JPH08201189A - Method for compensating electronic measuring instrument - Google Patents

Abstract

PURPOSE: To constantly obtain a correct differential pressure value regardless of the change in measurement environment by storing compensation data indicating characteristics inherent to a device by constituting an N-dimensional array with a digital signal corresponding to the electrical signal of a sensor as an address. CONSTITUTION: For the title compensation method constitution is made with sensors 3-5, a sensor for obtaining data for compensating the sensors, and an A/D-conversion means 6, a memory means 1 and a digital operation means 2, and further an output interface 7. Further, it is provided with an address where compensation data indicating inherent characteristics which are measured in advance are at equal interval for a digital signal and the interval constitutes an N-dimensional array (N>0) given by the power of 2. The compensation data are subjected to a high-speed operation by an external production computer. To a measurement point, n addresses successively close to the measurement point are referred (n>N) to calculate a true measurement value proportionally. Even if a measurement system is affected by a plurality of environmental variables, an accurate compensation can be made in a small amount of operation time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic measuring device and its compensating method for selectively measuring one of a plurality of physical quantities, and more particularly, to a measuring environment for measuring temperature and static pressure. The present invention relates to a temperature and static pressure effect compensating method and apparatus for an electronic differential pressure transmitter that always obtains a correct differential pressure value regardless of changes.

[0002]

2. Description of the Related Art The following method has been disclosed as a conventional temperature effect compensation method for a differential pressure sensor.

Regression Function Calculation Method The characteristics of the sensor are derived as an approximate function in accordance with a regression model relating to a temperature parameter that is assumed in advance.
The coefficient of the obtained approximate function is stored in the memory means, and at the time of measurement, the differential pressure value is calculated by calculating from the value of the output voltage or the temperature corresponding to each parameter based on the approximate expression.

Similar to the case of the regression table storage method, after deriving an approximate function of the sensor characteristic, each parameter, that is, the output voltage-differential pressure characteristic corresponding to the temperature value is converted into a two-dimensional array related to temperature. The differential pressure value or the correction amount corresponding to the output voltage is read out from the two-dimensional array and stored, and the corrected differential pressure value is output after combining the two values.

However, in both of the two conventional methods, the system in which the output voltage-differential pressure characteristic is influenced by temperature, or the system in which the output voltage-differential pressure characteristic is influenced by parameters other than temperature, that is, the differential pressure value ΔP, the sensor Output voltage E,
The parameter T is effective in the measurement system arranged by the following equation ΔP = f (E, T), but the output voltage −
In a measurement system in which the differential pressure characteristic is affected by a plurality of parameters (environmental variables) at the same time, it is impossible to obtain a sufficiently correct differential pressure value.

[0006]

The present invention is applied to the development of the conventional regression table storing method, and the target measured value y is not a function of only the output signal x of the sensor but a plurality of environmental variables a1 and a2. Even in a complex measurement system affected by the following equation, that is, a measurement system arranged by the following equation y = f (x, a1, a2, ...), it is possible to store the compensation data which is measured in advance and which shows the unique characteristic of the device. A method of compensating an electronic measuring device having a possible array space is provided.

Further, according to the present invention, by producing compensation data which is preliminarily measured and which shows the characteristic characteristic of the apparatus, by an external production computer other than the digital arithmetic means, the time required for manufacturing can be reduced even in the case of performing an advanced regression function approximation. A method of compensating an electronic measuring device that can be shortened.

Further, the present invention is applied to the development of the regression table storage method of the prior art, and the amount of calculation involved in the division when calculating the measured value from the compensation data read from the memory means can be small, and thus the calculation can be performed. The present invention provides a method of compensating an electronic measuring device that requires only a short time.

Further, the present invention is applied to the development of the conventional regression table storage method, and by referring to the compensation data close to the measurement point from the memory means, it is possible to obtain a highly accurate measurement value. A method of compensating an electronic measuring device is provided. Further, the present invention is applied to the development of the conventional regression table storage method, and the target measurement value y is not a function of only the output signal x of the sensor but is influenced by a plurality of environment variables a1, a2 ,. Even in such a measurement system, that is, a measurement system organized by the following equation y = f (x, a1, a2, ...), it is possible to obtain a measurement value with uniform accuracy from the compensation data read from the memory means with a small amount of calculation. The present invention provides a method of compensating an electronic measuring device that can be used.

An object of the present invention is to provide a temperature and static pressure influence compensation method for an electronic differential pressure transmitter that always obtains a correct differential pressure value irrespective of changes in temperature and static pressure related to a measurement environment. Especially.

[0011]

A method of compensating an electronic measuring device according to the present invention comprises a sensor for selectively sensing one of a plurality of physical quantities and converting it into an electric signal. One or more sensors for the purpose of receiving data for compensating the sensor by sensing one or more physical quantities other than the intended physical quantity of the sensor, and A / D conversion means,
Memory means for storing compensation data which has been measured in advance and shows a characteristic peculiar to the device and a calculation procedure, and digital calculation means for calculating the compensation data corresponding to the electric signal of each sensor by referring to the memory means according to the calculation procedure. And an interface for displaying or transmitting the output of the digital operation means, and displaying or transmitting the measured value of the target physical quantity by displaying or converting the measured value into an electric quantity proportional to the measured value. Then, the compensation data stored in the memory means, which is measured in advance and shows the characteristic characteristic of the device, is addressed to a digital signal corresponding to the electric signal of each sensor N (N> 0).
It is configured by means for constructing and storing a dimensional array.

Further, according to the method of compensating the electronic measuring apparatus of the present invention, the digital signal corresponding to the output signal of each sensor measured in advance is read into an external production computer other than the digital calculating means to perform high-level calculation. It is composed of a characteristic means.

Furthermore, the method of compensating an electronic measuring device according to the present invention relates to a digital signal in which compensation data which is measured in advance and which shows an inherent characteristic of the device corresponds to the output signals of all or some of the sensors. It is configured by means having an address having an interval and forming an array in which the interval is given by a power of 2.

Further, the compensation method for the electronic measuring apparatus according to the present invention is characterized in that the compensation data referred to by the memory means have n (n> N) addresses which are successively closer to the measurement point. It is configured by means for

Further, in the compensating method for the electronic measuring apparatus according to the present invention, the digital signals a1, a2, ..., Ak, ..., AN corresponding to the output signals of the respective sensors obtained at the time of measurement are provided.
Is each address section (a1 _i , a1 _{i + 1} ) of the array, (a
2 _j , a2 _{j + 1} ), ..., (ak _m , ak _{m + 1} ), ..., (aN _z ,
aN _{z + 1} ) when given in the middle, it is constituted by means for proportionally calculating the target true measured value f (a1, a2, ..., Ak, ..., AN).

[0016]

According to the present invention, the compensation data which is measured in advance and shows the characteristic characteristic of the device is stored in the form of an N (N> 0) -dimensional array whose address is the digital signal corresponding to the electric signal of each sensor. By doing so, the address corresponding to the electric signal of each sensor obtained at the time of measurement can be searched and the compensation data can be referred to from the memory means, so that highly accurate measurement can be realized.

Since the digital signals corresponding to the output signals of the respective sensors measured in advance are read into an external production computer other than the digital arithmetic means and the arithmetic operations are performed, the time required for manufacturing is shortened.

The compensation data, which is measured in advance and shows the characteristic characteristic of the device, has addresses at equal intervals with respect to digital signals corresponding to the output signals of all or some of the sensors, and the intervals are powers of two. Therefore, the division in calculating the measurement value can be done by bit shifting, and the amount of calculation can be small. The number n of compensation data to be searched for the measurement point can be selected within a range satisfying n> N in consideration of the balance between the measurement accuracy and the calculation amount.

[0019]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the input / output characteristics of a measurement system including a semiconductor strain gauge and outlining the influence of temperature and static pressure. It is assumed that an electronic differential pressure transmitter that uses a semiconductor strain gauge as a differential pressure detecting means is configured as shown in FIG. In the figure, the differential pressure, temperature, and static pressure, which are physical quantities, are sensed by the differential pressure sensor 3, the temperature sensor 5, and the static pressure sensor 4, respectively, and an electric signal corresponding to the strength is output.
The multiplexer 8 switches and inputs the electric signal of each sensor for each unit time, thereby enabling the pair of PGA 9 and the A / D converter 6 to perform amplification and A / D conversion. Further, the PGA 9 does not include elements such as a variable resistor and a variable capacitor that require adjustment, but the amplification degree can be fixed by the signal of the microprocessor 2. The differential pressure signal, the temperature signal, and the static pressure signal digitized by the A / D converter are input to an arithmetic processing unit whose main part is a microprocessor.
The arithmetic processing unit comprises a volatile memory 1 and a non-volatile memory 1'in addition to the microprocessor 2, and the output signal of the arithmetic is
The result is displayed by the output interface 7 or converted into an electric signal and transmitted to the outside.

With such a configuration, when the input / output characteristics peculiar to each of the measurement systems including the semiconductor strain gauge are shown in the schematic diagram of FIG. 1, for example, at each measurement point (E, T,
The measurement data corresponding to P) shall be collected as indicated by triangles. In the figure, the differential pressure signal is the E axis, the temperature signal is the T axis,
The static pressure signal is taken on the P axis, and the functional system with E, T, P as the domain and ΔP as the range, that is, the following equation ΔP = f (E, T, P)
Represents the characteristics organized into. Usually, the number of actual measurement points is not so large, so the measurement data between adjacent measurement points are m-order polynomial, sine function, exponential function,
Function approximation is performed by the least squares method or the spline function approximation method that uses a logarithmic function as a regression function. However, since this calculation requires a large amount of calculation, the measurement data is taken out of the measurement system and shown in FIG. The calculation is performed using a production computer other than the calculation processing device. Using the obtained regression function, the measurement data corresponding to the equidistant measurement points are reconstructed and arranged in the form of the array shown in FIG. 3 or 4. Now, the array of compensation data showing the unique characteristics of the device thus created is stored in the non-volatile memory 1'of the arithmetic processing device, and the digitized differential pressure signal E and temperature signal T read at the time of measurement. , The compensation data f (E _i , E _i , T _j , P _k ) corresponding to the measurement points (E _i , T _j , P _k ) close to the static pressure signal P
T _j , P _k ) can be read.

However, since the number of stored compensation data is finite and discrete, the measurement data corresponding to an arbitrary measurement point must be linearly approximated by an arithmetic processing unit and interpolated. An example of the interpolation method will be described below with reference to FIG. The array of compensation data to be stored in advance in the non-volatile memory is the measurement point (E, T, P) when the regression function that approximates the measurement data is used.
Regarding one of the three environment variables, the measurement data for the measurement points (E, T, P) that were translated by 1/2 interval for the other two environment variables were calculated, and the figure was calculated. An array of compensation data is created as shown in the schematic diagram of FIG. However, FIG. 3 is based on the following equation.

[0022]

[Equation 2]

When the differential pressure signal E ', the temperature signal T', and the static pressure signal P'are obtained at the time of measurement,

[0024]

[Number 3] _{E i <E '<E i} + 1 / 2ΔE T j <T'<T j + 1 / 2ΔT P k <P '<P k + 1 = P k + ΔP ... meet the (number 3) E _i, By searching T _j and P _k , six adjacent compensation data dP1 = f (E _i , T _j , P _k ), dP2 = f (E _{i + 1} , T _j , P _k ), dP3 = f (E _i , T _{j + 1} , P _k ), dP4 = f (E _i + 1 / 2ΔE, T _j + 1 / 2ΔT,
P _{k + 1} ), dP5 = f (E _i −1 / 2ΔE, T _j + 1 / 2ΔT,
P _{k + 1} ), dP6 = f (E _i + 1 / 2ΔE, T _j −1 / 2ΔT,
P _{k + 1} ) is referenced from the non-volatile memory and read out to the arithmetic processing unit. The arithmetic processing unit performs arithmetic operation according to the following equation to obtain corrected measurement data f (E ', T', P ').

[0025]

Equation 4] a = dP1 + (dP2-dP1 ) (E'-E i) / ΔE + (dP3-dP1) (T'-T j) / ΔT b = dP4 + (dP5-dP4) (E'-E i - 1 / 2ΔE) / ΔE + ( dP6-dP4) (T'-T j -1 / 2ΔT) / ΔT f (E ', T', P ') = a + (b-a) (P'-P k) / ΔP (Equation 4) The true differential pressure value dP = f (E ′, T ′,
P ') is displayed by the output interface or converted into a certain electric signal and transmitted outside the measurement system.

Although the embodiment in which N = 3 and n = 6 has been described above, an example in which the interpolation method is different will be described with reference to FIG.

The array of compensation data stored in advance in the non-volatile memory is such that the measurement data for the measurement points (E, T, P) are equidistant with respect to each environmental variable when the measurement data is constructed using a regression function that approximates the measurement data. To calculate an array of compensation data as shown in the schematic diagram of FIG. However, FIG. 4 is based on the following equation.

[0028]

(Equation 5)

When the differential pressure signal E ', the temperature signal T', and the static pressure signal P'are obtained at the time of measurement,

[0030]

E _i <E ′ <E _{i + 1} = E _i + ΔE T _j <T ′ <T _{j + 1} = T _j + ΔT P _k <P ′ <P _{k + 1} = P _k + ΔP (Equation 6 ), E _i , T _j , P _k that satisfy the above condition are searched, and four adjacent compensation data dP1 = f (E _i , T _j , P _k ), dP2 = f (E _{i + 1} ,
T _j , P _k ), dP3 = f (E _i , T _{j + 1} , P _k ), dP4 =
f (E _i , T _j , P _{k + 1} ) is referenced from the non-volatile memory and read out to the arithmetic processing unit. The arithmetic processing unit performs arithmetic operation according to the following equation to obtain corrected measurement data f (E ', T', P ').

[0031]

Equation 7] f (E ', T', P ') = dP1 + (dP2-dP1) (E'-E i) / ΔE + (dP3-dP1) (T'-T j) / ΔT + (dP4- dP1) (P′−P _k ) / ΔP (Equation 7) The true differential pressure value dP = f (E ′, T ′,
P ') is displayed by the output interface or converted into a certain electric signal and transmitted outside the measurement system.

Although the respective embodiments have been described above, the present invention is not limited thereto and can be variously modified and carried out without departing from the scope of the invention.

[0033]

In the compensation method for the electronic measuring device according to the present invention, since the compensation data obtained by performing the measurement in advance can form and store a multidimensional array, each compensation data obtained at the time of measurement can be obtained. The compensation data corresponding to the electric signal of the sensor can be referred from the memory means, and highly accurate measurement can be realized. The input / output data of each sensor measured in advance is read into the external production computer and the calculation is performed, so that the time required for manufacturing can be shortened. In addition, since the compensation data can be configured by performing an advanced calculation with an external production computer, the calculation time for calculating the measurement value is short by selecting the conditions that optimize the accuracy and the amount of calculation during measurement. However, highly accurate measurement values can be obtained. The number n of addresses searched for the measurement point is n
Since it can be selected within the range that satisfies> N, the optimum condition can be selected in consideration of the accuracy at the time of measurement and the amount of calculation.

Therefore, in a system for selectively measuring a certain physical quantity, it is possible to realize an electronic measuring device capable of highly accurate correction in a short calculation time even when the measurement system is affected by a plurality of environmental variables. You can

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an output voltage-differential pressure characteristic of a semiconductor strain gauge.

FIG. 2 is a block diagram showing a process of compensating for temperature and static pressure effects of a semiconductor strain gauge.

FIG. 3 is an explanatory diagram showing an example of a procedure for calculating a differential pressure value from compensation data.

FIG. 4 is an explanatory diagram showing an example of a procedure for calculating a differential pressure value from compensation data.

[Explanation of symbols]

1, 1 '... memory means, 2 ... digital arithmetic means, 3 ... differential pressure sensor, 4 ... static pressure sensor, 5 ... temperature sensor, 6 ... A /
D converter, 7 ... Output interface, 8 ... Multiplexer, 9 ... PGA.

Claims (5)

[Claims] 1. A sensor intended to selectively sense one of a plurality of physical quantities and convert it into an electric signal.
One or more sensors for the purpose of obtaining data for compensating the sensor by receiving one or more physical quantities other than the intended physical quantity of the sensor, A / D conversion means, and a characteristic of the device that is measured in advance. Memory means for storing compensation data indicating the characteristics of and a calculation procedure, and digital calculation means for calculating the compensation data corresponding to the electric signal of each sensor by referring to the memory means according to the calculation procedure.
In a method of compensating an electronic measuring device, comprising: an interface for displaying or transmitting the output of the digital operation means, the compensation data stored in the memory means and indicating the characteristic peculiar to the device, is A compensating method for an electronic measuring apparatus, characterized in that an N (N> 0) -dimensional array having a digital signal corresponding to an electric signal of a sensor as an address is configured and stored. 2. The compensation data according to claim 1, which is preliminarily measured and shows the characteristic peculiar to the device, reads a digital signal corresponding to an output signal of each sensor, which is preliminarily measured, into an external production computer other than the digital arithmetic means, A method for compensating an electronic measuring device, which is created by performing an appropriate calculation. 3. The compensation data according to claim 1 or 2, which is preliminarily measured and which shows the characteristic characteristic of the device, has an address which is equidistant with respect to the digital signals corresponding to the output signals of all or some of the sensors. A method of compensating for an electronic measuring device having an array, the spacing of which is given as a power of 2. 4. The compensation data read according to the electric signal of each sensor obtained at the time of measurement from the memory means according to claim 1, 2 or 3, and n (n) > N) A method for compensating an electronic measuring device which retrieves and reads from the memory means to the digital operation means. 5. The digital calculation means according to claim 1, 2, 3 or 4, wherein the digital signals a1, a2, ..., A corresponding to the output signal of each sensor obtained at the time of measurement.
k, ..., aN are address sections (a1 _i , a
1 _{i + 1} ), (a2 _j , a2 _{j + 1} ), ..., (ak _m , a
k _{m + 1} ), ..., (aN _z , aN _{z + 1} ) when given in the middle, the true measured value f (a1, a2, ..., a) of interest
k, ..., aN) can be expressed by the following equation: Compensation method for an electronic measuring device that calculates according to.