JPH07101894B2 - 2-wire signal transmission system - Google Patents

Description

The present invention relates to a two-wire signal transmission system for transmitting a change in physical quantity or the like to a load via two wires, and particularly to a set value from outside the transmitter. The present invention relates to a two-wire type signal transmission system in which data such as can be set using a terminal.

<Prior Art> FIG. 7 is a block diagram showing a configuration of a conventional two-wire signal transmission system. This signal transmission method is disclosed in Japanese Patent Application No.
-128868, it was proposed as "Invention title: 2-wire signal transmission method".

Reference numeral 10 denotes a transmitter that converts a physical quantity such as a process variable into an electric signal and transmits the electric signal. Electric power is supplied from a DC power supply 11 via a load 12. The electric signal is transmitted as a current signal through the transmission lines l ₁ and l ₂ , and the voltage change occurring across the load 12 is detected to know the process variable.

The current signal is converted into a unified current of 4 to 20 mA and transmitted by the transmitter 10 set to a range corresponding to the pressure in the pipe, for example. In this case, for example, when it is desired to change or monitor the pressure range, it is convenient if the transmitter 10 can be operated from outside.

Therefore, the handheld terminal 13 is connected to the transmission lines l ₁ and l ₂ by using the connection lines l ₁ ′ and l ₂ ′ as required, and the transmitter 10 is provided with a dedicated data communication function with the handheld terminal 13. In addition, a method of transmitting digital data such as parameter changes from the handheld terminal 13 to the transmitter 10 is adopted.

Reference numeral 14 is a receiving instrument that incorporates a DC power supply 11, a load 12, and the like.

Next, the inside of the transmitter 10 will be described in detail.

SNR is a sensor that detects pressure / differential pressure and converts it into an electric signal. The converted analog signal is converted into a digital signal by the analog / digital converter A / D and stored in the memory MEM via the microprocessor μP. Stored in the random access memory portion of the. The microprocessor μP uses the stored digital signal to execute a predetermined operation such as linearization according to the operation procedure written in the read-only memory portion of the memory MEM, and the digital-analog converter D / A is used. Output to the output circuit OPC.

The output circuit OPC digital / analog converter D / A receiving instrument 15 a voltage signal converted into an analog signal through a transmission line l _1, l ₂ is converted into a unified current signal I _L of 4~20mA in To transmit. Further, the output circuit OPC uses a part of the current signal I _L to power the internal circuit of the transmitter 14.

The IFC is an interface for data communication with the handheld terminal 16, is connected between the transmission lines l ₁ and l ₂ and the microprocessor μP, and digital signals from the transmission lines l ₁ and l ₂ are used as parallel data. Microprocessor μ
It has a function of transmitting the data from the microprocessor μP to the transmission lines l ₁ and l ₂ as a serial signal.

Next, the inside of the handheld terminal 13 will be described in detail.

SER is a setting device operated by an operator and has a built-in monitor. Transmitter 10 model requirements, range changes,
Various settings or requests such as detection of abnormality or display of the value of the current signal I _L can be made.

μP 'is a microprocessor, for example, the setting device SER
The data is input and the digital signal is transmitted to the transmitter 10 through the interface IFC 'according to the processing procedure stored in the memory MEM'. Further, the microprocessor μP ′ fetches the response data from the transmitter 10 into the memory MEM ′ via the interface IFC ′, and further decodes it according to the processing procedure stored in the memory MEM ′.
Displayed on the monitor of the setting device SER.

Next, a method of data communication in the signal transmission device configured as described above will be described using the flow chart shown in FIG.

Prior to data communication, according to the initial program stored in the memory MEM ′ of the handheld terminal 13,
Start from the steps shown in FIG.

First, a digital code requesting the model name of the transmitter 10 is sent from the handheld terminal 13 to the transmitter 10 (step).

The transmitter 10 converts this serial digital code into parallel data via the interface IFC and takes it into the microprocessor μP. The microprocessor μP decodes this digital code and answers (steps) its model name to the handheld terminal 13 via the interface IFC.

The handheld terminal 13 is a microprocessor μP '
This answer back is decrypted by the memory ME and the communication procedure corresponding to this model name stored in the memory MEM ′ is stored.
A communication procedure such as a thermometer and a differential pressure gauge stored in M'is selected, and the initial program is terminated (step).

After that, the necessary information is set by the setter SER according to the communication procedure corresponding to the selected model name, and communication with the transmitter 10 is performed.

<Problems to be Solved by the Invention> However, in such a conventional two-wire signal transmission system, data such as parameter arrangement (address) of the converter 10 and its contents is previously stored in the memory of the handheld terminal 13. Therefore, when the handheld terminal 13 is completed and then the version is upgraded (addition of a product group), it cannot be handled unless the handheld terminal 13 is replaced. Therefore, there is an inconvenience that it is inconvenient to expand the product.

<Means for Solving the Problems> In order to solve the above problems, the present invention relates to a transmitter that converts a change in a physical quantity into an electric signal and transmits the electric signal to a load via a two-wire transmission line as a current signal. Two wires that are arbitrarily connected to a transmission line and that send a digital signal to the transmitter via the transmission line to change the parameters of the transmitter and the like and perform data communication between the transmitter and the terminal In the signal transmission system of the formula, the type of the unique parameter of each transmitter such as the data name, the data format, or the availability of setting, which is specified and stored in the memory of the transmitter by the index such as the number or the symbol, and the like The data is specified by the index and its increase / decrease, and is read from the transmitter to the terminal in a predetermined transmission frame, and the terminal classifies the contents of this read parameter. Therefore, it is changed as necessary, and the changed contents are transmitted from the terminal to the transmitter in a predetermined transmission frame.

<Operation> The type and data related to parameters unique to each transmitter such as name, data format, and whether or not it can be set are specified by an index and stored for each transmitter.
After the terminal identifies and reads the type and its data related to the parameters stored in these transmitters to the terminal by the index and increase / decrease, the terminal changes the content of the read parameters as necessary. Then, send this result back to the transmitter to set / change,
Alternatively, the corresponding data is read out to the terminal.

Similarly, when accessing another transmitter, the type and its data relating to the unique parameter specified by the index built in that transmitter are read, selected, and changed.

Thus, each time the transmitter is accessed, the parameters of the transmitter are called to the terminal and used.

By adopting such a transmission method, it is possible to give the terminal versatility and facilitate the expansion of the product group.

<Examples> Examples of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. The parts having the same functions as those of the signal transmission system shown in FIG. 7 are designated by the same reference numerals, and the description thereof will be appropriately omitted.

Reference numeral 15 is a transmitter for converting a physical quantity such as a process variable detected by the detector SNR into a current signal I _L and transmitting it to the receiving instrument 14, and its power source is transmitted as a current signal from the DC power source 11 via the load 12. Is supplied to the container 15. This current signal is converted into a constant voltage by the output circuit OPC and used as the internal power supply of the transmitter 15.

The pressure / differential pressure is detected by the sensor SNR and converted into an electric signal, and the converted analog signal is converted into a digital signal by the analog / digital converter A / D and is stored in the memory MEMS via the microprocessor μP. It is stored in the random access memory (RAM) part.

The microprocessor μP uses the stored digital signal to read data from a memory MEMS such as a read only memory (RO).
A predetermined operation such as linearization is executed according to the operation procedure written in the M) part.

The result of this operation, the digital / Analogue converter D / A converted into an analog signal is output to the output circuit OPC, transmission lines where they are reconverted into a unified current signal I _L of 4~20mA
It is transmitted to the receiving instrument 14 via l ₁ and l ₂ .

In this case, an area for storing the data from the sensor SNR is secured in the memory MEMS, and in addition to the area for storing programs for executing various calculations on this data, the transmitter 15 An area MEMP that can store the parameters unique to is secured.

Next, the data stored in this area MEMP will be described with reference to FIG.

As shown in FIG. 2, the area MEMP is electrically rewritable and has, for example, index numbers 1, 2, and 60.
The name indicating the contents to be set in the "Name" column corresponding to each number is displayed in the "Type" column as the data format,
For example, whether it is a character, a numerical value, or selection (predetermined item, for example, setting unit m / s,%, etc.)
The data is displayed in the “Data value” column, respectively.
Is stored as a parameter unique to the.

Specifically, for example, as the number 1, the lower limit value in the “Name” column, the numerical value in the “Type” column, the 100 in the “Data value” column,
As the number 3, dumping in the “name” column, selection in the “type” column, 5 in the “data value” column, tag number in the “name” column, character in the “type” column, “5” in the “name” column TAG1 is stored in the “Data value” column. As the number 20, “Name” stores the current output value, “Type” field stores the numerical value, and “Data Value” field stores the numerical value currently output by the transmitter 15 constantly rewriting. There is.

Next, another example of the data stored in this area MEMP will be described with reference to FIG.

In the data structure of the parameters shown in FIG. 2, necessary items are searched by numbers, so if there are many items to be searched, it will take time to search for the target items. Therefore, the data structure shown in FIG. 3 improves on this point. First, as an initial display, for example, the user's instrument name or the like is displayed. The data structure after this has a two-layer structure of "menu step" and "other steps".

There are “menu step” in the upper column, “parameter step” in the lower column, and “selection data step” in addition to these, which can discretely select various values such as damping of number 5. Used in case of change operation in case of parameter.

In the "menu step", for example, setting data is stored as the menu A, a variation adjustment factor is stored as the menu B, ... Is stored as the menu C, and so on. The "parameter step" also stores various names such as zero and span as parameters 1 and 2 and has a two-layer structure as a whole.

Then, for example, a necessary menu is selected in the "menu step", and the contents thereof are selected in the parameter steps to specify the contents of the "menu step".

The interface IFC is connected between the transmission lines l ₁ and l ₂ and the microprocessor μP, and is a handheld terminal.
The digital signal transmitted from 16 via the transmission lines l ₁ and l ₂ is transmitted as parallel data to the microprocessor μP, and conversely the data from the microprocessor μP is returned to the transmission lines l ₁ and l ₂ as a serial signal. To do.

Next, the inside of the handheld terminal 16 will be described in detail.

SERH is a setting device operated by an operator, and its keyboard layout is as shown in FIG. 4, and a monitor (not shown) is built in. Various parameters stored in the transmitter 15 shown in FIGS. 2 and 3 can be selected, set, and changed.

μP ′ is a microprocessor, for example, the setting device SERH
The data from is input, and a digital signal is sent to the transmitter 15 via the interface IFC ′ according to the processing procedure stored in the memory MEMH. Further, the microprocessor μP ′ fetches the response data from the transmitter 15 into the memory MEMH via the interface IFC ′, further decodes it according to the processing procedure stored in the memory MEMH, and displays it on the monitor of the setting device SERH.

Next, the contents of the keyboard for operating these processing procedures will be described with reference to FIG.

The POWER key is used to turn on the power, the CLR key is used to erase the display, and the ENT key is used to change the data. Since each key is provided with a code such as A, B, C, ..., The description will be given using these as appropriate.

The keys M to O, the keys Q to S, the keys U to W, and the key Y are ten keys, and are used for setting numbers and the key Z is used for giving a decimal point. The UPLD of the key E is used for the transmission of all its unique parameters and its data from the transmitter to the handheld terminal, whereas the DNLD of the key F is conversely read by the UPLD key from the handheld terminal to another transmitter. It is used when transmitting all the data and copying the contents of one transmitter to another transmitter. The keys K and L INC and DEC are used to change various units stored in the selection data step shown in FIG. The MENU of the key P is used when selecting various data in the menu step of FIG. The PARAM of the key T is used when selecting the parameter in the parameter step in FIG. DATA of the key X is used when reading the data again. ALPHA is used when setting an alphabet, and +/- are sign keys, and at the same time are space keys, but are normally used as sign keys.

The keys A to C are used to search for parameters that are used relatively often, and the HOME key is used for parameters that are often used among the parameters stored in the menu step shown in FIG. 3, such as output display and actual input value. , The key to selectively search the output% value, etc., the SET key is used to search only the frequently used setting data among the parameter steps shown in FIG. 3, and the ADJ key is the zero key, This is used when you want to selectively search only frequently used parameters when you need to make fine adjustments such as span adjustment. To actually select the contents of these HOME keys, SET keys, ADJ keys, use PARAM By repeatedly pressing the key, the target parameter is selectively selected according to the corresponding content.

Further, the DIAG of the key D is a key used when diagnosing the abnormality of the transmitter.

Although there are various keys as described above, the PA of the key T can be used to retrieve the necessary data in the data structure shown in FIG.
By repeatedly pressing the RAM, the contents can be sequentially displayed on the monitor in the order of the numbers shown in FIG. 2, for example.

The procedure for performing the above various operations is stored as a program in the memory MEMH of the handheld terminal 16.

Next, a data communication method using the signal transmission system configured as described above will be described using the flow chart shown in FIG.

First, in step, the MENU key or PARM key of the handheld terminal 16 is pressed to issue a request for reading the contents stored in the memory from the handheld terminal 16 to the transmitter 15. The transmitter 15 decodes the content, reads the corresponding content from the memory MEMS through the interface IFC (step), stores it in the memory MEMH of the handheld terminal 16 (step), and displays it on the monitor (step).

The data transmission frame in this case is constructed as shown in FIG.

The code indicated by SA at the head of the serial data is the transmission number of the handheld terminal 16. Next, CTL indicates the number of the receiving device, although it is not always necessary. The third ACTL is control information and indicates, for example, distinction between character information, numerical information, and selection information. The fourth is a menu address, which sets the hierarchical structure shown in FIG. 3, where M _a is the menu step, M _b is the parameter step, and M _c is the selected data step address. It Fifth
The second is an information field, in which the contents of auxiliary display such as name, data, and unit are set. Finally, a check code is added as BBC.
Data is transmitted in the above transmission frames.

On the other hand, on the monitor of the handheld terminal 16, as shown in FIG. 6 (b), the transmission frame shown in FIG.

In the handheld terminal 16, based on the contents displayed on this LCD, the above key operations are performed as necessary, and the contents are selected / changed (step) and the result is pressed by pressing the ENT key, as shown in FIG. It is transmitted to the transmitter 15 as a digital signal in the form of a transmission frame (step).

Then, in step S15, the transmitter 15 changes the content of the memory MEMP according to the data content transmitted from the handheld terminal 16.

In the above description, the handheld terminal 16 and transmitter 15
The main explanation was data transmission between two instruments, but in addition to this, in addition to the handheld terminal, an integrated instrumentation system including a large computer may be connected to the terminal. Etc. may be mixed and used.

<Effects of the Invention> According to the present invention as specifically described above with reference to the embodiments, data unique to each transmitter can be specified by an index such as a number and stored, and the terminal stores the data. Since the unique data that has been created is specified by a method that does not depend on the model, such as an index or its increase / decrease, and is read and selected and changed, the terminal can easily support even if the product group connected to the terminal is expanded. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a data configuration diagram showing an example of a data configuration of a memory of the transmitter shown in FIG. 1, and FIG. 3 is a transmission shown in FIG. 4 is a data configuration diagram showing another example of the data configuration of the memory of the container, FIG. 4 is a layout diagram showing the arrangement of the keyboard of the handheld terminal shown in FIG. 1, and FIG. 5 is an operation of the embodiment shown in FIG. Fig. 6 is a flow chart showing the procedure of Fig. 7, Fig. 6 is a data configuration diagram showing the relation between the transmission frame of communication data between the transmitter and the handheld terminal shown in Fig. 1 and its display, Fig. 7
FIG. 8 is a block diagram showing the configuration of a conventional two-wire signal transmission system, and FIG. 8 is a flow chart showing the operation of the signal transmission system shown in FIG. 10, 15 …… Transmitter, 11 …… DC power supply, 12 …… Load, 13,
16 …… Handheld terminal, 14 …… Reception instrument, SNR
…… Detector, MEM, MENS …… Memory, μP …… Microprocessor, OPC …… output circuit, IFC …… interface, l ₁ , l ₂ …… Transmission line, SER, SERH …… setter.

Claims (1)

[Claims] 1. A transmitter for converting a change in a physical quantity into an electric signal and transmitting it as a current signal to the load via a two-wire transmission line, and a digital signal via the transmission line, which is arbitrarily connected to the transmission line. In a two-wire signal transmission system in which data is transmitted between the transmitter and the terminal by using a terminal for sending data to the transmitter and changing parameters and the like of the transmitter. The type and the data related to the unique parameter of each transmitter such as the data name, the data format, and the availability of setting, which are specified and stored by the index such as a number or a symbol, are specified by the index and the increase or decrease. In a predetermined transmission frame, it is read from the transmitter to the terminal, and the terminal must read the content of the read parameter according to the type. 2-wire signal transmission system of the corresponding change in, characterized by transmitting the modified contents to said transmitter from said terminal at said predetermined transmission frame.