JPS6169221A - Signal receiver - Google Patents

Abstract

PURPOSE:To attain a monolithic control circuit and to facilitate easy miniaturization of a signal receiver by transmitting only a current showing the signal value through an impedance element for reception to perform reception and flowing freely a power supply current to a load circuit. CONSTITUTION:A current IC flowing to a resistor RC serving as an impedance element for reception is defined as IC = (inter-line voltage VL - load side voltage VC)/RC. Therefore a current IS=IL-IC is satisfied by controlling the impedances of variable impedance element Z1 and Z2 so as to fix both the VL and VC and the controlling a current I1. In other words, a current IS flowing to a resistor RS has only a signal component of 0-16mA in case the line current IL is equal to 4-20mA, for example, by setting the current IC at a level equal to a bias component. Then the reception value can be detected by the voltage VS. Furthermore, a power supply current of maximum 4mA can be freely supplied when the current IL is equal to 4-20mA.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving device that receives a signal indicated by a current value in an industrial process or the like and controls a device to be controlled such as pulp.

[Conventional technology]

In industrial processes etc., pulp etc.? For remote control, a wound device commonly referred to as a positioner is provided,
A signal sound is transmitted from a central control device using a current value that varies depending on a range of 4 to 20 mA (D), which is received by a receiving device and then controlled according to the current value.

However, in the past, a two-wire transmission line was required for transmitting the signals and current values, and a separate two-wire power supply line was required to supply all the necessary sources on the receiving device side. Therefore, a total of four lines are required, which increases the amount of wire required for the lines and the number of man-hours for laying them, leading to winter defects that increase equipment costs.

As a countermeasure against this, a basic configuration has been proposed in the separate application filed by the present applicant [Receiving device From the current varying as mA etc., 0 to 1
In addition to extracting all of the current, such as 6 mA, which shows a signal value that changes due to tightness, all of the bias components, such as 4 mA, are extracted and used for the local power supply.

[Problem that the invention seeks to solve]

However, in the same application, the first
This requires a second control circuit and a means for fully controlling the reference voltage applied to these circuits, making the configuration complicated and expensive, and making it difficult to reduce the housing space. This has caused problems such as total inhibition.

The purpose of the present invention is to fundamentally solve all of the drawbacks of the conventional technology.
The present invention provides a highly effective receiving device using only circuits.

Means for Solving Problem C] Therefore, the present invention achieves the object with the following configuration.

In other words, the first variable impedance element and the impedance element for reception are inserted in series with the two-wire transmission line, and the impedance of the variable impedance element is adjusted in the direction of making the line voltage of the transmission line constant. At the same time, a series circuit consisting of an impedance element and a second variable impedance element connected in series is connected in parallel with these elements, and the current flowing through the series impedance element is controlled to be kept at a constant value according to the gold bias component. is controlled by a single control circuit, and is connected in parallel to the second variable impedance element on the load circuit.

[Effect]

Therefore, the impedance system for reception has a signal value? Only the current indicated by the signal is passed through, thereby allowing reception to be performed, and the power supply current can be freely passed through the load circuit within the range of the bias component.

〔Example〕

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

Figure 1 is a block diagram showing the whole.
, tt, the two-wire transmission line is the line L
1. A first variable impedance element (hereinafter referred to as an element) Z+ is inserted, and a resistor R3 is connected in series as a receiving impedance element, while a resistor R3 is connected in parallel with these. , a resistor Re as a series impedance element, and a series circuit including the second element 22 are connected.

In addition, a control circuit CNT is connected in parallel with the element z as a load circuit, and the circuit CNT K is connected to the line terminal tz.
Line voltage Vt, load side voltage Vc of resistor Rc, terminal voltage Vs of resistor Rs, and actual measured values from the drive device &DR, which will be described later, are given with respect to the side base, and the control circuit CNT calculates the voltage The first and second control voltages V according to Vl and Vc
d+, Vd2, and control the impedance of each element Z+, Zx to keep the voltages Vt, t'', for example, IOV, and the voltage Vat, for example, ■, constant values, and the received value based on the voltage Vs and the actual measurement from the drive device DR. A control calculation corresponding to the value is performed, and a control signal is sent to the electric and vacancy changer E/P, which will be described later.

In this case, the current Ic Ir flowing through the resistor Re
! .

It is shown by the following formula.

Therefore, the impedance of element z1 is controlled in the direction of keeping Vt constant, and the impedance of element Z! is controlled in the direction of keeping Vat constant. If the impedance of is controlled and the current Itk7XI passing through it is reduced, the current Ic becomes one foot regardless of the load power application 3, and the following equation is established.

IL= I3 + It 4p h = Is + I
c5., Work s = Work 1 Work C... (2) That is, by setting it equal to Ic t - bias component, when the line current IL is, for example, 4 to 20 mA, the electric work 8 connected to the resistor R8 has only a signal component of 0 to 16 mA.Next, the received value can be detected using the voltage Vs.

Also, if IL is 4 to 20mAf7), maximum 4mA
Supplying a power supply current of

In addition, on the central control device side (not shown in the figure), the line current IL is sent out by a constant current circuit. Do 9, receiver 1QI
Even if the input impedance of I changes, it will affect the current value! J
'e never give.

Furthermore, if a change in voltage VC affects the operation of each load circuit, a voltage stabilizing circuit may be inserted into a portion where electrical construction 2 communicates.

In addition, element Z1. Z2 is a transistor,
Controllable variable impedance such as photo coupler? It is sufficient to use the one that presents the desired results.

Figure 2 shows the block diagram of the control circuit CNT, processor CPU such as microprocessor, fixed memory IJROM, variable memory IJRAM, analog 1 log, etc.
Digital converter (hereinafter referred to as ADC) A/D.

Digital to analog converter (hereinafter referred to as DAC) D/A1
~D/Ask are arranged around the k and are connected by a bus line, so that all the instructions in the fixed memory IJROM are executed by the processor CPU, and the predetermined data are transferred to the fully variable memory IJRAM.
Control operations are performed while accessing the

Further, the voltage VC shown in FIG. 1 is stabilized in the voltage stabilizing section REG, and is then supplied as a local power source E to each section.

On the other hand, there is a processor CP on the input side of the ADC-A/D.
A multiplexer MPX controlled by U is provided, by means of which each voltage VL, Vc, Vs and the actual value from the drive DR is sequentially and iteratively selected and
After each signal is converted into a digital signal by the C/A/D, it is sent to the processor CPU.
Depending on these, the processor CPU
In order to provide control data to ~D/As, it is converted into an analog signal and a control signal for the control voltages Vt+, Vdz and the electro-pneumatic converter E/P is sent out.

The third reason is that the flowchart of the control situation by the processor CPU is incorrect, and the multiplexer MPX and ADC-A
After the seventh line of #101, the voltage SVL is fetched via /D, and compared with the first reference voltage Vr+ stored in the smooth fixed memory IJROM.
Vrl? "102" is judged, and if it is negative (NO), the control voltage %Vd is determined according to the value of VL.

Modify "103" and step 102 is YES.
) Repeat this until .

Next, in the same way as step 101, take in a voltage of 1vC.
111 k, and as in step 102, by comparing with the second reference voltage Vr2, 'Vc=Vr
+ 7112 k Judgment, if C is N, step 1
03, control voltage 'Vd2 until this becomes Y
Make the correction "113".

That’s all! After setting 1lVyVct constant, step 1
Similarly to 01, voltage 'Vs capture' 121. and,
After taking in the S actual measurement value from the drive device DR ``122'' and performing 1 control calculation 123i according to these, the DA
Control signal is sent via CD/As'``124''
i, and repeat steps 101 and subsequent steps.

Figure 4 shows the entire structure of the receiving device #:? 6 in the block diagram shown
9. The received output from the receiving device RE shown in FIG.
This drives the pulp ■ to fully control the opening, and the current opening is detected as an actual value by a potentiometer connected to the drive shaft, and is given to the receiving device RE. ing.

5 and 6 are block diagrams similar to FIG. 1 showing other embodiments; in FIG. 5, the resistor Rck
Railway terminal t! In FIG. 6, the resistor Rs
It is the same as in Fig. 1 except that the i-line terminal side 1 is inserted.

Note that the control circuit CNT is required to select the detection reference potential of each voltage depending on the insertion position of the resistors Rs and Rc.
According to this, the configuration of Figure 2? Just make some changes.

Therefore, the purpose is achieved with only a single control circuit CNT, and all of the circuits CNT H are controlled by digital circuits, so that the control situation becomes stable and miniaturization becomes easy.

However, instead of the resistor Rs, an impedance element such as a diode, or a circuit for detecting the redundant current value may be used, and a constant voltage diode may be used as the resistor Rc. can.

In addition, it is only necessary to set the bias component purple according to the flow of the line and the required power source of the load circuit according to the flow, and it is also possible to use it as a full load circuit such as a motor.

In addition, in FIG. 4, the entire drive may be performed by a motor or the like, and in addition to the pulp V, a damper, a pump, etc.? Similarly, the present invention can be modified in various ways as well as the equipment to be controlled.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the control circuit is single, it can be easily miniaturized, and significant effects can be obtained in terms of control and power supply to various devices to be controlled. .

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is an overall block diagram, Fig. 2 is a block diagram of the control circuit, Fig. 3 is a flowchart of the control situation, and Fig. 4 is the total amount of components on the receiving device side. Are the block diagrams shown in Figures 5 and 6 for other embodiments? 1st to show
A block diagram similar to that shown in FIG. L...2-wire transmission line, ZI+Z2...element (variable impedance element), Rs, Re...
・Resistor (impedance I-piece), CNT ・・
・Control circuit (load circuit), CPU... Processor, ROM...Fixed memory, RAM...
Variable memory IJ, MPX - multiplexer, A
/D...ADC (Analog-to-digital converter)
, D/A iris~D/A3...DAC (digital-to-analog converter), VL...line voltage, Ic
...Current.

Claims (1)

[Claims] A device for receiving a signal indicated by a current value of a line current passing through a two-wire transmission line, comprising: a first variable impedance element inserted in series with the transmission line; and a first variable impedance element connected in series with the variable impedance element. a series circuit including a receiving impedance element, a series impedance element and a second variable impedance element connected in parallel to the first variable impedance element and the impedance element, and constant line voltage of the transmission line; a control circuit that controls the impedance of the first variable impedance element in a direction to make the impedance of the first variable impedance element constant, and controls the impedance of the second variable impedance element in a direction that makes the current value flowing through the series impedance element constant;
A receiving device comprising a load circuit connected in parallel with the second variable impedance element.