JPS5940339B2 - 2-wire code transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-wire code transmission method for remotely reading the indicated amount of a meter such as a gas or water meter by pulse code transmission.

Generally, the decimal value of a certain digit is determined, for example, by pulse code transmission from an encoder of a transmitting meter to a receiving section. When sending a number, common timing information is required between the transmitter and the receiver. At this time, the conventional method requires a large number of transmission lines. That is, one wire is used to send and receive a synchronization pulse signal which is timing information, one wire is used to supply power to energize the transmitter circuit, and one wire is used to send and receive a code pulse signal.
In addition, a total of four transmission lines, including one as a common ground line, are required. An object of the present invention is to provide a method for realizing a two-wire pulse code transmission device in which timing information is created in a receiving section, sent to a transmitting section, and a pulse code signal matching the timing information is sent from the transmitting section. It's about doing.

The present invention will be explained below with reference to the drawings.

FIG. 1 is an electrical connection diagram of an embodiment of the present invention. In FIG. 1, 1 is a receiving section, 2 is an encoder of a transmitting section, and 3.
4 is a transmission line. 12 is a synchronous pulse generator, and 11 is a DC power supply.

The synchronizing pulse signal generated by the irregular pulse generator 12 is transmitted via the transmission line 3 as a voltage level signal superimposed on the power supply voltage of the DC power supply 11. Reference numeral 21 denotes a constant voltage stabilizing circuit which extracts only the DC voltage from the voltage level signal and supplies it to each part of the encoder as power.

Reference numeral 22 denotes a line amplifier which level-shifts the power supply voltage superimposed portion from the voltage level signal and amplifies the waveform of the synchronizing pulse signal.

23 is a synchronization detection circuit, 24 is a parallel-to-serial conversion circuit, and 25 is a signal detection circuit.

The parallel-to-serial conversion circuit 24 obtains a step pulse from the output of the line amplifier 22 and converts the parallel signal from the signal detector 25 into a serial signal. A line driver 26 converts the serial code signal output from the parallel-to-serial converter circuit 24 into a current level signal and transmits it to the receiving section 1 via the transmission line 4.

In the receiving section 1, the current level signal flows through a resistor 19, and the voltage across the resistor 19 is guided to a waveform shaping circuit via output terminals 13 and 14. The operation of the apparatus configured in this way will be explained with reference to FIGS. 2 and 3. FIG. 2 is an electrical connection diagram showing a specific configuration of important parts of the encoder 2 shown in FIG. FIG. 3 is a time chart of the main signals. A synchronizing pulse signal superimposed on the DC power supply voltage is transmitted from the receiving section 1 to the terminal 27 in the waveform shown in FIG. 3a. The transistor TRl, the resistor R3, and the Zener diode RD2 are the first
The constant voltage stabilizing circuit 21 shown in the figure is configured to extract the power supply voltage required by each circuit of the encoder 2 from the input waveform a.
Resistance Rl. Resistor R2, Zener diode RDl. Transistor TR2 and resistor R4 are the line amplifier 22 in FIG.
is configured to extract the voltage level signal from the input waveform and shape the waveform. Rl, R2, and RDl are circuits that level shift the input waveform and determine the high-level and low-level thresholds of the synchronizing pulse signal. The synchronization detection circuit 23 generates the synchronization pulse shown in FIG. do. The parallel signal read into the parallel-to-serial conversion circuit 24 becomes a serial code pulse signal as shown in FIG. . In other words, the parallel-to-serial conversion circuit 24
When the output is low level, TR3 is cut off and the signal current becomes zero, and when it is high level, TR3 is conductive, and in this case, an output sign pulse signal current determined by the input voltage of TR3 and resistor R5 flows. This output code pulse signal current is detected as a voltage across the resistor 19 of the receiving section 1. A specific example of the operation described above will now be described with reference to FIG.

FIG. 4 is an electrical connection diagram of the waveform shaping circuit of the receiving section 1. When the output current flowing through the transmission lines 3 and 4 is small, that is, when the voltage across the resistor 19 is small, the transistor TR
4 is an off state. When the output current increases and the voltage across the resistor 19 exceeds a certain value, the base current of TR4 flows and TR4 turns on. In this state, the voltage across the resistor 19 is clamped to the voltage between the base and emitter of TR4. This clamp voltage is usually a small value of 0.4 to 0.7. Now, set the operating values of each element in the circuit as follows.

Resistance 1935Ω Clamp voltage: 0.7V This is the worst condition.

Transmission line: 3.46Ω This value varies depending on the installation conditions of the receiver and transmitter.

The output code pulse signal current flowing through TR3 is 20 mA, or the current flowing through the zero synchronization detection circuit 23 and the parallel-to-serial conversion circuit 24 is 5 mAR 31 KΩ. I'll ignore it and explain.

The synchronized pulse signal voltage generated between the terminals 15 and 14 is transmitted to the terminals 27 and 28, but the voltage between them (hereinafter referred to as the "manual pulse voltage") changes depending on the transmission line resistance and the output current flowing through the transmission line. Setting each element as above,
The fact that the line amplifier 22 can be operated without being affected by changes in the input pulse voltage will be explained next. terminal 15,
A synchronizing pulse signal with a high level of 15 V and a low level of 10 V is generated between 14 and 14.

The input pulse voltage will decrease below this value. Transmission line resistance 6Ω
, when the output sign pulse signal current is 20 mA, the reduction in high level is maximum. Calculating this case, the high level input pulse voltage is 14.1V. Transmission line resistance 0Ω,
When the output sign pulse signal current is 0 mA, the decrease in the low level is the minimum. Calculating this case yields 9.6. Since the difference between the two is 4.4, which is a sufficiently large value, by selecting the Zener voltage of RDl to an appropriate value between 14.1V and 9.7V, the line amplifier 22 can sufficiently discriminate the synchronization pulse signal.

Further, even under the condition that the output code pulse signal and the high level value of the current are minimum, the voltage across R19 is calculated to be 1.19, and the code pulse signal detection operation of the receiving section is also good.
In the embodiment described above, the synchronization pulse signal is transmitted as a voltage level signal and the code pulse signal is transmitted as a current level signal, but conversely, the synchronization pulse signal is transmitted as a current level signal and the code pulse signal is transmitted as a voltage level signal. It is also possible to do this.

An embodiment of this method will be briefly described below with reference to FIG. FIG. 5 is an electrical connection diagram of an embodiment using this method. In FIG. 5, a synchronizing pulse signal having a current level superimposed on a constant current value is generated by a transistor TR4 and a resistor R5 as a synchronizing pulse signal generator. A line amplifier 22 is constituted by a transistor TR2 and resistors Rl and R4, and the value of R1 is set so that when the synchronized pulse current signal is at a low level, TR2 is off and when it is at a high level, it is on. When TR3 is turned on and off based on the sign pulse of the output of the parallel-to-serial converter circuit 24,
An output sign pulse voltage is generated across terminals 27 and 28. This voltage is detected from terminals 13 and 14, and changes the value of Zener diode RD3 to a high level between terminals 13 and 14.
By selecting an appropriate value between the low level, a shaped amplified waveform can be obtained from the collector of TR5. The operation of other parts is similar to the embodiment shown in FIG. As detailed above, according to the method of the present invention, it is possible to realize a two-wire pulse code transmission device with a relatively simple configuration, reducing the cost of wire materials, reducing the cable accommodation space, and reducing the need for terminal components. The effects of this, such as reduction, are significant.

[Brief explanation of drawings]

Fig. 1 is an electrical connection diagram showing one embodiment of the method of the present invention, Fig. 2 is a detailed electrical circuit diagram of the main part of one embodiment, Fig. 3 is a time chart thereof, and Fig. 4 is an electrical connection diagram showing an embodiment of the method of the present invention. This is an electrical circuit diagram of the main parts. FIG. 5 is an electrical circuit diagram showing another embodiment. 1...
...Receiving section, 2... Encoder, 3, 4...
...Transmission line, 11...DC power supply, 12...
... Synchronous pulse generation circuit, 13, 14...
Received signal detection terminal, 21... Constant voltage stabilization circuit, 22... Line amplifier, 23... Synchronization detection circuit, 24... Parallel-to-serial conversion circuit, 2
5... Signal detection circuit, 26... Line driver.

Claims (1)

[Claims] 1 A synchronizing pulse signal is transmitted from the receiving section to the transmitting section via a pair of transmission lines, and a code pulse signal synchronized with the synchronizing pulse is transmitted from the transmitting section to the receiving section, and the transmitting section is powered by the power supply of the receiving section. In the code transmission device that is only energized, the synchronizing pulse signal is transmitted from the receiving section to the transmitting section as a voltage or current level signal, and the synchronizing pulse signal is transmitted as a current or voltage level signal from the transmitting section to the transmitting section. A two-wire code transmission method characterized by transmitting to a receiving section.