JP2002071850A - How to set the data sampling interval for measuring instruments - Google Patents

Abstract

(57) [Summary] [Problem] To correct a time error generated between an actual time taken at a fixed timing from outside during measurement and an internal time of a measuring instrument without adversely affecting a data sampling interval. To do. Kind Code: A1 Abstract: A measuring instrument performed without any deviation between an actual time as time information fetched from the outside at a constantly constant timing and an internal time generated by an internal clock of the measuring instrument. In the method for setting a data sampling interval according to the above, the data sampling interval is determined based on a difference between an interval between two real times before and after the captured time and a corresponding interval between internal times. Is determined, and the error is determined by reflecting the error in a countdown value preset in the counter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time difference between an actual time fetched from the outside at a fixed timing during a long-time measurement and an internal time generated by an internal clock of the measuring instrument. The present invention relates to a method of setting a data sampling interval in a measuring instrument that can correct a serious error without adversely affecting the data sampling interval.

[0002]

2. Description of the Related Art A long-term measurement by a measuring instrument such as a waveform recorder is performed by sampling measurement data at a constant data sampling interval.

In this case, as a technique for keeping the data sampling interval constant, a high-precision crystal oscillator is incorporated in the measuring instrument itself, and the internal clock generated based on a high-precision pulse obtained from the crystal oscillator is used. The data sampling interval can be kept constant.

However, in the case of the above-mentioned conventional method, a very expensive crystal oscillator must be used, and it is costly to equip a general-purpose measuring instrument provided at a relatively low price. There was a problem that it was difficult.

[0005] For this reason, in the case of the above-mentioned general-purpose measuring instrument, accurate time information (for example, a time signal of a radio broadcast or a radio wave from a standard frequency station) is received at a predetermined timing from the outside. In this document, this is referred to as “real time.” The time difference between the actual time and the internal time generated from the pulse (internal clock) generated by the crystal oscillator with relatively inaccurate accuracy is defined. A method of correcting the data sampling interval so as not to cause the error has already been performed.

[0006] The above-mentioned conventional method does not cause any problem particularly when the data sampling interval is sufficiently longer than the time lag for correction.

[0007]

However, when the data sampling interval is relatively short with respect to the time lag at which the data sampling is corrected, there is a problem that the data sampling interval at the time of correction is greatly shifted. .

That is, in a measuring instrument that obtains a pulse from a general quartz oscillator having an accuracy of about 100 ppm and sets the internal time, a system that corrects the time every other hour is assumed. An error of up to 0.36 seconds will occur.

The error of 0.36 seconds has a small influence because the error occupies a very small ratio of about 0.6% immediately before the correction if the data sampling interval is about 1 minute. However, if the data sampling interval is, for example, 1 second, the error occupies as large as 36% immediately before the correction, and the data sampling interval is greatly shifted.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the conventional method, the present invention uses a measuring instrument which obtains an internal time from a crystal oscillator having relatively low accuracy, and generates a signal between an actual time and an internal time during a long-time measurement. An object of the present invention is to provide a method of setting a data sampling interval in a measuring instrument that can correct a temporal error without adversely affecting the data sampling interval.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and its structural feature is that the actual information as time information fetched from the outside at a constant timing is always provided. In a method of setting a data sampling interval in a measuring instrument, which is performed without a difference between a time and an internal time generated by an internal clock of the measuring instrument, the data sampling interval is equal to two times before and after the captured time. An error on the side of the internal time is obtained based on a difference between the time interval and the corresponding internal time interval, and the error is reflected on a countdown value preset in the counter. Is to determine. In this case, it is preferable that the error be stored in a non-volatile memory and reused at the next power-on.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a functional book diagram showing a schematic configuration example of a measuring instrument provided for carrying out the present invention. A measuring unit 12 to be fetched, a central processing unit (CPU) 13 for calculating measurement data and the like fetched from the measuring unit 12 and for overall control of each component, and a memory (ROM, ROM, (RAM, non-volatile memory) 14, a display 15 for displaying required data such as measurement data, a real-time information input unit 16, and an interface 17 for transmitting and receiving data to and from the outside.

The measuring unit 12 in the measuring unit 11
For example, a general crystal oscillator 22 having an accuracy of about 100 ppm
And a 20-bit counter 23 that repeats the operation of inverting the output signal when the count number set down is reduced to 0 and the count number set based on the correspondence relationship with the pulse of, for example, 20 MHz generated by the crystal oscillator 22.
And the output signal of, for example, 1 Hz from the counter 23 is 1
Phase synchronization circuit (PLL circuit) for converting to 00 Hz signal
24.

For this reason, if the crystal oscillator 22 generates 20 MHz
Assuming that a pulse of z is generated and the preset countdown value is “1,000,000”, a signal of 1 Hz is output from the counter 23 and the measuring unit 1
If the data sampling interval in 2 is 10 mSec, the PLL circuit 24 can convert the signal to a 1: 100 signal to create an internal clock of 10 mSec. As a result, in the measuring unit 12, 100 Hz
Under the data sampling interval (sampling frequency), measurement data such as waveform data can be converted into digital data and taken in.

FIG. 2 is a flow chart showing an example of the processing procedure of the present invention applied to the measuring instrument 11, and the internal time generated by the internal clock is obtained by obtaining time information from the outside. The operation is performed as follows while adjusting the timing, that is, the constant timing at which the real time is always obtained intermittently.

That is, a process for storing the current internal time of the measuring instrument 11 in the memory as the “current time” is performed, or at the same time by always keeping a constant interval from the process, via the time information input unit 16. The “real time of the current capture”, which is the captured time information, is replaced with the internal time of the measuring device 11.

The "real time taken in this time" is 1
If it is the first time, the “current time” already stored in the memory 14 is changed to the “previous time” and stored, and the process is terminated.

On the other hand, the "real time taken for this time" is 1
If it is not the first time, subtract the "last time" from the "current time" currently stored, so that the internal time between the "last time" and "this time" Processing for obtaining a correction interval (time difference) is performed.

In this way, the correction interval (time difference) between the "previous time" and the "current time" for the internal time
After the is obtained, the correction amount (time difference) between “this time actual time” and “this time” is obtained by subtracting “current time taken this time” from “current time”. Processing is performed.

After the correction interval and the correction amount (time difference) are obtained, a process of obtaining an error of the internal time generated by the internal clock is performed by dividing the correction amount by the correction interval.

After the error of the internal time is obtained in this way, the countdown value preset in the counter 23 is changed based on the error (if the error is a plus value, it is added to the original countdown value). , A negative value is subtracted). Specifically, for example, the error of the frequency of the obtained internal clock is +5.
If it is 0 ppm, the initial countdown value "1,
"00000" to "1,000,000 050".

After the process of changing the countdown value is performed, the "current time" is changed to the "previous time" and saved, and the process is terminated.

Since the present invention is carried out through the above-described processing procedure, the error of the internal time obtained each time the real time “real time of this time” is continuously taken twice is calculated by the counter 23. This is increased or decreased by reflecting it in the initial countdown value, so that the internal time stamp can be corrected to correspond to the actual time.

Therefore, even if measurement is performed for a long time using the measuring device 11, an error of the internal time generated during the measurement can be corrected without adversely affecting the data sampling interval. It is possible to eliminate the occurrence of such a situation.

In the present invention, the error is stored in a non-volatile memory in the memory 24 so that even if the power is turned off and the measurement is stopped, the error is re-read from the non-volatile memory at the next power-on. By taking it out and using it, measurement can be restarted at a data sampling interval obtained from a relatively accurate internal clock.

[0026]

As described above, according to the present invention, the internal time is calculated based on the difference between the two real time intervals before and after the actual time and the corresponding internal time interval. Since the data sampling interval can be determined by calculating the error on the side and reflecting the error on a countdown value set in advance in the counter, a measuring instrument that obtains an internal clock from a relatively inaccurate crystal oscillator can be used. Even if the measurement is performed over a long period of time, the data sampling interval can be prevented from being adversely affected.

In addition, by storing the error in a non-volatile memory, the measurement is stopped after the power is turned off, and the error is taken out of the non-volatile memory again at the next power-on, so that a relatively accurate result can be obtained. You can get the internal clock.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a schematic configuration example of a measuring instrument provided for implementing the present invention.

FIG. 2 is a flowchart showing an example of a processing procedure of the present invention which is applied to the measuring instrument shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Measuring instrument 12 Measuring part 13 Central processing unit (CPU) 14 Memory (ROM, RAM, nonvolatile memory) 15 Display 16 Time information input part 17 Interface 22 Crystal oscillator 23 Counter 24 Phase synchronization circuit (PLL circuit)

Claims (2)

[Claims] 1. A measurement performed without eliminating a difference between an actual time as time information taken in from the outside at a timing that is always constant and an internal time generated by an internal clock of a measuring instrument. In the method for setting a data sampling interval in a device, the data sampling interval is determined based on a difference between an interval between two real times before and after the acquired time and a corresponding interval between internal times. A method for setting a data sampling interval in a measuring instrument, wherein an error on a time side is obtained and the error is determined by reflecting the error in a countdown value preset in a counter. 2. The system according to claim 1, wherein the error is stored in a non-volatile memory and reused at the next power-on.
2. A method for setting a data sampling interval in a measuring instrument according to item 1.