JPS59201538A - 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 performing transmission/reception while superimposing a digital signal on an analog signal and also transmitting a digital signal including the own identification code from the transmitter. CONSTITUTION:Transmitters Tx1-Txn control individually a current value I applied from power supply sections PS1-PSn to plural two-wire transmission lines La1, Lb1-Lan, Lbn 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 a value of the analog signal represented by the current value I and displays it. On the other hand, a communication equipment CE connected in bridge selectively to the transmission lines changes the current value I in pulsive form, transmits the value to the transmitter TX as a digital signal, the transmitter TX changes the current value I in response to the receiving, transmits the value as a digital signal including the own identification code, and the signal is received by the communication equipment CE.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an analog/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 current value of this analog signal is said to indicate the measured value.

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 perform 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 unified signals is carried out centrally at supervisory control panels, etc., which accommodates approximately 1,000 transmission lines for unified signals, so these transmission lines are When making adjustments and checking the operating status by remote control via a road, it is required to be able to easily confirm where the differential pressure transmitter, electromagnetic flowmeter, etc. on the other side is installed. It becomes.

[Object and structure of the invention]

The present invention has been made based on the conventional demands, and allows for free transmission and reception of digital signals in addition to analog signals between transmitters such as differential pressure transmitters and electromagnetic flowmeters. , the transmitter shall transmit a digital signal containing its own individual code/ζ Analog
The purpose of the present invention is to provide a digital communication method, and in order to achieve this purpose, a current value supplied from a power source is changed by an oscillator to generate an analog signal. A voltage drop element is inserted into the circuit, the current value is superimposed on the analog signal passing through the voltage drop element, and the current value is changed in a pulse-like direction in the positive and negative directions by a communication device to generate a digital signal, and the digital signal is transmitted to the transmitter. At the same time, the current value is superimposed on the analog signal, and the current value is changed in a pulse-like manner in the positive and negative directions by the transmitter to generate a digital signal including the individual code of the transmitter, and the digital signal is converted into a digital signal by the transmitter. It was constructed with the characteristic of ``receiving υ.''

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

FIG. 1 is a block diagram of the entire configuration, and shows the lines La1,
: A plurality of power supply units PS+ to PSn are provided to supply current to each of a plurality of two-wire transmission lines (hereinafter referred to as transmission lines) consisting of Lbi to Lan□bn, and at the other end of the transmission line. , differential pressure transmitter, electromagnetic flow meter, etc. transmitter TXI~
Txn are connected to each other, and transmitters Txl-Txn
controls the current value (■) individually and passes it to the transmission line as an analog signal.

In addition, resistors Rt+ -RLn are inserted in series as voltage drop elements in each transmission path via the terminal board TB, and in the circuit of the power supply section PSn, the terminal voltage of the resistor RLn is converted from analog to digital. device (hereinafter referred to as ADC
), converts it into a digital signal, drives a display such as a numeric display, receives the analog signal value indicated by the current value, and then displays it.

On the other hand, the oscillators Txl~T than the resistors RLI -Rtn
The terminal board TBK that accommodates the transmission line on the xn side is the communication device C.
E is selectively bridge-connected, and this superimposes the analog signal and changes the current value connected to the resistor RLn in a pulse-like positive and negative direction, and sends it as a digital signal to the transmitter Txn, which transmits the signal. The transmitter Txn transmits the current value in response to the reception.
c is similarly changed and transmitted as a digital signal to the communication device CE, so that 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 (2) flowing through the resistor RL changes over time t, and is a waveform diagram showing how the current value (2) flowing through the resistor RL changes over time t.
In this case, the analog signal Sa determined according to β is 4 to 2
Although it changes in the range of 0mA, when transmission from the communication device CE is performed, the digital signal S
During the period c, the current value ■ changes in the positive and negative directions in a pulse-like manner in addition to being superimposed with the analog signal Sa, resulting in 72 gbit) BF.

Start bit 7688% 1st bit B1 to 8th bit BB
is sent.

Note that the valley bit is indicated by a change in the positive/negative direction, and the pulse width of the flag (Pi) BF is set particularly wide and always changes in the positive/negative direction. 8th pitch) B8 is, for example, a logical value! When it is 1'', it changes in the positive and negative directions, and when it is a logical value or 0'', it remains unchanged.

This current value change causes a voltage drop change in resistor RL,
The voltage between the lines La and Lb on the transmitter 1''x side changes and is applied to the transmitter Tx, whereby the digital signal Sc is received by the transmitter Tx.

Then, after the end of the digital signal Sc, the transmitter Tx
After a certain period t8, during the period of the digital signal St, the 'current value ■ is similarly changed, and the flag pin (BFN) start bit Bs and the first bit B+ to the eighth bit B8 indicating its own unique code and data are transmitted. Say yes.

Therefore, 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 the transmission and reception of one byte consisting of 8 bits is shown, or depending on the situation, a desired number of bytes consisting of a predetermined number of bits may be transmitted and received in each of the digital signals Sc and St.

Note that the changes in the positive and negative directions of each bit are the same current value, and their average value is zero, so the ADC-
In A and /D, if an integrating circuit etc. is inserted on the input side,
It is completely unrelated to the reception of the analog signal Sa.

FIG. 3 is a block diagram of the communication device CE, which mainly includes a processor CPUc such as a microprocessor, a fixed memory ROMc, a variable memory RAMc, a keyboard KBc,
Displays such as numeric displays DPc, universal asynchronous transmitter/receiver (hereinafter referred to as transmitter/receiver) UARTc and interface I/Fc are arranged around the motherboard, 1B
They are connected by Uc, and fixed memo')R
The program stored in OMc is transferred to processor CP'Uc.
is executed, and performs control operations while accessing predetermined data to the variable memory RAMc.

In this case, if desired data is given from the keyboard KBc, the processor CPUc controls the transmitter/receiver unit UARTc accordingly, and also sends a gate pulse Pcgl via the interface I/Fc!
AND gate G to send as H'' (high level)
c1. When Gc2 is on, 9, transmitter/receiver UARTc
An increasing pulse Pu and a decreasing pulse Pd of each line H# sent from the line H# are given to the current control section CCc, and the current controlling section CCc passes the entire current Ic from the line terminal T1 to T2 in accordance with the increasing pulse Pu. , the control unit CCc sets the line terminal T1 to the positive terminal and the line terminal T to the positive terminal in response to the decreasing pulse Pd.
A control voltage with 2 as the negative electrode is sent out.

Therefore, when the current Ic passes, the current value I passing through the resistor RL becomes the sum of the current It indicating the analog signal Sa and the current Ic, and increases, but when the control voltage is sent out, the current value I passing through the resistor RL increases. The voltage increases and the current value decreases.

In addition, the line voltage between the lines La and Lb is applied to one input of the comparator CPc via a P-wave device FLc such as a band single-wave device that passes only the frequency component of the digital signal St, and is applied to one input of the comparator CPc. Reference voltage Ecs applied to the input
A comparison is made with the reference voltage gas, and a level higher than the reference voltage gas is extracted as a received output.

Therefore, after the transmission of the digital signal Sc is completed, in response to the reception output indicating the flag bit BF of the digital signal St being given via the interface I/Fcfc,
Gate pulse Pcg2 from interface I/Fc
sH" and turns on Gca, a reception output indicating the start bit Bs and subsequent bits is given to the transmitter/receiver UARTc, and the display DP
c displays the individual code of the transmitter Tx and the received data.

FIG. 4 is a circuit diagram of the current control section CCc, and the resistor R
The increasing pulse Pu from Gcr is
In addition to being amplified by the differential amplifier Ar, the resistors R2 and R3 are used to turn on the transistor Q1, such as a field effect type transistor.
A current Ic passes through.

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

On the other hand, the decreasing pulse Pd from the AND gate GC2, which passes through the same low-band f-wave generator as described above using the resistor R5 and the capacitor C2, is inverted and amplified by the differential amplifier A2, and also turns on the transistor Q2, which is similar to that described above. In order to
Local power supply E inserted in series via resistors Ra and Ry
The voltage of CL is sent out as a control voltage.

Note that the terminal voltage of the resistor R7 is negatively fed back to the differential amplifier A2 via the resistor R8, thereby maintaining the current from the local power supply EcL 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, and a cord 2 is led out, and a clip is attached to the tip of the cord 2. 3 is connected, and can be freely attached to and detached from the line LaLb.

FIG. 6 is a block diagram of the transmitter Tx, in which the processor CPUt, fixed memory ROMt, variable memory RAMt, transmitter/receiver UARTt, interface I/Ft, etc., similar to those in FIG. 3, are V-connected to the bus BUt. As in Figure 3, the processor CPUt performs control operations, but the ADC-A/Dt converts the output of the sensor SS that detects differential pressure, flow rate, etc. into a digital signal, and the ADC-A/Dt that converts the output of this A digital signal that converts the digital signal processed and sent by the processor CPUt into an analog signal.
An analog converter (hereinafter referred to as DAC) D/At and an address setter ASTt for setting individual codes using digital switches and the like are provided.

Further, a power supply circuit PSt is connected to the line terminal T1,
In this case, a current of 4 mA is introduced from the line La,
After stabilization, the local power supply Et is supplied to each part, and the line La I4. The line voltage between the f
It is applied to the comparator CPt via the voltage converter FLtk, as in FIG. 3, where it is compared with the reference voltage Ets as in FIG. AND
The signal is supplied to the transmitter/receiver unit UARTt via the gate Gt+.

Therefore, in response to the detection of the flag (by), the gate pulse Ptg of %Hrr is sent out, and the AND gate Gt+
is turned on and the digital signal Sc is received, and after the reception of the digital signal Sc is completed, the processor CPUt turns on the interface I/Ft' according to the elapse of the period t.
(If the gate pulse Ptg2 of "l: H" is sent out and the transmitting/receiving unit UARTt is controlled, the transmission data that changes in the positive and negative directions in a spiral shape is sent out via the AND gate Gt2"f which is turned on. and adder ADDt
is given to one input of

Then, the processor CPUt sets the address setter AST.
In order to provide the individual code corresponding to the output of t to the transmitter/receiver unit UARTt, transmission data including the individual code is sent from the AND game)Gt27)''.

Note that the other input of the adder ADDt is connected to the sensor SS.
When the analog signal corresponding to the measured value is constantly given and the gate pulse Ptg□ is not activated, the DA
Only the output of CD/At is given to the current control section CCt, which has a current value corresponding to the measured value as an analog signal S.
On the other hand, when the gate pulse P jg2 is generated and the transmission data is sent out from the transmitter/receiver UARTt, the adder ADDt adds the power of both hands, so that it is superimposed with the analog signal Sa and the current controller The current flowing through CCt changes in the positive and negative directions in a pulse-like manner and is transmitted as a digital signal St including an individual code.

The value of the analog signal Sa and the digital signal St
The same effect can be obtained even if the processor CPUt adds the data and sends the data from the DAC-D/At, omitting the adder ADDt.

Further, the oscillator Tx has a nonvolatile memory such as an EAROM, and stores necessary data therein so that even if the power is cut off, these data are retained.

FIG. 7 is a circuit diagram of the current control unit cct. Similar to the transistor Q1 side in FIG. After amplification, transistor Q+
The internal impedance of z is controlled and a current determined by this is passed through resistors R12 and Rlg.

However, as in FIG. 4, the terminal voltage of resistor R13 is negatively fed back to differential amplifier A11 via resistor R14, and the current value corresponding to the output value of adder ADD t is maintained. It has become.

FIG. 8 is a block diagram of only one system showing another embodiment, in which the ADC-A/D and display device DP in FIG.
A low impedance ammeter A is inserted into the O range, and this is used to indicate the analog signal Sa, and also connects the terminal voltage of the resistor RL inserted into the transmission circuit to the communication device CE. In this case, the analog signal Sa is also received by converting the signal into a digital signal using the ADC-A/Dc and driving the display device DPca.

Note that the data transmitting/receiving section DSR is similar to that shown in FIG.

Therefore, it is up to the user to connect the communication device CF to the terminal board etc. that accommodates the transmission path and perform the desired data transmission and reception with the transmitter Tx.After confirming the installation location of the transmitter Tx using the individual code, Variable memo') Various adjustment values, setting values, etc. stored in the RAMt can be updated by remote control, and the operating status of the transmitter TX can be checked remotely. You can reach your goal by making only a few additions.

However, in FIGS. 1 and 8, the power for the transmitter Tx is supplied by a separate line, or
Other impedance elements may be used in place of the resistor RtQ, and in the second part, a parity check bit may be added to each byte, or a specific byte may be allocated for an individual code. Reeds, Figure 3,
The configurations shown in Figs. 4, 6, and 7 can be selected arbitrarily depending on the situation, and the shape shown in Fig. 5 is not limited to the hand-held type.
Various modifications are possible, such as a panel-mounted type and a switch that selects and connects the transmission path.

[Effect of the invention J 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. ,
Not only can the location of the transmitter be confirmed reliably, but it also does not affect the reception of analog signals, so it is extremely effective in remotely adjusting and monitoring the operating status 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. 5 is an external perspective view of the communication device, FIG. 6 is a block diagram of the transmitter, FIG. 7 is a circuit diagram of the current control section in FIG. 6, and FIG.
The figure is a block diagram of only one system showing another embodiment. Tx, Tx+ -TXll... transmitter, PS
, PS+~PSn...power supply section, La, Lb
, La+, Lb+~Lan, Lbn...Line, CE...Communication device, Engineering...Current value, Rt, +
Rt+~RLn...Resistor (voltage drop element),
Sa...Analog signal, Sc, St...Digital signal, CPUc. CPUt...Processor, ROMc, ROMt・
・9◆Fixed memory 5, RAMc, RAPVlt...
Variable memory, UARTc, UARTL...Send/receive Ig
Department, KBc...Fist keyboard, DPclDPca11
Fist display, I/Fc, I/Ft...interface, ASTt---Address setting device, FLc, FL
t...F wave generator, CPc, CPt...Comparator, Ecs, Ets...Reference voltage, CCc, CCt...
...Current control unit, ECL...Local power supply, D/At
...DAC (digital/anacog converter), 5W
t--Switch circuit, Ct--Capacitor, A
/Dc...ADC<analog-digital converter)
, 3...Clip. Patent applicant Yamatake Honeywell Co., Ltd. Agent Masaki Yamakawa (and one other person) Figure 1B Figure 2■ Figure 4

Claims (7)

[Claims] (1) A communication method in which the current value supplied from the power source is changed by an oscillator to generate an analog signal;
1. The current value is superimposed on the analog signal that passes through the voltage drop element, and the current value is changed in a pulse-like direction in the positive and negative directions by the current value transmitter to generate a digital signal, and the digital signal is received by the transmitter, and 1. The current value is superimposed on the analog signal, and the current value is changed in a pulse-like manner in a positive and negative direction by the transmitter to generate a digital signal including an individual code of the transmitter, and the digital signal is received by the communication device. analog and digital communication methods. (2) The analog-to-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, characterized in that a transmitter that transmits a digital signal containing an individual code set by an address setting device is used. (7) The analog according to claim 1, which uses a communication device equipped with a circuit that receives analog (a) based on the terminal voltage of a voltage drop element inserted into the transmission circuit.・Digital communication methods.