JP4861089B2 - Instrumentation data transmission apparatus and instrumentation data transmission method - Google Patents

Description

  The present invention relates to an instrumentation data transmission apparatus for a plant, and more particularly to a data transmission apparatus and an instrumentation data transmission method for collecting data obtained by sensors.

  For example, in a complex plant such as a nuclear power plant, thousands or more sensors are installed in order to collect process data such as plant pressure and temperature. The values measured by these sensors are input to the monitoring control device in order to operate the plant normally and safely.

  Currently, many commonly used sensors have an analog interface that outputs a measured value as a current value of 4 mA to 20 mA, and the interface based on the analog current value has become an industry standard. By connecting a cable from the sensor to the process input unit of the monitoring control device, the monitoring control device can measure the current sent from the sensor and know the process data measured by the sensor.

  Process data transmission by current value is (1) independent of the resistance of the cable to be connected, (2) highly resistant to noise, and (3) when the cable is disconnected, the current value is 0 mA, which is a normal range. Since it deviates from 20 mA, there is a merit that the monitoring and control device can detect disconnection, and sensors using this standard are widely available on the market.

  On the other hand, this method requires a dedicated cable from each sensor to the process input unit of the monitoring control device. Therefore, if the number of sensors is large, the amount of cables becomes enormous. A partial solution to reduce the amount of cable is to provide remote process I / O equipment in the field and digital multiplex communication with the supervisory controller. Although this method can significantly reduce the amount of cable from the field, the amount of cable from the sensor to the remote process I / O device is still large because the remote process I / O device is a relatively large device.

  In order to eliminate the drawbacks of analog transmission as described above, a field bus has been developed as a process data transmission system using digital technology. Typical field buses include PROFIBUS and Foundation Fieldbus. Both PROFIBUS and Foundation Fieldbus are international standards as IEC-61158-2 “Digital data communications for measurement and control”. However, in order to use these field buses, a sensor having a dedicated interface is required.

As a method for connecting a sensor having an interface with an analog current value that is easily available to a field bus, there are methods disclosed in Patent Document 1, Patent Document 2, and Patent Document 3. These are converters for connecting an analog interface to a fieldbus digital interface.
US Pat. No. 7,706,007 (“Analog Current / Digital Bus Protocol Converter”) Japanese Patent Laid-Open No. 10-247292 ("Field Equipment") JP 2002-124997 A ("Fieldbus connection device")

  If the conversion device from the analog interface to the digital interface shown in Patent Documents 1 to 3 is used, the number of devices inevitably increases, and a new failure mode is brought into the plant monitoring and control system.

  It is necessary to pay particular attention to such failure modes that cannot be detected from the monitoring control device side. As a failure mode that cannot be detected from the supervisory control device side, there is a failure mode in which the converter always outputs a constant digital value even though the analog signal changes. In general, a fieldbus shares a cable, so that the cable can cause a common cause failure in exchange for the merit of reducing the cable.

  The present invention has been made in consideration of the above-described points, and an object of the present invention is to solve the problem of reliability in obtaining a digital signal by converting analog signals measured by a plurality of sensors.

In order to achieve the above object, in the present invention,
A plurality of current / voltage conversion means for obtaining an analog current signal corresponding to the process amount measured by the sensor and converting it into a voltage signal, and converting an analog voltage value output from each of the current / voltage conversion means into a digital value Analog / digital conversion means, a plurality of network transmission means for transmitting a digital value output from the analog / digital conversion means to the network as data of a predetermined format together with the sensor number, and the current / voltage conversion means A cutting switching unit that periodically cuts a voltage signal applied to the analog / digital conversion unit, and a timer that sets a cutting period in the cutting switching unit.

  The present invention can accurately follow a change in an analog signal and obtain a highly reliable digital measurement signal.

(First embodiment)
FIG. 1 shows the configuration of the first embodiment of the present invention. In FIG. 1, a sensor 1 of an analog interface measures a process amount of a plant, for example, pressure, temperature, etc., and outputs it through a cable 2 as a current value of 4 mA to 20 mA. Normally, the cable 2 is laid for a long distance in the plant, for example, several tens of meters to several hundreds of meters, but in this embodiment, several tens of centimeters to several meters is sufficient.

  In order to duplicate the signal from the sensor 1 and send it to the monitoring control device, two series devices of a system and b system are installed. Hereinafter, the configuration and operation will be described using the a system as an example, but the configuration and operation are the same for the b system.

  The switch (SW) 4a cuts off the potential difference between both ends of the resistor 3a to which the output current of the sensor 1 is applied in accordance with a signal from the timer 5a. The analog / digital converter 6a measures the signal, converts the measured voltage into a digital value, and transmits the digital value to the network interface 7a. The network interface 7a converts the digital value into a format corresponding to the digital network, and periodically transmits it to the monitoring control device (not shown) via the network.

  Here, FIG. 2 shows an example of this format, in which a header H, a sensor number SN for identifying a sensor, and a value V are arranged at the end.

  Returning to FIG. 1, when the switch 4a receives a signal periodically sent from the timer 5a, the switch 4a disconnects the connection to the analog / digital converter 6a. However, the cycle in which the timer 5a sends a signal is sufficiently longer than the cycle in which the network interface 7a sends data. For example, when the network interface 7a transmits data with a cycle of 0.5 seconds, the cycle in which the timer 5a sends a signal to the switch 4a is 10 seconds. When the switch 4a is disconnected, the potential difference input to the analog / digital converter 6a becomes zero. This is the same as when the current loop from the sensor 1 is broken, and means a signal outside the limit value.

  That is, the instrumentation data transmission device of the first embodiment intentionally periodically transmits a signal outside the limit value. Therefore, when there is some abnormality in the analog / digital converter 6a, the network interface 7a, or the network and the update of data is stopped, the supervisory control device does not receive a signal outside the limit value that should be sent periodically. . As a result, the supervisory control device detects an abnormality in the analog / digital converter 6a, the network interface 7a, or the network. The current value can also be measured by an induction coil instead of the resistors 3a and 3b.

  FIG. 3 shows the internal configuration of the network interfaces 7a and 7b used in the embodiment of the present invention. The network interfaces 7a and 7b take the data from the analog / digital converter 6a into the input register 71 and give the taken data to the multiplier 72.

  The input register 71 records a value periodically sent from the analog / digital (A / D) converter 6 a, and a multiplier 72 to which the output of the input register 71 is given is recorded in the input register 71. Is multiplied by the value set in the gain recording unit 75 and set in the transmission register 73.

  The multiplier 72 is given a feedback signal from the network connection unit 74 through a feedback circuit having a gain recording unit 75, a gain setting unit 76, and a reception register 77, adjusts the gain, and connects the output to the network. To the unit 74.

  The network connection unit 74 is directly connected to the network, converts the digital data recorded in the transmission register 73 into an electrical signal, and sends it to the network. At the same time, the electric signal from the network is converted into digital data and set in the reception register 77.

  With the network interface configured as described above, the gain adjustment of the sensor can be performed from the monitoring control device via the network. In the above description, the gain is adjusted for the digital value output from the analog / digital converter. However, the gain can be adjusted for the analog value input to the analog / digital converter. In this case, the gain of the amplifier is adjusted based on the value recorded in the gain recording unit 75.

(Second Embodiment)
FIG. 4 shows a second embodiment of the present invention. In the first embodiment, the a-system and b-system timers are shared by 5a. The timer 5a alternately disconnects the switches 4a and 4b. As a result, as long as there is no abnormality in the analog / digital converters 6a and 6b, the network interfaces 7a and 7b, or the network, the supervisory control device can always receive a sensor signal from the a system or the b system.

(Third embodiment)
FIG. 5 shows a third embodiment of the present invention. The first embodiment is modified, and two sensors 1 and 9, cables 2 and 11 connected to the respective sensors, and a resistor 3a are shown. And 3c correspond to one switch 4a and one analog / digital converter 6a.

  In the third embodiment, the switch 4a switches between the sensor 1 and the sensor 9 by a periodic signal from the timer 5a. For example, the signals of the sensors 1 and 2 are switched every 0.25 seconds. At the same time, timer 5a sends a signal to network interfaces 7a and 7b to indicate which sensor is selected.

  In the third embodiment, since one analog / digital converter 4a can be used to handle input signals from a plurality of sensors, the cost can be reduced.

  FIG. 6 shows network interfaces 7a and 7b in the third embodiment of the present invention. Among the components shown in FIG. 6, the reference numerals 78a to 77 are the same as those in the third embodiment.

  And the sensor number setting part 78a is implement | achieved as an interface with a man-machine interface, for example, a push button, a dial-type switch, or a barcode reader, and a plant site engineer sets a sensor number. The set sensor number is recorded in the sensor number setting unit 78a.

  The transmission register 73 sets the value in a prescribed format, but extracts the sensor number 4-2 from the sensor number setting unit 78a and sets it. The network control unit 74 records the value of the sensor number 4-2 and uses it for identifying the destination when inputting data. The display control unit 78b extracts the sensor number of the data received from the network recorded in the reception register 77 and displays it on the display unit 78c. The display unit 78c is, for example, a numerical display device using LEDs or a liquid crystal display.

  FIG. 7 shows a format of digital data received from the network, which is composed of a header H for identifying the digital data, a sensor number SN as a data destination, a command C, and a value V.

  Returning to FIG. 6, the network connection unit 74 examines the header H and the sensor number SN, and receives only when the header H is a predetermined value and the sensor number SN matches the sensor number recorded by itself. The received data is set in the register 77.

  The gain setting unit 76 checks the data set in the reception register 77 and sets the value V in the gain recording unit 75 when the command C matches the value of a predetermined gain setting command.

  In the above description, the display control unit 78b extracts the sensor number 6-2 from the reception register 77, but it goes without saying that it can be extracted from the network interface 74, the transmission register 73, or the sensor number setting unit 78a.

  According to the third embodiment, the field engineer can easily set the sensor number and can easily check the set sensor number when the instrumentation data transmission apparatus of the present invention is connected to the sensor.

(Fourth embodiment)
FIG. 8 shows a fourth embodiment of the present invention. In the first embodiment, the cable connected to the sensor 1 is independent of the a system 2 as the b system 8-1.

  With the configuration of the fourth embodiment, for example, even when the resistor 3a is disconnected, a current flows through the resistor 3b. Therefore, it is possible to monitor the sensor signal using the b system. In this case, the load resistance is doubled. However, if the sensor 1 is within the range allowed by the specification of the sensor, since the current proportional to the measured value is output regardless of the load resistance, the b system is not adjusted. The measured value of the sensor 1 can be transmitted to the monitoring control device.

(Fifth embodiment)
FIG. 9 shows a fifth embodiment of the present invention. FIG. 9 is obtained by adding batteries 12a and 12b to the fourth embodiment shown in FIG. In the first embodiment and the fourth embodiment, the switches 4a and 4b have a function of periodically cutting off the input to the analog / digital converters 4a and 5b.

  In addition, in the fifth embodiment, the switches 4a and 4b periodically switch the input to the battery 12a or 12b based on the signals of the timers 5a and 5b. The battery 12a or 12b generates, for example, 120% of the upper limit of the voltage input from the resistors 3a and 3b to the analog / digital converter 6a or 6b. Therefore, the control device can distinguish the value when switched to the battery 12a or 12b from the signal value output from the sensor 1.

  For example, the input is disconnected at time 0 seconds, the input is switched to the battery 12a or 12b at time 10 seconds, and then the input is disconnected at time 20 seconds. Thereafter, the disconnection of the input and the switching to the input battery 12a or 12b are alternately repeated at a cycle of 10 seconds.

  Furthermore, the gain of the analog / digital converters 4a and 5b can be automated by using a network interface having a gain adjustment function shown in FIG.

  According to the fifth embodiment, whether or not the analog / digital converters 4a and 4b can accurately measure the voltages of the batteries 12a and 12b can be monitored through the network. As the batteries 12a and 12b, for example, lithium batteries with little voltage fluctuation over a long period of time are used. Moreover, it is also possible to use the low voltage power supply of an instrumentation data transmission apparatus instead of a battery.

The block diagram which shows the structure of the instrumentation data transmission apparatus by the 1st Embodiment of this invention. Explanatory drawing which shows the format of the data which the network interfaces 7a and 7b transmit to a network. The block diagram which shows the structure of the network interface 7a or 7b in this invention. The block diagram which shows the structure of the instrumentation data transmission apparatus by the 2nd Embodiment of this invention. The block diagram which shows the structure of the instrumentation data transmission apparatus by the 3rd Embodiment of this invention. The block diagram which shows the structure of the network interface 7a or 7b in the 3rd Embodiment of this invention. Explanatory drawing which shows the format of the data sent to the transmission apparatus from the monitoring control apparatus in the 3rd Embodiment of this invention. The block diagram which shows the structure of the instrumentation data transmission apparatus by the 4th Embodiment of this invention. The block diagram which shows the structure of the instrumentation data transmission apparatus by the 5th Embodiment of this invention.

Explanation of symbols

1 sensor, 2 current loop, 3a, 3b resistance, 4a, 4b switch, 5a, 5b timer,
6a, 6b analog / digital converter, 7a, 7b network interface,
9 Second sensor, 11 Second current loop, 12a, 12b Battery for correction,
71 input register, 72 multiplier, 73 transmission register, 74 network connection,
75 Gain recording section, 76 Gain setting section, 77 Receive register,
78a Sensor number setting part, 78b Display control part, 78c Display part.
H header, SN sensor number, digital value obtained from V sensor output,
C command.

Claims (7)

  A plurality of current / voltage conversion means for obtaining an analog current signal corresponding to the process amount measured by the sensor and converting it into a voltage signal, and converting an analog voltage value output from each of the current / voltage conversion means into a digital value Analog / digital conversion means, a plurality of network transmission means for transmitting a digital value output from the analog / digital conversion means to the network as data of a predetermined format together with the sensor number, and the current / voltage conversion means An instrumentation data transmission device comprising: disconnection switching means for periodically disconnecting a voltage signal applied to the analog / digital conversion means; and a timer for setting a period of disconnection in the disconnection switching means.   2. The instrumentation data transmission device according to claim 1, wherein the disconnection switching unit disconnects a voltage signal applied from the current / voltage conversion unit to the analog / digital conversion unit at one place at a time. . The invention according to claim 1, further comprising a plurality of sensors, wherein the disconnection switching means receives voltage signals from a plurality of the current / voltage conversion means corresponding to the plurality of sensors in a batch, and from the timer. Switching the voltage signal based on the signal and providing it to the analog / digital conversion means;
The instrumentation data transmission device, wherein the network transmission means sets the number of the sensor to be transmitted to the network in synchronization with the disconnection switching means by a signal from the timer.   2. The invention according to claim 1, wherein the network transmission means includes an input register for temporarily recording a digital signal from the analog / digital conversion means, and a gain adjustment section for adjusting a gain to adjust data in the input register. And an output register for recording the data adjusted by the gain adjustment unit in a predetermined format, and the data recorded in the output register are periodically read out and transmitted to the network and transmitted from the network. Network connection unit that receives data sent by specifying a destination in the received data, a reception register that records data received by the network connection unit, and data related to a gain adjustment request from the data recorded in the reception register Request for adjustment from the data Instrumentation data transmission apparatus characterized by comprising a gain setting unit for setting the gain adjustment unit reads in. The invention according to claim 4, wherein the network transmission means includes:
Sensor number setting means for inputting the number of the sensor to be connected;
Display means for displaying the sensor number;
An instrumentation data transmission device comprising: a display control unit configured to read from the reception register and set in the display unit when a sensor number set from the monitoring control unit is transmitted via a network . In the invention of claim 1,
A constant voltage generating means for generating a constant voltage is provided,
The disconnection switching means is
An instrumentation data transmission apparatus characterized in that the input to the analog / digital conversion means is periodically switched to input or disconnection from the constant voltage generating means and the current / voltage means. An analog current signal corresponding to the state quantity measured by a plurality of sensors is obtained and converted into a voltage signal, the converted analog voltage value is converted into a digital value, and the converted digital value is combined with the sensor number. In a measurement data transmission method for transmitting to a network as data in a prescribed format,
The current / voltage conversion is performed by multiplexing in series, and the analog / digital conversion and the network transmission are multiplexed.
The voltage signal is periodically cut and then analog / digital converted.
Instrumentation data transmission method characterized by the above.

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