JPS5848198A - 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] Two-wire transmission pocket for transmitting physical quantities such as force, flow rate, temperature, etc.
related.

In general, in 111 types of plants, various physical quantities (hereinafter referred to as "one scoop constant amount") are collected from each plant in order to know the status of each plant. For management purposes, the measured quantity of each process is sent to a receiving section that is centrally installed in one place such as a control room.As a means of transmission, the measured quantity is converted into an electrical signal, and a cape is used as the transmission means. A means is taken to send the information to the receiving section via i. In addition, transmission i #i usually occurs during construction. For simplicity and cost reasons, a two-wire transmitter is used, since it requires only 2 an inch of wire. A conventional two-wire transmission device will be explained below with reference to Fig. 1.
Ru. A transmitter 2 that outputs a current according to a Busses' measured quantity 1 is connected to a cable 3. It is connected to the receiving section 4 via. This cable 8 transmits the output of the transmitter 2 to the receiving section 4, and also supplies power to the transmitter 2 from the power supply section 5 installed in the receiving section 4. In the receiving section 4, the O signal from the transmission liF2 is converted into a digital signal in the receiving instrument 7 via a current-voltage converting resistor 6 that converts it into a voltage. The control computer 8 converts this digital signal into a process control signal to control the process.

In this configuration, the transmitter 2 also receives the supply of current corresponding to the measured quantity IK from the power supply section 5, and transmits the change in the supplied current to the injured part 4 as the output of the transmitter 2. Therefore, since power supply to the same transmitter 2 also serves as signal transmission, two transmission lines can be used. Because of these advantages, the transmitter 2 is widely used for process control in various plants. It is used. Furthermore, the format of the transmitted signals is also unified, and the compatibility with the receiving side is high.

By the way, in the above-mentioned transmitter 2, the information to be transmitted is limited to the field size IK, such as the setting span of the transmitter 2, υ self-diagnosis information (hereinafter referred to as additional information), etc. due to the management of the transmitter 2. In order to obtain the necessary information, measures must be taken such as installing a separate transmission line for additional information.

However, with this type of means, the two wires in front of the two-wire transmitter 2
The advantage of being able to supply signals and power over real transmission lines is lost.

Therefore, the invention was made based on the above circumstances.940
The purpose of this is to transmit the quantity to be measured and additional information without impairing the advantages of the two-wire transmitter and without compromising the consistency between the quantity to be measured and the receiving side.
The present invention provides a wire transmission device.

An embodiment of the present invention will be described below with reference to FIG. 2 and FIG. 31a. Subtract al
a current control circuit 1j that controls the output of the signal to be measured, and a time series circuit that converts the additional information signal IS such as the set span value of the transmission device into a time series signal. A signal conversion circuit 14, the current control circuit 12, and a tm output circuit 16 that sends the dead time series signal selected by the selection path JjK or the measured quantity signal from the current control circuit 12 to the transmission line 11 as a current output. It is made up of many things. Furthermore, the output of this current output circuit 16 is connected to the current control circuit 11, and the current control circuit 12 and the current output circuit 16 constitute a feedback circuit. In addition, the selection time of the selection 1 path 15 is the tights circuit J-811.
C is set to 1, and when the selection circuit 15 selects the time series signal conversion circuit 14 side, the operation tie (y signal) is sent from the timer circuit 18 via the operation signal line 19 to the time series signal conversion circuit 14. Then, the extended counting circuit 20 is connected to the simultaneous series signal converting circuit 1M, and the counting circuit 20 starts operating the time series signal converting circuit 14. The time-series signal conversion circuit 140 counts digital signals that are time-series signals.The counted nine digital signals are held until the next operation of the time-series signal conversion circuit 14, and at the same time, the time-series signal conversion circuit 140 counts digital signals that are time-series signals. The subtraction circuit 11 of the next stage is averaged and input as an analog signal to the negative terminal of the subtraction circuit 11 of the next stage. On the other hand, the Hiro column quantitative signal 1-0 is input to the positive terminal of this subtraction circuit 11], -ζ0WI
The subtracted outputs of the signals of the four parties are input to the current control path 12.

Then, on the receiving side, the receiving section 4 that receives the measured quantity signal and the bypass filter 23 that extracts the additional information signal are connected to the transmission line 11 via the current-voltage conversion resistor 6. A horn parator 24 is connected to the output side of the filter a-XS, and extracts a time series signal containing additional information.

Next, the operation of the device for forming the K11l as described above will be explained. Let T1 be the time during which the selection circuit 15 selects the time-series signal conversion circuit 14, T be the time during which the current control path 11 is selected, and T be the selection period 150. TmT, +T. First, selection path 15 is set at time T
1, the time-series signal conversion circuit J4ti operates according to the operation signal from the time-series circuit 18, and the additional flavor signal 13' is converted into a time-series signal f. This time series signal is the selection circuit 1
5 to the current output circuit 16, where the current [f
and output to the transmission 1177. On the other hand, at the same time, the time-series signal conversion path 14 starts operating, and the counting circuit 20 starts operating.
counts the digital signals that are the time series signals. The counted value is then converted by the D-A conversion circuit 21 into an analog signal, which is the average value of the digital signal during the time period T1□. This analog signal is input to the negative terminal of the subtraction circuit 1).

The average value of the tb time series signal at time T1 is subtracted - path 11
K is input to the negative terminal of .

The value counted by the counting circuit 20 is held until the next time-series signal conversion circuit 14 starts operating. t> Selection circuit 15O - held for period T. Therefore, the analog signal from the D-A conversion path 21 is 4 times T.
During this period, the signal is input to the negative terminal of the subtraction circuit IJ. Next, when the selection circuit 15 is switched and the current control circuit 12@ is selected, the measured quantity signal 10a sampled from the Bootes is input to the positive lII riko of the subtraction circuit 11. , the analog signal from the D-me conversion path 21, which is the average value of the time Ill of the time-series signal, and the measured quantity 10 are subtracted. This subtracted output is a current output from the current control circuit 12 via the selection circuit 15.
The current output signal is inputted to the line 16, and sent from the same current output line 16 to the transmission line 11 as a wrinkle Va=amount signal. Then, when the selection circuit 15 again selects the time-series signal conversion sub-path 14, the first counting path 20 starts counting anew, and the same operation is repeated thereafter. The above subtraction process is performed with and ζ.
, it is possible to eliminate the influence of the additional information signal on the fixed amount signal, and one period '1' of the reception @xs"co selection path 15
The average value of the received signal KTh becomes proportional only to the signal being measured. If we assume that this ζ□ is the 310th time chart, then the selection time of the additional information signal is 'r, and the selection time of the constant quantity signal Ts1 is one cycle of the selection path T.
, additional information 0 time series "column signal is Dl*Dh measurable quantity measurable content signal 11, since the receiver 4 responds to the average value of the i combined received signal which receives the measurable quantity signal, each period T
If the additional information signal of s is different from Dl and Dl and has an elongated volume, the average value changes dramatically, causing an inconvenience.Therefore, the measured quantity signal may be corrected using the average value of the additional information O of each cycle. , the average value aDs of the additional information signals DI and Dl is higher than that of the additional information signals DI and Dl, and therefore, the difference in the average values makes the amount of the signal M1 higher than that of A. Thank you #iArashii. In this way, the only difference in the average value in each period T is the difference in the spread measurand signal.

In addition, feedback is applied from the current output circuit 16 to the current control circuit 12, and the quantitative signal to be measured, which has undergone subtraction processing, is transferred from the current distribution control line 12 line subtraction circuit 11 to the output oil line 16. is controlled by the output of the current output circuit 16 and input to the current output circuit 16.

In this way, the current output circuit 16 outputs the required current to the transmission line 17 in proportion to all quantitative signals 1011C within the range of the upper and lower limits of the transmission signal which are unified. Then, the transmission signal transmitted to the transmission line 17 is received @22
The measured quantity signal is received by the conventional receiving section 4.
The average value is measured. The additional information signal is converted into a voltage by the current-voltage conversion resistor 6, and taken out by the bypass filter 23. The signal taken out by the filter 23 is returned to the next stage, the comparator 24, into a digital signal converted into a time-series signal by the time-series signal-to-current conversion circuit 14. In this way, The amount to be measured and additional information can be obtained.Also, if we consider the effect that transmitting the additional information of the present invention has on conventional receiving instruments, the transmitter and receiving instrument normally used for A4 bus control will be able to obtain the It has a low-pass characteristic with a time constant of several seconds to 1θ seconds so as not to be affected by disturbances to the process.On the other hand, since the transmission speed of digital signals is about IK bits/second to 1M bits/second, there is no chance of a failure. In a wA transmission device, if the selection time of the time-series signal '!1
(between 10 bits) 0 additional information transmission speed IK bits/
When transmitting with a digital signal of 3 seconds, the selection time TI is l.
This will be O milliseconds. . Therefore, the current control circuit 12
If the timer circuit 18 is set so that the selection time T3 on the side is sufficiently longer than T, the selection time T1 will be much shorter than the cycle TK of the selection 1 path 15. Therefore, considering the four-path characteristics of the receiving instrument, the KFi receiving instrument does not respond to the extremely short 11 RIK sent information as described above, and the 7. Respond to signal number 7 on time. Therefore, even if a two-wire transmission device is used to receive the measured quantity, the present invention does not cause any damage to the conventional receiving instrument itself. For example, in the above embodiment, the amount of additional information is converted into a digital signal and transmitted.
When transmitting a signal of an amount of additional information using a different frequency, setting a number *a corresponding to the absolute value of the amount of additional information and transmitting that frequency as the amount of additional information,
Various values of the amount of additional information are determined by the pulse width O of the 21 m pulse.
It is also possible to transmit 7't-2 type O' pulses having different pass-through ratios depending on the amount of additional information.

Further, the content of the additional information is not limited to the span setting value and self-diagnosis information of the transmission device, but also, for example, the amount to be measured can be converted into a digital signal and transmitted as additional information. By doing this, the measuring instrument that was originally receiving the measured quantity as an analog signal can be converted into a digital signal by adding additional information to know the exact table value. By obtaining the measured quantity, the accurate measured quantity can be determined.

Based on the above, in addition to the measured quantities of puruses in various plants, P2. By inserting self-diagnosis information into the signal of the measured quantity with an extremely short *na of the transmission equipment installed at the field site, it is possible to transmit the self-diagnosis information to the field transmission equipment at the remote receiving section. It is possible to control the state of do not have. Furthermore, since the additional information does not have any influence on the signal of the measured quantity, the 21I residual transmission device offers excellent compatibility in that it can be adapted to the internationally standardized two-wire transmission signal type 11. can do.

[Brief explanation of drawings]

Part 1 is a block diagram of a transmission system using a conventional 12-wire transmitter, Part 21 is a diagram of a transmission system according to the present invention, and Part 3 is a configuration showing an embodiment of the transmission device. is a time chart showing the relationship between the fixed amount signal and the additional information signal in the synchronization of the second selection path. 11・-sK nasal tract, Jj-・Current control i [1 circuit,
14゛... Time series signal conversion-path, 15... Selection-path, 16... Turtle flow car path, J 8-... Timer circuit, 209... Counting circuit, Jr J-D-me conversion circuit. To the applicant's attorney's office Takehiko Suzue Figure 1

Claims (1)

[Claims] In a transmission device that measures a quantity to be measured in a process and sends out an electrical signal according to the quantity to be measured, the output current is outputted according to the quantity to be measured, and a signal with a level s1 quantity within a range of one foot and the above-mentioned additional information are used. means for selecting and outputting the time-series signals of and at respective set selection times, a current output path for converting the selected signal into a current and outputting it to a transmission line, and this current output circuit. 2. A two-wire transmission device, comprising: means for feeding back the output of the time series signal to the current control circuit, and controlling the output current based on the average value of the time series signal and the signal of the measured quantity.