JPH06281477A - Continuous analysis device - Google Patents

Abstract

PURPOSE:To appropriately correct the variation of a measured value, and also appropriately calibrate a temperature correction factor itself, and thereby obtain an accurate measured value at all times by providing the device with a correction factor calibration means calibrating a temperature correction factor stored in a correction factor memory means. CONSTITUTION:Gas concentration at a gas analysis section 20 or the temperature of sample gas is measured. A temperature sensor 24 also transmits a signal corresponding to the measured temperature to a control section 22. In the control section 22, these signals are converted into digital data by means of amplifiers 23 and 24 and A/D converters 25 and 26 provided for these sensors respectively so as to be inputted to a CPU 28. The CPU 28 consisting of a microcomputer, computes a correct measured value, that is, a corrected measured value from the data of an analysis section by operating on data in accordance with a specified program stored in a memory section 29, so as to output the resultant to an output section 27. In the case of zero-span calibration which is appropriately performed, a temperature correction parameter used for correction at the time of measurement is calibrated. By this constitution, an accurate measured value can thereby be obtained at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various analyzers (for example, continuous gas analyzers, continuous water analyzers, etc.) for continuous measurement in time.

[0002]

2. Description of the Related Art A continuous gas analyzer continuously measures the concentration of various gases such as exhaust gas from a combustion furnace and sampling gas from an atmosphere control furnace (including the case of intermittent measurement at regular intervals). Widely used for. The continuous gas analyzer is a type of gas to be measured (for example, CO, CO
(2, NO, etc.) and various principles and types are used depending on the concentration level, but in many analyzers, the measured value varies depending on the temperature of the sample gas or the temperature of the analysis unit (or sensor). There's a problem. In order to suppress the fluctuation of the measured value due to such temperature, conventionally, (1) the sensor itself for performing the measurement is changed to a sensor with a small temperature change (2) the whole analysis unit is placed in a thermostatic chamber (3) the analysis unit ( Alternatively, a method is used in which the variation of the measured value output with respect to the temperature of the (measured gas) is measured in advance, the correction coefficient and the like are stored in the memory, and the correction coefficient is used during the measurement.

[0003]

The method of (1) above is
Depending on the required measurement level, such a sensor may not exist. The method (2) requires a large heat-retaining tank, a control mechanism for adjusting the temperature, and the like, so that the entire analyzer becomes very large and the cost increases. There is also a problem that it takes time until the temperature of the analysis unit stabilizes. In the method of (3), when the temperature-output characteristic changes depending on each device, the correction coefficient must be calculated for each device, and it corresponds to the case where the device characteristics change over time. There is a problem that you can not.

The present invention has been made to solve such a problem, and an object thereof is to provide a measurement value due to a temperature change of an analysis part or an object to be measured, although it has a simple structure. Change of temperature is corrected properly by temperature correction coefficient,
Moreover, it is an object of the present invention to provide a continuous analysis apparatus capable of always obtaining a correct measurement value by appropriately calibrating the temperature correction coefficient itself in response to individual differences of the analysis apparatus, aging, and the like.

[0005]

As shown in FIG. 1, a continuous analyzer according to the present invention, which has been made to solve the above problems, a) measures an object to be measured and outputs an original measured value. Analysis unit 11, which b) measures the temperature of the analysis unit 11 and outputs a temperature measurement value, c) a correction coefficient storage unit 14 which stores a temperature correction coefficient, and d) a correction coefficient storage unit. Using the temperature correction coefficient stored in 14, the original measurement value output from the analysis unit 11 is corrected based on the temperature measurement value output from the temperature measuring unit 12 to calculate the corrected measurement value. Means 15, and e) a correction coefficient based on the original measurement value output from the analysis unit 11 at the time of measuring the zero-span sample, the temperature measurement value output from the temperature measuring means 12, and the known concentration value of the zero-span sample. Temperature correction member stored in the storage means 14 It is characterized in that it comprises a correction coefficient calibration unit 13 for calibrating.

[0006]

When the measurement is performed by the analysis unit 11, the temperature measuring means 1
2 measures the temperature of the analysis unit 11. The original measurement value output from the analysis unit 11 and the temperature measurement value output from the temperature measurement unit 12 are both input to the analysis value calculation unit 15. The original measurement value output from the analysis unit 11 and the temperature measurement value output from the temperature measurement unit 12 are also sent to the correction coefficient calibration unit 13. The analysis value calculation means 15 is the correction coefficient storage means 1
4, the temperature correction coefficient and the temperature measuring means 12
The original measurement value from the analysis unit 11 is corrected on the basis of the temperature measurement value from the above to calculate a corrected measurement value. The above is the operation during normal measurement.

The correction coefficient calibrating means 13 calibrates the temperature correction coefficient stored in the correction coefficient storing means 14 in the zero-span calibration which is appropriately performed. That is, when the zero gas and the span gas (the standard gas containing the measurement target component having a known concentration at the upper limit of the measurement concentration range), which are gases that do not contain the measurement target component, are appropriately measured by the analysis unit 11, the correction coefficient calibration means 13 Compares the original measurement value output from the analysis unit 11 with a known concentration value (zero gas zero concentration, span gas known concentration), and at that temperature (temperature measured by the temperature measuring means 12) based on the result. Calibrate the temperature correction factor. Further, if necessary, the temperature correction coefficient is calibrated over the entire temperature range.

[0008]

EXAMPLE A continuous gas analyzer according to an example of the present invention will be described with reference to FIGS. As shown in FIG. 2, the continuous gas analyzer of this embodiment is composed of a gas analyzer 20 and a controller 22. The gas analysis unit 20 introduces the sample gas, measures the concentration of the measurement target component (for example, nitric oxide NO gas) contained therein, and sends a signal corresponding to the measured concentration value to the control unit 22. The gas sensor 20 includes a temperature sensor 2
4 is attached to measure the temperature of a concentration sensor (not shown) or sample gas in the gas analysis unit 20. The temperature sensor 24 also sends a signal corresponding to the measured temperature to the control unit 22.

In the control section 22, the amplifiers 23 and 24 and the A / D converters 25 and 26 respectively provided with these signals are provided.
Is converted into digital data (hereinafter, the data obtained by A / D conversion of the signal from the gas analysis unit 20 is referred to as analysis unit data, and the data obtained by A / D conversion of the signal from the temperature sensor 24 is referred to as temperature data). Input to the CPU 28. CPU2
Reference numeral 8 denotes a microcomputer, which performs the following data processing according to a predetermined program stored in the storage unit 29 to calculate a correct measurement value (correction measurement value) from the analysis unit data and output the output unit. To 27.
Further, in the zero / span calibration that is appropriately performed, the temperature correction parameter used for the correction during the measurement is calibrated. The output unit 27 outputs an analog output (DC 0 to 1 V or DC 2 to 20 mA or the like) for recording on a recorder or the like.

The processing performed by the CPU 28 will be described with reference to the flowcharts of FIGS. First, the control unit 22 determines whether the analyzer is currently operating in the measurement mode or the calibration mode by checking the state of the switch in the operation unit 31 or the state of the flag in the storage unit 29. (Step S1). If it is in the measurement mode, the process proceeds to step S2 and thereafter.

In the measurement mode, the CPU 28 first inputs the analysis part data x from the gas analysis part 20 (step S).
At the same time, the temperature data T is input from the temperature sensor 24 (step S3). And the RAM in the storage unit 29
More four parameters for temperature correction a (T), b (T),
By reading out α and β and substituting these values in the following equation, the temperature-corrected measured value (corrected measured value) y
Is calculated (step S4). y = α ・ a (T) ・ f (x) + (b (T) + β) (1)

The meaning of the equation (1) is as follows. The analysis unit data output from the gas analysis unit 20 when measuring a zero gas that does not contain the component to be measured (concentration y = 0) is xa0, and when the sample gas having a concentration y is measured, the gas analysis unit 20 Let xa be the analysis unit data output from. By converting xa−xa0 = x, the difference x between the analysis part data xa and the analysis part data xa0 at the time of zero gas measurement is obtained.
And the relationship between the density y and the difference data x (hereinafter, simply referred to as analysis portion data) is expressed as y = f (x) (2). However, due to the characteristics of the gas analysis unit 20, the measurement value output by the gas analysis unit 20 varies depending on the temperature T even when the gas having the same concentration y is measured. Therefore, the parameters (function of temperature T) a (T) and b (T) for correcting the change in the measured value output due to temperature are introduced into the equation (2) to obtain y = a (T) · f (x ) + B (T) ... (3). These a (T) and b (T) are parameters for the primary temperature correction, and for each temperature T within the temperature range in which this analyzer is used, in the form of a table or a function. Predetermined. Initially, a (T) and b (T) are supplied with initial values by being written in an EEPROM (included in the storage unit 29) when the device is manufactured.
After that, it is appropriately changed at relatively long time intervals in accordance with the individual difference and aging of each analyzer.

Α and β are parameters that do not depend on the temperature T, and are secondary correction parameters used for further finely correcting the temperature correction by a (T) and b (T). That is, until a (T) and b (T) are changed, a (T) and b (of the analyzer at that time are measured every calibration processing described later (that is, at relatively short time intervals). It is used to further correct the deviation from the temperature correction by T). Therefore, equation (1) is updated at relatively long intervals,
Secondary correction parameters α (β) for fine correction in time, which are updated at relatively short intervals, are added to primary correction parameters a (T), b (T) for fine correction in temperature. It is defined as a correction formula with consideration.

The CPU 28 sends the corrected measurement value y calculated in step S4 to the output unit 27 to record it on recording paper or display it on a display. (Step S5). Then, it is judged whether or not all the measurements are completed (step S
6) If not finished yet, return to step S2 to input the next analysis section data x. When all the measurements have been completed, the measurement mode processing ends.

If it is determined in step S1 that the mode is the calibration mode, the process proceeds to step S11 in FIG. 4 and the following calibration process is performed. First, the measurer causes a zero gas and a span gas having a concentration y = ym (known) to flow into the gas analysis unit 20,
Take measurements. The CPU 28 inputs the analysis unit data output from the gas analysis unit 20 as x01 and xm1, respectively, and inputs the temperature value output from the temperature sensor 24 as T1 (step S11). In addition, the primary temperature correction parameters a1 (T) and b1 at the present time stored in the RAM of the storage unit 29.
(T) (function of temperature T) is read (step S12).
By substituting these values into the above equation (3), originally, 0 = a1 (T1) · f (x01) + b1 (T1) ym = a1 (T1) · f (xm1) + b1 (T1) should be obtained. There is (a (T) and b (T) are originally defined to be like this). However, the actual characteristics of the device may be further deviated from the correction by a (T) and b (T) due to individual differences of the analysis device and aging. So C
The PU 28 uses the current temperature correction parameter a1 (T1),
b1 (T1) is left as it is and α
By further introducing the secondary correction parameters of 1 and β1, 0 = {a1 (T1) · α1} · f (x01) + {b1 (T1) + β1} (4) ym = {a1 (T1) · α1 .Alpha.1 and .beta.1 are determined so that f (xm1) + {b1 (T1) +. Beta.1} (5) (step S1
3). As a result, at the present time when zero / span calibration is performed, the above equation (4) that takes into account the secondary correction parameters α1 and β1
Alternatively, the temperature correction according to (5) leads to the most accurate measurement value.

The relationship between the temperature T and a1 (T), b1 (T) and α1, β1 is shown in FIGS. 5 (a) and 5 (b) (however, FIG.
In (a), the functions a1 (T) and b1 (T) are converted into a (T) and b, respectively.
(T).) As shown in FIG.
(T), b (T) (a1 (T), b1 (T)) are (in the form of a table or a function) with respect to the total temperature T in the operating temperature range of the analyzer.
It is set. On the other hand, when the zero gas and the span gas are measured at the temperature T1 as described above and the measured value is calibrated with the true concentration, the temperature correction parameter does not ride on the points a (T1) and b (T1) on the curve, At a place slightly deviated from that, the calibrated temperature correction parameter {a (T1) · α
1} and {b (T1) + β1} are plotted. FIG. 5 shows that only α1 and β1 are extracted and plotted with respect to the temperature T.
It is a graph of (b).

The CPU 28 determines the α thus determined
1 and β1 are stored in the RAM of the storage unit 29 together with the temperature T1 (step S14). It should be noted that the following processing may be introduced here in order to remove the abnormal point of the calibration. That is, first, the CPU 28 displays a graph as shown in FIG. 5A or 5B on the display of the display unit 30. The measurer looks at this graph and sees this calibration point {a1 (T1) ・ α
1}, {b1 (T1) + β1} (or α1, β1) is abnormal, judging from the tendency of each calibration point up to now (whether it is not jumping), and it is an abnormal point. In that case, the operation for removing the point is performed from the operation unit 31.

Next, the CPU 28 makes the primary correction parameter a.
The operator is asked whether or not to update 1 (T) and b1 (T) (step S15). If the operator replies that it is unnecessary, the calibration process ends here. Therefore, in the subsequent measurement modes (see FIG. 3), the R
Using a1 (T), b1 (T) and α1, β1 stored in the AM, the temperature is corrected by the above equation (1), and the corrected measured value is calculated.

When the operator replies in step S15 of the calibration mode (FIG. 4) that the primary correction parameters a1 (T) and b1 (T) are to be updated, the CPU 28 stores αi accumulated since they were last updated. , Βi is examined (step S16). Those numbers (that is, zero since the last time a1 (T) and b1 (T) were updated.
If the number of span calibrations) is less than a predetermined number, the reliability of newly created a2 (T) and b2 (T) will be low, so the CPU 28 determines that updating is inappropriate and The process ends. In step S16, a1 (T), b1
When it is determined that a sufficient number of data of αi and βi for updating (T) are accumulated, a new first-order temperature correction parameter a is obtained by the least square method based on the data αi and βi.
Create 2 (T) and b2 (T). At this time, α =
1 and β = 0 are set (step S17).

[0020]

With the continuous analyzer according to the present invention, the temperature characteristics of the analyzer and the object to be measured which are different for each analyzer and change over time can be accurately grasped by performing the zero-span calibration as appropriate. Since the temperature correction coefficient is calibrated, accurate measurement values are always obtained. Moreover, since the temperature of the measured value can be corrected by simply providing a control unit composed of a microcomputer and an electric circuit without using a large-scale device such as a constant temperature bath, it is possible to reduce the size of the entire device. Can be manufactured at low cost. Further, since it can be applied to any analysis method, it is possible to directly use the optimum analysis method and analysis apparatus according to the measurement target and the required measurement level. The present invention is not limited to the gas analyzer, but can be applied to an apparatus such as a water measuring apparatus that continuously measures any measurement target (including a case where intermittent measurement is performed at regular intervals).

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a block diagram showing the configuration of a continuous gas analyzer which is an embodiment of the present invention.

FIG. 3 is a flowchart of measurement mode processing performed by the continuous gas analyzer according to the embodiment.

FIG. 4 is a flowchart of a calibration mode process performed by the continuous gas analyzer according to the embodiment.

FIG. 5 is a graph showing an example of changes in temperature correction parameters.

[Explanation of symbols]

11 ... Analysis unit 12 ... Temperature measurement means 13 ... Correction coefficient calibration means 14 ... Correction coefficient storage means 15 ... Analysis value calculation means 20 ... Gas analysis section 22 ... Control section 24 ... Temperature sensor 27 ... Output section 28 ... CPU 29 ... Storage Part 30 ... Display part 31 ... Operation part

Claims (1)

[Claims] 1. A) an analysis unit for measuring an object to be measured and outputting an original measurement value; b) a temperature measuring means for measuring the temperature of the analysis unit and outputting the temperature measurement value; and c) temperature correction. The original measurement value output from the analysis unit based on the temperature measurement value output from the temperature measurement means, using the correction coefficient storage unit that stores the coefficient and d) the temperature correction coefficient stored in the correction coefficient storage unit. Analytical value calculation means for correcting the above to calculate a corrected measurement value, and e) the original measurement value output from the analyzer during measurement of the zero-span sample, the temperature measurement value output from the temperature measurement means, and the zero-span sample. A correction coefficient calibration means for calibrating the temperature correction coefficient stored in the correction coefficient storage means on the basis of the known concentration value of the continuous analysis apparatus.