JP6858655B2 - How to adjust the calibrator - Google Patents

Description

The present invention relates to a method of adjusting a calibrator for calibrating a converter of an electromagnetic flowmeter.

The electromagnetic flow meter is, for example, a device provided with a detector and a converter and capable of measuring the flow velocity, flow rate, etc. of a fluid. The electromagnetic flowmeter includes a detector and a transducer. The detector generates a magnetic field in the measuring tube through which the fluid passes, and outputs a signal based on the electromotive force generated by the passage of the fluid. The converter performs a process of converting into a flow rate value or the like based on the signal output by the detector.

FIG. 4 is a diagram illustrating calibration of the electromagnetic flowmeter. In the electromagnetic flowmeter as described above, the calibrator 600 is used when calibrating the input / output of the converter such as gain adjustment and current output adjustment (see, for example, Patent Document 1). The calibrator 600 is, for example, a device capable of generating a reference flow rate signal, which is a signal of a voltage waveform corresponding to a reference flow rate, in a pseudo manner according to an exciting current from a detector. At this time, for example, by providing a plurality of resistance elements and dividing the pressure by the resistance elements, it is possible to generate reference flow rate signals corresponding to the plurality of ranges.

Japanese Unexamined Patent Publication No. 2016-206080

Since the calibrator is a device that calibrates the converter, it outputs a signal related to a voltage in a wide range of several tens of nV to several mV so that the accuracy is 0.05% or less, and a plurality of reference flow signals. Is required to be generated with high accuracy. Therefore, when adjusting the calibrator, a high-precision digital voltmeter capable of measuring nV orders, equipment capable of creating a temperature-compensated environment, and the like are required. Therefore, a high cost has been spent in order to maintain high accuracy of the calibrator itself. Further, in order to reduce the number of adjustment points of the calibrator, a high-precision (high absolute precision) resistance element or the like is used, but the cost is high.

The present invention solves such a problem, and an object of the present invention is to provide, for example, an adjustment method of a calibrator capable of performing adjustment with high accuracy and stability while measuring low cost.

In order to achieve the above-mentioned object, the adjustment method of the calibrator according to the present invention includes a first inverter circuit that inverts the polarity of the reference signal generated by the signal generator and outputs the reference signal, or the reference signal generated by the signal generator or the first. 1 A first voltage divider that selects and outputs one of the signals output by the inverter circuit, a first voltage divider circuit that outputs a plurality of voltage dividers corresponding to a plurality of ranges, and a first voltage divider circuit. A second voltage divider that selects and outputs any one of the plurality of signals output by the second multiplexer, a second voltage divider circuit that divides the signal output by the second multiplexer and outputs it as a reference flow signal, and a second voltage divider circuit. 2 A method of adjusting a calibrator including a second voltage divider circuit that inverts the polarity of the signal output by the multiplexer and outputs it, and a third voltage divider circuit that divides the signal output by the second inverter circuit and outputs it as a reference flow signal. Therefore, among the signals output by the first voltage divider circuit, the voltage between the input terminals of the second voltage divider circuit and the third voltage divider circuit and the voltage between the output terminals are measured by the signals in the highest voltage range. It has a step of calculating the magnification related to the voltage dividing in the second voltage dividing circuit and the third voltage dividing circuit, respectively, based on the value of the voltage related to the measurement.

According to the present invention, among the signals output by the first voltage divider circuit, the measurement of the voltage value used for calculating the magnification related to the voltage divider in the second voltage divider circuit and the third voltage divider circuit when adjusting the calibrator is performed. Since the measurement is performed by the signal in the above range of the highest voltage, it is not necessary to perform the measurement using a high-precision voltmeter. In addition, the temperature of the environment has little influence on the measurement, and the temperature control can be relaxed. Therefore, the cost of adjusting the calibrator can be suppressed.

It is a figure which shows the structure of the calibrator 100 which concerns on embodiment of this invention. It is a figure which shows the example of the partial pressure in a calibrator 100. It is a figure which shows the procedure which concerns on the adjustment of the calibrator 100 which concerns on embodiment of this invention. It is a figure explaining the calibration of an electromagnetic flowmeter.

Embodiment.
FIG. 1 is a diagram showing a configuration of a calibrator 100 according to an embodiment of the present invention. As shown in FIG. 1, the calibrator 100 of the present embodiment includes a first inverter circuit 110, a first multiplexer circuit 120, a first voltage divider circuit 130, a second multiplexer circuit 140, a second inverter circuit 150, and a second inverter. It includes a pressure circuit 160 and a third voltage divider circuit 170. It also includes a signal generator 200, an arithmetic control device 300, an input device 400, and a display device 500.

The signal generator 200 is a device that generates a reference signal. The signal generator 200 controls, for example, the pulse width of a DA (digital / analog) converter (not shown) or a PWM (Pulse Width Modulation) signal to generate an arbitrary reference signal within a predetermined range. be able to. In the present embodiment, it is assumed that a reference signal of −2.5V to 2.5V (ratio of PWM duty is 0.0 to 1.0) is generated. Here, the signal generator 200 may be a device other than the calibrator 100.

The first inverter circuit 110 inverts the polarity of the reference signal sent from the signal generator 200. Here, the reference signal sent directly from the signal generator 200 is used as the plus side signal. Further, the reference signal whose polarity is inverted by the first inverter circuit 110 is used as the minus side signal. A positive side signal and a negative side signal are input to the first multiplexer circuit 120. Then, based on the excitation direction switching signal sent from the arithmetic control device 300, either the input positive side signal or the negative side signal is selected and output.

FIG. 2 is a diagram showing an example of partial pressure in the calibrator 100. In the calibrator 100, as will be described later, when a range switching signal for switching a range is sent from the arithmetic control device 300, a signal obtained by dividing the reference signal can be selected and output. The voltage division ratio in FIG. 2 is an approximate value. The first voltage dividing circuit 130 has a plurality of voltage dividing resistor elements, and can output signals relating to a plurality of ranges (voltage bands) by the voltage dividing. In the first voltage dividing circuit 130 of the calibrator 100 of the first embodiment, the voltage dividing corresponding to the seven ranges of the first range R1 to the seventh range R7 can be performed. Here, the voltage of the signal in the first range R1 is the voltage in the highest range. The voltage decreases in the order of the second range R2, the third range R3, the fourth range R4, the fifth range R5, and the sixth range R6, and the voltage of the signal in the seventh range R7 becomes the voltage in the lowest range.

When the range switching signal for switching the range is sent from the arithmetic control device 300 described later, the second multiplexer circuit 140 selects and outputs one of the plurality of signals output by the first voltage dividing circuit 130. Further, the second inverter circuit 150 inverts the polarity of the signal output by the second multiplexer circuit 140. The second voltage divider circuit 160 has a resistance element, and has a voltage divider circuit R (+) that divides the signal output by the second multiplexer circuit 140 and outputs a signal that becomes a reference flow signal. The input terminal in the second voltage dividing circuit 160 is CP1, and the output terminal is A. The third voltage divider circuit 170 has a resistance element, and has a voltage divider circuit R (−) that divides the signal output by the second inverter circuit 150 and outputs a signal that becomes a reference flow signal. Let CP3 be the input terminal and B be the output terminal in the third voltage divider circuit 170.

The conventional calibrator 600 uses a resistance element used for voltage division with high absolute accuracy. If the absolute accuracy of the resistance element is high, for example, a signal in the highest voltage range is output, and the voltage related to the output is measured. Then, the other ranges can be adjusted based on the values derived by calculating the rated value of the resistance element from the measured voltage.

The arithmetic control device 300 performs an arithmetic related to a pseudo voltage output which becomes a reference flow rate signal when adjusting, inspecting, and calibrating and checking the converter based on the input numerical value and the like. The input device 400 is a device for the operator to input instructions, data, and the like. The display device 500 displays based on the display signal from the arithmetic control device 300.

In the calibrator 100 of the present embodiment, the signal and the measurement location related to the measurement are devised so that the calibrator 100 can be adjusted without performing the measurement with a high-precision voltmeter. By not having to measure the voltage on the order of nV, it is possible to relax the temperature control in the environment at the time of measurement. Further, even if the absolute accuracy of the resistance element used in the calibrator 100 is not necessarily high, the accuracy of the pseudo voltage when calibrating and checking the converter is the same as when an expensive resistance element having high absolute accuracy is used. ..

FIG. 3 is a diagram showing a procedure for adjusting the calibrator 100 according to the embodiment of the present invention. The procedure of the adjustment method of the calibrator 100 will be described with reference to FIG. Here, an operator or the like performs measurement of adjustment items (parameters) such as voltage values related to adjustment and calculation. Further, the calculation control device 300 shall perform the calculation of the adjustment items based on the measured parameters. Further, the order of processing is not limited to the flow shown in FIG. 3 as long as the calculation based on the measured voltage can be performed.

First, it is assumed that the first voltage dividing circuit 130 outputs a signal related to the seventh range R7. Then, the voltage between CP1 and CP3 related to the zero point in the 7th range R7 is adjusted to be 0 μV (step S1). This adjustment is performed by, for example, a trimmer included in the second inverter circuit 150. The voltage between CP1 and CP3 before being input to the second voltage divider circuit 160 and the third voltage divider circuit 170 can be measured without using a high-precision voltmeter even in the case of a signal in the seventh range R7. it can.

Next, it is assumed that the first voltage dividing circuit 130 outputs a signal related to the first range R1. Then, based on the excitation direction switching signal sent from the arithmetic control device 300, while switching the signal, the four items shown in (a) to (d) are measured by the voltmeter (step S2). Here, since the output voltage of the signal in the first range R1 is measured in the order of mV even between A and B, the measurement can be performed without using a high-precision voltmeter.
(A) Measured voltage VPAB1 between AB by the positive side signal in the first range R1
(B) Measured voltage between AB by the negative signal in the first range R1 VMAB1
(C) Measured voltage VP1 between CP1 and CP3 by the positive side signal in the first range R1.
(D) Measured voltage VM1 between CP1 and CP3 by the negative side signal in the first range R1.

Further, in the first voltage dividing circuit 130, measurement is performed for each of the six items shown in (e) to (j) with respect to the second range R2 to the seventh range R7 (step S3). The voltage between CP1 and CP3 before the signal is input to the second voltage divider circuit 160 and the third voltage divider circuit 170 is measured in mV order even in the case of the signal in the seventh range R7. Therefore, the measurement can be performed without using a high-precision voltmeter.
(E) Measured voltage VP2 between CP1 and CP3 by the positive side signal in the second range R2
(F) Measurement voltage VP3 between CP1 and CP3 by the positive side signal in the third range R3
(G) Measured voltage VP4 between CP1 and CP3 by the positive side signal in the 4th range R4
(H) Measurement voltage VP5 between CP1 and CP3 by the positive side signal in the 5th range R5.
(I) Measurement voltage VP6 between CP1 and CP3 by the positive side signal in the 6th range R6
(J) Measurement voltage VP7 between CP1 and CP3 by the positive side signal in the 7th range R7

Here, the signal generated by the signal generator 200 is based on PWM. For example, the measured voltage determined by the instantaneous value in one measurement is likely to include an error due to ripple. Therefore, in step S2 and step S3, when the measurement is performed, the voltage is measured 30 times or more in 10 seconds or more for each item. Then, the average value of the voltage in each item is calculated, and the measured voltage finally obtained in each item is used.

The measured voltage is input as data by the operator via the input device 400, for example. The calculation control device 300 calculates other adjustment items based on the data input via the input device 400. The arithmetic control device 300, for example, based on the measured voltage VPAB1 and the measured voltage VP1 of (a) and (c) measured in step S2, determines the magnification GP in the second voltage dividing circuit 160 as in the following equation (1). Calculate (step S4).

GP = VP1 / VPAB1 ... (1)

Further, based on the measured voltage VMAB1 and the measured voltage VM1 of (b) and (d) measured in step S2, the magnification GM in the third voltage dividing circuit 170 is calculated as shown in the following equation (2) (step). S5).

GM = VM1 / VMAB1 ... (2)

Further, the value of the voltage at the zero point in the first range R1 to the seventh range R7 is calculated by the following equations (3) to (9) (step S6). Here, the zero point VZ1 in the first range R1 is the midpoint between the measured voltage VP1 and the measured voltage VM1. Then, the voltage of the zero point VZ2 to the zero point VZ7 in the second range R2 to the seventh range R7 is calculated by multiplying the zero point VZ1 in the first range R1 by the voltage dividing ratio of each voltage dividing resistor.
VZ1 = VP1 + VM1 ... (3)
VZ2 = VZ1 x VP2 / VP1 ... (4)
VZ3 = VZ1 x VP3 / VP1 ... (5)
VZ4 = VZ1 x VP4 / VP1 ... (6)
VZ5 = VZ1 x VP5 / VP1 ... (7)
VZ6 = VZ1 x VP6 / VP1 ... (8)
VZ7 = VZ1 x VP7 / VP1 ... (9)

As described above, according to the calibrator 100 of the present embodiment, the zero point is reached by measuring (a) to (j) and performing the calculations of equations (1) to (9). The calibrator 100 can be adjusted without measuring a minute voltage. Since the voltage of the signal related to the first range R1 and the voltage on the input side of the second voltage dividing circuit 160 and the third voltage dividing circuit 170 are measured, it can be measured even with a voltmeter that is not highly accurate. Then, the adjustment can be performed without preparing temperature-compensated environmental equipment or the like. Even if the absolute accuracy of the resistance elements in the first voltage divider circuit 130, the second voltage divider circuit 160, and the third voltage divider circuit 170 of the calibrator 100 is not high, the converter can be calibrated and checked by performing this adjustment. The accuracy of the pseudo voltage at this time is the same as when an expensive resistance element with high absolute accuracy is used. Therefore, the cost of the resistance element can be suppressed. Further, even in the calibration of the calibrator 100 itself, the adjustment can be performed without preparing a high-precision digital voltmeter, temperature-compensated environmental equipment, and the like, so that the cost related to the adjustment can be suppressed.

Next, a case where the pseudo voltage is output when the pseudo voltage of the adjusted calibrator 100 is inspected for correct adjustment or the converter is calibrated and checked will be described. Assuming that the voltage to be generated between AB is V, the voltage between CP1 and CP3 is V × (GP + GM) / 2. At this time, the relationship between the range number and the PWM pulse width duty (ratio 0.0 to 1.0) that is the source of the reference signal is set as follows.

If VP1 ≧ V × (GP + GM) / 2> VP2, the first range R1 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ1}
/ (VP1-VZ1) ... (10)
If VP2 ≧ V × (GP + GM) / 2> VP3, the second range R2 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ2}
/ (VP2-VZ2) ... (11)
If VP3 ≧ V × (GP + GM) / 2> VP4, the third range R3 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ3}
/ (VP3-VZ3) ... (12)
If VP4 ≧ V × (GP + GM) / 2> VP5, the fourth range R4 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ4}
/ (VP4-VZ4) ... (13)
If VP5 ≧ V × (GP + GM) / 2> VP6, the fifth range R5 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ5}
/ (VP5-VZ5) ... (14)
If VP6 ≧ V × (GP + GM) / 2> VP7, the sixth range R6 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ6}
/ (VP6-VZ6) ... (15)
If VP7 ≧ V × (GP + GM) / 2, the 7th range R7 is obtained. At this time,
PWM = 0.5 + 0.5 × {V × (GP + GM) /2-VZ7}
/ (VP7-VZ7) ... (16)

As described above, the magnification GP in the second voltage dividing circuit 160, the magnification GM in the third voltage dividing circuit 170, and the zero point VZ1 to the zero point VZ7 are values obtained by calculation. The arithmetic control device 300 displays the value of the voltage V to be generated on the display device 500, and converts it into a PWM pulse width duty and a range number based on the calculations according to the equations (10) to (16). Then, the pulse width duty is written in a storage device (not shown) included in the signal generator 200. Further, by writing the range number to a storage device (not shown) included in the second multiplexer circuit 140, an accurate voltage V can be output between AB.

As described above, according to the calibrator 100 in the present embodiment, when the voltage V to be generated by the input device 400 is specified, the voltage is displayed on the display device 500 and the equations (10) to (16) are displayed. Based on this, the PWM pulse width duty and the range number were determined so that an accurate voltage V could be output between AB. Further, when actually calibrating and checking the converter, the arithmetic control device 300 converts the voltage into V by inputting values related to the flow rate such as% value and flow velocity with respect to the flow rate and the flow rate range, and further, the pulse width of PWM. Since it can be converted into a duty and a range number, an accurate voltage V can be output between AB. Further, the exciting current from the converter is measured, and when the polarity is switched or the exciting current is changed, the exciting direction is switched by the first multiplexer circuit 120, and the voltage V of the signal changed by the exciting current is calculated. By rewriting and writing to the signal generator 200 and the second multiplexer circuit 140, it is possible to create a reference current flow signal that is close to the measurement in the actual detector.

100, 600 ... Calibrator, 110 ... 1st inverter circuit, 120 ... 1st multiplexer circuit, 130 ... 1st voltage divider circuit, 140 ... 2nd multiplexer circuit, 150 ... 2nd inverter circuit, 160 ... 2nd voltage divider circuit, 170 ... 3rd voltage divider circuit, 200 ... signal generator, 300 ... arithmetic control device, 400 ... input device, 500 ... display device.

Claims (4)

The first inverter circuit that inverts the polarity of the reference signal generated by the signal generator and outputs it,
A first multiplexer that selects and outputs either the reference signal or the signal output by the first inverter circuit, and
A first voltage divider circuit that outputs multiple signals that have been divided for multiple ranges,
A second multiplexer that selects and outputs any one of the plurality of signals output by the first voltage dividing circuit, and
A second voltage divider circuit that divides the signal output by the second multiplexer and outputs it as a reference flow rate signal.
A second inverter circuit that inverts the polarity of the signal output by the second multiplexer and outputs it.
It is a method of adjusting a calibrator including a third voltage dividing circuit that divides the signal output by the second inverter circuit and outputs it as the reference flow rate signal.
Among the signals output by the first voltage divider circuit, the voltage between the input terminals and the output terminals of the second voltage divider circuit and the third voltage divider circuit is measured by the signal in the range having the highest voltage. And the process to do
A method for adjusting a calibrator, which comprises a step of calculating a magnification related to the divided voltage in the second voltage dividing circuit and the third voltage dividing circuit, respectively, based on the value of the voltage related to the measurement, and adjusts the adjustment items. A step of measuring the voltage between the input terminals of the second voltage divider circuit and the third voltage divider circuit by the signals corresponding to the plurality of ranges output by the first voltage divider circuit, and the step of measuring the voltage between the input terminals of the third voltage divider circuit, respectively.
The method for adjusting a calibrator according to claim 1, further comprising a step of calculating a voltage at a plurality of zero points in the range based on a voltage value related to measurement. (A) Voltage between the input terminals of the second voltage divider circuit and the third voltage divider circuit by the signal in the range of the highest voltage related to the reference signal (b) The highest voltage related to the reference signal. Voltage between the output terminals of the second voltage divider circuit and the third voltage divider circuit due to the signal in the range of voltage (c) The signal in the range of the highest voltage related to the signal output by the first inverter circuit. Voltage between the input terminals of the second voltage divider circuit and the third voltage divider circuit (d) The second voltage divider by the signal in the range of the highest voltage related to the signal output by the first inverter circuit. The method for adjusting a calibrator according to claim 1 or 2, wherein the voltage between the circuit and the output terminal of the third voltage dividing circuit is measured. Equipped with an arithmetic control device and a display device
The arithmetic control device calculates the voltage between the output terminals of the second voltage divider circuit and the third voltage divider circuit based on the voltage value related to the measurement and the calculation and the magnification related to the voltage division, and the calculation is performed. The method for adjusting a calibrator according to any one of claims 1 to 3, which is displayed on a display device.

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