JPS59201539A - Analog-digital communication method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an analog-to-digital communication method that is applied when transmitting an analog signal and a digital signal through the same transmission path in industrial measurement, etc. .

[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 20 minutes.
A unified signal such as 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, and in order to adjust them and check their operating status, staff must patrol and carry out maintenance and maintenance work.
Inspection work must be carried out, and there is a growing demand for a means that can make adjustments, check operating conditions, etc. by remote control using existing equipment.

In addition, the reception of the unified signal is performed centrally at the supervisory control panel, etc., which accommodates about 1000 transmission lines for the unified signal, so it is difficult to receive the unified signal through these transmission lines. When making adjustments and checking the operating status by remote control, it is required to be able to easily confirm where the differential pressure transmitter, electromagnetic flow meter, etc. on the other side is installed. ing.

[Object and structure of the invention]

The present invention has been made based on the conventional demands, and enables the free transmission and reception of digital signals in addition to being superimposed on analog signals between transmitters such as differential pressure oscillators and electromagnetic flowmeters. The purpose is to provide an analog-digital communication method in which the transmitter transmits a digital signal including its own individual code.To achieve this purpose, the transmitter transmits the current value supplied from the power source. In the communication method of changing the voltage of the power supply unit into an analog signal, the voltage of the power supply unit is changed into a digital signal, the digital signal is received in the transmission unit, and the signal is superimposed with the analog signal in the transmitter. The current value is changed in a curved manner to produce a digital signal including the individual code of the oscillator, and the digital signal including the individual code is generated based on a change in the terminal voltage of a voltage drop element inserted into the transmission path through which the analog signal passes. The device is characterized in that it receives a signal and also receives the analog signal.

〔Example〕

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

FIG. 1 is a block diagram of the entire configuration, showing the lines Lal,
A plurality of two-wire transmission lines (hereinafter referred to as transmission lines) K consisting of Lbx to Lan and Lbn are selectively connected via connectors CN to communication devices CB1 to CEn each having a power supply unit PS that supplies current to each of the two-wire transmission lines K. Transmitters Tx1 to Txn such as a differential pressure transmitter and an electromagnetic flowmeter are connected to the other end of each transmission line.
XI to Txn individually control the current value controllers and communicate them to the transmission line as analog signals.

Furthermore, a resistor RC is inserted as a voltage drop element in series with the power supply section PS in the communication devices CEl-CEn, and an analog signal is received based on the terminal voltage of the resistor RC.

The voltage of the power supply PS of the communication device CE changes in a pulsed manner, and this changes the line voltage ■, which is transmitted as a digital signal and received by the transmitter Tx. It has become.

On the other hand, in response to the reception of the digital signal, the transmitter Tx superimposes it on the analog signal, changes the current value ■ in a loop shape, and transmits it as a digital signal. It is received as a change in the terminal voltage.

FIG. 2 is a waveform diagram showing how the line voltage V and the current value connected to the transmission line change according to time t, υ, and the transmitter Tx.
In this case, the analog signal Sa, which is determined according to the measured value of The line voltage ■ changes in a pulse-like manner,
As a result, flag bit BF, start bit B8,
The first bit B1 to the eighth bit B8 are transmitted.

Each bit is indicated by an increase in the line voltage ■, and the flag bit 1-BF is set to have a particularly wide cross pulse width, and the flag bit BF and start pitch 1-B8 always change in the positive direction. However, the first bit B1 to the eighth bit (Bs) indicating data are, for example, logical values "
When the logic value is 1'', the signal changes in the positive direction, and when the logic value is 0, it remains unchanged.

This line voltage change is detected by the transmitter Tx, thereby receiving the digital signal Sc.

Then, after the end of the digital signal Sc, the transmitter Tx
After a certain period t8, the period of the digital signal St,
After being superimposed with the analog signal Sa, the current value is changed in a pulse-like manner, and the flag bit BF is set.

Star! - Bs and the first bit B1 to the eighth bit B8 indicating its own individual code and data are transmitted in the same way as the digital signal Sc.

At this point, the communication device CE receives the digital signal St containing the individual code of the transmitter Tx as a change in the terminal voltage of the resistor C.

However, in this example, only the transmission and reception of one byte consisting of 8 bits is shown, but depending on the situation, a desired number of bytes consisting of a predetermined number of bits can be transmitted and received in each of the digital signals Sc and St. .

Further, the same effect can be obtained by changing the direction of change of each bit in the negative direction or in a pair of positive and negative directions.

FIG. 3 is a block diagram of the communication device CD, which mainly includes a processor CPUc such as a microprocessor, a fixed memory ROMc, a variable memory RAMc, and a keyboard KBc1.
Display device such as numeric display DP c d%DPca.

Universal asynchronous transmitter/receiver (hereinafter referred to as transmitter/receiver) UAJ
%Tc, interface I/Fc, and analog-to-digital converter (hereinafter referred to as ADC) A/Dc
etc. are arranged around the periphery, and are connected to each other by a bus line BUc.The processor CPUc executes the program stored in the fixed memory IJROMc, and performs control operations while accessing predetermined data to the variable memory RAMc. It has become a thing.

and \, if desired data is given from the keyboard KBc, the processor CPUc controls the transmitter/receiver unit UARTc accordingly, and also controls the interface I/
In order to send out the gate pulse Pcgx as "H" (high level) via Fc, the AND gate GC1 is turned on all the time, and the pulse-like output sent from the transmitting/receiving section UARTc is given to the switch circuit SWc, and the The switch circuit SWc is driven according to the waveform shown in FIG.

Then, the local power supplies ECL and Ecu of different voltages, which constitute the power supply part PS together with the switch circuit SWc, are alternately and pulse-like switched from the low voltage local power supply ECL to the high voltage local power supply Ecu, and are connected in series with these. Via the inserted resistor Rc, a voltage that changes in a pulsed manner is sent out as a digital signal Sc between the line terminals TI and T2.

In addition, the terminal voltage of the resistor Rc is determined by a wave wave generator FL such as a band f wave generator that passes only the frequency component of the digital signal St.
CD is applied to one input of the comparator CPc, and a comparison is made with the reference voltage Ecs applied to the other input, and a level higher than the reference voltage Ees is extracted as a received output. ing.

Therefore, after the transmission of the digital signal Sc is completed, in response to the reception output indicating the flag pin 1-BF of the digital signal St being given via the interface I/F c, the gate signal Pcgz is sent from the interface I/F c. Send as H11, AND gate GC2
When turned on, a reception output indicating after the start bit Bs is given to the transmitter/receiver unit UA, RTc, and in accordance with this output, the individual code and reception data are displayed on the display DPcd.

On the other hand, the terminal voltage phantom 5 of the resistor IR,c is applied to the averaging unit AVRc, such as an integrating circuit, through a P-wave device FLca, such as a low-frequency f-wave device, which blocks the frequency components of the digital signals Sc, St. In this process, the analog signal Sa is extracted, and then converted into a digital signal by A and DC-A/DcK, and provided to the processor CPUc.

Therefore, the output of ADC-A/Dc is
It is processed by PUc and then sent to display device DPca, thereby receiving and displaying the measured value indicated by analog signal Sa.

FIG. 4 is a block diagram of the transmitter Tx, including the same processor CPUt and fixed memory OMt as in FIG.

The variable memory IJ RAMt, transmitting/receiving unit UART t, interface I/Ft, etc. are connected to the bus BUt, and the processor CPUt performs control operations as in Fig. 3, but it detects differential pressure, flow rate, etc. sensor SS
A, DC-A/Dt that converts the output of
, and a digital-to-analog converter (hereinafter referred to as DAC) D/At, which processes the output of the processor CPUt and converts the digital signal into an analog signal.
, and an address setter ASTt for setting an individual code using a digital switch or the like.

Further, a power supply circuit PSt is connected to the line terminal Tl,
In this case, a current of 4 mA is taken from the line Ll, stabilized, and supplied to each part as a local power supply Et, and the line voltage between the lines La and Lb is determined by the digital signal S.
Similarly to FIG. 3, it is applied to the comparator CPt via a j5 wave generator FLt such as a band P wave generator that passes only the frequency component of c.
s, the comparator Crt produces a received output, which is applied to the interface I/Ft, and the AND gate Gt
1 to the transmitter/receiver unit UARTt.

Therefore, in response to the detection of the flag bit BF, an H'' gate pulse Ptgl is sent out, the ANI) gate Gtx is turned on, and the reception of the digital signal SC is stopped. Depending on the progress,
Processor CPUt is interface I/Ft
At the same time as transmitting the nHH gate pulse Ptg2 through is applied to one input of the device ADD t.

At this time, the processor CPU uses the address setting device A.
Based on the output of STt, an individual code is also given to the transmitter/receiver unit UARTt, so the individual code is included in the transmitted data.

Note that the other input of the adder ADDt is constantly given an analog signal according to the measured value by the sensor SS, and when the gate pulse Ptgz is not generated, ])A
Only the outputs of C and D/At are given to the current control section CCt, which receives a current of a value corresponding to the measured value by analog signal S.
On the other hand, if the gate pulse Ptgs is generated and the transmission data is sent out from the transmitter/receiver unit UA Tt, the sub-inputs can be added in the adder ADDt. The current flowing through section CCt changes in the positive direction in a pulsed manner and is transmitted as a digital signal St.

Similarly, the value of the analog signal Sa and the data of the digital signal St may be added in the processor CPUtL/rc and then sent out from the DAC-D/At.

In addition, the transmitter Tx has an accidental memory such as EAROM, in which necessary data is stored, and this data is retained even if the power is cut off. There is.

FIG. 5 is a circuit diagram of the current control section CCt, and the resistor 5'
The output from the adder ADD is passed through a low-frequency r-wave filter for noise removal using Ral and a capacitor C11, and is amplified by a differential amplifier All. , the current determined by this is connected to 6 resistors and 12. It is assumed that communication is via Rxs.

However, the terminal voltage of the resistor R1a is negatively fed back to the differential amplifier Alt through the resistor 6 14, and the adder ADD
The current value is maintained in accordance with the output value of t.

Therefore, it is possible to freely transmit and receive desired data to and from the transmitter Tx.After checking the installation location of the transmitter Tx using the individual code, various adjustment values stored in the variable memory lJRAMt of the transmitter Tx can be set. , setting values, etc. can be updated by remote control, the operating status of the transmitter Tx can be checked remotely, and the objective can be achieved with only a few additions to conventional equipment. .

However, in FIGS. 1 and 4, the power supply for the oscillator Tx may be supplied to a separate line, and in FIG. 2, a bit for validity check is provided for each byte. The configurations shown in FIGS. 3 to 5 can be modified in various ways depending on the situation.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, data can be freely transmitted and received with transmitters such as differential pressure transmitters and electromagnetic flowmeters without significantly changing existing equipment, and
In addition to being able to reliably confirm the location where the transmitter is installed, analog signals can be received independently of digital signal transmission and reception, making it useful for remote adjustment and operation status monitoring of various transmitters.
Remarkable effects can be obtained.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Figure 1 is a block diagram of the entire configuration, Figure 2 is a waveform diagram of line voltage and current values, Figure 3 is a block diagram of a communication device, and Figure 4 is a transmitter. FIG. 5 is a circuit diagram of the current control section in FIG. 4. TX1~TXn11#l111 transmitter, p S@* *
*Power supply section, Lax, Lbl-Lan, Lbn e
@*e track, CE]~CEn fist...communication device,■
...Current value, ■...φ line voltage, Rc...Resistor (heavy pressure drop element), Sa...Analog signal, S
c, St...Digital signal, CPUc, CPUt
---ψ processor, ROMc%ROMt -@-・
Fixed memory, RAMc. RAM t...variable memory, UA Tc, UAR,
Tt...transmitter/receiver section, KBc...1,000-board, D
PcaDPcd・Dispute・Display device, I/Fc, I/Ft・
・Skewer-interface, FLcd, FLca, FLt
---・F wave device, CPc, CPt ----- Comparator,
Ecs. Ets...Reference voltage, CC1...Current control section,
ECL, ECLI * ・e *Local power supply, D/At
---DA, C (digital-to-analog converter), A
STt...Φ・Address setter, SWc, S'Wt
--...Switch circuit, Ct...Ce capacitor, A/
Dc - ADC (analog-digital converter)
. Patent applicant: Yamatake L. Newell Co., Ltd. Agent: Masaki Yamakawa (and one other person)

Claims (6)

[Claims] (1) In a communication method in which a current value supplied from a power supply unit is changed (by an oscillator) to produce an analog signal, the voltage of the power supply unit is varied in a pulse form to produce a digital signal;
The digital signal is received in the transmission unit, and the transmitter superimposes the digital signal on the analog signal and changes the current value in a pulse form to generate a digital signal including an individual code of the transmitter, and the analog signal is transmitted. receiving a digital signal including the individual code based on a change in the terminal voltage of a voltage drop element inserted into the transmission path, and
An analog/digital communication method characterized by receiving the analog signal. (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 resistor is used as the voltage drop element. (4) Claim 1, characterized in that it uses a transmitter controlled by a processor that executes a program.
Analog/digital communication method described in Section 1. (5) The analog/digital communication method according to claim 1, characterized in that a power supply unit is provided with local power supplies of different voltages and changes the voltage in a pulse-like manner by switching between the local power supplies. . (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.