JPH04243399A - Two-wire transmitter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention converts a physical quantity to be measured by a sensor into an electrical signal, processes this signal by a signal calculation means including a microprocessor, and sends it as a current signal to the load side via a transmission line. It relates to a two-wire transmitter that performs digital communication by superimposing a communication signal from a handheld terminal onto a transmission line as necessary, and in particular, a digital signal sent from this handheld terminal that involves a setting change. The present invention relates to a two-wire transmitter that has been improved so that a response signal of the two-wire transmitter to a current signal is not affected by a current signal caused by a previous setting change.

0002

2. Description of the Related Art FIG. 4 is a block diagram showing the overall configuration including a conventional two-wire transmitter. Reference numeral 10 denotes a two-wire transmitter that converts physical quantities such as process variables into electrical signals and transmits them, and is supplied with power from a DC power supply 11 via a load 12 . The electrical signal is transmitted as a current signal by the transmission lines L1 and L2, and the voltage change occurring across the load 12 is detected to determine the process variable.

[0003] The current signal is transmitted, for example, from a two-wire transmitter 10 set to a range corresponding to the pressure in the piping, from 4 to 20 meters away.
It is converted into a unified current IL of A and transmitted. In this case, it would be convenient if the two-wire transmitter 10 could be operated from outside, for example, when changing or monitoring the pressure range.

For this reason, the handheld terminal 13 is connected to the transmission lines L1 and L2 using connection lines L1' and L2' as necessary, and the handheld terminal 13 is connected to the two-wire transmitter 10. Equipped with a dedicated data communication function,
Digital data such as parameter changes is transmitted from the handheld terminal 13 to the two-wire transmitter 10.

Next, each component configured as described above will be explained in detail. Of these, 10 two-wire transmitters
is structured as follows. SNR is a sensor that detects pressure/differential pressure and converts it into an electrical signal. The electrical signal converted by the sensor SNR is converted into a digital signal by an analog/digital conversion circuit ADC, and stored in a random access memory (RAM) portion of the memory MEM1 via the microprocessor μP1.

The microprocessor μP1 uses the stored digital signal to execute predetermined operations such as linearization and damping according to the operation procedure written in, for example, a read-only memory (ROM) portion of the memory MEM1. /Output to the output circuit OPC via the analog conversion circuit DAC. On the other hand, microprocessor μP
The predetermined calculation result in step 1 is digitally displayed with the necessary number of digits on the built-in monitor LCD.

The output circuit OPC outputs the voltage signal converted into an analog signal by the digital/analog conversion circuit DAC.
It is converted into a unified current signal IL of 20 mA and transmitted to the load 12 via transmission lines L1 and L2. Further, the output circuit OPC generates a power source for the internal circuit of the two-wire transmitter 10 using a part of the current signal IL.

IFC1 is an interface for data communication with the handheld terminal 13, and is connected between the transmission lines L1 and L2 and the microprocessor μP1, and receives digital signals from the transmission lines L1 and L2. parallel data
It also has the function of transmitting data from the microprocessor μP1 as a serial signal to the transmission lines L1 and L2 via the output circuit OPC.

The interface IFC1 also receives a predetermined number of bits of "1" and "0" from the microprocessor μP1.
The output circuit OPC is used as a modulated communication signal that modulates the data of "1" so that, for example, it does not emit a burst wave when it is "1" and emit a burst wave when it is "0". The burst waves input from the transmission lines L1 and L2 are demodulated into "1" and "0" data and transmitted to the microprocessor μP1.

Next, the handheld terminal 13 is constructed as follows. The SER is a setting device operated by an operator and has a built-in monitor. Various settings or requests can be made, such as requesting a model of the two-wire transmitter 10, changing the display cycle, changing the range, detecting an abnormality, damping, or displaying the value of the current signal IL. μP'
is a microprocessor into which, for example, data from a setting device SER is input, and is processed through an interface IFC' according to a processing procedure stored in a memory MEM'.
A digital signal is sent to the wire transmitter 10. This digital signal is transmitted in the same modulation format as the interface IFC1 of the two-wire transmitter, for example, as a burst wave.

The microprocessor μP' also receives response data modulated in a predetermined modulation format from the two-wire transmitter 10.
memory MEM' through the interface IFC'
The data is read into the memory MEM', decoded according to the processing procedure stored in the memory MEM', and displayed on the monitor of the setting device SER.

Next, the two-wire transmitter constructed as described above will be explained with a focus on signal processing using the flowchart shown in FIG. Normally, data corresponding to the physical quantity to be measured is read from the sensor SNR (step 1), and signal processing A to 4 is performed as shown in steps 2 to 4 according to the calculation program stored in the memory MEM1.
C is executed, the setting change in step 5 is skipped, and the signal processing D in step 6 is performed to reach step 7, where it is output as an analog current signal to the transmission lines L1 and L2. below,
This is repeated.

Next, when the setting signal set by the setting device SER is input from the handheld terminal 13 as a modulated communication signal via the transmission lines L1 and L2 (step 8),
The interface IFC1 converts it into a corresponding parallel digital signal and sends it to the microprocessor μP1 (step 9). After this, microprocessor μP1
interrupts signal processing A and stores this digital signal in memory ME.
Import into M1 and start the necessary signal processing (Step 3
).

[0014] Then, one frame is inserted between signal processing B and C.
A response signal in units of characters (characters) is divided on a frame basis and responses are sent out A (step 10) and B (step 11).
), C (step 12) and digitally transmits to the handheld terminal 13 (step 13). On the other hand, the microprocessor μP1 decodes the data for changing the setting signal received in step 9, and when the data is decoded (step 5), changes the setting and sends the data to the digital/analog converter D.
The current signal IL is changed via the AC and the output circuit OPC.

[0015]

However, the two-wire transmitter described above has the following drawbacks. As can be seen from FIG. 5, the response signal is divided and sent to the transmission lines L1 and L2 as shown in steps 10 to 12 between signal processing by the microprocessor μP1. When a setting change, such as a span change, is made as shown in FIG. 6, the analog current signal IL undergoes a large current change ΔIL, as shown in FIG.
Since the digital signal received by the handheld terminal 13 is disturbed, there is a problem that correct two-way communication cannot be performed.

[0016]

[Means for Solving the Problems] In order to solve the above problems, the present invention converts a physical quantity to be measured by a sensor into an electrical signal, processes this by a signal calculation means including a microprocessor, and transmits two signals. This is a two-wire transmitter that transmits a current signal to the load side via a transmission line, and if necessary connects a handheld terminal to the transmission line and superimposes a digital communication signal to perform digital communication. , an interface that receives the digital signal sent from the previous handheld terminal and sends the contents of the setting change to the previous microprocessor, and the digital signal necessary for the setting change is taken from this interface. a communication processing means for confirming that the response signal has been sent to the previous transmission line via the previous interface; a confirmation means for confirming that the sending of the response signal has been completed; and a confirmation from the confirmation means. The device is equipped with a setting change means for changing settings based on a notification, and is configured to send out a previous current signal in response to the setting change.

[0017]

[Operation] The interface of the two-wire transmitter receives the digital signal sent from the handheld terminal and sends the content of the setting change to the microprocessor. The communication processing means confirms that the digital signal necessary for changing the settings has been received from this interface, and sends a response signal to the previous transmission line via the previous interface. Next, the confirmation means confirms that the transmission of this response signal is completed, and based on this confirmation, the setting change means changes the settings. Therefore, the output current signal is not significantly changed due to setting changes during transmission of the response signal, and correct bidirectional communication can be realized.

[0018]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. Note that parts having the same functions as those of the conventional two-wire transmitter shown in FIG.

14 is a two-wire transmitter, and the sensor SNR
The physical quantity detected by
is read into the memory MEM2 under the control of. Memory M
The calculation program necessary for signal processing is stored in EM2 in advance, and the microprocessor μP2 uses this calculation program to perform predetermined calculations such as linearity correction and differential pressure calculation, and converts the digital/analog conversion circuit D.
An analog signal is output to the output circuit OPC via AC. The output circuit outputs a current signal IL corresponding to this analog signal.
and transmits it to the load 12.

On the other hand, a digital modulated communication signal corresponding to the setting data set by the setting device SER is transmitted from the handheld terminal 13 to the two-wire transmitter 14 via transmission lines L1 and L2. The interface IFC2 of the two-wire transmitter 14 receives this modulated communication signal, detects it, converts it into a predetermined digital signal, and sends it to the microprocessor μP2 as parallel data.

The microprocessor μP2 decodes the contents of this parallel data and sends a response signal to the transmission lines L1 and L2 via the interface IFC2, which is received by the handheld terminal 13.

Next, the signal processing of the digital signal in this case will be explained in detail using the flowchart shown in FIG. The signal from the sensor SER is normally read in step 14, processed in step 15 according to a predetermined program stored in the memory MEM2, and outputted to the load 12 as a current signal IL.

[0023] Here, the two-wire transmitter is connected to a handheld computer.
When a digital modulated communication signal is received from terminal 13,
The process moves to step 16 by an interrupt, and the conventional processing of the microprocessor μP2 is stopped, and this communication processing is performed. This communication process checks the modulated communication signal, and also imports necessary setting data, such as span change, into the memory MEM2 under the control of the microprocessor μP2, and executes the process corresponding to this setting data to store the data in the memory. M.E.
M2 and starts response transmission.

As shown in steps 17 and 18, the response is transmitted in units of one frame (character), and is divided into response signals A, B, etc. using serial data during signal processing by the microprocessor μP2, and then sent to the interface. It is superimposed on the current signal IL and sent to the transmission lines L1 and L2 via the face IFC2 and the output circuit OPC.

Step 19 is a step of a confirmation means for confirming that all response signals have been sent. Here, the process returns to step 17 and the transmission of these response signals is repeated until all frames of the response signal consisting of a predetermined number of frames have been transmitted. When the process is completed, a determination is made to proceed to step 20.

When the transmission of this response signal is confirmed, the microprocessor μP2 transmits the response signal to the handheld terminal 13.
The content changed based on the setting change sent from the DAC is sent to the digital/analog conversion circuit DAC, converted into an analog signal, and transmitted via the output circuit OPC to the transmission lines L1 and L2.
The current signal IL is sent out as a current signal IL (step 20).

When the above situation is viewed as a signal on a transmission line, it becomes as shown in FIG. As can be seen from this figure, the setting signal is sent after the sending of the response signal is completed, so the response signal received by the handheld terminal 13 is as shown in FIG.
As shown in , it is not disturbed by the current change ΔIL.

In the above description, the power supply for the two-wire transmitter is supplied from the DC power supply 11 on the load side. However, the present invention is not limited to this, and the present invention is not limited to this. The circuit is operated by rectifying the AC power source independently of the load side, and the signal from the sensor is simply sent to the load 12 by a two-wire transmitter that transmits the current using two transmission lines. can be applied in the same way.

[0029]

[Effects of the Invention] As described above in detail using the embodiments, according to the present invention, the current signal is changed based on the setting change after the transmission of the response signal from the two-wire transmitter is completed. As a result, the current is not changed during the transmission of the response signal, and the reception of the digital signal at the handheld terminal is ensured.

[Brief explanation of the drawing]

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

FIG. 2 is a flowchart explaining the operation of the two-wire transmitter shown in FIG. 1;

FIG. 3 is a waveform diagram showing communication waveforms on the transmission line of the two-wire transmitter shown in FIG. 1;

FIG. 4 is a block diagram showing the configuration of a conventional two-wire transmitter.

FIG. 5 is a flowchart explaining the operation of the two-wire transmitter shown in FIG. 4;

FIG. 6 is a waveform diagram showing communication waveforms on the transmission line of the two-wire transmitter shown in FIG. 4;

[Explanation of symbols]

10, 14 2-wire transmitter 11 DC power supply 12 Load 13 Handheld terminal IFC1, IFC2 Interface μP1, μP
2 Microprocessor MEM1, MEM2 Memory

Claims (1)

[Claims] Claim 1: A physical quantity to be measured by a sensor is converted into an electrical signal, which is processed by a signal calculation means including a microprocessor, and transmitted as a current signal to the load side via two transmission lines, as required. In a two-wire transmitter that performs digital communication by connecting a handheld terminal to the transmission line and superimposing a digital communication signal, the transmitter receives the digital signal sent from the handheld terminal and changes settings. an interface that sends the contents to the microprocessor, and a response signal that sends a response signal to the transmission line via the interface after confirming that the digital signal necessary for changing the settings has been taken in from this interface. a communication processing means for confirming that sending of the response signal is completed, a confirmation means for confirming that sending of the response signal is completed, and a setting change means for changing the setting based on a confirmation notification from the confirmation means, and configured to correspond to the setting change. A two-wire transmitter, characterized in that it transmits the current signal.