JPH01302996A - Analog/digital communication method - Google Patents

Abstract

PURPOSE:To favorably perform the remote adjustment and the operating state supervision of various kinds of transmitters by turning a current value superimposed upon an analog signal into s digital signal by changing it into a pulse shape in a positive and a negative directions by the transmitter, and allotting an individual code by communication equipment. CONSTITUTION:The current values to be supplied from power source parts PS1...PSn are turned into the analog signals by changing them by the transmitters TX1...TXn. The current values are changed by the communication equipment CE into the pulse shape in the positive and the negative directions as being superimposed upon the analog signals connected to voltage dropping resistors RL1...RLn to transmission lines La1, Lb1...Lan, Lbn to which these analog signals are connected so as to be turned into the digital signals. Then, these digital signals are received by the transmitters TX1...TXn, and simultaneously, their current values are changed by the transmitters TX1...TXn into the pulse shape in the positive and the negative directions as superimposing them upon the analog signals, and the digital signals containing the individual codes of the transmitters are formed. These signals are received by the communication equipment CE, and the individual codes are allotted by the communication equipment CE.

Description

[Detailed Description of the Invention] [Industrial Application Field] 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. be.

[Conventional technology]

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.

[Problem to be solved by the invention]

However, differential pressure transmitters, electromagnetic flowmeters, etc. are generally installed in a distributed manner over a wide area, and in order to adjust them and check their operating status, staff must patrol and conduct maintenance work.
Instead of having to carry out inspection work, 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 said to be carried out centrally at the supervisory control panel, etc., which accommodates about 1000 transmission lines for unified signals, so these transmission lines When making adjustments and checking the operating status by remote control via the transmitter, for example, if the transmitter has a predetermined ID set with a dip switch, etc.
If you need to replace the transmitter or change the settings, you can easily find out where the other party's differential pressure transmitter, electromagnetic flowmeter, etc. are installed. Conceivable.

[Means to solve the problem]

The present invention provides a communication method in which a current value supplied from a power source is changed by an oscillator to generate an analog signal, in which a voltage drop element is inserted into a transmission path through which the analog signal passes, and the voltage drop element is inserted into a transmission path through which the analog signal passes. The current value is superimposed on the analog signal and then changed in a pulse-like manner in a positive/negative direction by a communication device to produce a digital signal.The nuclear digital signal is received by the transmitter, and the current value is superimposed on the analog signal and then changed into a digital signal. A transmitter changes pulses in positive and negative directions to produce a digital signal including an individual code of the transmitter, the digital signal is received by the communication device, and the individual code is arbitrarily assigned by the communication device. It is configured as a feature.

〔Example〕

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

Figure 1 is a block diagram of the entire configuration, and the line La1+
A plurality of power supply units PS4 = PSn are provided for supplying current to each of a plurality of two-wire transmission lines (hereinafter referred to as transmission lines) consisting of Lbt to Lan + Lbn, and at the other end of the transmission line, Transmitter T such as differential pressure transmitter, electromagnetic flow meter, etc.
Xt"Txn is connected to each transmitter Txl"
Txn individually controls the current value I and passes it to the transmission path as an analog signal.

In addition, resistors RLI to RLn are inserted in series as voltage drop elements in each transmission path via the terminal board TB. The current is applied to a converter (hereinafter referred to as ADC), which converts the signal into a digital signal, drives a display DP such as a numeric display, and receives and displays the value of the analog signal indicated by the current value ■.

On the other hand, the oscillators TXI~Tx than the resistors RL, ~RLn
A communication device CE is selectively connected to the terminal board TB that accommodates the n-side transmission path, and this superimposes the analog signal and changes the current value connected to the resistor RLn into positive and negative pulses. transmitter T as a digital signal.
When transmitted to xn, this is received by the transmitter Txn, and in response to the reception, the transmitter Txn similarly changes the current value and transmits it to the communication device CE as a digital signal, so this is what is received by the communication device CE. It becomes.

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 over time t.
The current value I changes in the range of A, but when transmission from the communication device CE is performed, the current value I changes in the positive and negative directions in a pulse-like manner while being superimposed with the analog signal 8m during the period of the digital signal Sc. , which causes flag bit B
y, start bit B8, and first bit B1 to eighth bit B are transmitted.

Each bit is indicated by a change in the positive/negative direction, and the flag (P) BP has a particularly wide pulse width and always changes in the positive/negative direction. For example, B@ changes in the positive and negative directions when the logical value is %1'', and remains unchanged when the logical value is !0''.

This current value change causes a voltage drop change in resistor RL,
The voltage between the lines La and Lb on the oscillator Tx side is applied to the oscillator Tx as voltage correction, so that the digital signal Sc is received by the oscillator Tx.

Then, after the end of the digital signal Sc, the transmitter Tx
After a certain period t, the current value is changed in the same way during the period of the digital signal St, and the flag bit BF1, the start bit Bs, and the first bit B1 to the eighth bit B, which indicate its own unique code and data. , send.

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

7'('x) 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 may be transmitted and received in each of the digital signals Sc and St. Ru.

Wow, 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 Figure 1.
In an A/D, if an integrating circuit or the like is inserted on the input side, it becomes completely unrelated to the reception of the analog signal Sa.

FIG. 3 is a block diagram of the communication device Cg, which mainly includes a processor CPUc such as a microprocessor, a fixed memory ROMc, a variable memory RAMc, a keyboard KBc,
A display device such as a numeric display device DPc, a two-versal asynchronous transmitter/receiver unit (hereinafter referred to as a transmitter/receiver unit) UARTc, an interface I/Fc, etc. are arranged around it, and are connected to each other by a bus line BUc, which is connected to a fixed memory ROMc. The processor CPUc executes the stored program 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 U input RTc accordingly, and also controls the interface I/
In order to send out the gate pulse pcgl%H'' (high level) via Fc, AND game) Gcl,
When Gc2 is turned on, the increasing pulse Pu and the decreasing pulse Pd of @H# sent from the transmitter/receiver UARTc are given to the current controller CCc, and the increasing pulse Pu
In response to this, the current control unit CCc passes a current Ic from the line terminal T1 to T2, and in response to the decreasing pulse Pd, the control unit CCc sends out a control voltage that makes the line terminal T1 a positive pole and the line terminal T2 a negative pole. .

Therefore, when the current IC is connected, the current value flowing through the resistor RL increases as the sum of the current Ij indicating the analog signal Sa and the current IC. On the other hand, when the control voltage is sent out, the current value flowing through the resistor RL increases La.

The voltage between Lb increases and the current value decreases.

Further, the line voltage between the lines La and Lb is applied to one input of the comparator CPc via an f-wave device FLc such as a band f-wave device that passes only the frequency component of the digital signal St. Base voltage Bcts applied to the other input
A comparison is made with the reference voltage EC1, and a level higher than the reference voltage EC1 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 By of the digital signal St being given via the interface 1/Fc, the gate pulse Pt-%H is sent from the interface 1/Fc.
” and turn on Ag2 ND gate Gc3, start pitch) Bs
A reception output indicating the following is given to the transmitter/receiver unit UARTc,
In response to this output, the display DPc displays the individual code of the transmitter Tx and the received data.

FIG. 4 is a circuit diagram of the current control section CCc, in which the resistor R
The increasing pulse Pu from the AND gate Gcl is passed through the low-frequency r-wave filter for noise removal by the capacitor CI and the capacitor CI, and is amplified by the differential amplifier AI. vessel R2,R
A current Ic passes through the terminal 3.

Hiko, the terminal voltage of the resistor R is negatively fed back to the differential amplifier A1 via the resistor R4, so that the current 1
c is kept at a predetermined value.

On the other hand, the decreasing pulse Pd from the AND gate GC2 which passes through the image area f-wavelength filter similar to the above using the resistor R5 and the capacitor C2 is inverted and amplified by the differential amplifier A2, and is also inverted and amplified by the transistor Q2 similar to the above. To turn on, the voltage of the local power supply ECL inserted in series is sent out as a control voltage via resistors Rs and R7.

Note that the terminal voltage of the resistor R7 is negatively fed back to the differential amplifier A2 via the resistor R8, and the current from the local power supply ECL 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, and a code 2 is led out.
A clip 3 is connected to the tip of the line, so that it can be freely attached to and detached from the lines La+Lb.

FIG. 6 is a block diagram of the transmitter Tx, in which the same processor CPUt, fixed memory ROMt, variable memory RAMt, transmitter/receiver UARTt, interface I/Ft, etc. as in FIG. 3 are connected to the bus BUt. As in Figure 3, the processor CPUt performs the control operation, but the ADC-A/Dt, which converts the output of the sensor SS that detects differential pressure, flow rate, etc., into a digital signal, and its output A digital/analog converter (hereinafter referred to as DAC) D/At that converts the digital signal processed and sent by the processor CPUt into an analog signal, and an address setter ASTt for setting an individual code using a digital switch etc. are provided. Additionally, if necessary, individual codes can be set using digital signals from the communication device.

In addition, a power supply circuit pst is connected to the line terminal Tl, and in this case, it takes in a current of 4 mA from the lines t and a, stabilizes it, and then supplies it to each part as a local power supply Et. The line voltage between is applied to the comparator crt in the same way as in FIG. Similar to FIG. 3, it is compared with the reference voltage Ets, and the comparator CPt produces a received output.
It is given to the interface I/Ft and also given to the transmitter/receiver unit UARTt via ANDGt+.

Therefore, in response to the detection of the flag bit By, a gate pulse Ptg1 of %H'' is sent out, the AND gate Gt+ is turned on, and the reception of the digital signal Sc is repeated. Depending on the progress,
Processor CPUt via ink-face I/Ft! While sending out the gate pulse Ptg2 of H'',
If the transmitter/receiver unit UARTt is controlled, the input ND turned on
Transmission data that changes in the positive and negative directions in a pulse-like manner is sent out through the gate Gt2, and is applied to one input of the adder ADDt.

Tasoshi, processor CPUt is address setter A8Tt
In order to give an individual code corresponding to the output of
Sent from tz.

In addition, the other input of the adder ADDt is connected to the sensor SS.
When the analog signal corresponding to the measured value by DA is constantly applied and the gate pulse Ptg2 is not generated, DA
Only the output of CD/At is given to the current controller CCt, and a current corresponding to the measured value is passed as an analog signal Sa, while a gate pulse Ptgz is generated and the transmission data is transmitted to the transmitting/receiving section. Sent from UARTt\
For example, since the internal inputs are added in the adder ADDt, the current controller CC is superimposed with the analog signal Sa.
The current flowing through t changes in the positive and negative directions in a pulse-like manner and is transmitted as a digital signal St including an individual code.

Then, the value of the analog signal Sm and the data of the digital signal St are added in the processor CPUt, and then D
The same applies if the signal is sent from AC-D/At and the adder ADDt is omitted.

Further, the oscillator Tx has a nonvolatile memory such as ExROM, 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 by All, transistor Qo
The internal impedance of the resistor is controlled, and the current determined by this is passed through the resistors Ru and RI9.

However, as in FIG. 4, the terminal voltage of the resistor RI3 is negatively fed back to the differential amplifier All via the resistor RI4, and the current value corresponding to the output value of the adder ADDt is maintained. ing.

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

Note that the data transmitting/receiving unit DLR is similar to that shown in FIG.

Therefore, it is possible to connect the communication device CE to a terminal board etc. that accommodates the transmission line and perform desired data transmission and reception with the transmitter Tx. Tx variable memo! It is now possible to update various adjustment values, setting values, etc. stored in JRAMt by remote control, and it is also possible to remotely check the operating status of the transmitter Tx, with some additions to the existing equipment. You can reach your goal only by doing the following.

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 for the resistor RLO, and in Figure 2, a bit for parity check is added to each byte, or a specific byte is allocated for an individual code. The same applies to 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〕

As is clear from the above description, 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
Not only can the installation location of the transmitter be confirmed reliably, but it also has no effect on the reception of analog signals, making it extremely effective in remotely adjusting and monitoring the operating status of various transmitters.

[Brief explanation of the drawing]

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, TXIA-TXn fist...transmitter, P8,
Psi~PSn...power supply section, La, Lb + L
a+, Lb+~Lan, Lbn-fist...railway, CE...
...Communication device, ■...Current value, RL, RL, ~
RLn...Resistor (voltage drop element), 8a...
・・Analog signal, Sc, 5t --・・Digital signal, CPUcl CPUt ・φ・Processor, ROM
c. ROMt--Fixed memory, RAMc, RAMt
・・・・Variable memory, UARTc, UARTt・
...Transmission department, KBc ...Keyboard, DPc
. DPca+1@...Display device, I/FC1■/Ft -Interface, ASTt...φ Address setter, FLc, FLj...R wave device, C
Pc. cpt ----- Comparator, FJcs, Ets ell・
・Reference voltage, CCc, CCt...Current control section,
gcL...local power supply, D/At...IIC (digital-to-analog converter), SWt...switch circuit, Ct...capacitor, A/Dc...A
DC (analog-digital converter), 3...Clip.

Claims (1)

[Claims] In a communication method in which 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 a transmission path through which the analog signal passes, and the voltage drop element is superimposed on the analog signal passed through the voltage drop element. Furthermore, the current value is changed in a pulsed manner in the positive and negative directions by a communication device to generate a digital signal, and the digital signal is received by the transmitter, and after being superimposed on the analog signal, the current value is converted into a pulse by the transmitter. a digital signal containing an individual code of the transmitter,
receiving the digital signal by the communicator, and
An analog/digital communication method characterized in that the individual code is arbitrarily assigned by the communication device.