JP6428803B2 - Field equipment and detectors - Google Patents

Description

  The present invention relates to a field device in which a detector provided with a sensor converts a measurement signal into a physical quantity and transmits it to a converter as digital data. The present invention also relates to a detector in which a detector provided with a sensor converts a measurement signal into a physical quantity and outputs it as digital data.

  Conventionally, in a field device where a detector equipped with a sensor and a converter that converts the measured value into a unified signal for instrumentation and outputs it, all the electrical circuits required for calculation are mounted on the converter side. However, the measurement signal analog-transmitted from the detector is converted into a physical quantity, further converted into a unified signal for instrumentation, and output to the outside.

  In recent years, field devices have become more intelligent, called a smart sensor that performs conversion from measurement signals to measurement values that are physical quantities on the detector side, and transmits the obtained measurement values to the converter as digital data. Field devices are in practical use.

  FIG. 4 is a block diagram illustrating a configuration example of a conventional smart sensor 500. The smart sensor 500 includes a detector 510 and a converter 520 and is connected by a cable 530.

  The detector 510 includes a first microprocessor 511, a RAM 512, a ROM 513, a sensor 514, an amplifier 515, a filter 516, an A / D converter 517, and an internal power source 518. In the example of this figure, it is assumed that a measurement system of A system and B system is provided, and sensor 514, amplifier 515, filter 516, and A / D converter 517 are provided in two systems corresponding to A system and B system. It has been.

  In each system, an analog measurement signal acquired by the sensor 514 is amplified by an amplifier 515, a necessary band is extracted by a filter 516, and then digitally converted by an A / D converter 517.

  Then, the first microprocessor 511 performs calculation using the RAM 512 and the ROM 513 to convert it into a measured value that is a physical quantity, and outputs the obtained measured value as digital data to the converter 520 via the cable 530. .

  The converter 520 includes a second microprocessor 521, a RAM 522, a ROM 523, a 4-20 mA current output circuit 524, and an internal power supply 525. The digital data transmitted from the detector 510 is received by the second microprocessor 521 and subjected to predetermined processing using the RAM 522 and ROM 523, and the 4-20 mA current output circuit 524 is a unified signal for instrumentation. It is converted into 4-20 mA DC current and output to the external device 540.

  The smart sensor 500 is supplied with power from the external device 540 via a signal line that outputs a 4-20 mA DC current, and is used as the internal power source 525 of the converter 520 and the inside of the detector 510 via the cable 530. The power is supplied to the power source 518.

JP-A-10-221132

  When some trouble occurs in the detector 510, it becomes necessary to analyze the measurement signal output from the sensor 514 for investigation of the cause and the like. In general, the detector 510 installed in the field is often installed in a place where it is difficult for an operator to enter or work. Therefore, in such a case, analysis is performed using digital data output from the first microprocessor 511.

  However, the digital data output from the first microprocessor 511 is obtained by digitizing the measurement signal output from the sensor 514 by the A / D converter 527 so that the first microprocessor 511 is a physical quantity. Since it has been converted, it is not necessarily suitable for analysis of the measurement signal.

  In view of the above, an object of the present invention is to make it possible to easily analyze a measurement signal of a sensor in a field device in which a detector having a sensor converts a measurement signal into a physical quantity and transmits the digital signal to the converter. And Another object of the present invention is to make it possible to easily analyze a sensor measurement signal in a converter in which a detector provided with a sensor converts a measurement signal into a physical quantity and outputs the same as digital data. .

In order to solve the above problems, a field device of the present invention includes a sensor that acquires a measurement signal, an analog-to-digital converter that digitally converts an analog signal based on the measurement signal, and converts the digitally converted measurement signal into a measurement value A first arithmetic unit that outputs the digital signal, and a converter that receives the digital signal, converts the digital signal into an instrumentation signal, and outputs the instrument signal, A detector transmits the analog signal together with the digital data to the converter.
Here, the converter may include a monitoring terminal capable of measuring the transmitted analog signal.
The detector may include a plurality of sensors and an analog-digital converter corresponding to each sensor, and an analog signal related to each sensor may be selectively transmitted to the converter.
Further, the detector includes a digital-analog converter that selectively converts a plurality of digital signals output from the analog-digital converter corresponding to each of the plurality of sensors into an analog signal, and the digital An analog signal output from the analog converter may be transmitted to the converter.
The converter may calculate a measurement value based on the transmitted analog signal and collate with the measurement value transmitted as the digital data.
The converter may output an alarm when the difference between the measured value based on the analog signal and the measured value based on the digital signal exceeds a predetermined amount.
The converter may determine the soundness of the digital signal by comparing the measurement value based on the analog signal with the measurement value based on the digital signal.
Further, the converter may include a second arithmetic unit that performs an analysis process on the transmitted analog signal.
In addition, the converter may include a second arithmetic unit that inputs and processes the digital signal, and an insulating circuit provided in a stage preceding the second arithmetic unit.
In addition, the detector of the present invention includes a sensor that acquires a measurement signal, an analog-digital converter that converts an analog signal based on the measurement signal into a digital signal, and converts the digitally converted measurement signal into a measurement value as a digital signal. A first arithmetic unit that outputs the analog signal together with the digital signal.

  ADVANTAGE OF THE INVENTION According to this invention, in the field apparatus which a detector provided with a sensor converts a measurement signal into a physical quantity, and transmits to a converter as a digital signal, it becomes possible to analyze a measurement signal of a sensor easily.

It is a block diagram which shows the structure of the smart sensor of 1st Embodiment. It is a block diagram which shows the modification of the smart sensor of 2nd Embodiment. It is a block diagram which shows the modification of the smart sensor of 3rd Embodiment. It is a block diagram which shows the structural example of the conventional smart sensor.

Embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of a smart sensor 100 according to the present embodiment. The smart sensor 100 includes a detector 110 and a converter 120. The detector 110 and the converter 120 are connected to each other by a cable 130. The smart sensor 100 is configured in a form in which the detector 110 and the converter 120 are separated. The smart sensor 100 is a field device in which the detector 110 transmits measured values to the converter 120 as digital data, and can be a vortex flow meter, an electromagnetic flow meter, a Coriolis flow meter, a differential pressure transmitter, or the like. . In this embodiment, the detector 110 and the converter 120 are installed separately. Assume that access to detector 110 is less easy than access to transducer 120.

  The detector 110 includes a first microprocessor 111 (first arithmetic unit), a RAM 112, a ROM 113, a sensor 114, an amplifier 115, a filter 116, an A / D converter 117, and an internal power supply 118. In the example of this figure, the detector 110 includes a measurement system of A system and B system. In the detector 110, the sensor 114, the amplifier 115, the filter 116, and the A / D converter 117 are provided in two systems corresponding to the A system and the B system.

  In each system, the analog measurement signal acquired by the sensor 114 is amplified by the amplifier 115, a necessary band is extracted by the filter 116, and then digitally converted by the A / D converter 117.

  Then, the first microprocessor 111 performs calculation using the RAM 112 and the ROM 113 to convert it into a measured value that is a physical quantity, and outputs the obtained measured value to the converter 120 via the cable 130 as digital data. .

  The converter 120 includes a second microprocessor 121 (second arithmetic unit), a RAM 122, a ROM 123, a 4-20 mA current output circuit 124, an internal power supply 125, and a sensor A signal monitoring terminal 126.

  The second microprocessor 121 receives the digital data transmitted from the detector 110. The second microprocessor 121 uses the RAM 122 and ROM 123 to perform predetermined processing on the transmitted digital data. Then, the 4-20 mA current output circuit 124 converts the measured value into a 4-20 mA DC current that is a unified signal for instrumentation, and outputs it to the external device 140. However, other standard instrumentation signals may be employed.

  Further, an insulating circuit may be provided before the second microprocessor 121. For example, a capacitor, an insulating transformer, a photocoupler, or the like can be used for the insulating circuit. As a result, even in field devices that require grounding of the detector, the feedback current generated inside the device can be prevented from flowing to the external grounding (grounding). Control becomes possible, and the accuracy of the current output of the 4-20 mA current output circuit 124 can be improved. Further, noise resistance from both the converter 120 and the detector 110 side can be improved.

  The smart sensor 100 is supplied with power from the external device 140 via a signal line that outputs a 4-20 mA DC current. The smart sensor 100 uses the supplied power as the internal power supply 125 of the converter 120 and supplies it to the internal power supply 118 of the detector 110 via the cable 130. Note that a converter of a four-wire field device such as an electromagnetic flow meter or a Coriolis flow meter may be supplied with power from a commercial power source.

  In this embodiment, analog data (analog signal) output from the A-system filter A 116 a in the detector 110 is transmitted to the converter 120 via the cable 130. For this reason, the cable 130 includes three systems of electric wires: a digital data system (digital signal system), an analog signal system, and a power supply system.

  That is, the converter 120 is connected to the detector 110 with a signal line for digital communication, and can obtain a numerical value based on digital data obtained by converting the sensor signal. This numerical value can be said to be data obtained by converting a physical quantity corresponding to the sensor signal. In addition, the converter 120 is connected to the detector 110 by at least one signal line for analog signals, separately from the digital communication signal line. This analog signal is for transmitting at least one sensor acquisition signal from the detector 110 to the transducer 120. The converter 120 can monitor the sensor signal through the analog signal line.

The digital data (digital signal) referred to here is a signal obtained by digitizing a signal derived from an instantaneous value of a process value or a diagnostic value subjected to signal processing on the detector 110 side. This digital signal is, for example, a signal for transmitting such information to the converter 120 by serial communication or parallel communication, or binarizing the normal / abnormal state of the circuit on the detector 110 side (for example, high (High) or low (Low) binary signal. The digital data may be appropriately encoded as necessary and transmitted from the detector 110 side to the converter 120 side.
Here, the diagnostic value is a value of state diagnosis of the sensor A 114a and the sensor B 114b. The diagnostic value is a value serving as a basis for indicating normality or abnormality of the sensor.

  Further, the analog signal is a signal that indicates an instantaneous value of a process value or a diagnostic value that is analog-processed on the detector 110 side of various field devices. The analog signal is associated with a numerical value represented by, for example, a voltage level.

  For example, in the case of a vortex flowmeter, the analog signal is the signal itself output from the sensor (the signal after the charge amplifier (amplifier)). Alternatively, the analog signal is a signal that is passed (filtered) only in a band where the sensor signal exists. Or an analog signal is a signal showing the present value of the frequency which shows the flow velocity measured with a vortex flowmeter, such as a pulse signal showing the result compared after amplifying a sensor signal at a predetermined comparison level. Alternatively, the analog signal may be an analog signal related to temperature for correction of the vortex flowmeter (voltage output from the temperature measurement circuit) or an analog signal related to pressure (voltage output from the pressure measurement circuit). Further, the above various analog signals may be switched in a time division manner and transmitted from the detector 110 side to the converter 120 side.

  For example, in the case of an electromagnetic flow meter, the analog signal is the signal itself output from the sensor (the signal after the charge amplifier). Alternatively, the analog signal is a signal that passes only the band where the sensor signal exists. Alternatively, the analog signal may be an analog signal (signal related to electrode potential signal, interelectrode impedance, excitation current) acquired by a diagnostic circuit.

  For example, in the case of a Coriolis flowmeter or an ultrasonic flowmeter, the analog signal is the signal itself (the signal after the charge amplifier) output from the sensor. Alternatively, the analog signal is a signal that passes only the band in which the sensor signal exists. Alternatively, the analog signal may be an analog signal acquired by a diagnostic circuit.

  The analog signal transmitted to the converter 120 can be taken out from the outside of the converter 120 via the sensor A signal monitoring terminal 126. The analog signal may be further captured by the second microprocessor 121.

  The transmitted analog signal can be regarded as a sensor measurement signal because the amplifier A 115a amplifies the measurement signal of the sensor A 114a and passes through the filter A 116a. For this reason, by extracting an analog signal from the sensor A signal monitoring terminal 126 provided in the converter 120, the measurement signal of the sensor can be easily analyzed. Even if the operator opens the cover of the converter 120, connects the measurement input unit of the external measuring instrument to the sensor A signal monitoring terminal 126 in the converter, and measures and analyzes the analog signal. Good.

  The analog signal transmitted to the converter 120 can be used for purposes other than analysis of sensor measurement signals. For example, a device that captures an analog signal from the sensor A signal monitoring terminal 126 or a second microprocessor 121 that captures an analog signal calculates a measurement value based on the measurement signal of the analog signal and It can also be compared with the measured value of the sent digital data. In addition, the converter 120 is configured to output an alarm when the difference between physical quantities converted from the digital signal and the analog signal exceeds a predetermined range (for example, an allowable error range such as 1%). Also good. The allowable error is determined in advance based on, for example, measurement accuracy. That is, the second microprocessor 121 outputs an alarm when the difference between the measured value based on the analog signal and the measured value based on the digital signal exceeds a predetermined amount. This predetermined amount may be a ratio to the physical amount obtained as described above. The predetermined amount may be an absolute value of the physical quantity obtained as described above. As a result, diagnosis can be performed using duplicated signals (analog signals and digital signals) with different methods in safety instrumentation. That is, it is possible to increase the reliability of the measurement value and increase the detection rate of abnormal operation of the field device.

  In addition, a device that captures an analog signal from the sensor A signal monitoring terminal 126 or a second microprocessor 121 that captures an analog signal collates the measurement value based on the measurement signal of the analog signal with the measurement value of the digital data. Thus, the soundness (whether sound or not) of the transmitted digital signal may be determined. For example, the measurement value represented by the digital signal may contain a large error due to external noise or the like, but unhealthy events such as noise can be detected by the above soundness judgment. .

Here, in order to ensure the simultaneity of comparison between the analog signal and the digital signal, the acquisition timing of the digital signal and the acquisition timing of the analog signal are matched on the converter 120 side. For example, when the digital signal represents data before one calculation cycle, the analog signal is sampled and stored so that the data is one calculation cycle before. For this purpose, a delay circuit or a memory for storing data is provided as appropriate.
Or you may compare by the integrated value in time to the extent that a calculation period can be disregarded. That is, the period for taking the integrated value is made sufficiently longer than the calculation cycle. In this case, it is not necessary to adjust the calculation cycle, and the realization means becomes simpler.

  If the calculated measurement value and the measurement value of the transmitted digital data do not match, for example, if there is a permanent mismatch, the cable 130 has deteriorated. It is also possible to diagnose that it is the cause.

  In addition, by performing frequency analysis by FFT or the like on the analog signal taken in from the sensor A signal monitoring terminal 126, periodic noise caused by the surrounding environment such as pipe vibration or commercial power supply can be detected. Specifically, for example, this can be realized by performing frequency analysis of an analog signal read from the sensor A signal monitoring terminal 126 by the second microprocessor 121. Further, not only frequency analysis but also various other analysis processes can be performed to detect the behavior of the detection target.

  In addition, this embodiment is not restricted to the aspect mentioned above, A various deformation | transformation can be performed. For example, in the above-described embodiment, the measurement signal of the A system sensor is transmitted to the converter 120 as an analog signal. However, the measurement signal of another system sensor may be transmitted to the converter 120 as an analog signal. Then, the sensor measurement signal may be transmitted to the converter 120 as an analog signal for all systems.

[Second Embodiment]
FIG. 2 is a block diagram showing a configuration of the smart sensor 200 of the present embodiment. The smart sensor 200 includes a detector 210 and a converter 220 and is connected by a cable 130. As a feature of the present embodiment, the detector 210 includes a selector 119. In other words, the detector 210 is provided with the selector 119 to switch the output data of the filter A 116 a and the output data of the filter B 116 b and transmit the data to the sensor signal monitoring terminal 127 provided in the converter 120. Good.

  Regarding the switching operation of the selector 119, the second microprocessor 121 may give a switching instruction to the first microprocessor 111 so that the first microprocessor 111 performs switching control.

[Third Embodiment]
FIG. 3 is a block diagram illustrating a configuration of the smart sensor 300 according to the present embodiment. The smart sensor 300 includes a detector 310 and a converter 320 and is connected by a cable 130. In the present embodiment, as shown in the figure, the first microprocessor 111 selects one of the digital sensor measurement signals input from the A / D converter A 117a and the A / D converter B 117b, and performs D / A conversion. The analog signal is converted by the converter 151 and transmitted to the sensor signal monitoring terminal 127 provided in the converter 120.

  The first embodiment to the third embodiment have been described above. 1, 2 and 3 (110, 210 and 310, respectively) are provided with two A / D converters. However, the filter A 116a, The analog signal from the filter B 116b may be selectively input using a multiplexer (not shown). That is, in this case, the detector transmits a digital signal converted based on any of the plurality of analog signals to the converter.

  The sensor measurement signal transmitted from the detector 110 (or 210, 310) to the converter 120 (or 220, 320) may be converted into a predetermined general-purpose format and transmitted. For example, by converting to a voltage signal of 1-5 V, a general-purpose device can be used for taking out and analyzing an analog signal from the sensor A signal monitoring terminal 126.

  The functions of the first microprocessor 111 shown in FIG. 1, FIG. 2 and FIG. 3 are: A / D conversion value acquisition, A / D conversion value calculation, data transmission of these values to the second microprocessor 121 (serial Communication or parallel communication) and processing based on a data transmission (serial communication or parallel communication) command from the second microprocessor 121. Such a function can be realized not only by a microprocessor but also by an ASIC (gate array). When implemented with an ASIC, it is sufficient to have only the functions listed above, so less memory and peripherals (timer, serial communication, general-purpose I / O) are used than when implemented with a microprocessor. be able to. Thereby, this embodiment or its modification can be realized with lower power consumption, lower cost, or more area.

  In each of the smart sensors 100, 200, and 300, power is supplied from the external device 140. However, as a modified example, the following may be used. That is, in each of the detectors 110, 210, and 310, the internal power source 118 functions as a power source without receiving power supply from the converters 120, 220, and 320 side. Thereby, the detector which outputs a signal with respect to an external apparatus by the structure which does not require a converter can be comprised. That is, the detector in this example includes a sensor that acquires a measurement signal, an analog-to-digital converter that converts an analog signal based on the measurement signal into a digital signal, and converts the digitally converted measurement signal into a measurement value as a digital signal. And a first arithmetic unit that outputs the analog signal together with the digital signal.

DESCRIPTION OF SYMBOLS 100 ... Smart sensor, 110 ... Detector, 111 ... 1st microprocessor, 114 ... Sensor, 115 ... Amplifier, 116 ... Filter, 117 ... A / D converter, 118 ... Internal power supply, 119 ... Selector, 120 ... Converter 121 ... second microprocessor, 124 ... 4-20 mA current output circuit, 125 ... internal power supply, 126 ... sensor A signal monitoring terminal, 127 ... sensor signal monitoring terminal, 130 ... cable, 140 ... external device, 151 ... D / A converter, 200 ... smart sensor, 210 ... detector, 220 ... converter, 300 ... smart sensor, 310 ... detector, 320 ... converter

Claims (10)

A sensor for obtaining a measurement signal;
An analog-to-digital converter for digitally converting an analog signal based on the measurement signal;
A first computing unit that converts the digitally converted measurement signal into a measurement value and outputs the measurement value as a digital signal;
A detector with
A converter that inputs the digital signal, converts it into an instrumentation signal, and outputs it,
A field device comprising:
The field device characterized in that the detector transmits the analog signal together with the digital signal to the converter. The converter is
A monitoring terminal capable of measuring the transmitted analog signal;
The field device according to claim 1, wherein: The detector is
A plurality of sensors and an analog-digital converter corresponding to each sensor are provided.
Selectively transmitting an analog signal associated with each sensor to the converter;
The field device according to claim 1 or 2, characterized in that. The detector is
A digital-to-analog converter that selectively converts a plurality of digital signals output from the analog-to-digital converter corresponding to each of the plurality of sensors into analog signals,
Transmitting an analog signal output from the digital-analog converter to the converter;
The field device according to claim 1 or 2 , characterized in that. The converter is
Calculate a measurement value based on the transmitted analog signal, and collate with the measurement value transmitted as the digital signal,
The field device according to any one of claims 1 to 4, characterized in that: The converter is
An alarm is output when a difference between the measured value based on the analog signal and the measured value based on the digital signal exceeds a predetermined amount;
The field device according to claim 5. The converter is
Determining the soundness of the digital signal by collating the measured value based on the analog signal with the measured value based on the digital signal;
The field device according to claim 5 or 6, characterized by the above. The converter is
A second arithmetic unit that performs an analysis process on the transmitted analog signal;
The field device according to any one of claims 1 to 7, characterized in that: The converter is
A second arithmetic unit that inputs and processes the digital signal;
An insulation circuit provided in a preceding stage of the second arithmetic unit;
The field device according to any one of claims 1 to 7, further comprising: A sensor for obtaining a measurement signal;
An analog-to-digital converter for digitally converting an analog signal based on the measurement signal;
A first computing unit that converts the digitally converted measurement signal into a measurement value and outputs the measurement value as a digital signal;
A detector comprising:
The detector outputs the analog signal together with the digital signal to the outside.
A detector characterized by that.

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