JPS60257629A - Receiver - Google Patents

Abstract

PURPOSE:To supply power only with a two-wire transmission line by controlling respectively the 1st variable impedance element inserted in series with the transmission line and the 2nd variable impedance provided in parallel with a load circuit. CONSTITUTION:The 1st control circuit comprising resistors R1, R2 and a differential amplifier A1 controls the impedance of a transistor (TR)Q1 in the direction making a line voltage VL constant in response to a voltage V1. Resistors R4, R5 and a differential amplifier A2 controls the impedance of a TRQ2 in the direction making the value of a current Ic passing through the resistor R3 constant in response to a voltage V2. A current Is flowing to a resistor Rs has the signal component only. A terminal voltage across the resistor Rs is convered into a digital signal by an analog-digital converter A/D1 and the signal is given to an operation circuit OP as a setting value.

Description

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

[Prior art]

In industrial processes, etc., when remotely controlling valves, etc., a receiving device called a positioner is generally installed.
A central control device transmits a signal indicating a current value that varies in the range of, for example, 4 to 20 mA, and a receiving device receives this signal and performs control according to the current value.

However, in the past, a two-wire transmission line was required to transmit the current value indicating the signal, and a separate two-wire power supply line was required to supply the power required by the receiving device. Four lines are indispensable, which increases the amount of wire required for the line and the number of man-hours for laying the line, resulting in high equipment costs.

There is.

[Summary of the invention]

The purpose of the present invention is to fundamentally solve these conventional drawbacks, and the unified signal of 4 to 20 mA used in industrial measurement originally represents a numerical value in the range of 0 to 16 mA. Note that it contains bias components such as
A first variable impedance element and a reception impedance element are inserted in series in a two-wire transmission line, and the impedance of the variable impedance element is controlled in a direction to keep the line voltage of the transmission line constant. A series circuit consisting of a series impedance element and a second variable impedance element is connected in parallel, and the current flowing through the series impedance element is controlled to be kept at a constant value according to the bias component, and then the second variable impedance element and the second variable impedance element are connected in parallel. By connecting a load circuit in parallel and using a bias component as a power source on the receiving device side, an extremely effective receiving device is provided in which power can be supplied only through a two-wire transmission line. .

〔Example〕

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

Figure 1 is a circuit diagram, and the two-wire transmission line connected via line terminals jl + j2 consists of lines LI+L2, whereas the emitter of transistor Q+ serves as the first variable impedance element.・The collectors are inserted in series, and a resistor RB is connected in series on the collector side as a receiving impedance element, while a voltage divider circuit consisting of resistors R11R2 is connected in parallel with these. A series circuit is connected between the emitter and the collector of a resistor R3 as a series impedance element and a transistor Q2 used as a second variable impedance element.

In addition, an integrated power supply stabilization circuit REG, a voltage dividing circuit formed by resistors R4 and R5, and a differential amplifier AI+A2 are connected in parallel with the transistor Q2 as a load circuit, and the power supply stabilization circuit REG is connected as a load circuit. circuit reg
Analog-to-digital converter (hereinafter referred to as ADC)
An arithmetic circuit OP1 consisting of A/D+, A/D2, a microprocessor, memory, etc., and a digital-to-analog converter (hereinafter referred to as DAC) D/A are also connected as load circuits.

Here, the resistor RI+R2 and the differential amplifier A1
constitutes the first control circuit, and adjusts the line voltage vL of the transmission path based on the reference voltage vr1 from the power supply stabilization circuit REG.
According to the voltage V divided by resistors R1 + R2,
The impedance of the transistor Q1 is controlled in a direction to keep the line voltage vL constant, thereby keeping the line voltage vL at a constant value of, for example, IOV, regardless of the line current ILO value.

Moreover, the resistor R41R5 and the differential amplifier A2 are connected to the second
The load circuit side voltage vc of the resistor R3 is configured based on the reference voltage vr2 from the power supply stabilization circuit REG.
The impedance of the transistor Q2 is controlled in the direction of keeping the value of the current Ic flowing through the resistor R3 constant according to the voltage z divided by the resistors R4 and R5, and the power supply current of each load circuit is Regardless of the current Ic, for example, 4 mA
is maintained at a constant value.

Therefore, current I + = flowing through resistor R, IR2
Since V L/(R+ + R2) is a constant value, the current IB flowing through the resistor RS is I s = I L (I
c + I, ), and by setting (Ia+I+) equal to the bias component, ■8 becomes, for example, O~16
In order to obtain only mA signal components, the terminal voltage of the resistor Rs is converted into a digital signal by the ADC-A/D, K, and this is given as a set value to the arithmetic circuit OP, and the actual measurement from the drive device DR, which will be described later, is If the value is similarly converted by the ADC-A/D2 and given to the arithmetic circuit OP, the circuit OP will send out a control signal by control calculation, and this will be sent to the D
By converting the AC-D/A into an analog signal and applying it to the electro-pneumatic converter E/P (to be described later) to control the opening of the valve, it is assumed that the set value and the measured value match. The opening degree is set.

In addition, in FIG. 1, negative feedback is applied to the differential amplifier Al+A2 by the above operation, and V, =vr
1. Since v2=vr2, the following equation holds true.

Here, since ■r+ + vr2 is stabilized, V and VC are also constant, and the following equation is obtained.

That is, (Ia+I+) is constant.

On the other hand, line current IL is expressed by a quadratic equation.

I B −IL −(I c + I + ) ・・
(5) Therefore, if IL is, for example, 4 to 20 mA, I C + I,
= 4 mA, Is = 0 to 16 mA, without interfering with the reception of the signal indicated by Is.
A maximum power supply current of AmA can be stably supplied to each load circuit.

Note that the central control device sends the line current IL to the constant current circuit, so even if the input impedance of the receiving device changes, the current value is not affected.

FIG. 2 is a block diagram showing the entire configuration of the receiving device, and the output from the receiving device RE shown in FIG.
/P, where the pressure P is given to the receiving device RE
A pressure corresponding to the output of the valve is sent to a drive device DR such as an air cylinder, which drives the pulp V to control the opening degree, and a potentiometer connected to the drive shaft controls the current opening degree. Detected as an actual measurement value, the receiving device R
It is given to E.

Therefore, power is supplied to the two-wire transmission line at the same time, and the amount of wire required and the number of man-hours for installation are significantly reduced, resulting in a reduction in equipment costs.

However, in FIG. 1, other controllable variable impedance elements such as field effect transistors and photocouplers may be used in place of the transistors Q and Q2, and impedance elements such as diodes may be used in place of the resistors R8 and R3. The same applies to the case where the reference voltage vrl +
Generate vr2 and connect all load circuits to L transistor Q2.
may be connected in parallel.

Note that the bias component of the line current may be determined according to the required power supply current of the load circuit, and a motor or the like may also be used as the load circuit.

In addition, in FIG. 2, the drive may be performed by a motor or the like, and the same applies to the equipment to be controlled such as dampers, pumps, etc. in the case of pulp (11), and the present invention can be freely modified in various ways.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the power required on the receiving side is simultaneously supplied only by the two-wire transmission line, so a power supply line is not required.
Line equipment costs are significantly reduced, and significant effects can be obtained in various receiving devices that receive signals indicated by current values.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, with FIG. 1 being a circuit diagram and FIG. 2 being a block diagram showing the entire configuration of the receiving device. L...2-wire transmission line, QI, Q2...transistor (variable impedance element), R5r Rs...
・Resistor (impedance element), R1+ R2+
R41R5・Resistor, RF, G・・Power supply stabilization circuit, AI+A2・・1 differential amplifier. Patent applicant Yamatake Honeywell Co., Ltd. agent Masaki Yamakawa (and 2 others) Procedural amendment (voluntary) Mr. Commissioner of the Japan Patent Office (Monday, Showa) 59.7.20 2. Invention title receiving device 3. Amendment person case Relationship Patent Applicant Name (Name) (666) Yamatake Newel Co., Ltd.'s amendment increases the loss of the 4th son.
6. Contents of the amendment (1) Although the ``are'' in the 1st line O of page 2 of the specification is known, such a field device is amended as follows. (2) I'AmAJ on page 3, line 6 of the Ministry of Finance is I'4mAJ
and correct it. (3) ``Indicates the entire configuration of the receiving device side'' on page 8, line 8 of the same Ministry of Japan.
and correct it. (4) The same Ministry, page 9, lines 4 to 6 (, R3...
"Ashi," shall be corrected as follows. The same effect can be achieved with a circuit configuration in which the current value is directly read without converting the input signal into voltage, or with a variable impedance element such as a constant current diode in place of the resistor R3. (5) On the same page of the circular, line 16, ``The present invention adds the following to J.Nogi. The present invention can be done, etc.”

Claims (1)

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