JPH0363879B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a differential pressure transmitter,
The present invention relates to a communication control device that is applied when transmitting and receiving data signals to and from a transmitter such as an electromagnetic flowmeter.

[Prior art]

Conventionally, in industrial measurement, when transmitting the measurement output of a differential pressure transmitter, electromagnetic flowmeter, etc. to a remote point,
Generally, a unified signal such as 4 to 20 mA is used, and the measured value is indicated by the current value of this analog signal.

However, transmitters such as differential pressure transmitters and electromagnetic flowmeters are generally installed and distributed over a wide area, and in order to adjust them and check their operating status, staff must patrol and maintain them. , inspection work must be carried out, and there is a growing demand for a means that can make adjustments, check operating conditions, etc. by remote control using existing equipment.

[Summary of the invention]

The present invention has an object of completely satisfying such conventional demands, and includes a transmitter/receiver unit that transmits and receives data signals to and from a transmitter, and a transmitter/receiver unit that normally relays input process signals as they are and outputs them to a controller. When the hold signal output from the transmitter/receiver is input, it holds the value of the process signal just before that and outputs this held process value to the controller, and the signal relay unit normally outputs the process signal output from the transmitter. A switch is provided to connect the transmitting/receiving section and the transmitter when a control signal that is supplied to the signal relay section and output from the transmitting/receiving section almost simultaneously with the hold signal is input, and the hold signal and the control signal are output from the transmitting/receiving section. During this time, data signals are transmitted and received between the transmitting/receiving section and the transmitter, and during this time, the process value held by the signal relay section is supplied to the controller.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing examples.

Figure 1 is a block diagram of the entire configuration. Between the transmitter TX, such as a differential pressure transmitter or an electromagnetic flowmeter, and the controller CT, there are two wires consisting of lines L _1a , L _2a , L _1b , and L _2b. A communication device CE is inserted into this transmission line, and a voltage drop element R _L and a low frequency amplifier are connected in series from the power supply B _L to the lines L _1a and L _2a . A current is supplied through the wave transmitter FL, and this current value is controlled by the transmitter TX according to the measured values such as differential pressure and flow rate, and is passed to the lines L _1a and L _2a as a process signal. There is.

This process signal is detected as the terminal voltage of the voltage drop element R _L , and this value is
analog-to-digital converter (hereinafter referred to as ADC)
After being converted into a digital signal by A/D,
It is updated and held by the hold register HRG, and the digital-to-analog converter (hereinafter referred to as
DAC) D/A converts it into an analog signal again to control the driver DR, and the value of the current supplied from the power supply B _C of the controller _CT to the lines L _1b and L _2b via the series voltage drop element RC. is determined and sent to the controller CT as a process signal.

Therefore, the process signal from the transmitter TX is relayed by the signal relay unit REP inserted into the transmission path and given to the controller CT, and in the controller CT, the process signal is transmitted based on the terminal voltage of the resistor R _C. The controller receives a process signal, performs a predetermined control calculation in response to this, and sends a control signal _SC to an operating end of a solenoid valve, electric valve, etc., thereby performing control in accordance with the process signal.

FIG. 2 is a timing chart showing the waveforms of each part in FIG. However, the transmitter/receiver section TRX in the communication device CE
When the starts operating, it sends out a connection signal c and a hold signal d, so the switch
The SW operates and connects the transmitter TX to the transmitter/receiver TRX via the transmission line on the L _1a and L _2a sides, and
Hold register HRG at the previous point in time
The output of the ADC/A/D is held and this held output is given to the DAC/D/A during the period of the hold signal d.As the process signal b, the value immediately before the hold signal d is generated is continuously sent out. On the other hand, as shown in Figure 2a, between the transmitting/receiving unit TRX and the transmitter TX, the process signal Sp is interrupted and the data signal S _D is transmitted and received, and upon completion of this, the process signal is transmitted again. aSp will be relayed as process signal b.

Therefore, even while the data signal S _D is being transmitted and received, the process signal b is given to the controller CT, so that there is no confusion in the control operation, and the data signal S _D By making the transmission period sufficiently short, the mismatch between the process signal aSp and the process signal b can be reduced, and the responsiveness of the control operation can be guaranteed.

FIG. 3 is a diagram showing the format of the data signal S _D. In order to improve the discrimination from noise etc.,
A start bit B _S is transmitted after a flag bit B _F with a particularly large pulse width or peak value, etc.
Following this, the first bit _B1 to the nth bit Bn indicating data are transmitted, and one byte is made up of n bits, but depending on the situation, a desired number of bytes can be sent consecutively. Transmitted as data signal S _Dc or S _Dt .

FIG. 4 is a block diagram of the transmitter/receiver section TRX.
Mainly includes a processor CPU _c such as a microprocessor, a fixed memory ROM _c , a variable memory RAM _c , a keyboard KB _c , a display device such as a numeric display DP _c , and a universal asynchronous transceiver (hereinafter referred to as a transceiver).
UART _c , interface I/F _c, etc. are arranged around the periphery, and they are connected to each other by bus bar BU _c . Processor CPU _c executes the program stored in fixed memory ROM _c , and changes the specified data. Control operations are performed while accessing memory RAM _c .

Here, if desired data is given from the keyboard KB _c , the processor CPU _c controls the transmitter/receiver UART _c accordingly, and also sets the gate pulse P _cg1 to "H" via the interface I/F _c .
(high level), AND gate
G _c1 is turned on, and the pulse signal sent from the transceiver UART _c is given to the amplifier A _C , where it is amplified and becomes the transmission data signal S _Dc , which is then passed through the DC blocking capacitor C _C to the terminals t ₁ and Via the switch SW, it is superimposed with the voltage of the power supply B _L , and then the oscillator
Sent to TX.

In addition, the terminal voltage of the resistor R _L is applied to the comparator through a wave transmitter FL _C such as a band wave wave generator that passes only the frequency component of the received data signal S _Dt from the transmitter TX.
A comparison is made between the reference voltage E _CS applied to one input of CP _C and the other input.
A level equal to or higher than the reference voltage E _CS is extracted as a received output.

Therefore, after the transmission of the data signal S _Dc is completed, a gate pulse is sent from the interface I/F c in response to the receiving output indicating the flag bit B _F of the received data signal S _Dt being given via the interface I/F _{c .} When P _cg2 is sent as "H" and AND gate G _C2 is turned on, a reception output indicating start bit B _S and onwards is given to the transmitter/receiver UART _c , and according to this output, reception by the display device DP _c Data is displayed.

Note that the connection signal c and the hold signal d are sent from the interface I/F _c according to the operation of the keyboard KB _c at the timing shown in FIG.
It is applied to the switch SW and the hold register HRG via terminals t ₃ and t ₄ .

Figure 5 is a block diagram of the transmitter TX, which includes the same processor CPU _t and fixed memory as in Figure 4.
ROM _t , variable memory RAM _t , transceiver UART _t ,
The interface I/F _t, etc. are connected by the bus BU _t , and the processor CPU _t performs control operations as shown in Figure 4, but the output of the sensor SS that detects differential pressure, flow rate, etc. is digitally transmitted. There are provided an ADC/A/D _t that converts the output into a signal, and a DAC/D/A _t that converts the output of the digital signal into an analog signal after the processor CPU _t processes the digital signal.

In addition, a power supply circuit PS _t is connected to the line terminal T ₁ , and in this case, a current of 4 mA is taken from the line L _1a , stabilized, and then supplied to each part as a local power supply E _t . The line voltage between _1a and L _2a is
It is applied to the comparator CP _t as in Fig. 4 through a wave transducer FL _t such as a band wave transducer that passes only the frequency component of the received data signal S _DC , and here, as in Fig. 4, It is compared with the reference voltage E _tS and the comparator CP _t produces a received output which is applied to the interface I/F _t and via the AND gate G _t1 to the transceiver UART _t .

Therefore, the flag bit of the received data signal S _DC
The reception output corresponding to B _F is the interface I/
F _t to the processor CPU _t , and in response, the processor CPU _t
The gate pulse P _tg1 is sent out as "H" via F _t , and at the same time, the control pulse P _tc is sent out to turn on the AND gate G _t1 , and at the same time, the switch circuit SW _t
Switch to AND gate G _t2 side.

Therefore, the start bit of the data signal S _DC
The reception outputs from B _S onward are given to the transceiver UART _t , and the data signal S _Dc is received, and the driver DR _t is turned off and the flow of the process signal Sp is stopped.

Next, in response to the completion of reception of the data signal S _DC , the processor CPU _t sends out an "H" gate pulse P _tg2 via the interface I/F _t , and controls the transmitter/receiver UART _t , which turns on. AND
A pulse signal is sent out via the gate G _t2 , and is given to the driver DR _t via the switching circuit SW _t , and a current corresponding to the pulse signal is sent to the driver.
DR _t and is transmitted as a data signal S _Dt .

When the transmission of the data signal S _Dt is finished and a certain waiting period has elapsed, the processor CPU _t sends a control pulse.
In order to stop sending out P _tc , the switch circuit SW _t is
The DAC/D/A _t side is restored, its output is given to the driver DR _t , and the flow of the process signal Sp indicating the measured value of the sensor SS is resumed.

Figure 6 is a circuit diagram of the drivers DR and DR _t , and the pulse signal or analog signal from the input IN is passed through the low frequency filter for noise removal by the resistor R ₁ and capacitor C ₁ , and the pulse signal or analog signal is sent to the differential amplifier A. ₁
In addition, in order to turn on and off the transistor Q ₁ such as a field effect type, or to control its internal impedance, a resistor R ₂ ,
A pulsed data signal or a DC process signal passes through _R3 .

Note that the terminal voltage of the resistor R ₃ is negatively fed back to the differential amplifier A ₁ via the resistor R ₄ , thereby maintaining the flowing current at a predetermined value.

Therefore, it is possible to insert the communicator CE between the transmitter TX and the controller CT and exchange desired data with the transmitter TX, and the data is stored in the variable memory RAM _t of the transmitter TX. It becomes possible to update various adjustment values, set values, etc. by remote control, and also to check the operating status of the transmitter TX remotely. can be achieved.

However, in Fig. 1, the power source for the oscillator TX may be supplied through a separate line, or other impedance elements may be used in place of the resistors R _L and R _C , and as shown in Fig. 3. In this case, a bit for parity check is added to each byte, or an individual code of the oscillator TX is added to the data signal S _Dt .

In addition, in the signal relay section REP in Fig. 1,
A capacitor memory may be used instead of the hold register HRG, and the ADC/A/D and DAC/D/A may be omitted.The switch SW in the same figure may not be a double throw type, but simply connected to the transmission line on the oscillator TX side. Transmitter/receiver
The same is true if the TRX is a single-throw type with bridging connection, and depending on the conditions, the switch SW may be omitted and the transmitting/receiving unit TRX may be always bridging connected to the lines L _1a and L _2a side. Various modifications are possible.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, it is possible to freely transmit and receive data to and from transmitters such as differential pressure transmitters and electromagnetic flowmeters without significantly changing existing equipment, and to control the controller. Since it does not affect the operation, remarkable effects can be obtained in remote adjustment and operation status monitoring of various transmitters.

[Brief explanation of drawings]

The figures show an embodiment of the present invention; FIG. 1 is a block diagram of the entire configuration; FIG. 2 is a timing chart showing the waveforms of each part in FIG. 1; FIG. 3 is a diagram showing the format of the data signal; 5 is a block diagram of the transmitter/receiver section, FIG. 5 is a block diagram of the oscillator, and FIG. 6 is a circuit diagram of the driver. TX...transmitter, CT...controller, TRX...transmission/reception section, SW...switch, REP...signal relay section, Sp...process signal, S _D , S _Dc , S _Dt ...data signal.

Claims (1)

[Claims] 1. A communication control device that transmits process signals between a transmitter and a controller via a two-wire line, comprising: a transmitting/receiving section that transmits and receives data signals to and from the transmitter; The input process signal is relayed as is and outputted to the controller, and when the hold signal output from the transmitter/receiver is input, the value of the process signal immediately before that is held, and this held process value is sent to the controller. a signal relay section that normally supplies the process signal outputted from the transmitter to the signal relay section, and when a control signal output from the transmitter/receiver section almost simultaneously with the hold signal is input, the transmitter/receiver section and the transmitter communicate with each other; When the transmitter/receiver is outputting a hold signal and a control signal, data signals are transmitted and received between the transmitter/receiver and the oscillator, and during this time, the signal relay unit transmits the hold signal and the control signal. A communication control device characterized in that a process value is supplied to the controller.