JPS59201535A - Analog/digital communication method and device - 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/digital communication method and its method that are applied when analog and digital signals are transmitted over the same transmission path in industrial measurement, etc. It is related to the device.

[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 flow sides, 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 9.
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.

[Object and structure of the invention]

The present invention has been made based on such a conventional demand, and the first object is to superimpose analog signals and It provides an analog/digital communication method that allows the free transmission and reception of digital signals, and in order to achieve this purpose, a communication method in which the current value supplied from the power supply section is changed by a transmitter to produce an analog signal. In the method, a voltage drop element is inserted into a transmission path through which the analog signal passes, and the current value is superimposed on the analog signal passed through the voltage drop element, and the current value is changed in a pulse-like manner in a positive and negative direction by a communication device to convert the current value into a digital signal. The digital signal is received by the transmitter, the current value is superimposed on the analog signal, and the current value is changed in the positive and negative directions by the transmitter to generate a digital signal, and the digital signal is converted into a digital signal. This configuration is characterized in that the communication is received by the communication device.

The second object is to provide an analog/digital communication device that can freely send and receive digital signals in addition to analog signals between a transmitter and a communication device. In a communication device consisting of a power supply unit that supplies current to a transmission line and an oscillator that is connected to the transmission line and changes the current value of the transmission line to generate an analog signal, a voltage drop inserted into the transmission line Motoko and
The voltage drop element is also superimposed with the analog signal bridge-connected to the transmission line on the transmitter side, and changes the current value of the voltage drop element in a pulse-like manner in positive and negative directions, and transmits it as a digital signal, and the same. a communication device that receives the digital signal transmitted from the communication device, superimposes it on the analog signal, and changes the current value of the transmission path in a positive/negative direction in a spiral shape to generate a digital signal; and the transmitter for transmitting data to the communication device.

〔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, line L1 +L
A power supply unit PS is provided to supply current to a two-wire transmission line (hereinafter referred to as a transmission line), and the other end of the transmission line is equipped with a transmitter such as a differential pressure transmitter or an electromagnetic flowmeter. When Tx is connected, the oscillator Tx controls the current value (2) and passes it to the transmission line as an analog signal.

In addition, a resistor RL is inserted in series as a voltage drop element in the transmission line, and the terminal voltage of this is applied to an analog-to-digital converter (hereinafter referred to as ADC), which converts it into a digital signal and converts it into a numeric display, etc. The display device DP is driven, and the value of the analog signal indicated by the current value is received and displayed.

On the other hand, both the resistor RL and the transmission line on the oscillator'rx side have
The communication device CE is connected as a bridge, and this superimposes the analog signal and changes the current value flowing through the resistor RL in a pulse-like positive and negative direction, and transmits it as a digital signal to the transmitter Tx.
This is received by the transmitter Tx, and in response to the reception, the transmitter TX similarly changes the current value and transmits it as a digital signal to the communication device CE, so it is assumed that this is received by the communication device CE. It has become.

FIG. 2 is a waveform diagram showing how the current value I flowing through the resistor RL changes over time t.
It changes within the range of A, but when the communication device CE sends a signal, the current value changes in the positive and negative directions in a pulsed manner during the period of the digital signal Sc, and is superimposed on the analog signal S8. , this results in 7 lag bits B
F, start bit Bs, and first bit B1 to eighth bit B8 are transmitted.

Each bit is indicated by a change in the positive/negative direction, and the pulse width of the flag (B) BF is set particularly wide and always changes in the positive/negative direction. Bs changes in the positive and negative directions when the logic value is "1", and remains unchanged when the logic value is "0".

This current value change causes a 1L voltage drop change in the resistor RL, and the line L1. It is applied to the oscillator TX as a voltage change across L2, thereby causing the digital signal S0
is received by the transmitter 'rx.

Then, after the end of the digital signal Sc, the transmitter TX
After passing the string ts for a certain period of time, the current value ■ is similarly changed during the period of the digital signal St, and the flag BF, start bit Bs, and first bit B1 to indicate data are changed.
8th Pitsu) Send Bs.

Therefore, as described above, the line L1. A voltage change occurs across L2, which is received by the communicator CE.

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 digital signal 5etSt.

Note that changes in the positive and negative directions of each bit result in the same current value, and their average value becomes zero, so the ADC-
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 CE, which mainly includes a processor CPUc such as a microprocessor, a fixed memory ROMc, a variable memory RAM0, a keyboard KBc,
A display device such as a numeric display DPc, a universal asynchronous transmitter/receiver unit (hereinafter referred to as a transmitter/receiver unit), a UARTc, an interface I/Fc, etc. are arranged around the periphery, and they are connected to each other by a bus BUc. The processor CPUc executes the program stored in the variable memory RAM c, and performs control operations while accessing predetermined data to the variable memory RAM c.

Here, if desired data is given from the keyboard KBc, the processor CPUc will respond to the transmitter/receiver unit U.
In addition to controlling ART c, interface
In order to send out the gate pulse Pcg□ as "H" (high level) through the transmitter/receiver UART o, AND gate Gcl+Gc2 is on,
An increasing pulse Pu and a decreasing pulse Pd of ``'' are applied to the current control section CCo, and the current controlling section CCc passes the current Ie from the line terminal T1 to T2 in response to the increasing pulse Pu, while passing the current Ie from the line terminal T1 to T2 in response to the decreasing pulse Pd. The control unit CCc sends out a control voltage with the line terminal Tl as a positive pole and the line terminal T2 as a negative pole.

Therefore, when the current Ic passes, the current value flowing through the resistor RL increases as the sum of the current value t indicating the analog signal Sa and the current Ic, but on the other hand, when the control voltage is sent out, , the voltage between the lines L1 r ''2 increases, and the current value I decreases.

In addition, the line voltage between the lines L1+"2 is applied to one input of the comparator cPc via an offshore transducer FLc such as a bandpass transducer that passes only the frequency component of the digital signal Si, and the other A comparison is made with a reference voltage Ec8 applied to the input of the reference voltage Ec8, and a level higher than the reference voltage Ec8 is extracted as a received output.

Therefore, after the transmission of the digital signal sc is completed, in response to the reception output corresponding to the flag bit BF of the digital signal St being given via the interface E/Fc,
When the gate pulse Peg2 is sent as "H" from the interface E/Fc and the AND gate Gc3 is turned on, the reception output corresponding to the start bit B8 and after is given to the transmitting/receiving section UART c, and is displayed according to the output of the gate. The received data is displayed by the device DPc.

Figure 4 is a circuit diagram of the current control section ccc, and the resistor R
1 and capacitor c1 through a low-pass filter for noise removal)
The differential amplifier A1 is amplified by fc5, and in order to turn on the field effect transistor Q1, the resistor R2+
After R3, he moved to heel style. is understood.

Note that the terminal voltage of the resistor R3 is negatively fed back to the differential amplifier A1 via the resistor R4, so that the current!
. is kept at a predetermined value.

On the other hand, the decreasing pulse Pd from Ga4 is inverted and amplified by the differential amplifier A2 through the same low-frequency E-wave generator as described above with resistor R5 and capacitor c2, and is also inverted and amplified by the differential amplifier A2. To turn on, the local power supply Ec is inserted in series through resistors R6+R7.
The voltage of L is sent out as a control voltage.

Note that the terminal voltage of one 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, a cord 2 is led out, and a clip is attached to the tip of the cord 2. 3 is connected and the line L1 r ” 2
It can be attached and detached freely.

FIG. 6 is a block diagram of the transmitter Tx, in which the same processor CPUt, fixed memory ROMt1, variable memory RAMt, transmitting/receiving unit UARTj, interface I/F j, etc. as in FIG. 3 are connected to the bus BUt. As in FIG. 3, the processor CPUj performs the control operation, but the ADC-VO2 converts the output of the sensor SS that detects differential pressure, flow rate, etc. into a digital signal, and the output of this is sent to the processor CPUj. A digital-to-analog converter (hereinafter referred to as DAC) D/At is provided for converting the digital signal processed and sent by the converter into an analog signal.

Further, a power supply circuit Pst is connected to the line terminal T1,
In this case, a current of 4 mA is taken from the line L1, stabilized and then supplied to each part as a local power supply Et, and the line voltage between the lines L1 and L2 is determined by the digital signal S.
Similarly to FIG. 3, the reference voltage Ets is applied to the comparator CPt via an F-wave device FLi such as a band-pass wave device that passes only the frequency component of c.
The comparator CPj generates a reception output, which is applied to the interface I/Ft, and also to the transmitter/receiver unit UARTj via Gtl.

Therefore, in response to the detection of the flag bit Bv, a gate pulse Ptg1 of 1" is sent out, the AND gate) Gtt is turned on, and the digital signal Sc is received. After the reception of the digital signal Sc is completed, a period t8 elapses. In response to this, the processor CPU t sends out an "H" gate pulse Ptg□ via the interface I/Ft, and controls the transmitting/receiving unit UART i, which then outputs a positive/negative pulse in the form of a pulse via the AND gate (Gt2) which is turned on. Transmission data varying in direction is sent out and applied to one input of an adder ADD j.

Note that the other input of the adder ADD j is connected to a sensor 88.
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 control section CCt, which has a current value corresponding to the measured value as an analog signal S.
On the other hand, if the gate pulse "tg2" is generated and the transmission data is sent from the transmitting/receiving unit UARTj, the adder ADDt adds the power of both hands, so it is superimposed with the analog signal SIL and the current control unit C(4
The current flowing through the terminal changes in the positive and negative directions in a pulse-like manner, and is transmitted as a digital signal st.

However, the same effect can be obtained even if the analog signal SaO value and the data corresponding to the digital signal St are added together in the processor CPUj and sent out from the DAC-D/Ai, and the adder ADDj is omitted. In addition, the transmitter TX is
It has a nonvolatile memory such as EAROM, and necessary data from the communication device CE is written into this memory. For this reason, data is retained even in the event of a power outage or the like.

FIG. 7 is a circuit diagram of the current control unit CCt. Similar to the transistor Ql side in FIG. After amplification by amplifier All, transistor Ql
The internal impedance of I is controlled, and the current determined by this is passed through the resistor "12+R13."

However, as in Fig. 4, the terminal voltage of the resistor R13 is negatively fed back to the differential amplifier All via the resistor R14, and the current value corresponding to the output value of the adder ADDj is maintained. There is.

FIG. 8 is a block diagram of the entire configuration showing another embodiment. A low impedance ammeter A is inserted in place of the ADC-A/D and display DPO in FIG. The terminal voltage of the resistor RL inserted into the transmission circuit is input to the communication device CE, converted into a digital signal by the ADC-A/Dc, and then sent to the display. Defeat DP ca! Also here, it is assumed that the analog signal S is received.

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

Therefore, it is possible to freely connect the communication device CE to a terminal board etc. that accommodates a transmission line and perform desired data transmission and reception with the transmitter 'rx.
It is now possible to update various adjustment values, setting values, etc. stored in the t by remote control, and it is also possible to remotely check the operating status of the transmitter With only a few additions, the desired goal can be achieved.

However, in FIGS. 1 and 8, the power source for the oscillator 'rx may be supplied to a separate line, or another impedance element may be used for the resistor RLO power. , a bit for parity check is added to each byte, or a digital signal S
The configurations shown in FIGS. 3, 4, 6, and 7 can be selected arbitrarily depending on the situation, and the configurations shown in FIG. The shape of
It is not limited to a hand-held type, but may be a panel-mounted type, etc., and a switch may be used to select and connect the transmission path, or the transmitter CF may only transmit, and the transmitter 'rx may only receive. In some cases, it is sufficient, etc.
Various modifications are possible.

〔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 it does not affect the reception of analog signals, significant effects can be obtained in remotely adjusting H1,'il 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 the entire configuration showing another embodiment. 'rx...-transmitter, PS...power supply section, Ll. L2...Line, CE...Communication device, ■...Current value, PL,...Resistor (voltage drop element), Sa...
...Analog signal, sc, sj ...Digital signal, CPUo, CPUt@...Processor, RO
M, , ROM1...Fixed memory, RAMc,
RAMt --- Variable memory, UARTc, UARTj
-@-・Transmission/reception section, KBce...Keyboard, DP
e r DP elk...Display, I/Fc+
I/Fj・・・Interface, FLc, FLt・
...Okiwaki, CPc, CPj...Comparator, Ecs
+ Ets...Reference voltage, CCc, CCt・
...Current control unit, EcL...Local power supply, D/At
...DAC (digital-to-analog converter), SW
t...Switch circuit, Ct・e...-capacitor, A
/Dc...--ADC (analog-digital converter)
, 3...Clip. Patent applicant Yamatake Honeywell Co., Ltd. Agent Masaki Yamakawa (and one other person) Poverty 1 Figure 2 ■

Claims (7)

[Claims] (1) 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 connected to the voltage drop element. After being superimposed on the analog signal, the current value is changed in positive and negative directions by a communication device to produce a digital signal, and the digital signal is received by the transmitter, and the current value is superimposed on the analog signal and then changed into a digital signal. An analog/digital communication method characterized in that the current value is changed in positive and negative directions by the transmitter to generate a digital signal, and the digital signal is received by the communication device. (2) A communication device comprising a power supply unit that supplies current to a transmission line, and a transmitter connected to the transmission line and changing the current value of the transmission line to generate an analog signal, which is inserted into the transmission line. The voltage drop element is superimposed with the analog signal bridge-connected to the transmission line on the oscillator side, and the current value of the voltage drop element is changed in a pulse-like manner in positive and negative directions. a communication device that transmits as a digital signal and receives a similar digital signal; and a communication device that receives the digital signal transmitted from the communication device and superimposes it with the analog signal, and then converts the current value of the voltage drop element into a positive or negative pulse shape. An analog/digital communication device comprising: the transmitter that changes direction and transmits the signal as a digital signal to the communication device. (3) The analog according to claim 1 or 2, 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 section.・Digital communication methods or devices. (4) The analog/digital communication method or device according to claim 1 or 2, characterized in that a communication device is used that is detachable from the transmission path. (5) The analog/digital communication method or device according to claim 1 or 2, characterized in that a resistor is used as the voltage drop element. (6) The analog/digital communication method or device according to claim 1 or 2, characterized in that it uses a transmitter and a communication device that are controlled by a processor that executes a program. (7) Claim 1 or 2, characterized in that a communication device is used that is equipped with a circuit that receives an analog signal based on the terminal voltage of a voltage drop element inserted into a transmission circuit.
The analog/digital communication method or device described in Section 1.