JPH01117498A - Transmitter - Google Patents

Abstract

PURPOSE: To optionally monitor a sensor detection output and an operation value and to make it possible to rationally judge over-scale by converting a sensor detection value into an operation value by a receiver. CONSTITUTION: A transmitter(TX) 3 such as a differential transmitter and an electromagnetic flowmeter controls a current value I like a pulse, transmits a detection output PVW based on the measuring range of a sensor as a digital signal through a transmission line. The terminal voltage of a resistor RL is applied to a receiver(RX) 4, which receives the digital signal, converts a prescribed range 0 to 100% in the received digital signal into an operation value PVW and provides the operation value PV to a main control part(MC) 6 such as a computer through a bus 5. The MC 6 executes control operation based on the value PVW applied from the RX 4 and sends control data to an equipment to be controlled through the bus 5 to control the equipment. Thereby the RX 4 can monitor also the detection output PV based on the measuring range of the sensor as necessity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission device that transmits the detection force of a sensor via a two-wire transmission line.

[Conventional technology]

Conventionally, in industrial measurement, the U.S. patent cylinder 4.520°4
As disclosed in No. 88, when transmitting the detected power of a differential pressure sensor, flow meter, etc. as a measured value to a remote point, a unified signal of 4 to 20 mA or the like that is passed through a two-wire transmission line is generally used. The current value of this analog signal indicates the measured value.

However, depending on the characteristics of the sensor, the detection force of the sensor may have a non-linear proportional relationship with the measured quantity, and it is necessary to convert this into a linear proportional relationship. In addition, the operational values used for control calculations, etc. do not necessarily use the measurement range of the sensor, but rather extract a predetermined range from this and use a relative value of 0 to 100%. Transmitters including sensors perform these conversion calculations, and setting or adjusting the conversion calculation status must be done manually for each transmitter. .

[Problem that the invention seeks to solve]

However, in the past, conversion calculations were performed in the transmitter, so the measured values transmitted to the receiver were only operational values extracted from the sensor's measurement range, and this could result in overflow for some reason. If scale occurs,
It is not possible to determine the extent to which the sensor's detection power exceeds the limit, making it impossible to make more rational judgments regarding abnormality countermeasures, and it is also impossible to adjust the predetermined range of the operating value according to changes in operating conditions. To make a change, it is generally necessary to readjust each transmitter that is distributed over a wide area.
This causes problems such as requiring a large amount of man-hours.

Accordingly, a first object of the present invention is to provide a transmission device that can monitor the measurement range of the sensor (and the detection power as needed) on the receiver side.

A second object of the present invention is to provide a transmission device that can determine how much the actual detection power is overscaled when the operating value is overscaled on the receiver side.

A third object of the present invention is to provide a transmission device that eliminates the need for conversion calculations for the oscillator, simplifies its configuration, and eliminates the need for setting and adjusting the conversion calculation status.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

That is, in a transmission device that includes a transmitter that transmits the detected force of the sensor as an output via a two-wire transmission path, and a receiver that receives the output of the transmitter, the detected force based on the predetermined measurement range of the sensor is transmitted. The system is equipped with a transmitter that converts the signal into a digital signal and transmits the signal, and a receiver that includes arithmetic means that receives the digital signal and converts the digital signal into an operational value with a predetermined range of 0 to 100%.

(Function) Therefore, the transmitter only needs to convert the detected power of the sensor into a digital signal and transmit it without converting it into an operational value used for control calculations. Since the signal is converted into an operational value at the receiver, it is optional to use both the detection power of the sensor and the operational value on the receiver side.

〔Example〕

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

Figure 1 is a block diagram of the entire configuration, with lines 1+, 1g
A power supply unit (hereinafter referred to as PS) 2 is provided to supply current to a two-wire transmission line (hereinafter referred to as transmission line) consisting of A transmitter (hereinafter referred to as TX) 3, such as PV,) is to be transmitted.

In addition, a resistor R4 is inserted in series as a voltage drop element in the transmission path, and the terminal voltage of the resistor RL is applied to a receiver (hereinafter referred to as RX) 4, and the digital signal is received at RX4. And a predetermined range of 0 to 1
00% to the operating value (hereinafter referred to as pv), the main control unit (hereinafter referred to as
MC) 6, in which control calculations are performed based on the pv- given from RX4, and control data is sent to the controlled device (not shown in the diagram) via the bus 5.
This is to be controlled.

In addition, an operation unit (hereinafter referred to as 0P) 7 equipped with a cathode ray tube display, a keyboard, etc. is connected to the bus bar 5.
This allows the control status to be displayed and commands to be given to the MC6 and RX4.

On the other hand, a portable communication device (CT) 8 is bridge-connected to the transmission line on the TXa side of the resistor 2SRL, and this changes the current value ■ in a pulse form, and sends a digital command signal. If you send it to TX3 as
3, TX3 similarly changes the current value I in response to the reception, and outputs CT as a response signal of the digital signal.
This is to be received at CT8.

FIG. 2 is a waveform diagram showing how the current value I flowing through the resistor RL changes with time t. In this case, the digital signal is a pulse code that changes in the range 11 to I2 of 4 to 20+s^, for example. The measurement value word WPV determined according to the Pv of TX3 consists of 4 bytes each consisting of 8-bit bytes BYO to RY3, and the time length of each byte BYO to BY3 is, for example, 59m5e.
When tl is c, the time length of measurement value word WPv is 4
The rest period following t+s is 1. The measured value word WPv is defined as the current 1 flowing between the line terminals of TX3.
It is transmitted repeatedly with a change of 1, thereby always conveying the latest PVr to RX4.

In this state, in response to the end of transmission of the measurement value word WPv, the line terminal f1. Current 1c flowing between lx
Due to the change in command signals RF and Q with the same pulse code, a reception standby period t! that is shorter than the idle period tI occurs. When transmitted within
This causes a voltage drop change and is applied to TX3 as a voltage change across the line 11.1□ on the TXa side, whereby the command signal REQ is received by TX3.

Then, TX3 stops transmitting the measured value word WPv in response to the command signal REQ, and after a certain period of time t has passed after the end of the command signal REQ, the current! , the 4-byte measurement value word W□ and the 2-byte response word W□ to the command signal REQ are transmitted as one unit, and this transmission of time length 6t+ is performed as the start word WIE (II).
After repeatedly transmitting from the end word W0 (E) through the pause period t, the repeated transmitting of the measurement value word WPV is started again.

Therefore, a voltage change occurs between the lines It and lx as described above, and this is received by CT8.

In addition, the measurement value word W□ has the following bits in each bit BO to B31:
The first bit BO of the first byte BYO indicates the status ST, such as whether TX3 is normal or not, and the next bit Bl indicates whether the PVF has a linear proportional relationship with the measured quantity or a square one, depending on the sensor characteristics. Indicates whether S is a proportional relationship, and depending on the third bit B2, indicates the number of consecutive bytes NB, whether the number of consecutive bytes is 4 bytes or 6 bytes.
Depending on bits B4 to B7 on the ゛ side, the byte BY
1-BY3 indicates the type DA of pv transmitted, and from the next byte BY1 onwards, the value DF of PvF
It shows V.

Note that when pv is added to the response signal and transmitted by the words W, v+W,, the response word WIIK is transmitted in conjunction with the measurement value word WPv.

However, the number of bytes of each word and the number of bits of each byte may be determined depending on the situation, and the time lengths 1, .about.t3, etc. may also be selected according to the transmission speed.

FIG. 3 is a block diagram of the C70, centered on a processor (hereinafter referred to as CPU) 11 such as a microprocessor,
Fixed memory (hereinafter referred to as ROM) 12, variable memory (hereinafter referred to as
RAM) 13, a keyboard (hereinafter referred to as KB) 14, a display device such as a numeric display (hereinafter referred to as DP) 15, a universal asynchronous transmitter/receiver (hereinafter referred to as UART) 16, an interface (hereinafter referred to as I/F) 17, etc. are peripherals. busbar 1
The CPU II executes a program stored in the ROM 12 and performs control operations while accessing predetermined data to the RAM 13.

Here, if you give the desired data from KB14,
In response to this, the CPU II controls the UART 16 and sets the gate pulse Pcg to “H” via the I/FIT.
(high level), AND gate 19
is turned on, and a "H" transmission pulse sent from the UART 16 is given to the current control unit (hereinafter referred to as CC) 20,
In response to this, current 1c flows from line terminal T1 to T2.

In addition, the line voltage between the lines 1+, 1g is passed through a comparator (hereinafter referred to as CP) 22 through a filter (hereinafter referred to as FL) 21 such as a bandpass filter that passes only the frequency components of the digital signal.
A comparison is made with the reference voltage ECs applied to one input of the input and the other input, and the reference voltage Ec
A level equal to or higher than s is extracted as a received output.

Therefore, after the transmission of the command signal REQ is completed, the reception output indicating the first bit BO of the measurement value word WPv is
17, the gate pulse Pcg is sent out as "H" from the /F17 and the AND gate 23 is turned on, the reception output indicating the next bit Bl and subsequent bits is given to the UART 16. , the received data is displayed by the DP 15 in accordance with these outputs.

Note that even when TX3 is repeatedly transmitting the measurement value word W□, reception is performed in the same way, and the pv
8 can be displayed freely.

FIG. 4 is a circuit diagram of CC20, with resistor R.

The transmission pulse from the AND gate 19, which passes through a low-pass filter for noise removal using a capacitor CI, is amplified by a differential amplifier (hereinafter referred to as A) 31, and is used to turn on a transistor Q1 such as a field effect type transistor. , resistor R1,
Current 1c passes through R3.

Note that the terminal voltage of resistor R3 is applied to A via resistor R4.
31, thereby maintaining the current IC at a predetermined value.

FIG. 5 is an external perspective view of the C70, in which the DP15 and KB14 are arranged in a hand-held case 41, and
A cord 42 is led out, and a clip 43 as a line terminal T, Tt is connected to the tip of the cord 42, and can be freely attached to and detached from the line it, 1g.

FIG. 6 is a block diagram of the TX3, in which the CPU 51. ROM52, RAM53, UART54,
The I/F 55, etc. are connected by a bus bar 56, and the CPU 51 performs control operations in the same way as in FIG. Temperature sensor (hereinafter referred to as T) that detects
SS) 58 multiplexer (hereinafter referred to as
MPX) 59, and an analog-to-digital converter (hereinafter referred to as ADC) 60 for converting the output thereof into a digital signal.

In addition, a power supply circuit (hereinafter referred to as PSC) 6 is connected to the line terminal T.
In this case, a current of 4 mA is taken in from the line 1, stabilized, and then supplied to each part as a local power supply Et, and the line voltage between the lines 1tt1z is only the frequency component of the digital signal. The reference voltage Et
s, the CF 23 generates a reception output, which is applied to the UART 54 via an AND gate 64.

Therefore, after the transmission of the measurement value word WPV is completed, if the "H" gate pulse P1.1 is sent out according to the reception mode setting, the AND gate 64 is turned on.
During this period, when the command signal REQ is given, the corresponding reception output of the CF63 is given to the UART54, the command signal REQ is received, and from then on, the CC65 is turned off, and the measurement value word WPv
Stop repeating the transmission.

Then, after receiving the command signal REQ, - a certain period of time t
, the CPU 51 via the I/F 55
” and send out the gate pulses P1 and 8 of the UART
54, a transmission pulse is sent out via the AND gate 66 which is turned on and is applied to the CC65, and a current corresponding to each word WPv+W□ is sent to the CC65.
be distributed.

In addition, each word WPv+W indicating Pv2 and a response signal
When the transmission of □ is completed, the CPU 51 transmits the measurement value word W.
Only the transmission of the transmission pulse according to □ is repeated, and thereby Pv is again increased.

is repeatedly transmitted.

Note that the configuration of the CC 65 is similar to that shown in FIG. 4.

In addition, the TX3 is equipped with a non-volatile memory such as EAROM, in which necessary data is stored, and this data is retained even if the power is interrupted. ing.

Further, the CPU 51 controls the MPX 59 and the PSS 57.
Each detected force based on the entire measurement range of
It is stored in RAM53, and the detection power of PSS57 is
Coded as vr and sent to UART54, Pv
Although the measurement value word WPv indicating 2 is being transmitted,
Depending on the contents of the command signal REQ, the detection power of TSS58 may be transmitted in the same way, or the detection power of PSS57 and TSS
58 are transmitted alternately or in combination.

Note that the reception of the command signal REQ starts during a short reception waiting period t after the transmission of the measurement value word WPv is completed.
8, during which the command signal REQ
If reception is performed, the transmission of the gate pulse ptH is continued until the end of reception, whereas if no reception is performed during the reception standby period t2, the transmission of the gate pulse PLwl is continued as this period elapses. Since the signal is stopped and the reception state is released, erroneous response due to reception of noise or the like is prevented.

In addition, by inserting the pause period t and the fixed time t3,
On the RXA side, the idle period t1 is longer than the reception standby period t2.
By detecting the fixed time t, the start time of each word becomes clear, and from this point on, by taking in the number of bytes shown by the number of bytes NB in FIG. 2 as valid, the measurement value word WPv can only be received reliably.

FIG. 7 is a block diagram of RX4, and the CPU in FIG.
CPU71 and ROM similar to II? 2. Connect RAM 73 and I/F 74.75 via bus 76, and connect CPU
The CPU 71 performs the same operation as I and controls the reception.The I/F 74 receives input from multiple transmission paths, stores it in the RAM 73, and then the CPU 71 After converting to Pv8, I/F7
5 to MC6 and OF2, and 1/
In response to a command from MC6 or OF2 via F75, CPU 71 stores command contents and various data for conversion calculations in RAM 73, and converts the received digital signal in accordance with these.

FIG. 8 is a diagram showing the state of conversion from PVF to Pvw performed by the CPU 71, in which (A) shows the relationship between the oscillator output pv and the measurement iiPV, and (B) shows the relationship between PV, PVr, and Pv.
In (A), PvF increases from the minimum value FL to the maximum value Ft in direct proportion to the increase in PV.
It increases to + and saturates at Fu, and the entire measurement range is F, ~F.

This is the case where Pv is X0 to X. . and the corresponding F0 to FIG of PV7. In order to extract Pvw as a predetermined range and convert it to Pvw of 0 to 100% shown in (B), the following calculation can be performed.

PV, = m −PV + B ・−・−−
−−・・−(1) When the PV
After converting from F to Pv, it may be further converted to Pvw using equation (1), and then sent to the MC6 and OF2 via the I/F 75.

Note that F in equation (1).・IF(l and Xl..+X
(1 is given by a command from the OF2 keyboard or stored in advance in the ROM 72 or RAM 73, and these data may be updated as necessary.

However, it is on the RXA side, P Vw, P VF
Both of these can be monitored by OF2, and Pv
When o has overscaled, by checking Pv, it is possible to rationally judge whether or not overscaling of Pv poses a practical problem, and pv.

It becomes easy to change the extraction range of , and it becomes possible to respond freely to changes in the control situation. In addition, in TX3, the need to perform conversion calculations in particular is eliminated, and the operating load to be executed by the CPU 51 is reduced, and ROM52. The required capacity of the RAM 53 is reduced, making it easy to make these configurations simple and inexpensive, and eliminating the need to adjust the TX3 in response to changes in control conditions.
A reduction in man-hours is realized.

Therefore, PvF transmission is guaranteed even during signal transmission/reception with the C70, and the RX4 side always uses the latest Pv.

is obtained, and based on this, control calculation using <pv allows stable control that quickly responds to changes in PVF.

FIG. 9 is a diagram similar to FIG. 2 showing another embodiment,
In (A), the measurement value word WPv and the response word W■ are transmitted as one over 14 bytes with a time length of 14t+, and in (B), after receiving the command signal REQ, the measurement value word based on the latest PV is transmitted. After transmitting W and V twice, each word WPV+ of the measurement value and response signal is sent.
WIE is sent in the same way over 14 bytes.

Note that the measurement value word WPv is always the latest pv.

It is preferable for the RXA side to control if it transmits a value based on the PvF, but if the PvF changes within the permissible range, the previous value is repeatedly transmitted, and when the change exceeds the permissible range, the latest value is transmitted. It may also be something to do.

Alternatively, the TX3 may perform a linearization conversion calculation according to the characteristics of the sensor and transmit the result as pv, and the type of sensor may be determined depending on the situation.

In addition, as the calculation means of RX4, in addition to using the CPU 71, a combination of various calculation circuits or a ROM 72,
A conversion table stored in the RAM 73 or the like may be used,
Various modifications can be made, such as the same for performing control calculations in RX4.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, since the conversion to the operational value PVw is performed in the receiver, the PvF
Monitoring of Pvw and Pvw becomes optional, allowing rational judgment in the event of overscaling, and eliminates the need to adjust the transmitter's Pv, making it easy to deal with changes in control conditions, and making it possible to make decisions that are noticeable in various measurements. Effects can be obtained.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, Fig. 1 is a block diagram of the entire configuration, Fig. 2 is a waveform diagram showing changes in current value, Fig. 3 is a block diagram of the communication device, and Fig. 4 is current control. Fig. 5 is a perspective view of the external appearance of the communication device, Fig. 6 is a block diagram of the transmitter, Fig. 7 is a block diagram of the receiver, Fig. 8 is a diagram showing the status of conversion calculation, Fig. 9 The figure is a diagram similar to FIG. 2 showing another embodiment. L, Ig...Line 2...PS (power supply section) 3...TX (transmitter) 4...RX (receiver) 7...OP (operation section) 51.71...CPU (Processor) 52.72・
・ROM (fixed memory) 53.73 ・RAM
(variable memory) 57...PSS (pressure sensor) 58...TSS (temperature sensor) WPv...measured value word PV...transmitter output pv,...measured quantity pv,...operating value

Claims (10)

[Claims] (1) In a two-wire transmission device comprising a transmitter that transmits the detected force of the sensor as an output via a two-wire transmission path, and a receiver that receives the output of the transmitter, a predetermined measurement range of the sensor is provided. the transmitter that converts the detected power based on the digital signal into a digital signal and transmits it; and the receiver that includes a calculation means that receives the digital signal and converts it into an operational value with a predetermined range of 0 to 100%. A transmission device comprising: (2) The transmission device according to claim 1, characterized in that a transmitter including a plurality of sensors is used. (3) The transmission device according to claim 1, characterized in that it uses an oscillator that transmits a digital signal based on a change in the current value that passes through the two-wire transmission line. (4) The transmission device according to claim 1, wherein the predetermined range of the receiver is determined by an external command. (5) The transmission device according to claim 1, characterized in that a receiver equipped with a processor is used as the calculation means. (6) In a transmission device comprising a transmitter that transmits the detected force of the sensor as an output via a two-wire transmission line, and a receiver that receives the output of the transmitter, the transmitter is connected to the transmission line via a bridge and transmits the signal. a communication device that transmits a command signal to the device; 1. A transmission device comprising: the receiver comprising arithmetic means for receiving a digital signal and converting a predetermined range of the digital signal into an operational value of 0 to 100%. (7) The transmission device according to claim 6, characterized in that a transmitter including a plurality of sensors is used. (8) The transmission device according to claim 6, characterized in that it uses an oscillator that transmits a digital signal based on a change in the current value flowing through the two-wire transmission line. (9) The transmission device according to claim 6, wherein the predetermined range of the receiver is determined by an external command. (10) The transmission device according to claim 6, characterized in that a receiver equipped with a processor is used as the calculation means.