JPS60113158A - Trend graph display device - Google Patents

Abstract

PURPOSE:To display the lates precise progress simultaneously with display of a long-time progress by providing sampling circuits different in sampling period. CONSTITUTION:An analog signal 1 indicating a process quantity is supplied to a sampling circuit 3 through an A/D converter 2. The signal 1 is supplied to a sampling circuit 9 also through an A/D converter 8. The sampling period is made sufficiently shorter than that of the circuit 3. A memroy device 10 is provided with the first memory, where sampling data of the circuit 3 is stored, and the second memory where sampling data of the circuit 9 is stored. When a display device 11 is instructed to display the analog signal, a switch 7 is controlled to input the analog signal to the converter 8. Then, n-number of data having the longer sampling period are read out from the first memroy 1 in the device 10 and m-number of data having the shorter sampling period are read out from the second memory, and they are displayed on the device 10 in the order of sampling. Consequently, the long-time progress and the latest progress are displayed continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a trend graph display device for displaying temporal changes in process quantities in a plant.

[Prior art]

Conventionally, the equipment for this building was as shown in Figure 1. In the figure, the analog signal representing the full process quantity, (
2) is an analog-digital converter (hereinafter abbreviated as ADC), (31 is AI at a predetermined sampling rate)C(2)
), and in this specification, (2) and (3) are collectively referred to as an analog-to-digital converter. (4) is a memory device, (5) is a display device, and (6) is an example of a trend graph displayed by display device (5).

The memory device (4) stores the data of the latest n sampling points of the output of the sampling circuit (3).

For example, if the output of the ADC (2) is an 8-bit digital number, the memory device is composed of eight parallel circuits of one-stage shift registers, and the 8-bit data at the latest sampling point is the 8-bit digital number. The 8-bit data at the earliest sampling time is stored in the nth stage of the eight shift registers. When the next sampling point arrives, the data at that time is stored in the first stage of eight shift registers, the conventional data is shifted backward one stage at a time, and the data stored in the nth stage is shifted out. and disappear. The horizontal axis of display M (5) is time t, which corresponds to each stage of the shift register. For example, if the sampling period is Δt1, the data stored in the first stage of the shift register is This occurs after (r+-k)Δt□ from the data stored in the n-th stage. Therefore, it is easy to read out the contents of the memory device (4) and display it as a trend graph shown in FIG. 1 (6).

Incidentally, in a plant monitoring device (not shown), trend graphs for a large number of analog signals must be displayed as necessary, and trend graphs over a fairly long time interval must be displayed. For example, there are 500 types of analog signals to be displayed, which are converted into digital signals by ADC (2) in a time-sharing manner, and the sampling period Δt1 for each analog signal is set to 1.
In seconds, it takes 11,500 seconds to convert one type of analog signal to a digital signal and store it in the memory device (4).
It must be within seconds, and even if n = 600, the time that can be displayed on the trend graph is n△t□ = 600 seconds (=10
500 types of analog signals, 600 data for each signal are stored in the memory device (4), and an 8-bit (1 byte) memory element is required for each data. is 500 x 600 = 300
This will require a kilobyte memory element.

Therefore, in the conventional device, in order to increase the display time range of the trend graph within a certain capacity of the memory device (4), the sampling period △t1 must be increased, and △
When t1f is increased, a situation that requires precise observation occurs, and when observing an analog signal related thereto, there is a drawback that the interval between sampling points is too large.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and in this invention, a second analog-to-digital converter 6 having a short sampling period and a second analog-to-digital converter 1 are provided. latest m of output
When a trend graph of one analog signal is to be displayed, the analog signal is manually input to the second analog-to-digital converter, and then the sampling period is In the memory storing the output of the long analog-to-digital converter, the data related to the analog signal and the second
Data from memory is displayed on the volunteer at the time of sampling.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention. The same reference numerals as in FIG. 1 indicate the same or corresponding parts, (7) is a switch, (8) is an ADC, C9) is a sampling circuit, (
8) and (9) will be referred to as the second analog-to-digital converter, whereas 2) and (3) will be referred to as the first analog-to-digital converter. +1 (J is the first
The memory device corresponding to (4) in the figure is a memory device Q (j is a first memory that stores data at the latest n sampling points from the first analog-to-digital converter, and a second memory device and a second memory for storing data at the latest m sampling points from the analog-to-digital converter.

0]) is a display device corresponding to (5) in FIG.
0 is an example of a trend graph displayed by the spray device 0.

The sampling period Δt2 of the sampling circuit (9) is sufficiently smaller than the sampling period Δt1 of the sampling circuit (3). Since a large number of analog signals are input to the ADC+2) by switching in a time division multiplexing method, Δt
Even if □ is large, the processing time for one analog signal will be shortened, but since only one analog signal is input to ADC (8) via switch (7), even if △t2 is reduced by 2 Processing is possible.

When a command is issued to display any one analog signal on the display device a℃, the command causes the switch (
7), inputs the analog signal 'i to the ADC (8), and outputs n pieces of data corresponding to the analog signal from the first memory in the memory device (11) and m pieces of data from the second memory. If you read out the data and display these data on the display device at the time of sampling,
For example, a trend graph as shown at O2 in FIG. 2 can be displayed. That is, a long time elapsed time is displayed using n pieces of data with a large sampling period Δt1, and a recent elapsed time is displayed precisely using m pieces of data with a small sampling period Δt2. Note that the section in which m pieces of data with a sampling period Δt2 are displayed can be displayed by enlarging the scale of the horizontal axis t.

As described above, for a large number of analog signals, the sampling period Δt1 is increased so that the elapsed time can be stored, and when selecting and displaying an arbitrary analog signal among them, the analog signal is sampled for a short time. Period △
Since it is displayed together with the short-time progress sampled at t2, it is possible to display the long-term progress as a trend graph and at the same time accurately display the recent progress while keeping the capacity of the memory device 00 small. can.

In addition, in the above embodiment, an example was shown in which a trend graph in the format shown in FIG. 2 (12) is displayed, but the format of the trend graph is not limited to this. A trend graph can also be constructed by arranging points in order.Furthermore, in addition to displaying a trend graph, the display device (l) H) can also display bar graphs, digital values, etc. using the stored contents of the memory device u1. It can also be designed to do the following.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to display the progress of a long time range for a large number of analog signals as a trend graph, even under the limited capacity of a memory device, and also to accurately display the progress of a short period of time. can be displayed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional device, and FIG. 2 is a block diagram showing an embodiment of the present invention. (1)...analog signal, (2), +3)...first analog-digital converter, (7)...switch, +s), (9)...second analog-digital converter , +1 (to... memory device, 01)... display device. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] A first analog-to-digital converter 64 inputs an analog signal, converts it into a digital signal at a predetermined first sampling period, and outputs the converted signal. a first memory that stores data at a sampling time (an arbitrary positive number of ships), and a second sampling device that inputs an analog signal via a switch and uses the input analog signal with a period shorter than the first sampling period. A second analog-to-digital converter that periodically converts and outputs the digital signal, and stores data at the latest m sampling points (m is any positive integer) from the second analog-to-digital converter. A signal instructing to display any one analog signal among all analog signals related to the data stored in the second memory to the first memory causes the analog signal to be displayed on the switch. means for displaying the data corresponding to the analog signal in the first memory and the contents of the second memory at the time of sampling. Equipped with a trend graph display device.