JPH0353359Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> The invention relates to a signal transmission device that transmits changes in physical quantities etc. to a load via two wires, and in particular, it is used to transmit data such as setting values from outside the transmitter. The present invention relates to a signal transmission device that can be set using a remote communication device.

<Prior art> Figure 3 shows an overview of the conventional signal transmission device (Japanese Patent Application Laid-Open No. 62-64804, title of invention "Signal transmission device" filed on September 5, 1985), which is the basis of the improvement of the present invention. This will be explained below.

Reference numeral 10 denotes a transmitter that converts process variables and the like into electrical signals and transmits them, and is supplied with power from a DC power supply 11 via a resistor 12 serving as a load. Electrical signals are transmitted as current signals from transmission lines l ₁ and l ₂ via terminals T ₁ and T ₂ , and the process variable is determined by detecting the voltage change occurring across the resistor 12 . The current signal is converted into a unified current of 4 to 20 mA and transmitted by a transmitter 10 set to a range corresponding to the pressure in the pipe, for example. In this case, the transmitter 10 is used, for example to change or monitor the pressure range.
Data is exchanged via an optical communication circuit by a remote communication device 13 provided externally.

The signal transmission device configured as above will be explained in more detail.

14 is a sensor that detects pressure, differential pressure, etc. and converts it into an electrical signal, and the converted analog signal is sent to an analog-to-digital converter (A/D converter) 15
is converted to digital voltage. The converted digital voltage is subjected to calculations by the microcomputer 16 according to calculation procedures written in various memories, and then sent to a digital-to-analog converter (D/A converter).
A unified current of, for example, 4 to 20 mA is sent to the output terminals T ₁ and T ₂ via the built-in output circuit 18 via the output terminal 17 .

On the other hand, the remote communication device 13 is, for example, the transmitter 10
It has a key matrix to set the setting values, etc.
If the data corresponding to the position of this key has multiple remote communication devices or transmitters, a code bit is added to identify the transmitter itself or the other party, and the carrier wave is modulated with a digital signal to which a start bit and an end bit are added. The optically modulated signal shown in FIG.

The amplification/detection circuit 22 of the transmitter 10 includes a light receiving element 21
The optical modulation signal shown in FIG. 4 received by the sensor is amplified and detected to reproduce the digital signal shown in FIG. This serially inputted digital signal is converted from serial to parallel by a decoder 23 and taken into the microcomputer 16, where, for example, a setting value is changed.

When the microcomputer 16 completes necessary processing such as changing setting values, it outputs the response signal to the decoder 23 as a parallel digital signal.
The modulation circuit 24 optically modulates the digital signal parallel-to-serial converted by the decoder 23 in the same manner as shown in FIG.

In the communication device 13, the received optical modulation signal is reproduced into a digital signal as shown in FIG. 5 by the amplification/detection circuit 27 and displayed. The displayed content is, for example, the setting value set in the transmitter 10.

<Problems to be solved by the invention> However, such conventional signal transmission devices have problems such as when the light-receiving surface is hidden in the shadows due to the installation angle of the transmitter, or when a worker attempts to communicate from the control room. However, there is a problem in that it does not function effectively when there is a shield between the remote communication device and the transmitter.

<Means for Solving the Problems> In order to solve the above problems, this invention provides a remote communication device that remotely communicates data such as setting values through modulated light, and A transmitter that has an optical communication means for communication, processes changes in physical quantities from a sensor in relation to data, and transmits current to the additional power source via two transmission lines supplied with power, and a small number of remote communication devices. Both have a first capacitor that can be detachably connected to the drive circuit of the light emitting element and the transmission line, and a second capacitor that connects the light receiving element of the transmitter and the transmission line inside the transmitter. be.

<Operation> With such a configuration, even if there is a shield, remote communication can be performed as desired by simply connecting via a capacitor as necessary.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. Note that parts having the same functions as those of the signal transmission device shown in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted as appropriate.

_C1 is a capacitor which can cut off the DC component of the digital signal appearing at the output end of the drive circuit 19 of the remote communication device 28 and can be arbitrarily connected to the transmission line _l1 , and the connection terminal 29 is connected to the tip of the capacitor.

COM is the common potential point of the remote communicator 28 and can be connected to the transmission line _l2 at the connection terminal 30.

On the other hand, inside the transmitter 31, the light receiving element 21
A capacitor C ₂ is connected to the positive terminal T ₁ , which is connected to one end of the transmission line l ₁ .

Therefore, the capacitor C ₁ , transmission line l ₁ ,
A digital signal is transmitted via a path via capacitor _C2 .

Further, one end of the light emitting element 25 of the transmitter 31 and the positive terminal _T1 are connected by a capacitor _C3 , and one end of the light receiving element 26 of the remote communication device 28 and the transmission line _l1 are connected to a capacitor C having a connection terminal 32. Connected by ₄ . Therefore, even without optical communication between the light emitting element 25 and the light receiving element 26, a response can be sent from the transmitter 31 to the remote communication device 28 via the path via the capacitor _C3 , the transmission line _l1 , and the capacitor _C4 . can.

As can be seen from the above explanation, this embodiment uses a capacitor in contrast to the conventional signal processing device shown in FIG.
With a simple configuration of just adding C ₁ to C ₄ and connection terminals 29, 30, and 32, necessary communication can be performed even when there is a shield between the transmitter and the remote communication device. In particular, in the device shown in FIG. 3, the communication distance is approximately 5 meters, but in this embodiment, communication can be performed over a distance of 100 meters or more.

In the explanation so far, we have explained an example in which two-way communication between the remote communication device and the transmitter is possible, but the light emitting element 2
5. Only one-way communication may be used, omitting the light-receiving element 26 and its related parts.

Also, as in the transmitter 33 shown in FIG.
If an inductance L is inserted on the T ₂ side, it is possible to communicate with high sensitivity even if the capacitor C ₂ is connected to the negative terminal T ₂ from one end of the light receiving element 21.

<Effects of the Invention> As explained above in detail with the embodiments, according to the present invention, a remote communication device can be connected to a remote communication device with a simple configuration in which a capacitor and a connection clip are added to the remote communication device, and a capacitor is added to the transmitter. Communication is possible even when there is a shield between the transmitters.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a partial block diagram showing another embodiment of the present invention, FIG. 3 is a block diagram showing a conventional signal transmission device, FIG. 4 is a block diagram showing the structure of the optical modulation signal in FIG. 3, and FIG. FIG. 5 is a configuration diagram showing the configuration of the digital signal in FIG. 3. 10, 31, 33...transmitter, 13, 28...
Remote communication device, 11... DC power supply, 14... Sensor, 16... Microcomputer, 22...
Amplification detection circuit, 23... decoder, 24... modulation circuit, 21, 26... light receiving element, 20, 25...
Light emitting element.

Claims (1)

[Scope of utility model registration request] It has a remote communication device that remotely communicates data such as set values via modulated light, and an optical communication means that communicates with the remote communication device, and processes changes in physical quantities from the sensor in relation to the data. A transmitter that transmits current to a load via two transmission lines supplied with power, and a first transmitter that can be detachably connected to at least a drive circuit for a light emitting element of the remote communication device and the transmission line. A signal transmission device comprising: a capacitor; and a second capacitor that connects a light receiving element of the transmitter and the transmission line inside the transmitter.