Telemeter and communication method using the same

Abstract

To provide a telemeter capable of transmitting status data of a remotely monitored object received by a PLC to a host monitoring device even when the CPU operation is stopped.SOLUTION: In a telemeter 1 having a CPU 3 which generates transmission data 24 from an output 22 of a PLC 9 and a modem 4 which is connected to a public line 101 and which transmits the state of a remotely monitored object (pump 40) to a host monitoring device 100, a bypass line 15 which transmits the output 22 from the PLC 9 directly to the modem 4, and a switching unit 5 are newly provided. When the CPU 3 is operating normally, the output 22 of the PLC 9 is transmitted to the CPU 3 by the switching unit 5, and after being processed by the CPU 3, is transmitted from the modem 4 to the host monitoring device 100 as outputs 24, 25. When the CPU 3 stops, the output 22 of the PLC 9 is transmitted directly to the modem 4 from the bypass line 15, and is then transmitted as is to the host monitoring device 100 via the public line 101.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a telemeter using a public line and a communication method using the same, and more particularly to a telemeter configuration that can reliably transmit status signal data acquired at a telemeter installation location such as a pumping station to a higher-level monitoring device, and a communication method in the event of an abnormality. [Background technology]

[0002] Conventionally, monitoring and control systems have been known in which data from monitored objects is captured in a communication terminal installed on-site, and the status of the monitored object is transmitted to a remote location via communication, or commands are sent to on-site equipment to remotely control it. For example, telemeters are widely used in water supply and sewerage systems, water distribution facilities, and industrial production facilities in remote locations. When using telemeters, public lines such as analog dedicated lines have been widely used as communication lines. Currently, the use of always-on lines via networks such as broadband lines is increasing, but broadband lines tend to be expensive, and because of the difficulty of installing communication lines in mountainous areas, there are many cases where service is not provided in installation locations (such as airports) where costs are high. Therefore, there is still a strong demand for public lines.

[0003] A known technology for such a monitoring system using a telemeter is that described in Patent Document 1. Patent Document 1 discloses a telemeter that uses a dedicated line and that, when a calculation unit in the telemeter hangs up, is provided with a switching unit (switching logic) that switches to a message generated by a standby calculation unit, and is provided with a modem that transmits messages from the calculation unit or the standby calculation unit over the dedicated line, thereby allowing communication to continue even when the telemeter hangs up. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-154443 Summary of the Invention [Problem to be solved by the invention]

[0005] In the telemeter disclosed in Patent Document 1, if the calculation unit hangs up, the telegram generated by the standby calculation unit includes a fixed value appropriate for operating the equipment, thereby allowing control to continue. However, the telegram generated by the standby calculation unit does not contain the normal value at the actual pump station, which causes a problem in that normal operation cannot be continued.

[0006] The present invention has been made in view of the above background, and its object is to provide a telemeter and a communication method using the same that can reliably transmit a fault signal at the telemeter installation location to a higher-level monitoring device even if the processor of the telemeter communication device hangs up. Another object of the present invention is to provide a telemeter and a communication method using the same in which a switching unit is provided in the telemeter for switching the transmission path and transmission content when the processor hangs up, thereby enabling normal monitoring functions to continue. [Means for solving the problem]

[0007] Representative features of the invention disclosed in this application are as follows. According to one aspect of the present invention, the present invention is applied to a telemeter having a telemeter communication device connected to a public line and a programmable logic controller (PLC) that receives a fault signal from a monitored object and transmits it to the telemeter communication device. The PLC has a function of outputting a data string indicating a fault condition to the telemeter communication device upon receiving the fault signal. The telemeter communication device has a processor that receives the data string from the PLC and generates normal-state transmission data to be transmitted to a host monitoring device, a modem that communicates with the host monitoring device via the public line, and a switching unit. The switching unit outputs the data string from the PLC to either the processor or the modem. A bypass line is also provided to connect the PLC and the modem when the processor is not operating normally. The switching unit is configured with a selector switch that connects the PLC to the processor when the processor is operating normally and connects the PLC to the bypass line when the processor is not operating normally. The processor and the PLC are connected via an RS232C communication line, and the modem and the PLC are connected via an RS232C communication line.

[0008] According to another feature of the present invention, the changeover switch includes a first relay with an a-contact that connects the output of the PLC to the input line of the processor, and a second relay with a b-contact that connects the output of the PLC to the bypass line. These first and second relays are controlled by a timer relay. The timer relay outputs a control signal when the processor is operating normally and stops outputting the control signal a predetermined time after the processor stops operating normally. The processor creates normal transmission data by adding additional information, including identification information and date and time information of the monitored object, to the data string received from the PLC.

[0009] According to yet another feature of the present invention, when the telemeter modem receives a data string via the bypass line, it connects to a preset destination and automatically transmits the data string. The data string generated by the PLC may include identification data indicating a "failure" in the telemeter communication device, and the processor may change the identification data in the data string from "failure" to "no failure" upon successfully receiving the data string from the PLC. The public line modem has two input ports, and when a signal is received at one input port via the bypass line, it establishes a communication path via the public line to the destination according to a preset procedure and automatically transmits the received normal transmission data or the data string from the PLC to the higher-level supervisory device. [Effects of the Invention]

[0010] According to the present invention, the modem connected to the public line and the PLC that receives the pump station status signal can be connected by a bypass line via a switching unit, so that even if the processor in the telemeter communication device hangs up, the PLC output can be switched to be sent to the modem, and a fault signal from the remotely monitored object can be reliably sent to the host monitoring device as transmission data in the event of a fault. Furthermore, the host monitoring device that receives the transmission data can easily determine whether the processor in the telemeter has stopped or is operating normally based on the length and content of the transmission data, so the host monitoring device can perform monitoring work with high accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a configuration of a telemeter 1 according to an embodiment of the present invention. [Figure 2] 2 is a partial block diagram showing the internal configuration of the telemeter communication device 2 of FIG. 1, where (A) shows the connection state of the switching circuit 5 when the CPU 3 is operating normally, and (B) shows the connection state of the switching circuit 5 when the CPU 3 is stopped and not operating normally. [Figure 3]1A and 1B are diagrams showing the transmission status of transmission data in an embodiment of the present invention, where (A) shows the flow of transmission data when CPU3 is operating normally, and (B) shows the flow of transmission data when CPU3 is stopped. [Figure 4] 4A and 4B are diagrams showing the contents of the transmission data in FIG. 3, in which (A) is transmission data 50 generated by the PLC 9, and (B) is transmission data 60 processed by the CPU 3. FIG. [Figure 5] FIG. 10 is a diagram showing the data structure of transmission data 50A and 60A according to a first modified example of the present invention. [Figure 6] FIG. 10 is a diagram showing the data structure of transmission data 50B and 60A according to a second modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0012] The present invention will be described in detail below with reference to specific embodiments. First, a telemeter 1 according to a first embodiment of the present invention will be described with reference to Fig. 1. The telemeter 1 is a device provided for monitoring the status of target equipment by a host monitoring device 100, and is mainly composed of a PLC 9 (Programmable Logic Controller) and a telemeter communication device 2 that collects signals transmitted from the PLC 9 and transmits them to the external host monitoring device 100. The telemeter 1 receives an output, i.e., a fault signal 21, generated when a fault occurs in a remotely monitored object, in this case a pump 40 at a pumping station, etc., at the PLC 9, converts the output into a predetermined data string 22, transmits it to the CPU 3, and after processing the data by the CPU 3, transmits it as transmission data 25 to the host monitoring device 100 via a modem 4 over a public line 101.

[0013] In recent years, real-time monitoring using broadband lines has become common for data acquisition from remotely monitored objects to the host monitoring device 100. Meanwhile, in addition to or instead of real-time monitoring using broadband lines, monitoring using a telemeter 1 using a public line has also become common. The telemeter 1 often employs a timely transmission method (sending data only when an abnormality occurs), and a signal is sent to the host monitoring device 100 when a failure occurs in the remotely monitored object. Therefore, if a failure occurs in the CPU 3 constituting the telemeter 1, the telemeter 1's communication function may stop, potentially preventing it from sending a signal indicating an abnormality to the host monitoring device 100. Furthermore, when an abnormality occurs, the host monitoring device 100 may be unable to determine whether the telemeter 1 is malfunctioning or the remotely monitored object (pump 40) is malfunctioning. Therefore, in this embodiment, a signal indicating an abnormality can be reliably sent to the host monitoring device 100 even when the CPU 3 of the telemeter 1 stops due to a hang-up or other reason. In the telemeter 1 of this embodiment, the output of the PLC 9 is not fixed to the input lines 11 and 12 and input to the CPU 3, but rather the output from the PLC 9 is passed through the CPU 3 and transmitted directly to the modem 4. In this way, a switching circuit (switching unit) 5 and a bypass line 15 are provided in the telemeter 1.

[0014] The PLC 9 is a control device (controller) used to control and monitor equipment and facilities, and uses a microprocessor to run software. Here, the PLC 9 monitors the operation of a pump 40 installed in a pumping station. When a fault signal 21 indicating a fault is detected, the PLC 9 generates a data sequence 22 indicating the fault and transmits it to the telemetry communication device 2 via the RS232C line 11. The data sequence 22 is a short signal, e.g., a few bits to a few bytes, and defines a bit sequence corresponding to the status of each part of the pump. Each bit is assigned a flag (e.g., bit “1”) indicating an abnormality in the corresponding part or a normal flag (e.g., bit “0”) indicating a normal state. Thus, the data sequence 22 has a content such as “001000…,” and the host monitoring device 100 can determine the detailed status of the pump 40 by determining which bit in the data sequence 22 contains a “1” indicating an abnormality. The definition of each bit in the data sequence 22 output by the PLC 9 and the number of bits to be set for the data sequence are arbitrary, and can be set as a program in the PLC 9 according to the number of objects to be monitored. Furthermore, when there are a plurality of pumps 40, such as 40-1, 40-2, . . . , a data column 22 having a data capacity corresponding to each of the pumps 40-1, 40-2, .

[0015] The CPU (Central Processing Unit) 3 is a processor that executes a program to generate a message to be transmitted, i.e., normal-state transmission data 24, from the received data sequence 22 and transmits the message to the modem 4. Any type of processor may be used, including not only a CPU but also other processors, such as an MPU (Micro-Processing Unit). The modem 4 is a well-known communication device for bidirectional communication with the upper-level supervisory device 100 using a public line 101 such as a telephone line. The modem 4 used in this embodiment has a first input port 4a for inputting the normal-state transmission data 24 from the CPU 3 and a second input port 4b for inputting the data sequence 23 from the bypass line 15. Upon receiving the normal-state transmission data 24 from the first input port 4a, the modem 4 establishes a connection with a preset destination (here, the upper-level supervisory device 100) in accordance with an instruction from the CPU 3 or a preset procedure, and transmits the abnormal-state transmission data 23 as transmission data 25. Furthermore, when the modem 4 receives the data sequence 23 from the second input port 4b, it establishes a connection with the designated destination (here, the host supervisory device 100) according to a preset procedure and automatically transmits the data sequence 23 as transmission data 25. To enable this connection, the modem 4 stores information such as the telephone number (or IP address, etc. used to specify the destination) of the host supervisory device 100 (not shown), the communication method, and the communication speed. The modem 4 is equipped with a retry function, which attempts to connect multiple times if the destination (the host supervisory device 100) is busy. Note that the number of destinations set in the modem 4 is not limited to one. For example, it may be configured so that other destinations can be set in addition to the host supervisory device 100, and data can be transmitted sequentially to multiple destinations. The normal output line 13 between the CPU 3 and the modem 4 for public lines may be, for example, an RS232C standard communication line or a USB standard communication line. Note that USB (Universal Serial Bus) is a registered trademark of Implementers Forum, Inc., USA.

[0016] The switching circuit 5 is a circuit configured by combining one or more changeover switches, and when the CPU 3 is operating normally, it maintains the connection between the RS232C line 11 and the input line 12 so that the output from the PLC 9 is input to the CPU 3. When the CPU 3 is not operating normally (when it is stopped or hung up, etc.), it disconnects the connection between the RS232C line 11 and the input line 12 and connects the RS232C line 11 to the bypass line 15.

[0017] In this way, when the CPU 3 in the telemeter communication device 2 is not operating normally, the switching circuit 5 switches to the connection line in the event of a failure, i.e., the bypass line 15, and switches so that the data sequence 22 from the PLC 9 indicating the status of the pump station is sent directly to the second input port 4b of the modem 4.

[0018] FIG. 2 is a partial block diagram showing the internal configuration of the telemeter communication device 2 shown in FIG. 1. The telemeter communication device 2 includes a CPU 3, a timer relay (TR) 8, and a switching circuit 5. The TR 8 has an internal timer and maintains a high output signal to a control signal line 17 when an external input signal (here, an operation signal from the CPU 3 via an operation signal line 16) is high. When the input signal from the operation signal line 16 changes from high to low, the timer is activated. After a predetermined time (e.g., several milliseconds to several seconds) has elapsed, the output signal to the control signal line 17 is switched from high to low, thereby switching the connection state of the switching circuit 5. Because the TR 8 does not immediately stop outputting a signal output stop signal when reception of a normal operation signal is interrupted, the CPU 3 may temporarily enter a busy state due to processing requirements, preventing malfunction. It is recommended that the CPU 3 in this embodiment be provided with an automatic recovery function that automatically resets the CPU 3 and returns it to a normal state if the CPU 3 hangs up for a long period of time. When the input signal from the operation signal line 16 changes from low to high, TR8 immediately switches the output signal to the control signal line 17 from low to high.

[0019] The switching circuit 5 is a switching unit including two relay-type changeover switches, a first relay 6 and a second relay 7, and outputs an input signal (RS232C line) to either the first output side (normal input line 12) or the second output side (bypass line 15) in accordance with an external control signal (here, the output of a timer relay 8 input via a control signal line 17). A known RS232C switch can be used. The first relay 6 is a contact-a switch that connects its contacts when an external control signal is received. The second relay 7 is a contact-b switch that connects its contacts when no external control signal is received.

[0020] 2(A) shows the case where CPU3 is operating normally, in which CPU3 continues to output a normal operation signal, and when TR8 receives this normal operation signal, it outputs a high signal to switching circuit 5, and switching circuit 5 receives this signal and activates first relay 6 and second relay 7. When first relay 6 receives a control signal from TR8, its relay device operates and the previously open switch closes, connecting RS232C line 11 and input line 12 to CPU3 (contact a). At the same time, when second relay 7 receives a control signal from TR8, its relay device operates and the previously closed switch opens, disconnecting RS232C line 11 and bypass line 15 (contact b).

[0021] If the CPU 3 stops operating for some reason, as shown in Figure 3(B), the normal operation signal from the CPU 3 via the operation signal line 16 disappears, and TR8 stops outputting signals to the switching circuit 5 via the control signal line 17 after a set time has elapsed since the normal operation signal was no longer received. As a result, the first relay 6 switches from closed to open, disconnecting the RS232C line 11 from the input line 12 to the CPU 3, and at the same time, the second relay 7 switches from open to connect the RS232C line 11 to the bypass line 15.

[0022] In this embodiment, when the operation of the CPU 3 stops and no signal is received from the timer relay 8, the switching circuit 5 automatically switches the output path of the abnormal signal from the PLC 9 from the CPU 3 to the modem 4. When the operation of the CPU 3 returns to normal, the normal operation signal is again continuously output from the CPU 3 to the TR 8, and the switching circuit 5 restores the state of FIG. 2(A) from the TR 8.

[0023] FIG. 3 illustrates the transmission status of transmission data (message) in an embodiment of the present invention. In the PLC 9, the data sequence (transmission data 50) set by the PLC 9 includes a status data section 51, which is a string of multiple bits indicating the status of each part of the pump 40 when the pump 40 breaks down. FIG. 3(A) illustrates the data transmission status when the CPU 3 is operating normally. In a pumping station, when an abnormality occurs in the pump 40, the PLC 9, which monitors the status of the pump 40, creates a data sequence indicating the status of each part and stores it in the status data section 51 as transmission data 50, which is then sent to the telemeter communication device 2. In other words, the transmission data 50 is the data sequence from the PLC 9 itself. As shown in both FIGS. 3(A) and 3(B), the transmission data 50 created by the PLC 9 is transmitted to the telemeter communication device 2 via the RS232C line 11.

[0024] In FIG. 3(A), CPU 3 is operating normally, so switching circuit 5 transmits the output of RS232C line 11 to input line 12 to CPU 3. CPU 3 performs necessary data processing on input status data section 51 and transmits the result as transmission data 50 to modem 4 via the normal output line. There are various possible data processing methods for status data section 51 that can be performed by CPU 3. The simplest example is a process in which transmission data 60 is created by adding a station data section 61 after status data section 51. Transmission data 60 is transmitted to modem 4 via normal output line 13, and modem 4 transmits transmission data 60 as is to host supervisory device 100. Here, the contents of transmission data 50 and 60 will be further explained using FIG. 4.

[0025] 4A and 4B are diagrams showing the contents of the transmission data 50 and 60 shown in FIG. 3, with (A) showing the transmission data 50 output from the PLC 9. A status data section 51 generated by the PLC 9 includes multiple bits 52a, 52b, 52c, etc. The number of bits included in the status data section 51 is arbitrary, for example, 16 bits. The multiple bits 52a, 52b, 52c, etc. correspond to each part of the pump 40, and indicate the status of each part as either "0" (normal) or "1" (abnormal).

[0026] FIG. 4B shows transmission data 60 transmitted to modem 4 after data processing by CPU 3. Here, CPU 3 adds a plant data section 61 to the end of status data section 51. The plant data section 61 stores, for example, time data 62 indicating the date and time when PLC 9 detected the occurrence of a fault, and a machine number 63 indicating the equipment identification information of pump 40. The pumps 40 and their machine numbers 63 installed at each pump plant are pre-registered in host monitoring device 100. Therefore, upon receiving transmission data 60, host monitoring device 100 can determine which pump 40, in which pump plant, and at which location the fault occurred, and when. The plant data section 61 may be any number of bits long, and may be approximately 16 or 32 bits, or even longer.

[0027] Returning to FIG. 3 again, FIG. 3(B) shows the transmission data 50 transmitted from the modem 4 to the host supervisory device 100 when the CPU 3 freezes or stops for some reason, such as a hang-up. When the CPU 3 stops, the transmission data 50 cannot be transmitted from the CPU 3 to the modem 4. Therefore, in this embodiment, after a predetermined time has elapsed since the CPU 3 stopped, the connection state of the switching circuit 5 is switched from the PLC 9 to the bypass line 15. In this state, the transmission data 50 output from the PLC 9 is transmitted directly to the second input port 4b of the modem 4 via the bypass line 15 by the switching circuit 5. When the modem 4 receives the transmission data 50 via the bypass line 15, it establishes a communication path via a public line by calling the host supervisory device 100, which is a preset destination, and transmits the transmission data 50 to the host supervisory device 100 as is.

[0028] In this manner, when the host monitoring device 100 receives the transmission data 50 or 60 from the modem 4, it records the transmission data 50 or 60 together with the sender identification information in a storage device (not shown). Here, the sender identification information can be, for example, the telephone number of the modem 4 that made the call and the date and time of reception. As can be seen in FIG. 3, there are two types of transmission data (50, 60) received by the host monitoring device 100. One is the transmission data 60 received when the CPU 3 of the telemeter 1 is operating normally, and the other is the transmission data 50 received when the CPU 3 is not operating normally. In this way, the host monitoring device 100 can easily determine whether the CPU 3 is stopped or not based on the difference in bit length of the transmission data 50, 60 and the content of a specific bit (here, the abnormal data section 55). In this embodiment, not only can it be easily determined whether the CPU 3 of the telemeter 1 is normal or not by the difference between the received transmission data 50 (in the event of a malfunction) and the transmission data 60 (in the normal state), but also, when the transmission data 60 in the event of an abnormality is received, the upper level monitoring device 100 can add date and time information, device information, etc., to fill in the missing parts of the data when the CPU 3 is stopped, and store the data in a storage device (not shown).

[0029] FIG. 5 shows the contents of transmission data 50A and 60A according to a first modification of the present invention. The transmission data 50A sent by the PLC 9 is the transmission data 50 shown in FIG. 4 with one bit added to the abnormality data section 55. The configuration of the status data section 51 is the same as that of the transmission data 50 shown in FIG. 4. The transmission data 50A is transmitted to the CPU 3 with the PLC 9 adding a 16-bit status data section 51 and a 1-bit abnormality data section 55. That is, the PLC 9 adds an abnormality data section 55 indicating the fault status of the telemeter communication device 2 to the status data section 51 to be transmitted, and outputs the result as the transmission data 50A. The abnormality data section 55 is identification data indicating whether or not the telemeter communication device 2 is faulty. If the telemeter communication device 2 is normal, a "0" is stored therein, and if an abnormality such as a stop or hang-up occurs, a "1" is stored therein. When creating the transmission data 50A, the PLC 9 reserves a storage area for the abnormality data section 55 and sets a "1" in bit 55a as a default value. If the telemeter communication device 2 is normal, when the CPU 3 receives the data string (transmission data 50A) from the PLC 9, it overwrites the contents of the abnormality data section 55 with "0" indicating normality, adds a station data section 61, and transmits the data as transmission data 60A to the modem 4. The contents of the station data section 61 are the same as those shown in Fig. 4. The transmission data 50A, with part of it rewritten in this way and the station data section 61 added, is transmitted from the modem 4 via the public line 101 to the upper level supervisory device 100 as transmission data 60A.

[0030] If the CPU 3 of the telemeter communication device 2 hangs up (stops), the transmission data 50A from the PLC 9 is sent directly to the modem 4 via the bypass line 15. The modem 4 then transmits the received transmission data 50A directly to the host monitoring device 100. The host monitoring device 100 can determine whether the CPU 3 of the telemeter communication device 2 is malfunctioning based on whether the content of the bit 55a of the abnormality data section 55, which indicates the status of the CPU 3 of the telemeter communication device 2, is "1" or "0." The host monitoring device 100 then displays information or a warning indicating the malfunction on a display screen (not shown). In this way, even if the CPU 3 hangs up (stops), the transmission data 50A with the content of the bit 55a set to "1" is sent to the host monitoring device 100, so that the status of the pumping station can be communicated to the host monitoring device 100. The operator of the host monitoring device 100 can determine that a malfunction has occurred in the telemeter 1 of a specific remotely monitored object (e.g., a pumping station).

[0031] 6A and 6B show the contents of transmission data 50B and 60A according to a second modification of the present invention. As shown in FIG. 6A, transmission data 50B set by PLC 9 includes transmission data 50 shown in FIG. 4, plus an abnormal data section 55, and a data area 56a for the additional data is reserved in advance by CPU 3. An initial value, e.g., a series of "0" bits, is stored in data area 56a in advance. As a result, transmission data 50B sent from PLC 9 is approximately 32 bits long. The number of bits in abnormal data section 55 and the number of bits in free data section 56 can be set arbitrarily, ranging from several bytes to several tens of bytes, or even more.

[0032] The abnormal data section 55 has the same meaning as the bit 55a shown in Fig. 5. When the CPU 3 of the telemeter communication device 2 is normal, the transmission data 50B from the PLC 9 is transmitted to the CPU 3. When the CPU 3 creates transmission data 60A from the transmission data 50B, it rewrites the content of the abnormal data section 55 from "1" (abnormal) to "0" (normal), and writes time data 62 and a machine number (equipment number) 63 indicating the station data into the empty data section 56. The content of the transmission data 60A after writing is the same as the content of the transmission data 60A shown in Fig. 5.

[0033] If the CPU 3 of the telemeter communication device 2 hangs up (stops), the transmission data 50B from the PLC 9 is sent directly to the modem 4 via the bypass line 15, and the modem 4 sends the transmission data 50B to the host monitoring device 100. The host monitoring device 100 can unequivocally confirm that the telemeter communication device 2 has failed based on the contents of the abnormal data section 55, which indicates the state of the CPU 3 of the telemeter communication device 1, and can display information or a warning to that effect on a display screen (not shown). In addition to the abnormal data section 55, the host monitoring device 100 can also determine whether the bit string following the abnormal data section 55 is a sequence of consecutive 0s, and can confirm that information corresponding to the time data 62 and the serial number 63 is not present, thereby determining that the telemeter communication device 2 has failed. Furthermore, even if the data format of the transmission data 50B and 60A in Figure 6 omits the abnormal data section 55, the upper level monitoring device 100 can determine that the telemeter communication device 2 is malfunctioning by determining whether the bit string after the abnormal data section 55 is data consisting of consecutive 0s.

[0034] As described above, in the first and second variants of this embodiment, the data string set by the PLC 9 includes the abnormality data section 55 indicating the state when the telemeter communication device has failed, and the failure state is set in advance. Therefore, the upper level supervisory device 100 can determine whether the telemeter communication device 2 has failed by verifying the length of the transmitted transmission data 50A, 60A, the presence or absence of a bit "1" indicating an abnormality in the abnormality data section 55, the contents of the data, etc.

[0035] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments and various modifications are possible within the scope of the invention. [Explanation of symbols]

[0036] 1 Telemeter 2. Telemetry communication device 3 CPU 4 Modem 5 Switching circuit 6. First relay (a contact) 7 Second relay (b contact) 8 Timer Relay 9 PLC 11 RS232C line 12 (normal) input line 13 Normal output line 15 Bypass line 16 Operation signal line 17 Control signal line 21 Fault signal 22, 23 Data column 24 Normal transmission data 25 Transmission Data 40 Pump 50, 50A, 50B (from PLC) transmission data 60 Send data (from CPU) 100 Upper level monitoring device 101 Public Line

Claims

1. A telemeter having a telemeter communication device connected to a public line and a PLC that receives a fault signal from a monitored object and transmits the fault signal to the telemeter communication device, the PLC has a function of outputting a data string indicating a fault state to the telemeter communication device when receiving the fault signal; The telemeter communication device a processor that receives the data string from the PLC and generates normal-time transmission data to be transmitted to a higher-level supervisory device; a modem for the public line; a switching unit for outputting a data stream from the PLC to either the processor or the modem; A telemeter characterized by providing a bypass line for directly transmitting the data string from the PLC to the modem when the processor is not operating normally.

2. 2. The telemeter according to claim 1, wherein the switching unit has a changeover switch that connects the PLC to the processor when the processor is operating normally, and connects the PLC to the bypass line when the processor is not operating normally.

3. 3. The telemeter according to claim 2, further comprising a timer relay for transmitting a control signal for controlling the changeover switch to connect the PLC and the processor when the processor is operating normally.

4. 4. The telemeter according to claim 3, wherein the changeover switch includes a first relay with an a-contact that connects the output of the PLC to the input line of the processor, and a second relay with a b-contact that connects the output of the PLC to the bypass line.

5. The telemeter according to claim 4, wherein the processor creates the normal transmission data by adding additional information including identification information and date and time information of the monitored object to the data string received from the PLC.

6. 6. The telemeter according to claim 5, wherein said modem, upon receiving said data string via said bypass line, connects to a preset destination and automatically transmits said data string.

7. 7. The telemeter according to claim 6, wherein the PLC includes, in the data string, identification data indicating that the telemeter communication device has a failure.

8. 8. The telemeter according to claim 7, wherein, upon receiving the data string from the PLC, the processor changes the identification data in the data string to identification data indicating that there is no fault.

9. 9. The telemeter according to claim 8, wherein the processor and the PLC are connected by an RS232C communication line, and the modem and the PLC are connected by an RS232C communication line.

10. a PLC that receives a fault signal from a monitored object and outputs a data string including the fault signal; A telemeter having a processor that generates transmission data to be transmitted from the output of the PLC to a host monitoring device, and a modem for a public line that connects the transmission data from the processor to a public line, and that transmits a signal indicating the status of a remotely monitored object to the host monitoring device using the modem, a switching unit for switching between a communication line for transmitting the transmission data from the PLC to the modem and a bypass line for transmitting the transmission data from the PLC to the modem; the switching unit connects the output of the PLC to the communication line when the processor is operating normally, and switches the output of the PLC to connect to the bypass line when the processor is not operating normally; A communication method in a telemeter, characterized in that the modem establishes a communication path on the public line and transmits to the upper level monitoring device the transmission data from the processor or the data string transmitted from the PLC via the bypass line.

11. 11. The communication method in a telemeter according to claim 10, wherein the processor generates the transmission data by adding additional information to the PLC data string output via the switching unit.

12. The modem has two input ports; 12. A telemeter communication method according to claim 11, wherein when the transmission data or the data string is input to any of the input ports via the bypass line, the transmission data or the data string is automatically transmitted by connecting to a predetermined destination.

Images