Field bus system and virtual field apparatus

Abstract

In a system for performing signal transmission, through a field bus, between field devices and higher-rank apparatuses connected on a transmission line, the field devices are of the analog signal type, and a substitution means is provided between the analog type field devices and the field bus so that the substitution means acts to perform communication on the field bus as a substitute for the field devices. By the substitution means, the field devices can be gradually changed to those adapted to the field bus as occasion demands, so that an existing system can be transformed step by step into a field bus system.

What is claimed is:  
     
         1 . A field bus system for connecting to a pair of transmission lines a plurality of field devices which detect physical amounts and/or output operation amounts at a field-side of said transmission lines, a higher-rank apparatus at a higher-rank side of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices, and an external power supply at thee higher-rank side of said transmission lines, said external power supply supplies electric power to said transmission lines, said field bus system further conducting communication by using digital signals between said field devices and said higher-rank apparatus through said transmission lines, said field devices include at least one analog signal type field device whose input/output signals are analog signals and at least one digital signal type field device whose input/output signals are digital signals, said at least one digital signal type field device being connected to said transmission lines, said field bus system comprising: 
 a processing device at the field-side of said transmission lines, said processing device performs processing including signal conversion between communication signals including an analog signal input and/or output to and/or from said at least one analog signal type field device and communication signals including a digital signal used on said transmission lines,    wherein said processing device converts the electric power on said transmission lines to another electric power which is applied to said at least one analog signal type field device to drive said at least one analog signal type field device,    wherein said processing device is connected to said transmission lines,    wherein said at least one analog signal type field device is connected to said processing device, and    wherein said digital signal type field device communicates with said higher-rank apparatus without using said processing device.    
     
     
         2 . A virtual field apparatus for connecting to a pair of transmission lines of a field bus system at least one analog signal type field device, said field bus system conducts communication by digital signals between field devices at a field-side of said transmission lines, said field devices including said at least one analog signal type field device which detects physical amounts and/or output operation amounts in at least a plant and whose input/output signals includes analog signals, and at least one digital signal type field device which detects physical amounts and/or output operation amounts in at least the plant and whose input/output signals include digital signals, said field bus system further connecting to said transmission lines a higher-rank apparatus at a higher-rank side of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices via said transmission lines, said at least one digital signal type field device being connected to said transmission lines, and an external power supply at the higher-rank side of said transmission lines, said external power supply applies electric power to said transmission lines, said virtual field apparatus comprising: 
 a digital signal connection terminal connected to said transmission lines at the field-side of said transmission lines;    a plurality of analog signal connection terminals, wherein at least one analog signal connection terminal is connected to said at least one analog signal type field device;    a signal converter for performing signal conversion between a communication signal including an analog signal which is inputted or outputted at said at least one analog signal connection terminal and a communication signal including a digital signal used on said transmission lines; and    an electric power converter, connected to said digital signal connection terminal, for converting the electric power on said transmission lines to another electric power and applying said another electric power to said at least one analog signal type field device to drive said at least one analog signal type field device via said at least one analog signal connection terminal,    wherein said digital signal type field device communicates with said higher-rank apparatus without using said virtual field apparatus .    
     
     
         3 . A field bus system for connecting to a pair of transmission lines a plurality of field devices which detect physical amounts and/or output operation amounts at a field-side of said transmission lines, a higher-rank apparatus at a higher-rank side of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices, and an external power supply at the higher-rank side of said transmission lines, said external power supply supplies electric power to which drives said field devices at a high-rank side of said transmission lines, said field bus system further conducting communication by using digital signals between said field devices and said higher-rank apparatus through said transmission lines, said field devices include a plurality of analog signal type field devices whose input/output signals are analog signals and at least one digital signal type field device whose input/output signals are digital signals, said at least one digital signal type field device being connected to said transmission lines, said field bus system comprising: 
 a processing device at the field-side of said transmission lines, said processing device performs signal conversion between communication signals including an analog signal input and/or output to and/or from an analog signal type field device and communication signals including a digital signal used on said transmission lines,    wherein said processing device converts the electric power on said transmission lines to another electric power which is applied to said analog signal type field devices to drive said analog signal type field devices,    wherein said processing device is connected to said transmission lines,    wherein each of said analog signal type field devices is connected to said processing device, and    wherein said digital signal type field device communicates with said higher-rank apparatus without using said processing device.    
     
     
         4 . A virtual field apparatus for connecting to a pair of transmission lines of a field bus system a plurality of analog signal type field devices, said field bus system conducts communication by digital signals between said field devices at a field-side of said transmission lines, including said analog signal type field devices which detects physical amounts and/or output operation amounts in at least a plant and whose input/output signals includes analog signals, and at least one digital signal type field device which detects physical amounts and/or output operation amounts in at least the plant and whose input/output signals include digital signals, said field bus system further connecting to said transmission lines a higher-rank apparatus at a higher-rank of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices via said transmission lines, said at least one digital signal type field device being connected to said transmission lines, and an external power supply at the higher-rank side of said transmission lines, said external power supply applies electric power to said transmission lines, said virtual field apparatus comprising: 
 a digital signal connection terminal connected to said transmission lines at the field-side of said transmission lines;    a plurality of analog signal connection terminals, wherein at least one analog signal connection terminal is connected to each of said analog signal type field devices;    a signal converter for performing signal conversion between a communication signal including an analog signal which is inputted or outputted at said at least analog signal connection terminal and a communication signal including a digital signal used on said transmission lines; and    an electric power converter, connected to said digital signal connection terminal, for converting the electric power on said transmission lines to another electric power and applying said another electric power to said at least one analog signal type field device to drive said at least one analog signal type field device via said at least one analog signal connection terminal,    wherein said digital signal type field device communicates with said higher-rank apparatus without using said virtual field apparatus.    
     
     
         5 . A field bus system for connecting to a pair of transmission lines a plurality of field devices which detect physical amounts and/or output operation amounts at a field-side of said transmission lines, a higher-rank apparatus at a higher-rank side of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices, and an external power supply at the higher-rank side of said transmission lines, said external power supply supplies electric power to said transmission lines, said field bus system further conducting communication by using digital signals between said field devices and said higher-rank apparatus through said transmission lines, said field devices include at least one analog signal type field device whose input/output signals are analog signals and at least one digital signal type field device whose input/output signals are digital signals, said at least one digital signal type field device being connected to said transmission lines, said field bus system comprising: 
 a processing device at the field-side of said transmission lines, said processing device performs processing including signal conversion between communication signals including an analog signal input and/or output to and/or from said at least one analog signal type field device and communication signals including a digital signal used on said transmission lines,    wherein said processing device includes a power supply which converts the electric power on said transmission lines to another electric power and applies the another electric power to said at least one analog signal type field device to drive said at least one analog signal type field device,    wherein said processing device is connected to said transmission lines,    wherein said at least one analog signal type field device is connected to said processing device, and    wherein said digital signal type field device communicates with said higher-rank apparatus without using said processing device.    
     
     
         6 . A virtual field apparatus for connecting to a pair of transmission lines of a field bus system at least one analog signal type field device at a field-side of said field bus system, said field bus system conducts communication by digital signals between field devices at the field-side of said transmission lines, including said at least one analog signal type field device which detects various data regarding at least a plant and whose input/output signals includes analog signals, and at least one digital signal type field device which detects various data regarding said at least a plant and whose input/output signals include digital signals, said field bus system further connecting to said transmission lines a higher-rank apparatus at a higher-rank side of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices via said transmission lines, said at least one digital signal type field device being connected to said transmission lines, and an external power supply at the higher-rank side of said transmission lines, said external power supply applies electric power to said transmission lines, said virtual field apparatus comprising: 
 a digital signal connection terminal connected to said transmission lines at the field-side of said transmission lines;    a plurality of analog signal connection terminals, wherein at least one analog signal connection terminal is connected to said at least one analog signal type field device;    a signal converter for performing signal conversion between a communication signal including an analog signal which is inputted or outputted at said at least one analog signal connection terminal and a communication signal including a digital signal used on said transmission lines; and    an electric power converter, connected to said digital signal connection terminal, for converting the electric power on said transmission lines to another electric power and applying said another electric power to said at least one analog signal type field device to drive said at least one analog signal type field device,    wherein said digital signal type field device communicates with said higher-rank apparatus without using said vertical field apparatus.    
     
     
         7 . A virtual field apparatus according to  claim 6 , wherein said various data regarding said at least a plant detected by said at least one analog signal type field device includes physical amounts and/or output operation output amounts of said at least a plant, and 
 wherein said various data regarding said at least a plant detected by at least one digital signal type field device includes physical amounts and/or output operation amounts of said at least a plant.    
     
     
         8 . A field bus system for connecting to a pair of transmission lines a plurality of field devices which detect various data at a field-side of said transmission lines, a higher-rank apparatus at a higher-rank side of said transmission lines, said higher-rank apparatus monitors and/or controls said field devices, and an external power supply at the higher-rank side of said transmission lines, said external power supply supplies electric power to said transmission lines, said field bus system further conducting communication by using digital signals between said field devices and said higher-rank apparatus through said transmission lines, said field devices include at least one analog signal type field device whose input/output signals are analog signals and at least one digital signal type field device whose input/output signals are digital signals, said at least one digital signal type field device being connected to said transmission lines, said field bus system comprising: 
 a processing device at the field-side of said transmission lines, said processing device which performs signal conversion between communication signals including an analog signal input and/or output to and/or from said at least one analog signal type field device and communication signals including a digital signal used on said transmission lines,    wherein said processing device includes a power supply which converts the electric power on said transmission lines to another electric power and applies the another electric power to said at least one analog signal type field device to drive said at least one analog signal type field device,    wherein said processing device is connected to said transmission lines,    wherein said at least one analog signal type field device is connected to said transmission lines through said processing device, and wherein said digital signal type field device communicates with said higher-rank apparatus without using said processing device.    
     
     
         9 . A virtual field apparatus according to  claim 8 , wherein said various data regarding said at least plant detected by said at least one analog signal type field device includes physical amounts and/or output operation output amounts of said at least a plant, and 
 wherein said various data regarding said at least a plant detected by at least one digital signal type field device includes physical amounts and/or output operation amounts of said at least a plant.