Data processing: measuring – calibrating – or testing – Measurement system – Time duration or rate
Reexamination Certificate
2003-08-11
2004-12-28
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Time duration or rate
C702S125000, C713S400000
Reexamination Certificate
active
06836747
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a measured data synchronization system comprising a plurality of measuring instruments (for example, measuring devices and sensors) for measuring objects under measurement and outputting measured data, and a data processing apparatus connected to the plurality of measuring instruments via a signal line and which acquires and processes the measured data output by the measuring instruments. More specifically, the present invention relates to a measured data synchronization system which performs data processing using measured data for which synchronization among measuring instruments is ensured.
2. Description of the Prior Art
If a plurality of measuring instruments are used for measurement and measured data is acquired from these measuring instruments for data processing, it is necessary to ensure the synchronization of measurement results among the measuring instruments. A measured data synchronization system is intended to ensure the synchronization of measured data before data processing. Traditionally, there have been various kinds of systems for ensuring synchronization (for example, refer to the Japanese Laid-open Patent Application 1999-355256).
FIG. 1
illustrates an example of prior art measured data synchronization systems. In
FIG. 1
, data processing apparatus
10
is a computer or the like and is connected to general-purpose signal line
100
. Measuring devices
2
A to
2
C are measuring instruments, have clocks
21
and synchronization circuits
22
, and are connected to general-purpose signal line
100
. Clock
21
outputs times. Synchronization circuit
22
is connected to clock
21
, as well as to the synchronization circuits
22
of mutually adjacent measuring devices
2
A to
2
C via dedicated signal lines
200
. General-purpose signal line
100
is, for example, an Ethernet (registered trademark). Dedicated signal line
200
is less susceptible to signal deterioration and reliably transmits signals.
Behaviors of such a system as mentioned above are explained here.
First, the behavior of achieving synchronization among the clocks
21
of measuring devices
2
A to
2
C is explained. Of the clocks
21
of measuring devices
2
A to
2
C, the clock
21
of the measuring device
2
A, for example, is defined as the reference clock. The synchronization circuit
22
of measuring device
2
A acquires times from clock
21
and outputs the acquired time as a synchronization signal to the synchronization circuit
22
of measuring device
2
B via the dedicated signal line
200
. When given an input of the synchronization signal from measuring device
2
A, the synchronization circuit
22
of measuring device
2
B immediately outputs this synchronization signal to the synchronization circuit
22
of measuring device
2
C via dedicated signal line
200
. Then, according to the time contained in the synchronization signal, the synchronization circuits
22
of measuring devices
2
B and
2
C synchronize their respective clocks
21
with the clock
21
of measuring device
2
A. Synchronization circuits
22
perform these behaviors as frequently as possible to achieve synchronization.
Next, behaviors wherein measuring devices
2
A to
2
C perform measurements and data processing apparatus
10
processes data are explained. Data processing apparatus
10
outputs a start measurement command towards measuring devices
2
A to
2
C via general-purpose signal line
100
, thereby enabling measuring devices
2
A to
2
C to perform measurements. When measurement is completed, measuring devices
2
A to
2
C append the time of synchronized clocks
21
to the measured data and output the measured data containing the time towards data processing apparatus
10
via general-purpose signal line
100
. Moreover, the data processing apparatus uses the measured data and the time contained therein to achieve synchronization among measuring device
2
A to
2
C before performing data processing.
Another example of prior art systems is explained by referring to FIG.
2
.
Note that elements identical to those of
FIG. 1
are referenced alike and excluded from the description. In
FIG. 2
, data processing apparatus
11
is provided in place of data processing apparatus
10
. Data processing apparatus
11
has clock
12
and is connected to general-purpose signal line
100
. In addition, measuring devices
3
A to
3
C are provided in place of measuring devices
2
A to
2
C. Measuring devices
3
A to
3
C are connected to general-purpose signal line
100
.
Behaviors of such a system as mentioned above are explained below. Data processing apparatus
11
outputs a start measurement command to measuring devices
3
A to
3
C via general-purpose signal line
100
, and also retains the time of clock
12
when the command is output. Then, measuring devices
3
A to
3
C perform measurements according to the start measurement command from data processing apparatus
11
. When measurement is completed, the measuring devices output measured data to data processing apparatus
11
via general-purpose signal line
100
. Data processing apparatus
11
processes the measured data sent from measuring devices
3
A to
3
C, assuming that the measured data was acquired at the point of time that the apparatus retains. This type of system configuration is generally referred to as SCADA (Supervisory Control and Data Acquisition).
As described above, the system shown in
FIG. 1
ensures synchronization in such a way that synchronization circuits
22
adjust the times of clocks
21
to each other via dedicated signal lines
200
. However, each of measuring devices
2
A to
2
C requires a clock
21
and synchronization circuit
22
. Moreover, dedicated signal lines are required to connect synchronization circuits
22
. Synchronization circuits
22
require complicated processing (for example, compensation for the time delays of synchronization signals resulting from the lengths of dedicated signal lines
200
or reconstruction of deteriorated waveforms) to achieve synchronization. In addition, dedicated signal line
200
tends to be more expensive than general-purpose signal line
100
because the dedicated signal line is specifically designed to reliably send synchronization signals. In addition, if a dedicated signal Line is extended due to an increase in the number of measuring devices including
2
A to
2
C or for reasons of the locations where measuring devices
2
A to
2
C are installed, the waveforms of synchronization signals may deteriorate or the delay time may be prolonged, thereby significantly increasing synchronization errors among measuring devices
2
A to
2
C. These factors restrict the number of measuring devices, including
2
A to
2
C, that can be connected or the locations where these measuring devices can be installed.
On the other hand, systems such as the SCADA system shown in
FIG. 2
do not achieve synchronization among measuring devices
3
A to
3
C but use, as a reference, the time when data processing apparatus
11
outputs a command. However, the time required for measuring devices
3
A to
3
C to acquire measured data or the communication delay involved in data transmission generally differs among measuring devices
3
A to
3
C: these effects would result in synchronization errors. Needless to say, the synchronization errors become larger as the number of measuring devices including
3
A to
3
C increases, or depending on the locations where measuring devices
3
A to
3
C are installed. It becomes especially difficult to synchronize measured data if the sampling frequency is made higher, causing the measurement interval to become shorter.
SUMMARY OF THE INVENTION
An object of the present invention is to realize a measured data synchronization system wherein data processing is performed using measured data for which synchronization among measuring instruments is ensured.
REFERENCES:
patent: 4135181 (1979-01-01), Bogacki et al.
patent: 5428645 (1995-06-01), Dolev et al.
patent: 5579513 (1996-11-01), Strohmer
patent:
Barlow John
Dougherty Anthony T.
Westerman Hattori Daniels & Adrian LLP
Yokogawa Electric Corporation
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