JPS59201541A - Analog-digital communication method - Google Patents

Abstract

PURPOSE:To attain freely the transmission/reception of a data between a transmitter such as of a differential pressure transmitter and of an electromagnetic flowmeter and a communication equipment by transmitting/reception an analog signal and a digital signal, and transmitting a digital signal including the own identification code from a transmitter. CONSTITUTION:Transmitters Tx1-Txn control a current value I applied from power supply sections PS1-PSn to plural two-wire transmission lines La1, Lb1- Lan, Lbn individually to form an analog signal. A terminal voltage of a resistor RLn inserted in series with the transmission lines drives a display device DP via an A/D converter and displays a value of the analog signal represented by the current value I after receiving. On the other hand, a communication equipment CE connected selectively in bridge to the transmission lines changes the current value I in pulse form transmits it to the transmitter Txn as a digital signal, the transmitter Txn changes the current value I in response to the receiving, and transmits the value to the communication equipment CE as a digital signal including the own identification code, and the signal is received.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention transmits analog signals and digital signals through the same transmission path in industrial measurement and the like.

It relates to an analog/digital communication method applied when

[Prior art]

Conventionally, in industrial measurement, when transmitting the measurement output of a differential pressure transmitter, electromagnetic flow meter, etc. to a remote point, it is generally 4 to 2 times.
A unified signal such as 0 mA is used, and the measured value is indicated by the current value of this analog signal.

However, differential pressure transmitters, electromagnetic flowmeters, etc. are generally installed and distributed over a wide area, so it is necessary to adjust them and check their operating status / 4? In order to do this, staff must make rounds and perform maintenance and inspection work, and there is a need for a method that can use existing equipment to remotely check the operating status of the adjustment machine. It has come to be.

In addition, the reception of the unified signal is performed centrally at the supervisory control panel, etc., which accommodates approximately 1000 transmission lines for the unified signal. When making adjustments and checking the operating status by remote control, it is required to be able to easily confirm where the other party's differential pressure transmitter, electromagnetic flow meter, etc. are installed. .

[Object and structure of the invention]

The present invention has been made based on such a conventional demand, and allows for free transmission and reception of digital signals between a transmitter such as a differential pressure transmitter, a cell phone, a flow meter, etc. and a communication device, and also enables transmission and reception of digital signals. The purpose is to provide an analog/digital communication method in which a digital signal containing its own individual code is transmitted from the transmitter, and in order to achieve this purpose, the current value supplied from the power supply section is changed by the transmitter. In the communication method, a -1 voltage drop element is inserted in the transmission line through which the analog signal passes, and the current passing through the voltage drop element is changed into a pulse shape by a communication device and transmitted as a digital signal. is received by the transmitter and converted into the analog signal.The change in the current value is stopped, and the current flowing through the voltage drop element is changed into a pulse shape and transmitted as a digital number 45 including its own individual code, and the digital signal is is configured such that the communication device receives the information in the communication device.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing embodiments.

The first prisoner is a plotter diagram of the entire configuration, and the line La1+L
Power supply units PSI to Pn that supply current to each of a plurality of two-wire transmission lines (hereinafter referred to as transmission lines) consisting of 'OI to Lan + Lbn are provided, and at the other end of each transmission line, Transmitter TXl for differential pressure generator, electromagnetic flow meter, etc.
Txn is connected to each transmitter TX1 to Txn.
controls the current value individually, and sends it to the transmission line as an analog signal.

In addition, resistors RLl to RLΩ are each inserted in series as voltage drop elements in each transmission path via the terminal plate TB, and in the circuit of the resistor RLn, the terminal voltage of this is connected to an analog-to-digital converter ( Hereinafter, the current value A, DC) is applied as a digital signal, and then a display DP such as a numeric display is driven to receive and display the value of the analog signal indicated by the current value ■.

A communication device CE is selectively connected to the transmission line on the side, and when this changes the current value I in a pulse shape and transmits it as a digital signal to the transmitter T'xn, this is transmitted to the transmitter Txn. is received and upon reception the transmitter Tx
Since n changes the current value in the same way and transmits it as a digital signal to the communication device CE, this is received by the communication device CE.

Note that this is the same for any oscillator Tx and resistor RL.

FIG. 2 is a waveform diagram showing how the current value I flowing through the resistor RL changes with time t.
Although it changes within the range of A, in response to the start of transmission from the communication device CE, the line terminal T of the communication device CE,
Due to the current Ic flowing between ITZ, the current value I is approximately 36 m.
When the flag bits BP increasing up to A are transmitted, the transmitter Tx stops the distribution of the analog signal Sa.
JI is sent.

Note that flag bit BF and start bit BS C,
The current value is always about 20 mA or more, but the first bit B1 to the eighth bit B8 indicating the data, for example, maintain about 20 mA or more when the logic value is "1", and about 4 mA when the logic value is 11011. It has become a thing.

This current value change causes a voltage drop change in resistor RL,
The voltage between lines La and Lb on the transmitter Tx side changes,
is applied to the oscillator Tx, thereby generating the digital signal S
c is received by the transmitter Tx.

Then, after the end of the digital signal Sc, the transmitter Tx
ts for a certain period of time! The period of the digital signal St after passing through,
Similarly to the current value I, change the current value I, and set the flag bit BF and start bit B.

Then, it transmits the first bit B1 to the eighth bit B8 indicating its own individual code and data.

As a result, a voltage change occurs between the lines La and Lb as described above, and this is received by the communication device CE.

However, in this example, only one byte consisting of 8Q-) is transmitted and received, but depending on the situation, a desired number of bytes consisting of a predetermined number of bits are transmitted and received in each of the digital signals Sc and St.

Note that the transmitter Tx returns to its original state after a predetermined period t82 after the end of transmission of the digital signal St, and transmits the analog signal S.
Start distribution of a.

FIG. 3 is a block diagram of the communication device CF, which mainly includes a processor CPUc such as a microprocessor, a fixed memory ROMc, a variable memory RAMc, a keyboard KBc,
Display devices such as numeric display DPc, universal asynchronous transmitter/receiver unit (hereinafter referred to as transmitter/receiver unit > UARTc, Inter 7Ace I/Fc, etc.) are arranged around the periphery, and are connected to each other by bus BUc, and are stored in fixed memory ROHc. The processor CPUc executes the programmed program and performs control operations while accessing predetermined data to the variable memory RAMc.

Here, if desired data is given from the keyboard KBc, the processor CPUc controls the transmitting/receiving unit UARTc and interface I/F
In order to send out the gate pulse Pcgl as If HI+ (high level) via C, the AND gate Ge is turned on, and the H'' transmission pulse sent from the transmitter/receiver UARTc is given to the current controller CCc. , In response to this, a current Ic flows from the line terminal TI to T2.

In addition, the line voltage between the lines wILa and Ll) is applied to one input of the comparator cpc via a P-wave device FLc such as a band F-wave device that passes only the frequency component of the digital signal St. , the reference voltage EC applied to the other input
8 and a level higher than the reference voltage Ecs is extracted as a received output.

Therefore, after the transmission of the digital signal Sc is completed, the gate pulse PCg2 is sent from the inter 7Ace/Fc in response to the reception output indicating the flag BF of the digital signal St being given via the interface I/Fc.
When the AND gate Ge2 is turned on, the reception output indicating the start bit Ha and subsequent bits is given to the transmitter/receiver UARTc, and the display DP is output according to the output of this.
The individual code of the transmitter TX and the received data are displayed by c.

FIG. 4 is a circuit diagram of the current control section CCc, in which the resistor R
1 and capacitor C, and a low-frequency F-wave device for noise removal) The transmission pulse from Gel is amplified by the differential amplifier AI, and then turns on the field-effect transistor Q1. Therefore, current Ic passes through resistors R2, R,.

Note that the terminal voltage of the resistor R3 is negatively fed back to the differential amplifier A via the resistor R4, so that the current I
c is maintained at a predetermined value.

FIG. 5 is an external perspective view of the communication device CE, in which a display device DPc and a keyboard KBc are arranged in a hand-held case 1, a cord 2 is led out, and a clip is attached to the tip of the cord 2. 3 is connected, and the line L a r L
It can be freely attached to and detached from b.

FIG. 6 is a block diagram of the transmitter Tx, which includes a processor CPUt and a fixed memory ROMt similar to those in FIG.

The variable memory P-A M t, the transmitting/receiving unit UARTt, the interface I, /Ft, etc. are connected to the bus BUt, and the processor CPUt performs control operations as in FIG. 3, but the differential pressure, ADO・A/' converts the output of sensor SS that detects flow rate etc. into digital signal
Dt, and a digital-to-analog converter (hereinafter referred to as DAC) that converts the digital (digital)v signal whose output is processed by the processor CPUt and sent out to an analog signal (hereinafter referred to as DAC) D
/A t , etc., and an address setter ASTt for setting an individual code using a digital switch or the like.

The power supply circuit PSb is connected to the line terminal T1,
In this case, a current of 4.171 A is taken from the line La, stabilized, and supplied to each part as a local power supply Et, and the line voltage between the lines La and Lb is based only on the frequency component of the digital signal Sc. It is applied to the comparator cpt as in FIG. 3 through a P-wave device FLt such as a band F-wave device to be passed, and here, it is compared with the reference voltage Ets as in FIG. generates a reception output and provides it to the interface I/Ft, and also outputs the AND game)
Gt, to the transmitter/receiver UARTt.

Therefore, the reception output corresponding to the flag bit BF of the digital signal Sc is given to the processor CPUt via the interface I/Ft, and in response, the processor CPUt sends the gate pulse Ptg+ to 'H' via the interface I/Ft. ” and send it as 1b1
” Send control pulse Ptc+, A, ? JD Gate Gt,
At the same time as turning on the switch circuit SWh is switched to the AND gate GtZ side.

Therefore, the reception output after the start bit Bs of the digital signal is sent to the transmitting/receiving section UARTt, and the digital signal Sc is received.The current control section CCt is turned off, and the distribution of the analog signal Sa is stopped. do.

Then, after receiving the digital signal Sc, the period ts+
According to the progress of the process, the processor CPUt connects the gate node Ptg2 via the interface E, /Fj
At the same time, if the transmitter/receiver 41 unit UARTt is controlled, a transmission pulse is sent out via the ON ANDG (GtZ), and is given to the current control unit CCt via the switch circuit swtt, and the digital signal S
A current corresponding to t flows through the current control section CCt.

However, the processor CPUt is the address setter ASTt.
Since the individual code corresponding to the output of the digital signal St is given to the transmitter/receiver unit UART t, the individual code is included in the digital signal St.

When the transmission of the digital signal St is completed and the period t82 has elapsed, the processor CPUt stops sending out the control pulse Pjc1, so the switch circuit 5Wtt switches the DAC-
The D/At side is restored, and its output is given to the current control unit CCt, and the flow of the analog signal Sa indicating the measured value of the sensor Ss is resumed.

Note that the configuration of the current control section CCt is similar to that shown in FIG. 4.

In addition, the transmitter Tx is equipped with a non-volatile memory such as EAROM, in which necessary data is stored, and this data is retained even if the power is cut off. .

Therefore, it is possible to connect the communication device CE to a terminal board etc. that accommodates the transmission path and perform desired data transmission and reception with the transmitter Tx. After confirmation, it becomes possible to update various adjustment values, setting values, etc. stored in the variable memory RAMt of the transmitter Tx by remote control, and it also becomes possible to remotely check the operating status of the transmitter TX. Moreover, the objective can be achieved by only making some additions to the existing equipment.

However, in Fig. 1, it is assumed that the power supply for the oscillator Tx is supplied through a separate line, or the power supply for the oscillator Tx is
Other impedance elements may be used instead.

In addition, in Fig. 2, it is also possible to add a bit for security check for each byte, or to allocate a specific byte for an individual code.
The configurations shown in FIGS.
Various modifications are possible, such as a channel-mounted type and a switch for selecting and connecting transmission paths.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to freely transmit and receive data to and from transmitters such as differential pressure transmitters and electromagnetic flowmeters without significantly changing existing equipment, and
Since the location where the transmitter is installed can be reliably confirmed, a remarkable effect can be obtained in terms of remote adjustment and operation status monitoring of various transmitters.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, Fig. 1 is a block diagram of the entire configuration, Fig. 2 is a waveform diagram of current values, Fig. 3 is a block diagram of a communication device, and Fig. 4 is the current control in Fig. 3. FIG. 5 is an external perspective view of the communication device, and FIG. 6 is a block diagram of the transmitter. Tx+ ~Txn """ transmitter, PSL -PS
n @Fist*φ power supply section, La1. Lb1~Lan, Lbn
Φ--Line, CE--Communication device, ■--Current value, RLI~RLn...Resistor (voltage drop element), S
&...Analog converter, S c + S t-φ・
・Digital signal, CPUc, CPUt ・Φ・φ processor, ROλic +ROMt---Fixed memory,
RAMc, RAMt...-11 town change memory, UA
RT c, UART t・-O・transmission/reception unit, KBC
111111s key yI-? -do, DPCIIOL11
1 Display, I/'Fc, I/Ft-1...Interface, FLc, FLt@*e 1 Lachrymal wave generator, CPe
, CPt---Comparator, Ecs, Ets---
Reference voltage, CCc, CCt...Current control section, E
cL...Station name 5 power supply, D/'A t...Fist/DAC
(Digital-to-analog converter, ASTt...address setter, SWt+, 5Wtz, 1 switch circuit, Ct...capacitor, 311I111# clip. Patent applicant: Newel Co., Ltd. agent: Yamakawa Numerical (l Hill 7 Jh 1 person) Procedural amendments imported) 9. Dear Director General of Te License Agency ”“” ’58
．． f1.22 "1, Indication of the case 1982 Patent Application No. 76485 2, Name of the invention Analog/digital communication method 3, Person making the amendment ↓ j) Relationship to the case Patent Applicant's name (name) (666) Yamatake Newel Co., Ltd. 5, adds "maximum by rSa + 16 mA" to the correction target. (2) Delete "must" and "more than" in line 4 of page 7 of the same book. (3) Delete "See, above" in line 6 of the same page of the same book. that's all

Claims (6)

[Claims] (1) In a communication method in which a current value supplied from a power source is changed by a transmitter to generate an analog signal, a voltage drop element is inserted into a transmission path through which the analog signal passes, and the current flowing through the voltage drop element is is changed into a pulse form by a communication device and transmitted as a digital signal, which is received by the transmitter and used as the analog signal.The change in current value is stopped and the current flowing through the voltage drop element is changed into a pulse form. An analog/digital communication method characterized by transmitting a digital signal including its own individual code, and receiving the digital signal at the communication device. (2) The analog/digital communication method according to claim 1, characterized in that a two-wire transmission line is used as the transmission line, and an oscillator whose power source is a current supplied from a power supply unit is used. . (3) The analog/digital communication method according to claim 1, characterized in that a communication device that is detachable from the transmission path is used. (4) The analog/digital communication method according to claim 1, characterized in that a resistor is used as the voltage drop element. (5) The analog/digital communication method according to claim 1, which uses a transmitter and a communication device controlled by a processor that executes a program. (6) The analog/digital communication method according to claim 1, which uses a transmitter that transmits a digital signal containing an individual code set by an address setting device.