JPS6375571A - Processing method for offset value or the like - Google Patents

Abstract

PURPOSE:To easily process an offset value, etc., by measuring the offset value at a place where a current is zero and storing this offset value in an MPU. CONSTITUTION:A clamp meter is powered on by proper operation first. Then the offset value is measured by specific switching operation by a program in the MPU 14 at a place where there is neither a power source nor a magnetic field present, and the value is stored as a variable A. Then, a body to be measured is measured by an input part 10 and its measurement signal is converted by a range switching part 12 to a proper level. Then the measured current value digitized through an A/D converting circuit 13 is stored as a variable B in the MPU 14. Then, the MPU 14 subtracts the value of the variable A from the value of the variable B according to a relational equation measured current = real current + offset value, etc., thereby finding the real current value. Then, the arithmetic result is stored as a variable C, which is displayed 16 of an LCD display circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for processing offset values and the like in a crank fleet for direct current measurement.

(Prior art) Conventionally, for example, when measuring current using a Hall element,
Measurements are made using the Hall effect, which generates an electromotive force proportional to the strength of the magnetic field when a current and a magnetic field are present at a specific position. However, with a clamp meter, etc., even when the current is zero,
There is residual magnetism in the core of the clamp, which generates a minute voltage, and a minute voltage, or offset voltage, is input from the amplifier that amplifies the electrical signal from the Hall element.
Because it is amplified, errors may occur in the current measurement value.

The values of such minute voltages and offset voltages due to residual magnetism change when the usage environment such as temperature changes.

Therefore, offset values that cause measurement errors should be canceled out. Conventional clamp meters use a method in which a variable resistor is installed and adjusted each time the measurement is made to bring the offset value to zero.

(Problems to be Solved by the Invention) However, the above-mentioned method for processing offset/nod values, etc. has the following problems.

When adjusting the offset value etc. to zero by inserting a variable resistor as mentioned above, it is mechanically very difficult to operate the variable resistor to make the offset value completely zero. Everyone knows from experience that it is difficult.

Therefore, there is a problem in that complete zero adjustment of offset values and the like cannot be performed in a timely manner.

Further, in the conventional product, it is necessary to perform zero adjustment every time a measurement is made and every time a range is changed, so there is a problem that it is inefficient.

Therefore, an object of the present invention is to provide a method for processing offset values and the like that can easily process offset values and the like.

(Means for solving problems) In order to solve the above problems, the present invention has the following configuration.

That is, in a method for processing the offset value of a clamp meter for DC current measurement using a microprocessor and the voltage generated by residual magnetism, the offset value, etc. is measured at a location where the current is zero, and the offset value, etc. is transmitted to the MPU.
The method is characterized in that the object to be measured is stored, the object to be measured is measured, the stored offset value, etc. is subtracted from the measured value, and the result of the subtraction is used as an output value.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In this embodiment, an example will be described in which current is measured using a clamp meter equipped with a microprocessor.

First, the configuration of the clamp meter will be described based on the block diagram shown in FIG.

Reference numeral 10 denotes an input section, and the input section is formed by a pair of cores each having a Hall element arranged thereon.

Reference numeral 12 denotes a range switching section, which is composed of a suitable amplifier and amplifies the electrical signal generated at the input section 10 to a predetermined magnitude.

13 is an A/D converter, which converts the input value into numerical values.

14 is an MPU, the operation of which will be described later,
Data record 1. a. Controls calculations and control.

Reference numeral 16 denotes an output section, which outputs and displays the correction values output at M P t and J I 4. The display device uses an LCD.

18 is a power supply section.

Next, the operation will be explained with reference to the flowchart shown in FIG.

First, turn on the power to the clamp meter by performing appropriate operations.

Next, in order to measure the minute voltage and offset value due to the magnetism remaining in the core constituting the input section 10 of the clamp meter, the offset value, etc. is measured by operating a predetermined switch in a place where there is no power supply or magnetic field. The measured offset value and other values are stored in variable A. This control is performed by the MPU 14 according to a program written in advance.

Next, in order to measure the object to be measured, which is the original purpose, measurement is performed at the input section 10, and the measured signal is sent to the range switching section 1.
The measured current value converted into an appropriate level in step 2 and digitized through the Δ/D converter 13 is stored in a variable B by the MPU 14.

In the clamp meter of this example, zero adjustment is not performed in advance to cancel the offset value, etc., so the formula (ij [lI constant current) - (true current) → - (offset value, etc.) is established. do. Therefore, the true current to be determined is (true current) - (measured current) - (offset value, etc.), and the MPU 14 is caused to perform an operation to subtract the value of variable A from the value of variable B. Store the calculation result in variable C, and
Display the value on the LCD display circuit.

According to the method for processing offset values, etc. according to the present invention, instead of using a conventional method of canceling offset values, etc. to zero using a variable resistor, or more precisely near zero, the offset values, etc. are memorized, Since the method of processing by calculation is used, it is possible to display a corrected value, that is, a true value, which completely removes offset values and the like that cause errors in measured values.

Furthermore, according to this processing method, measurements such as off-set values only need to be performed once in the same environment (also, it is possible to measure not only current but also voltage, resistance, etc.).

Furthermore, it can be applied to measuring instruments other than clamp meters.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and many modifications can be made without departing from the spirit of the invention. Of course.

(Effects of the Invention) When the method for processing offset values, etc. according to the present invention is used, the offset values, etc., which were conventionally canceled by zero adjustment, are stored without being canceled and are subjected to arithmetic processing. This makes it possible to remove the error and display accurate values.

Furthermore, processing of offset values, etc., which were conventionally adjusted using variable resistors, can be easily performed, and an easy-to-use measuring instrument can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a clamp tester according to the present invention, and FIG. 2 is a flowchart showing a method of processing offset values and the like. 14...MPU. Figure 1 Figure 2 A, B, C: Variable 0/S゛offset

Claims (1)

[Claims] 1. In a method for processing offset values and voltages caused by residual magnetism of a clamp meter for DC current measurement using a microprocessor, the offset value, etc. is measured at a location where the current is zero, and the offset value, etc. is stored in the MPU, A method for processing an offset value, etc., characterized by measuring an object to be measured, subtracting the stored offset value, etc. from the measured value, and using the result of the subtraction as an output value.