JPH1164395A - Signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processor completely unnecessitating adjusting operation at a job site at the time of exchanging an A/D board, etc. SOLUTION: An A/D board corrected value storing area M1 and a PCT (PT (a transformer for a meter) or CT (current transformer)) corrected value storing area M2 are provided at an A/D board and the corrected value of these can be read/written from outside through RS 232 C in addition. At the time of exchanging the A/D board, a PCT corrected value stored in an old is read out and written in the area M2 of a new A/D board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for measuring system voltage, current, etc.
The present invention relates to a signal processing device including a conversion unit.

[0002]

2. Description of the Related Art In order to measure the voltage and current of a system, a signal taken through a PT (instrument transformer) or a CT (current transformer) is A / D converted and digitally processed. It is common. FIG. 4 shows a configuration diagram of an A / D board including the A / D conversion unit. PCT is PT
Or CT, and the output signal of the secondary winding is appropriately amplified by an operational amplifier AMP, and a low-pass filter LP
F, the signal is output to a signal processing unit at the subsequent stage through a sample hold circuit S / H and an A / D converter. The low-pass filter LPF is for preventing aliasing noise caused by digital processing of a signal. The operational amplifier AMP is connected to a variable resistor VR that can be adjusted by hardware or software, and a person in charge can appropriately adjust the variable resistor VR on site.

[0003]

By the way, in order to improve the accuracy of the measured values, it is necessary to electrically correct errors of the PCT itself and errors of the A / D board itself.
Therefore, in the conventional apparatus shown in FIG. 4, the error of the PCT and the A / D board itself is adjusted as a whole by adjusting the variable resistor VR.

[0004] However, the A / D board may be out of order because of the electric circuit section. Therefore, when the A / D board fails, it is necessary to replace the A / D board and adjust the variable resistor VR again on site. Generally, for this adjustment, it is necessary to connect a reference oscillator and a reference measuring instrument.
There has been a problem that the work becomes extremely complicated including preparation of those devices on site. In addition, when the scale of the measuring device is increased, the number of these A / D boards is increased to several tens to several hundreds, so that there is a problem that the work at the time of replacing the boards becomes more complicated.

An object of the present invention is to provide a signal processing apparatus which does not require any on-site adjustment work when replacing an A / D board or the like.

[0006]

According to a first aspect of the present invention, there is provided an A / D converter for A / D converting an output of a PT or a CT.
In a signal processing device provided with a D conversion unit and exchangeably provided in a measuring device, a correction value for an external circuit including the PT or CT and a correction value for an internal circuit of the signal processing device itself are stored. It is characterized by comprising a correction value storage means and an input / output interface means for writing or reading the correction value.

[0007] The correction value storage means in the signal processing device includes a PT.
Alternatively, since the correction value for the external circuit including the CT is stored, when exchanging the signal processing device such as the A / D board, the correction value for the external circuit is fetched via the input / output interface means, and the correction value is newly obtained. To the appropriate signal processing device. The correction value of the new signal processing device itself is stored in advance in the correction value storage means. Accordingly, the replacement operation can be easily performed on site without connecting a reference signal oscillator, a reference signal measuring device, or the like.

[0008] It should be noted that although the PCT is not frequently exchanged, even if the PCT needs to be exchanged, it can be easily exchanged by a similar process. That is, a new PCT correction value is obtained in advance, and this is overwritten on the correction value stored in the correction value storage means. In this case, there is no need to consider the correction value of the A / D board itself since it is already stored.

As described above, the correction value for the internal circuit of the A / D board itself and the correction value for the external circuit including the PCT do not need to be obtained on site because they are independent from each other. The ability to measure makes the on-site replacement very simple.

[0010]

FIG. 1 is a block diagram of an A / D board according to an embodiment of the present invention. This A / D board is different from the conventional A / D board shown in FIG. 4 in that the resistor connected to the operational amplifier AMP on the input side is not a variable resistor VR but a fixed resistor. A memory MEM including an area M1 for storing a correction value of the board itself and an area M2 for storing a correction value of the PCT itself is provided.
The point is that it has a 2C terminal. An NVRAM (non-volatile RAM) including an EPROM and an EEPROM is used as the memory MEM, and the stored state is maintained even when the power supply is stopped when the board is replaced.

The A / D board correction values in the area M1 of the memory MEM are individually obtained when the board is shipped from the factory, and are written via the RS232C. Also, the PCT correction values of the area M2 are individually stored via the RS232C. FIG. 2A shows P at the time of factory shipment.
This shows a connection state of each device when obtaining a CT correction value. As the PCT, a PCT that is newly installed or a PCT that is newly installed at the time of replacement is used, and the A / D board has already been adjusted and the A / D board correction value is stored in the area M1. An A / D board 4 is used. A signal obtained by appropriately amplifying the output of the reference oscillator 1 by the amplifier 2 is input to the primary side of the PCT as a reference value.
The secondary output is output to the measuring device 5 through the adjusted A / D board 4. In such a connection state, if the reference value is 1
00V, the output of the measuring instrument 5 is 101 V, the voltage amplification factor of the adjusted A / D board 4 is 1, and the turns ratio of CT3 is 1.
Then, the PCT3 correction value becomes 100/101.

FIG. 2B shows a connection state when a correction value of the unadjusted A / D board 4 is obtained. In this case, the adjusted PCT3, that is, the PCT correction value is known, and the value has already been stored in the area M2 of the memory MEM of the A / D board 4. In such a connection state, if the reference value is 100 V and the output of the measuring device 5 is 101 V, the correction value of the A / D board 4 is 100/101.

In the examples shown in FIGS. 2A and 2B, the output of the measuring device 5 is an analog value (101 V), but is actually an A / D converted digital value.

As described above, when the PCT is newly arranged or when the PCT is replaced, the PCT correction value is obtained in the connection state shown in FIG. 2A, and when the A / D board is replaced, the PCT correction value is obtained. A correction value of the A / D board is obtained in the connection state shown in FIG. The PCT correction value and the A / D board correction value obtained in this way are the A / D values that are actually located on site.
The data is written to the memory MEM of the board via the RS232C.

Next, a procedure for replacing an A / D board or replacing a PCT will be described with reference to FIG.

FIG. 3A is a flowchart showing a procedure at the time of replacing the A / D board.

First, in ST1, a correction value of a new A / D board to be newly attached is measured. This correction value is measured by the connection shown in FIG. This measured value is stored in area M1 of memory MEM in ST2.
232C. Next, in ST3, the PCT correction value of the old A / D board is read out via the RS232C. The read PCT correction value is written to the area M2 of the memory MEM of the new A / D board in ST4. Further, a new A / D board is attached in ST5. Note that writing and reading of correction values to and from the memory MEM can be easily performed by connecting a personal computer or the like to the RS232C.

According to the above procedure, all operations can be performed at an arbitrary place such as a factory instead of at the site.
Since the CT correction value is automatically transferred to the new A / D board, there is no need to measure the entire correction value with the new A / D board attached. For this reason, the operation becomes extremely simple.

FIG. 3B shows a procedure at the time of PCT exchange.

In this case, in step ST10, the correction value of the new PCT is measured by the connection shown in FIG. This measured value is written in the area M2 of the memory MEM, and then a new PCT is attached (ST12).

As described above, the memory MEM has the A / D
Since the correction value of the board itself and the correction value of the PCT are individually stored and can be arbitrarily written or read via the RS232C, the A / D
New A on site when replacing board or PCT
There is no need to make overall adjustments with the / D board or new PCT installed, each can be adjusted independently at a distant place such as a factory, and the correction value of the PCT or A / D board that is not replaced is Memory MEM of old A / D board
, And transfer and write to a new A / D board, it is possible to maintain high accuracy even at the time of replacement.

In the above-described embodiment, the replaceable device is an A / D board. However, a board including a signal analysis unit and the like may be used as long as the board has at least an A / D conversion unit. Good. In addition, a storage medium driving unit such as a floppy disk can be used for the input / output interface in addition to the RS232C.

[0023]

According to the present invention, when exchanging a signal processing device having an A / D converter or exchanging PT or CT,
There is no need to go to the site and make adjustments, which has the effect of greatly improving workability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an A / D board according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing connection states when measuring a PCT correction value and an A / D board correction value.

FIG. 3 (A) (B) A / D board replacement and PCT
9 is a flowchart showing a procedure at the time of replacement.

FIG. 4 is a diagram showing a configuration of a conventional A / D board.

Claims (1)

[Claims] An A / D converter for A / D converting the output of a PT or CT.
A signal processing device including a / D conversion unit and exchangeably provided in the measuring device, wherein a correction value for an external circuit including the PT or CT and a correction value for an internal circuit of the signal processing device itself are stored. A signal processing apparatus comprising: a correction value storage unit for performing the correction; and an input / output interface unit for writing or reading the correction value.