JP3057619B2 - 2-wire signal transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-wire type signal transmitter for transmitting a current output relating to a physical quantity to a load via two wires, and more particularly to a rotary encoder type switch for zero point and span. The present invention relates to a two-wire signal transmitter capable of adjusting the value of.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an arrangement of an amplifier setting section in which an external setting portion for performing a zero adjustment, a span adjustment and the like of a conventional two-wire signal transmitter is housed. Reference numeral 10 denotes a case of a two-wire type signal transmitter. This case 10 has a terminal portion 1 in which an output terminal connected to the load side by two transmission lines is housed.
1. Conduit 12 for leading out this transmission line, external setting unit 13, zero fine adjustment screw 14 arranged on the side of case 10.
Is provided.

Further, on the front surface of the external setting section 13, a check terminal 15, a fine adjustment screw 16 for a span, a coarse adjustment screw 17, a trimming adjustment trimmer 18, a coarse adjustment screw 19 for a zero point, and the like are provided. The board to which these are attached is fixed to the case 10 by screws 20A, 20B and 20C.

[0004]

However, the zero fine adjustment screw 14, the zero coarse adjustment screw 19, the span fine adjustment screw 16, the span coarse adjustment screw 17 and the like are independently and physically set externally. If it is arranged in the portion 13, there is a problem that the structure becomes complicated, the cost is increased, and it becomes an obstacle to downsizing.

[0005]

According to the present invention, a physical quantity to be measured is converted into an electric signal by receiving power from a load side through two transmission lines as a configuration for solving the above-mentioned problems. In a two-wire signal transmitter for processing this signal by a microprocessor and transmitting the signal to the load side, a mode switching signal is connected to the transmission line as required and a mode switching signal is converted to a digital signal from the load side to the microprocessor. A terminal to be transmitted, and determination means for decoding the preceding mode switching signal to determine whether the mode is a zero point adjustment mode or a span adjustment mode.
A rotary encoder type external setting switch for sending external setting data corresponding to the rotation direction and the number of rotations of the operation shaft to the microprocessor as a digital signal, and external setting data corresponding to each mode. And changing means for changing the setting data corresponding to each of the preset modes.

[0006]

[Operation] If necessary, a terminal connected to a transmission line converts a mode switching signal for determining whether to perform zero adjustment or span adjustment through the previous transmission line into a microprocessor as a digital signal. To be transmitted. The microprocessor is
The mode switching signal is decoded by the determining means to determine whether the mode is the zero point adjustment mode or the span adjustment mode.

The rotary encoder type external setting switch sends external setting data corresponding to the rotation direction and the number of rotations of the operation shaft to the preceding microprocessor as digital signals. The changing means fetches the external setting data corresponding to each mode, and changes the setting data corresponding to each preset mode. As described above, the span adjustment and the zero-point adjustment can be shared by simply providing a single rotary encoder type external setting switch in the two-wire signal transmitter, resulting in a simple configuration. This contributes to downsizing and cost reduction.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. Reference numeral 22 denotes a two-wire signal transmitter that converts a physical quantity such as a process variable into an electric signal and transmits the electric signal. The electric signal is transmitted as a current signal through the transmission lines L ₁ and L ₂ and the load 12
To detect the process variable by detecting the voltage change occurring at both ends.

[0009] The current signal is transmitted from a two-wire type signal transmitter 22 set in a range corresponding to the pressure in the pipe, for example, to 4 to 2 times.
It is converted to a unified current of 0 mA, transmitted to the receiving instrument 25 on the load side, and displayed on a monitor, for example, as a four-digit digital display.

In this case, for example, when it is desired to change the pressure range, change various parameters, or monitor, it is convenient if it can be operated from outside the two-wire signal transmitter 22. Therefore, the handheld terminal 26
Is connected to the transmission lines L ₁ and L ₂ as necessary using connection lines L ₁ ′ and L ₂ ′, and the dedicated data communication with the hand-held terminal 26 to the two-wire signal transmitter 22. A digital data such as parameter change is transmitted from the hand-held terminal 26 to the two-wire signal transmitter 22 with the function.

With respect to the overall configuration described above, the two-wire signal transmitter 22 is configured as follows. The SNR is a sensor that detects pressure / differential pressure and converts it into an electric signal. The converted analog signal is converted into a digital signal by an analog / digital converter A / D, and the converted signal is stored in a memory MEM via a microprocessor μP. Is stored in the random access memory part of

The microprocessor μP uses the stored digital signal to execute a predetermined operation such as linearization in accordance with an operation procedure written in, for example, a read-only memory portion of the memory MEM, and to execute a digital / analog conversion. The signal is output to the output circuit OPC via / A.

On the other hand, a predetermined
Calculation results are digital with the number of digits required for the built-in monitor LCD
Is displayed. Output circuit OPC is digital / analog conversion
The voltage signal converted into an analog signal by the device D / A is 4 to 2
0 mA unified current signal I_LConvert to transmission line
L₁, L _TwoTo the receiving instrument 25 via

The output circuit OPC uses a part of the current signal I _{1 to} generate a power supply for an internal circuit of the two-wire signal transmitter 22. In this case, for example, the monitor LCD current signal I _L
Is digitally displayed.

RTE is a rotary encoder type switch. By rotating its operation shaft, for example, two adjacent pulse pulse signals generated by the rotation are held while maintaining a predetermined phase difference determined by the rotation direction. The signal is sent to the interface circuit INF as a binary rectangular digital signal having the number of pulses corresponding to the rotation speed. The interface circuit INF outputs the pulse output from the switch RTE to the microprocessor μP as a digital signal obtained by shaping the pulse into a predetermined rectangular wave.

IFC is compatible with handheld terminal 26 and
-Interface for data communication, transmission line
L₁, L_TwoAnd the microprocessor μP
And the transmission line L₁, L_TwoDigital data from
To the microprocessor μP,
The data from the processor μP is used as a serial signal as a transmission line L
₁, L_TwoIt has a function to transmit to the side.

Next, the handheld terminal 26 is constructed as follows. SER is a setting device operated by an operator, has a built-in monitor, and has a two-wire signal transmitter 2
Mode change for switching between zero adjustment and span adjustment, model request, display resolution change, range change, abnormality detection,
Or to a variety of settings or request a display of the value of the current signal I _L.

.Mu.P 'is a microprocessor, for example, to which data from a setting unit SER is inputted, and a memory MEM.
The digital signal is transmitted to the two-wire signal transmitter 22 via the interface IFC 'in accordance with the processing procedure stored in the'. Further, the microprocessor .mu.P 'converts the response data from the two-wire signal transmitter 22 into an interface I.
The data is taken into the memory MEM 'through the FC', and further decoded according to the processing procedure stored in the memory MEM '.
It is displayed on the monitor of the setting device SER.

Next, a flow chart shown in FIG. 2 focusing on the operation of the characteristic portion of the two-wire signal transmitter constructed as described above
This will be described using a chart. First, the connection lines L ₁ ′, L ₂ ′ and the transmission lines L ₁ , L ₂
A mode switching signal MOD for determining whether to change the zero point or the span is transmitted to the two-wire signal transmitter 22 as a serial digital signal. The two-wire signal transmitter 22 converts this mode switching signal MOD into a parallel digital signal by the interface IFC and takes it into the microprocessor μP (step 1).

The microprocessor μP has a memory MEM
It is determined whether the span is to be changed or the zero point is to be changed using the mode determination calculation program stored in the predetermined area (step 2). For example, it is determined whether or not the transmitted mode switching signal MOD matches "1" in the case of the span and "0" in the case of the zero point.

If the value coincides with "0", the program is switched to a state in which the change of the zero point is accepted in step 3, and the process proceeds to step 4. In step 4, it is determined whether the rotation is in the increasing direction (right) or in the decreasing direction (left) by checking the phase of the digital signal corresponding to the rotation speed of the operation shaft of the switch RTE input from the interface INF.

In the case of right rotation, the zero point is counted as a value in the direction of increasing the zero point in step 5, and in step 6, the set data of the zero point is increased by the value corresponding to this rotation speed. If the rotation is to the left, the zero point is counted as a value in the increasing direction in step 7 and the set data of the zero point is decreased in step 8 by the value corresponding to this rotation speed. If it matches "1" in step 2, the program is switched to a state in which a change in span is accepted in step 9, and the process proceeds to step 10.

In step 10, the interface IN
From the phase of the digital signal corresponding to the rotation speed of the operation shaft of the switch RTE input from F, it is determined whether the rotation is in the increasing direction (right) or in the decreasing direction (left). If it is clockwise rotation, the data is counted as a value for increasing the span in step 11, and in step 12, the set data of the span is increased by the value corresponding to this rotation speed. Step 1 if counterclockwise
In step 3, the value is counted as a value in the direction of increasing the span, and in step 14, the set data of the span is decreased by a value corresponding to this rotation speed.

As described above, by using the mode switching signal MOD via the communication means in the two-wire signal transmitter, both the zero point and the span can be obtained simply by providing one switch RTE. It can be adjusted, and the external setting section can be greatly simplified as compared with the related art, which can contribute to downsizing and cost reduction.

In the above description, the mode switching signal MO
These are adjusted after switching the span and the zero point by D. However, the present invention is not limited to this. For example, the switch RTE is normally set to the zero setting mode and the mode switching signal MOD 'is received. It is also possible to switch to the span setting mode only for a certain period of time. That is, a timer is provided inside the two-wire signal transmitter 22, and after switching to the span setting mode, returning to the zero setting mode after a lapse of a predetermined time.

[0026]

According to the present invention, as described above in detail with the embodiments, one rotary encoder is provided with the functions of zero point adjustment and span adjustment, so that the number of parts is reduced. The structure is simple and the cost can be reduced. As a result, downsizing can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment shown in FIG. 1;

FIG. 3 is a plan view showing a part of the appearance of a conventional two-wire signal transmitter.

[Explanation of symbols]

 Reference Signs List 10 Case 11 Terminal section 13 External setting section 14 Zero fine adjustment screw 16 Fine adjustment screw 17 Coarse adjustment screw 19 Coarse adjustment screw 22 2-wire signal transmitter 23 DC power supply 25 Receiving instrument 26 Handheld terminal μP Microprocessor RTE switch INF Interface MEM Memory IFC Interface

Claims (1)

(57) [Claims] 1. A two-wire signal which receives a supply of power from a load side via two transmission lines, converts a physical quantity to be measured into an electric signal, processes this signal by a microprocessor, and transmits the signal to the load side. A terminal connected to the transmission line as required and transmitting a mode switching signal as a digital signal from the load side to the microprocessor; and a zero point by decoding the mode switching signal. Determining means for determining whether the mode is the adjustment mode or the span adjustment mode, and a rotary encoder for sending external setting data corresponding to the rotation direction and the number of rotations of the operation shaft to the microprocessor as digital signals. External setting switch, and changing means for taking in the external setting data corresponding to each mode and changing the setting data corresponding to each preset mode. To 2 wire signal transmitter to symptoms.