JPH04332099A - Signal transmission system - Google Patents

Abstract

PURPOSE:To easly secure the safeness of a plant by allowing a field meter to transmit an abnormality informing signal in a frequency band different from the transmission frequency band of a preceding digital signal to a bus line at the time of generating abnormality in the device itself. CONSTITUTION:When abnormality is generated in either one of field meters f1, f2, an abnormality informing signal having frequency in frequency band different from the frequency band of digital signals to be transmitted between both the field meters f1, f2 by time division multiplex transmission is transmitted to a controller 13 through a field bus 11. The controller 13 receives the abnormality informing signal from the bus 11 and knows the generation of the abnormality in the field meter f1 or f2. Consequently, the controller 13 can immediately detect abnormality independently of the scanning period of normal data collection and can easily secure the safeness of the plant.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention transmits a digital signal to a controller and a plurality of field instruments via a bus line that connects the two by time division multiplex transmission, and also applies a DC voltage to the bus line. This invention relates to a signal transmission device that superimposes operating power to a field instrument, and particularly relates to a signal transmission device improved so that when an abnormality occurs in a field instrument, the abnormality can be promptly transmitted to a controller. .

0002

2. Description of the Related Art FIG. 4 is a block diagram showing the structure of a conventional signal transmission device of this type. Reference numeral 10 denotes a controller installed in a control room, etc., and this controller 10 controls a plurality of field instruments F1, F2,...F installed in a field.
The two field buses 11 are connected in parallel to each other.

[0003] The controller 10 controls each field instrument F.
1, F2,...Fn through the field bus 11, and each field instrument F1, Fn.
2. Data collected by these field instruments F1, F2,...Fn while collecting signals of process variables detected by...Fn, such as temperature, pressure, differential pressure, etc., in a predetermined procedure.
control the plant operation using data.

On the other hand, each field instrument F1, F2,...F
n detects a process variable, converts it into a digital signal, and sends it to the controller 1 via the field bus 11.
Transmit to 0.

Next, a digital signal transmission procedure in the signal transmission device 12 configured as described above will be explained using FIG. 5. 5(a) shows the command sent from the controller, FIG. 5(b) shows the response of the field instrument F1, and FIG. 5(c) shows the response of the field instrument F2. 5(n) shows the response of the field instrument Fn, and FIG. 5(z) shows the scan cycle of the controller.

First, when the controller 10 sends a command signal CMD1 to call the field instrument F1 via the field bus 11, the field instrument F1 detects this and sends measured values such as status and temperature. It is returned to the controller 10 as a response RES1. As a result, the controller 10 collects the data detected by the field instrument F1.

Next, the controller 10 sends a command signal CMD2 to call the field instrument F2 via the field bus 11, and the field instrument F2 detects this and outputs the measured values such as status and temperature. Renpons R
It is returned to the controller 10 as ES2. As a result, the controller 10 receives the data detected by the field instrument F2.
Collect data.

In this manner, the controller 10 collects data up to n field instruments Fn and returns to field instrument F1. This scan period is Ts as shown in FIG. 6(z). As described above, the controller 10 collects data regarding the process status of each part of the plant and controls the operation of the plant.

[0009]

However, in the above-described signal transmission system, each field instrument F1, F2,...Fn including the status is scanned at a predetermined scan period Ts. When field instruments are connected to the same field bus, the scan period Ts is extended, and for this reason, when a field instrument malfunctions, it is no longer possible to immediately transmit the status signal to the controller. As a result, it is not immediately possible to know which field instrument has caused the abnormality.

For example, if it takes 100ms to transmit data from one field instrument and 100 field instruments are connected, one scan period Ts is 100ms.
x 100 units = 10 seconds, a maximum delay time of 10 seconds is required, and abnormalities cannot be detected immediately.

[0011]

[Means for Solving the Problems] As a main signal transmission method for solving the above problems, the present invention provides a time-sharing system that uses a bus line connecting a controller and a plurality of field instruments. By multiplex transmission, digital signals are transmitted to both sides, and a DC voltage is superimposed on the previous bus line to send the digital signal to the previous bus line.
In the signal transmission method that supplies operating power to field instruments,
When an abnormality occurs in the field meter, it sends an abnormality notification signal in a frequency band different from the transmission frequency band of the previous digital signal to the previous bus line.

0012

[Operation] When an abnormality occurs in the field instrument, it uses time division multiplex transmission to control an abnormality notification signal with a frequency band different from the frequency band of the digital signal transmitted to both sides via the bus line. Transmit to La. The controller receives this abnormality notification signal from the bus line and learns that an abnormality has occurred in the field instrument. When such an abnormality detection method is used, the controller can immediately know an abnormality regardless of the scanning cycle of normal data collection, so that it is possible to easily ensure the safety of the plant.

[0013]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. 13 is a controller, and this controller
The liner 13 is placed in a control room or the like, and is connected in parallel via the field bus 11 to n field instruments such as f1, f2, . . . placed at the site. The controller 13 basically executes field bus transmission control and monitoring/control of the plant operating status. Also, the field instruments f1, f2... are basically the field bus 11.
The measured value is transmitted to the controller 13. These will be explained in more detail below.

The controller 13 is composed of a DC power supply Eb, an abnormality receiving circuit ARC, a digital transmitting/receiving circuit DFR1, a computer CPU1, a display DSP, etc. The DC power supply Eb is connected to the field bus 11 via a power supply circuit (not shown), and each field instrument f1, f2...
It supplies DC operating power to operate these instruments. Furthermore, the abnormality receiving circuit ARC
The abnormality signal ABS of each field meter f1, f2 . . . transmitted from the field meters f1, f2 . . . via the field bus 11 is received.

The digital transmitter/receiver circuit DFR1 is connected in parallel to the field bus 11 and connects each field instrument f1, f.
2. Send commands to..., field instrument f1,
Digital data DD, which is a measured value of differential pressure, pressure, etc. detected at f2 . . . is received via the field bus 11.

Although not shown, the computer CPU 1 includes a RAM (random access memory) and a ROM (reader memory).
Depending on the state of the abnormal signal AS output based on the presence or absence of the abnormal signal ABS transmitted from each field instrument f1, f2... Digital transmitter/receiver circuit DFR1
It reads the digital data DD sent from and stores it in the memory, and uses this digital data DD to execute the calculations necessary for the operation of the process according to the program stored in the memory and outputs it to the display DSP. , and sends necessary data to the field bus 11.

On the other hand, a plurality of field instruments f1, f2, . . . having a similar configuration are connected to the field bus 11. Here, among these, field meter f1
The internal structure will be explained based on the following. The digital transmitter/receiver circuit DFR2 is connected in parallel to the field bus 11, and receives commands from the controller 13 or transmits measurement data output from the computer CPU2.

Furthermore, the abnormality notification circuit AIC is connected in parallel to the field bus 11, from which the field instrument f
1, and receives the abnormal signal AB1 from the computer CPU 2 and sends it to the field bus 11 in a frequency band different from that of the digital data DD, which is a normal transmission signal such as a measured value. An abnormality notification signal ABS having a frequency in the frequency band is sent out.

[0019] SNR is a sensor, and this sensor SNR
For example, the field meter f1 converts the pressure, temperature, etc. at the measuring point measured into electrical signals and outputs them to the analog/digital converter A/D. Analog/digital converter A
The digital signal converted by /D is sent to computer CPU2.
is output to.

The computer CPU 2 has a memory, which contains an arithmetic program for converting the measured differential pressure detected by the sensor SNR into an output corresponding to a predetermined range, or this field instrument. An abnormality diagnosis program for diagnosing abnormalities occurring in f1 itself is stored. The abnormality in this case refers to, for example, a case where there is a measurement input exceeding a preset range for the magnitude of the input differential pressure, or a case where a part of the RAM in the memory is not normal. The above configuration is the field instrument f
2, . . . are also similar to the field instrument f1.

Next, the transmission method of the signal transmission device 14 shown in FIG. 1 will be explained using a flow diagram showing the procedure of signal transmission shown in FIG. Under normal conditions, a command signal CMD1 is sent from the computer CPU1 to the field bus 11 via the digital transmitting/receiving circuit DFR1 according to a predetermined program, and the field instrument f1 transmits this command signal CMD1 to the digital transmitting/receiving circuit DFR2. Receive via. The computer CPU 2 receives this command signal C.
MD1 is decoded, and the differential pressure data measured by the sensor SNR, for example, is sent to the field bus 11 again via the digital transmitting/receiving circuit DFR2.

Computer CPU on the controller 13 side
1 receives this differential pressure data as a response RES1. Next, in the same manner, the command signal CMD2 is sent out to call the field instrument f2 and necessary data is collected. Hereafter, this is repeated for each field instrument.

However, during this information collection, if the field instrument f1 is determined to be abnormal due to a self-diagnostic program inputting a signal that exceeds a predetermined range, for example, the computer The CPU2 outputs an abnormality signal AB1.
is output to the abnormality notification circuit AIC, and the abnormality notification circuit AIC receives the control via the field bus 11 as shown in FIG.
An abnormality notification signal ABS having a frequency different from the normal frequency is output to the controller 13.

When the abnormality receiving circuit ARC of the controller 13 receives this abnormality notification signal ABS, it
An abnormality signal AS indicating that an abnormality has occurred is sent to U1. As a result, the computer CPU1 stops normal scanning as shown in FIG. 2 according to a predetermined program stored in the memory, and waits for the ID code output from the field meter f1.

On the other hand, as shown in FIG. 2, the abnormality notification circuit AIC of the field meter f1 outputs an ID code indicating itself after a certain period of time after outputting the abnormality notification signal ABS.

[0026] Therefore, the computer CPU 1 uses this I
By receiving the D-code, you will know which field instrument caused the accident, and you will be able to follow the rules to ensure driving safety according to a predetermined program stored in memory.
Take measures such as backing up the backup and disconnecting the field instrument.

FIG. 3 is an explanatory diagram illustrating another example of the abnormal signal transmission system of the present invention. In this case, as shown in FIG. 3, the field meters f1, f2, ..., fn are connected to each other in a frequency band different from the frequency band fn used for normal digital communication. . . . The abnormality notification signal ABS has a different frequency fA1, fA2, . . . fAn for each fn.

If such a transmission method is adopted, when the frequencies fA1, fA2, . . .
3, it is possible to immediately determine which field instrument has caused the abnormality.

[0029]

[Effects of the Invention] As described above in detail with the embodiments, according to the present invention, the controller sends and receives digital signals by sequentially scanning each field instrument at a predetermined scan period. However, when a field instrument has an abnormality, it sends an abnormality notification signal to the bus line in a frequency band different from the normal digital signal transmission frequency band, so the controller is independent of the normal scan cycle. Abnormalities in field instruments can be detected immediately. Therefore, the controller can promptly take measures such as ensuring the safety of the plant.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a signal transmission device that transmits using a signal transmission method according to the present invention.

FIG. 2 is an explanatory diagram showing a signal transmission procedure in the embodiment shown in FIG. 1;

FIG. 3 is an explanatory diagram illustrating a relationship for identifying a field instrument with an abnormality in the embodiment shown in FIG. 1;

FIG. 4 is a block diagram showing the configuration of a conventional signal transmission device.

FIG. 5 is an explanatory diagram showing a signal transmission procedure of the signal transmission device shown in FIG. 4;

[Explanation of symbols]

10, 13 Controller 11 Field bus 12, 14 Signal transmission device F1, F2, Fn, f1, f2 Field instrument CP
U1, CPU2 Computer ARC Abnormal reception circuit DFR1, DFR2 Digital transmission/reception circuit AIC
Abnormality notification circuit SNR sensor

Claims (3)

[Claims] Claims: 1. Digital signals are transmitted between a controller and a plurality of field instruments by time-division multiplexing via a bus line connecting the field instruments, and a DC voltage is superimposed on the bus line to control the field instruments. - In a signal transmission method for supplying operating power to a field meter, when an abnormality occurs in the field meter, the field meter sends an abnormality notification signal in a frequency band different from the transmission frequency band of the digital signal to the bus line. A signal transmission method characterized by: 2. The field instrument that has caused the abnormality outputs an ID code for identifying itself after a predetermined time after sending out the abnormality notification signal, and the controller transmits the abnormality notification signal. 2. The signal transmission system according to claim 1, wherein the time division scan is stopped from the time of identification, and the ID code is received to identify the abnormal field instrument. 3. The abnormality notification signal has a unique abnormality notification frequency set in a different frequency band for each field instrument, and the controller detects the signal of the field that has caused the abnormality from this abnormality notification frequency. 2. The signal transmission method according to claim 1, wherein the signal transmission method specifies a field meter.