputted by the second sensing station, based on the error determined in the determining. As a result, the measurement value module generates a compensated signal representative of a value that is substantially equal to the value of the actual physical phenomenon that is subjected to detection by the second sensing station.
• Detections made by the first sensing station preferably are separated by greater time intervals than are detections made by the second sensing station. Both sensing stations preferably make detections over a same predetermined time period.
• the output of the measurement error correction module preferably remains unchanged for use by the measurement value module, until a next uncompensated measurement signal is received from the indirect measurement module.
• the sensing stations may be spaced apart from each other, and may even be physically distant from each other, depending on predetermined design criteria, and their measurements can be obtained for use by the method of the invention regardless of the distance between the sensors.
• the system is capable of more universal application than are known measurement correction devices, is less complex than such devices, and is easier to use, especially because, according to one embodiment, at least one of the measurement value module and the measurement error correction module is a modular component.
• FIG. 1 is a block diagram of a system (1) according to a preferred embodiment of this invention, for determining the value of a measurement that changes over time.
• FIG. 2 represents two heterogeneous sets of measurement results employed in a method of the present invention.
• FIG. 3 consisting of FIGS. 3A and 3B, depicts a flow diagram of a method performed according to the present invention.
• FIG. 1 depicts a block diagram of a system (1) according to the present invention, for determining the value of a measurement that changes over time and increasing the measurement's accuracy so that it approximates substantially the actual or "true" value being measured.
• the system (1) comprises a plurality of sensing stations, such as stations (4') and (5') (only two are shown for convenience), and at least one worknode or user station (6').
• sensing station (4') includes a sensor (4) and an approximate measurement module (2)
• sensing station (5') includes a sensor (5) and an indirect measurement module (3).
• the sensor (5) may be spaced apart from the sensor (4), and may even be physically distant therefrom, depending on predetermined design criteria, and their measurements can be obtained for use by the method of the invention regardless of the distance between the sensor (4) and (5).
• the sensors (4) and (5) each provide an output signal in response to detecting a predetermined physical parameter or phenomenon, such as a predetermined type of energy, temperature, liquid, pressure or mass flow, or any other measurable physical quantity.
• the sensors (4) and (5) measure an electrical energy quantity, such as voltage and/or current, at different parts of a same electrical circuit (not shown).
• sensor (5) may be a voltmeter measuring the voltage output of a power generator located in one loop of the electrical circuit, and sensor (4) may be a voltmeter for measuring a voltage in another loop of the circuit powered by the same generator, or vice versa.
• fluid meters with operational precision may be employed to measure the quantity of fluid flow.
• the sensors (4) and (5) can measure different types of parameters that are related through a predetermined relationship, depending on applicable operating criteria.
• the sensor (5) may measure a parameter (e.g., current) that is related to the parameter (e.g., voltage) measured by the sensor (4) through a predetermined functional relationship.
• the present description is made in the context of the sensors (4) and (5) both measuring the same type of electrical energy parameter (e.g., voltage).
• the sensors (4) and (5) make detections and provide corresponding output signals over a same predetermined time period, but at distinct points in time, so that the signals from the sensors (4) and (5) are not eventually received at the user station (6') simultaneously.
• Those signals may be outputted from the sensors (4) and (5) at a same or different frequency, as long as they are outputted at different points in time.
• the user station (6') is able to recognize that the signals originated from those sensors (4) and (5) as opposed to from other sensors (not shown) that may transmit signals over a different time period.
• the interval between measurements taken by the sensor (5) is greater than the interval between measurements taken by the sensor (4).
• the approximate measurement module (2) and the indirect measurement module (3) each represent a separate physical component that undesirably introduces some error quantity into the measurements made by the sensors (4) and (5), respectively.
• the modules (2) and (3) may be A/D converters that introduce an error quantity into the measurements, wherein the error quantity depends on a characteristic error inherent in the respective 5 modules (2) and (3).
• the modules (2) and (3) may be voltage- frequency converters with a counter, although it should be noted that the modules (2) and (3) are not limited only to A D or voltage frequency converting devices.
• the relative error rate (i.e., characteristic error) inherent in the indirect measurement module (3) is less than that of the approximate measurement module (2).
• modules (2) and (3) are depicted as being physically separate from the sensors (4) and (5), respectively, in other embodiments the modules (2) and (3) and sensors (4) and (5), respectively, may be integrally formed.
• their output signals represent the original measurements made by the sensors (4) and (5), 5 respectively, but varied by (plus or minus) an error value corresponding to the characteristic error inherent in the respective modules (2) and (3).
• these output signals are hereinafter referred to as uncompensated parameter measurement signals, and may include random and systematic errors (described below).
• the measurements may vary over time owing to, for example, error fluctuations.O
• the user station (6') may be, e.g., a PC, laptop or other remote personal computer, a personal digital assistant, or the like.
• the user station (6') is communicatively coupled with the modules (2) and (3) through any suitable type of communication link, using, for example, telephone, cable, or other, wireless technologies, and at least part of the cornmunication link may be part of a communication network, such as the Internet (not5 shown) and/or some other network.
• the number and variety of user stations (6') that may be linked with the sensing stations (4') and (5') can vary widely, as can the number of sensing stations (4') and (5') that are employed, depending upon applicable operating criteria.
• the teaching of this invention may be employed in conjunction with any suitable type of user station device that is capable of communicating with other, O sensing components, and which preferably includes one or more user interfaces for enabling a user to input and/or perceive presented (e.g., displayed) information.
• the user station (6') preferably comprises a controller (11 ') and an associated data storage device (9), an output-user interface, such as a display (13), and a user-input interface (6"), all of which are communicatively coupled to the controller (11 ').
• the controller (11 ') controls the overall operation of the user station (6'), and includes, for example, one or more microprocessors and/or logic arrays for performing arithmetic and/or logical operations required for program execution.
• a measurement value module (11) and a measurement error correction module (6) may be included in the controller (11 '), although in other embodiments one or more of the modules (6) and (11) may be separate from the controller (11 ').
• one or both of the modules (6) and (11) are distinct modular components (e.g., microchips) that are adapted for universal application with various types of devices, such as the user station (6'), and those modules (6) and (11) may be included in or be separate from the user station (6').
• the modularity of the components (6) and/or (11) makes them less complex, more universally applicable, and easier to use relative to prior art error correction devices.
• the measurement error correction module (6) has a first input (7) coupled to an output of the approximate measurement module (2), and a second input (8) coupled to an output of the indirect measurement module (3).
• An output of the measurement error correction module (6) is coupled to a first input (10) of the measurement value module (11).
• a second input (12) of the module (11) is coupled to the output of the approximate measurement module (2).
• the module (11) generates output information that is provided to the display (13), which responds to receiving the information by presenting it to a user. Such information, as will be described below, represents a reference measurement value.
• the user-input interface may include, for example, a keyboard, a mouse, a trackball, touch screen, and/or any other suitable type of user-operable input device(s), and the output-user interface may include, for example, a video display, a liquid crystal or other flat panel display, a speaker, a printer, and/or any other suitable type of output device for enabling a user to perceive outputted information, although for convenience, only the display (13) is shown in Fig. 1.
• the data storage device (9) represents one or more associated memories (e.g., disk drives, read-only memories, and/or random access memories), and stores temporary data and instructions, as well as various routines and operating programs that are used by the controller (11 ') for controlling the overall operation of the user station (6').
• the programs stored in the device (9) includes instructions for performing a method in accordance with this invention, to be described below, although in other embodiments at least some of the instructions may be included within the module (6) and/or (11).
• the data storage device (9) preferably also stores data representing uncompensated parameter measurement signal values outputted by the indirect measurement module (3), data representing uncompensated parameter measurement signal values outputted by the approximate measurement module (2), and various other information obtained during performance of the method of the invention to be described below.
• One or more components of the system (1) may conform to various types of technology standards, such as, for example, PXI, VXI, IEEE 1451.4 (TEDS), FIELDBUS technologies, or any other suitable types of technologies.
• PXI PXI
• VXI VXI
• IEEE 1451.4 TMS
• FIELDBUS FIELDBUS technologies
• detections are made by the sensors (4) and (5) in the above-described manner and then, in the illustrated embodiment, their outputs are processed by the respective modules (2) and (3) at block 22.
• the modules (2) and (3) are analog-to-digital converters
• the sensor outputs are A/D-converted by the modules (2) and (3), which, in the present example, introduce an undesired error into those outputs, depending on the characteristic error inherent in the respective modules (2) and (3).
• Uncompensated parameter measurement signals outputted by the modules (2) and (3) are then provided to the user station (6')-
• the controller (I T) responds to receiving the initial signals from the respective modules (2) and (3) by, for example, identifying the sensors from which the received signals originated (by recognizing, for example, a predetermined unique identification code included in the signals), and also recognizing the types and number of the sensors and the type of parameter(s) detected thereby.
• identification and recognition functions may be performed in accordance with any suitable, known identification and recognition technique(s), and will not be described in further detail herein.
• a high-precision error compensation procedure then is performed.
• first values Yi representative ofthe uncompensated parameter measurement signals outputted by the indirect measurement module (3) (over the predetermined time period) and provided to the user station (6'), are stored in data storage device (9) in a first array of such values (block 24).
• the module (6) performs a number of procedures.
• anO arithmetic mean ofthe measurement results is determined.
• the array of first values Yi and the array of second values Y 2 are each subdivided into a first subset and a second subset thereof, wherein, the each subset includes a predetermined number (e.g., five) ofthe respective first or second values.
• the first values ofthe first subset of first values are summed in the equation (F11) and the first values ofthe second subset of 5 first values are summed in equation (Fl 2 ), and each sum is divided by n/2
• « represents the number of first values
• yi represents a first value (originally outputted by module (3))
• Y ⁇ l represents an average ofthe first subset of first values
• Y_ l represents an average ofthe second subset of first values.
• n the number of second values
• yi a second value (originally outputted by module (2))
• Yi represents an average the first subset of second values
• Y2 represents an average ofthe second subset of second values.
• a transpose of Y and 7 can be represented by (F3) below, and a transpose of Yj 2 and Y_ 2 can be represented by (F4) below:
• a ratio fo represents a first general approximation of a multiply-systematic effect in the error in the indirect measurement module as a proportion (fo -1), and essentially is a difference between the averages ofthe second and first subsets of second values to a difference between the averages ofthe second and first subsets of first values.
• the ratio k is determined using the following equation (F5) (preferably the middle portion is employed in the calculation), based on the averages determined above.
• a linear operator 7 representing the sensing station (4') can be represented in matrix form (F6) below, and, based thereon, another form ofthe above formula (F5) can be obtained, as represented by formula (F7) below.
• a "perturbed" form of formula (F7) can be represented as shown in the following expression (10).
• two eigenvalues of linear operator are ⁇ 1>2 ( )
• k ⁇ represents one possible value ofthe approximation ofthe multiply-systematic effect in the error in the indirect measurement module (3) as a proportion (k ⁇ -1); and k ⁇ represents another possible value ofthe approximation of the multiply-systematic effect in the error in the indirect measurement module (3) as a proportion (k -l).
• a multi- valued function (F15), defining the equation of a straight line (disposed at an angle), can be represented by: [0049]
• control passes to block 28 where data obtained based on at least some ofthe foregoing formulas is stored in the data storage device (9). Thereafter, control passes through connector A to block 30 of FIG. 3B.
• a determination is made as to whether k ⁇ or k ⁇ should be selected as being closest to k 0 , using a target function formed using min-max criteria. For example, according to a preferred embodiment ofthe invention, this procedure first includes assignment ofthe required type of function, using expression (F18):
• x t represents ideally the "true" value ofthe measurement (i.e., a substantial approximation thereof);
• ⁇ - is a transformation function representing the sensing station (5');
• i 1 represents measurement values taken by sensing station (5') and stored in device (9);
• Co is a value representing a common (systematic) effect expressed as an additive correction.
• value ⁇ 0 is near zero, and is less than the multiplicative systematic error.
• a constraint zone is formed based on the following formula (F19): where: y t l represents a first value, influenced by kj and k ⁇ (through formulas (F14) and (F15)) (i.e., a signal from the indirect measurement module (3) and stored in device (9); yf represents the second value (i.e., a signal from the approximate measurement module (2) and stored in device (9)); and ⁇ t represents a predetermined error constraint value defining the limit of acceptable yf values.
• the predetermined error constraint value preferably is substantially equal to a predetermined characteristic error inherent in the approximate measurement module (2), although in other embodiments other values may be employed instead, such as, for example, a characteristic error inherent in the module (3).
• the resulting calculated value x t is stored in the device (9) and provided to (or accessed from device (9) by) the measurement value module (11) (block 34). Thereafter, at block 36 the measurement value module (11) uses the result from formula (18) and a second value yf (originating from module (2)) in performing formula (F21) below, to calculate a corresponding error Af, that includes both random and systematic components:
• second value(s) y (originating from the approximate measurement module (2)) preferably are employed rather than first value(s) (originating from the indirect measurement module (3)).
• Those second values may be ones received in real time from sensing station (4'), or, in another embodiment, they may be previously received and/or stored second values, depending on predetermined operating criteria.
• values from the module (3) may be used in formula (F21) instead, depending on the application of interest.
• the random component (ofthe above error), which also is referred to as a random effect, is then calculated by module (11) using equation (F22) (block 36): rand (F22) where: A rand represents the random component; and D AX represents a known mathematical dispersion.
• the module (11) generates corresponding compensated signals 5 that are substantially close in value (or at least closer than the corresponding value outputted from module (2)) to the actual or "true” value ofthe corresponding parameter (phenomenon) subjected to measurement by the sensor (4) (block 42).
• Information outputted from the module (11) represents the compensated signal(s) (as well as a reference magnitude ofthe measured parameter) and is forwarded to the display (13),O which responds to receiving the information by presenting it to the user (block 44).
• the measurements originating from the sensor (4) and provided to the module (2) are corrected to improve their accuracy.
• the calculations preferably also account for this difference as well by converting values derived from a predetermined one ofthe sensors from one format (i.e., current) to another selected format (e.g., voltage), based on the predetermined relationship through which the parameter types are related, so that values ofthe same type are obtained for each sensor (4) and (5) for use in the formulas.
• a predetermined one ofthe sensors from one format (i.e., current) to another selected format (e.g., voltage), based on the predetermined relationship through which the parameter types are related, so that values ofthe same type are obtained for each sensor (4) and (5) for use in the formulas.
• the output from the module (6) to the module (11) is generated only after a signal is applied to the module (6) from the module (3), and the output from module (6) is maintained the same until a next signal received from module (3) is applied to and processed by the module (6) (or the module (6) processes a next subset of values received from module (3), depending on the embodiment employed).
• the signals that are subjected to compensation are the same signals for which the error is determined.
• the signals that are subjected to compensation may be ones that are received at module (11) after the error is determined based on earlier received signals.
• formulas (F21) to (F23) are performed by the module (6) instead ofthe module (11), and the error values determined in those formulas are provided from module (6) to module (11), which then employs them to compensate uncompensated parameter measurement signals.
• the principal problem in increasing the accuracy of processing technical measurements on the basis of mathematical methods of processing the results of measurements is eliminating systematic constituent errors in the measurements, which generally account for more than 90% of total errors in measurement.
• Traditional mathematical methods of processing data examine a set of measurement results as a homogenous aggregation ⁇ , and therefore they do not allow for the reduction of systematic constituent errors without conducting additional highly precise measurements.
• the invention provides a method for obtaining virtual reference measurements based on the use of two (or more) heterogeneous sets of measurement results ( ⁇ l ⁇ 2 in Fig. 2), and on that basis, reduces systematic constituent errors in measurements as well as incidental errors.
• the two heterogeneous sets of measurement results ( ⁇ l ⁇ 2 in Fig. 2) the following can be used, respectively: a set of results of multiple measurements, obtained as the measured parameter changes (decreases or increases) consistently, and a set of a priori information representing the measured parameter at each moment of time of the measurement.
• the method of processing measurements depends on the use of reliable a priori information representing the measured parameter at each moment of time of measurement. Generally, such a priori information is very frequently present in the process of measurement, and if the necessary a priori information about the measured parameter is absent, it can be obtained on the basis of additional measurements that need not be extremely precise. The fact that the accuracy of measurement is elevated to the reference level as a result ensures that a very significant effect is achieved in this case as well.
• a principal idea of a measurement procedure is the transformation of a closed mutually exclusive (isomorphic, as known in abstract algebra) system, "object of measurement — MM", into a unidirectional (homomorphous) system.
• This ideal condition with unidirectional (homomorphous) connections, "object of measurement — MM” corresponds to the true value ofthe measured parameter.
• the actual value of the measured parameter differs from the true value by the size ofthe measurement error.
• s ⁇ and s 21 are the values ofthe measured parameter on the first point ofthe first object of measurement at the moment in time ti and t 2 , respectively, and s 12 ands 22 are the values ofthe measured parameter on the second point ofthe second object of measurement at the moment in time ti and t 2 .
• j ⁇ andj 12 are, for example, direct current voltage values at the moments in time ti and t 2 .
• the linear operator ofthe type represented by expression (3") is a general form of recording conversions of a signal of measuring information in measuring instruments.
• Formula (4" represents a mathematical conversion of coordinates, most frequently used in the process of technical measurements.
• T( ⁇ ) T + ⁇ -T (5") where ⁇ is some small disturbance due to external influencing factors.
• the ambiguity ofthe characteristic values (7") ofthe disturbed operator (6") is manifested in the process of restoring the functional dependence (relationship) according to the results ofthe measurements. Therefore, consider multiple measurements, when the value ofthe physical amount on the object changes (increases or decreases) consistently, or evenly.
• the errors of multiple measurements represents the sum of two components, namely, the incidental component that is symmetrical relative to the true value ofthe measured amount, and the asymmetrical systematic component.
• the incidental component that is symmetrical relative to the true value ofthe measured amount is reduced rather easily by using traditional mathematical methods of processing measurement results, which examine a homogenous set of measurement results, corresponding to a closed mutually exclusive (isomorphic, as known in abstract algebra) system "object of measurement — MM.”
• the set of measurement results As a varying heterogeneous (non-homogeneous) aggregation, corresponding to unidirectional (homomorphous, according to abstract algebra) system "object of measurement — MM.”
• One part ofthe heterogeneous aggregation of measurement results may conditionally correspond to the information (indicators) ofthe object of measurement, and another part to the respective indicators of the means of measurement.
• Such algorithms for processing measurement results transform the system "object of measurement — MM" from a closed mutually-exclusive (isomorphic, in the language of abstract algebra) system into a unidirectional (homomorphous in the language of abstract algebra) system.
• the true value of the measured parameter corresponds to this ideal condition with unidirectional (homomorphous) connections "object of measurement — MM”
• the described information conversion can be considered to be standard, or referential.
• this method of increasing the precision of measurements has the primary features (properties) of a referential standard. These features include invariability, repeatability, comparability, and constancy. All of these features are attained by moving measured values closer to true magnitudes of measured values, due to the unidirectional (homomorphous) nature ofthe connections "object of measurement —
• a principal advantage ofthe method described is that it does not require the use of references to make reference measurements.

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