JP2003028900A - Non-contact voltage measurement method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a complex circuit configuration since an oscillator for allowing a current for measuring coupling capacity formed by a conductor and a detection probe to flow is required. SOLUTION: At least two capacitors having different capacitances are connected between a detection probe and a common potential point. A voltage to be measured is divided by a voltage-dividing circuit composed of coupling capacity formed between the detection probe and a conductor where a voltage to be measured is applied. The coupling capacity is calculated from the voltage that is divided when the capacitor is changed. Then, the voltage to be measured is obtained from the coupling capacity, thus measuring a voltage without any contact and simplifying a circuit configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device used for measuring various signals, and a non-contact voltage measuring method for measuring by using a detection probe insulated from the conductive part of a circuit under test. It relates to the device.

[0002]

2. Description of the Related Art When measuring an AC voltage applied to a conductor in an electric wire covered with an insulating coating, it is advantageous in safety that a probe can be applied to the coating without breaking the insulating coating, And it can be easily measured.

An invention of a method and apparatus for measuring an AC voltage applied to a conductor from such an insulating coating is described in Japanese Patent No. 3158063. The present invention will be outlined below.

FIG. 4 shows the configuration of such an AC voltage measuring device. In FIG. 4, reference numeral 71 is an AC signal to be measured, which has a voltage of Ex. Reference numeral 72 represents an electric wire coated with insulation to which the AC signal 71 is applied. Reference numeral 73 is a detection probe, and Cx is the value of the coupling capacitance formed with the conductor in the electric wire 72. Reference numeral 8 is an AC voltage measuring device to which the detection probe 73 is connected, and measures and displays the AC voltage.

FIG. 5 shows an example of the detection probe. In FIG. 5, 731 is a probe main body, and two probe main bodies 731 are arranged to face each other. The measurement is performed by sandwiching the electric wire 72, which is insulated by the two probe bodies 731.

FIG. 6 is a block diagram of the AC voltage measuring device 8. The measurement principle will be described based on this configuration diagram. First, the switch 83 is set to the A side, and the insulating coated electric wire 72 is sandwiched between the detection probes 73. A signal current Is of a predetermined frequency flows from the oscillator 84 to the detection probe 73 through the resistor 81.

The current detecting unit 82 detects the voltage across the resistor 81, the filter unit 85 extracts only the output frequency component of the oscillator 84 to obtain the value of the signal current Is, and the coupling capacitance value Cx is calculated from this value. To do.

Next, the switch 83 is set to the B side. Due to the voltage Ex of the AC signal 71, the current Ix flows through the capacitor Cx and the resistor 81 to the common potential point. Resistance 8 at this time
The voltage between both ends of 1 is measured by the current detection unit 82, and the filter unit 8
In step 5, only the frequency component of the AC signal 71 is passed to calculate the current Ix caused by the AC signal 71. Since the value of the coupling capacitance Cx is known as described above, this current Ix
The voltage Ex of the AC signal 71 can be obtained from the value of.

By doing so, the voltage applied to the conductor from above the insulation coating can be measured without breaking the insulation coating, so that the AC voltage can be simply and safely measured.

[0010]

However, such an AC voltage measuring device has the following problems.

To determine the coupling capacitance Cx, the oscillator 84
Therefore, a predetermined voltage signal is applied to the detection probe. Therefore, the oscillator 84, the filter unit 85, and the like are required, and there is a problem that the configuration becomes complicated.

Therefore, the problem to be solved by the present invention is
An object of the present invention is to provide a non-contact voltage measuring method and a device having a simple structure and capable of non-contact measuring an AC voltage.

[0013]

In order to solve such a problem, the invention according to claim 1 of the present invention is a method for measuring an AC voltage in a non-contact manner, the method including coupling between a conductor and a conductor. The detection probe is arranged so that a capacitance is formed, and capacitors 13, 14 are provided between the detection probe and the common potential point.
Is connected, the voltage applied to the conductor is divided by the coupling capacitance Cx, the divided voltage is detected, and the capacitors 13 and 14 are switched to determine the divided voltage value at that time. The coupling capacitance Cx is obtained, and the voltage applied to the conductor is obtained from the value of the coupling capacitance Cx. Non-contact measurement is possible without breaking the insulation.

According to a second aspect of the present invention, there is provided a non-contact voltage measuring device which measures the voltage applied to the conductor in a non-contact manner.
A detection probe arranged so as to form a coupling capacitance with the conductor, at least two capacitors 13 and 14 having different capacitance values, and these capacitors 13 and 14 are selectively connected to the detection probe and a common potential point. And a high input impedance amplifier 2 to which the voltage at the connection point between the detection probe and the capacitors 13 and 14 is input.
4 is selectively connected between the detection probe and the common potential point, the value of the coupling capacitance Cx is obtained from the value of the output voltage of the high input impedance amplifier 2 at that time, and the value of this coupling capacitance Cx is calculated. It is used to measure the voltage applied to the conductor. Non-contact measurement is possible without breaking the insulation.

According to a third aspect of the invention, in the second aspect of the invention, a bootstrap circuit is used as the high input impedance amplifier 2. A high input impedance amplifier can be easily constructed.

According to a fourth aspect of the present invention, there is provided a device for measuring an AC voltage in a non-contact manner, wherein the detection probe is arranged so that a coupling capacitance is formed between the detection probe and at least two capacitance values. The capacitors 13 and 14, the selection means 15 that selectively connects the capacitors 13 and 14 to the detection probe and the common potential point, and the voltage applied to the conductor divided by the detection probe and the capacitors 13 and 14. Has an A / D converter 4 for converting the digital signal into a digital signal, an arithmetic unit 5 to which the output of the A / D converter 4 is input, and a display unit 6 to which the output of the arithmetic unit 5 is input, The calculation unit 5 calculates the value of the coupling capacitance Cx from the input value, calculates the voltage applied to the conductor from this coupling capacitance Cx, and displays it on the display unit 6. Non-contact measurement is possible without breaking the insulation.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the non-contact voltage measuring device according to the present invention. In FIG. 1, 1 is an input unit, and 2 is a bootstrap circuit to which the output of the input unit 1 is input. The output of this bootstrap circuit becomes the measured voltage value.

The input section 1 includes a coupling capacitance 12 and a capacitor 1.
3, 14 and a switch 15. Reference numeral 11 is an input terminal to which the detection probe described with reference to FIG. 5 is connected. Reference numeral 12 represents the coupling capacitance formed between the detection probe and the electric wire coated with insulation, and Cx represents the capacitance value.

Reference numerals 13 and 14 are capacitors having capacitance values of C1 and C2, respectively, one end of which is connected to the side opposite to the input terminal 11 of the coupling capacitance 12, that is, the detection probe, and the other end of which is the contact A of the switch 15. , Connected to the same B. The common contact C of the switch 15 is connected to the common potential point.

The bootstrap circuit 2 comprises resistors 21 and 22, a capacitor 23 and an amplifier 24. The resistors 21 and 22 are connected in series, the output of the input unit 1 is applied to one end of this common connection circuit, and the other end is connected to a common potential point.

The input section 1 is connected to the non-inverting input terminal of the amplifier 24.
Is applied. That is, it is connected to the side of the series circuit of the resistors 21 and 22 that is not the common potential point side. The output terminal and the inverting input terminal of the amplifier 24 are commonly connected, and the capacitor 23 is connected between the common connection point and the connection point of the resistors 21 and 22.

With such a configuration, the input impedance of the bootstrap circuit 2 becomes a very high value due to the feedback effect. That is, the operation of the input unit 1 is not affected by the connection of the bootstrap circuit 2.

Next, the operation of this embodiment will be described. Note that the gain of the bootstrap circuit 2 is set to 1 for simplicity. First, the common contact C of the switch 15 is set to the contact A side. At this time, the input voltage Ex is the coupling capacitance 1
Since the voltage divided by 2 and the capacitor 13 is input to the bootstrap circuit 2, its output voltage Vout1 is

[Equation 1]

It becomes The coupling capacitance value is Cx, and the capacitance value of the capacitor 13 is C1. j is an imaginary unit, and ω is the angular frequency of the input signal.

From this equation,

[Equation 2]

Is obtained.

Next, the common contact C of the switch 15 is connected to the contact B.
Set to the side. Assuming that the output voltage of the bootstrap circuit 2 at this time is Vout2, in the same manner as the equation (1),

[Equation 3]

From this equation (3), the following equation (4) is obtained.

[Equation 4]

If the right sides of the equations (2) and (4) are equal,

[Equation 5] Is obtained, and by rearranging this equation (5),

[Equation 6] Is guided.

That is, since the capacitance values of the capacitors 13 and 14 are known, from the output Vout1 of the bootstrap circuit 2 when the capacitor 13 is connected and the output Vout2 of the bootstrap circuit 2 when the capacitor 14 is connected, The coupling capacitance value Cx can be obtained by the equation (6).

Further, by substituting the coupling capacitance Cx into the equation (2) or the equation (4), the voltage Ex of the input signal can be calculated.

FIG. 2 shows the output Vou of the bootstrap circuit 2 when the coupling capacitance Cx and the measured AC voltage are changed.
The measured values of t1 and Vout2 and the coupling capacitance Cx and the voltage Ex of the input signal calculated by the measured values are shown. In addition,
The capacitance value C1 of the capacitor 13 is 100 PF, and the capacitance value C2 of the capacitor 14 is 1000 PF.

The portion surrounded by a double line on the right side of FIG. 2 is the actual values of the coupling capacitance Cx and the input signal Ex. Conditions 1 to 3 set the coupling capacitance Cx to 1PF and the input voltage to 100 to 300V.
When changing to rms, the conditions 4 to 6 set the coupling capacitance Cx to 1
This is a case where the input voltage is changed to 100 to 300 Vrms with 0PF.

The left column of FIG. 2 shows the measured values of the output voltages Vout1 and Vout2 of the bootstrap circuit. Vout2 is about 1/10 of Vout1, and the reason is the above formula (1),
It is clear from the equation (3).

The second column from the left in FIG. 2 shows the value of the coupling capacitance Cx obtained from the equation (6), which is almost constant even if the value of the input voltage changes.

The third column from the left in FIG. 2 shows the value of the input voltage Ex obtained from the equation (2).

FIG. 3 is a block diagram showing another embodiment of the non-contact voltage measuring device shown in FIG. In FIG. 3, 3 is an input circuit, for example, the non-contact voltage measuring device of FIG. 1 is used. An A / D converter 4 converts the output voltage of the input circuit into a digital signal.

Reference numeral 5 denotes a calculation unit, which receives the output of the A / D converter 4 and performs the calculation of the equation (6) to obtain the coupling capacitance Cx.
Is calculated, and the voltage value of the input signal is calculated using the equation (2) or the equation (4). A display unit 6 displays the voltage value calculated by the calculation unit 5.

Although the output of the input unit 1 is input to the bootstrap circuit 2 in FIG. 1, the output is not necessarily the bootstrap circuit. Any amplifier or impedance conversion circuit having a high input impedance to the extent that the operation of the input unit 1 is not affected may be used.

Although the switch 15 is switched between the capacitor 13 and the capacitor 14 on the common potential side in FIG. 1, the switch may be switched on the detection probe side, or both of them may be switched. The point is that the capacitor can be selectively connected between the detection probe and the common potential point.

Although the number of capacitors to be switched is two in the embodiment of FIG. 1, three or more may be used. In this case, a plurality of values of the coupling capacity can be obtained, but if statistical processing or the like is performed, improvement in accuracy can be expected.

The detection probe may be made of a metal conductor when the voltage of the insulated conductor is measured, but the detection probe itself may be insulated when it is brought into direct contact with the conductor. Thus, various configurations are possible.

Further, in the embodiment of FIG. 3, if the input impedance of the A / D converter is sufficiently high, the high input impedance circuit such as the bootstrap circuit 2 of FIG. 1 can be omitted.

[0044]

As is apparent from the above description,
According to the present invention, the following effects can be expected. According to the invention of claim 1, there is provided a non-contact voltage measuring method for measuring a voltage applied to a conductor in a non-contact manner, wherein the detection probe is arranged so that a coupling capacitance is formed between the conductor and the conductor. Capacitors 13 and 14 are connected between the detection probe and the common potential point, the voltage applied to the conductor is divided by the capacitors 13 and 14 and the coupling capacitance Cx, and the divided voltage is detected. Then, the capacitors 13 and 14 are switched to obtain the coupling capacitance Cx from the value of the divided voltage at that time, and the voltage applied to the conductor is obtained from the value of the coupling capacitance Cx.

Since the voltage can be measured in a non-contact manner without breaking the insulation, there is an effect that the voltage can be easily measured. In addition, since it is not necessary to expose the conductor portion and the coupling capacitance of the detection probe is small, the flowing current is very small, so there is little risk of electric shock, and there is an effect that measurement can be performed safely.

Further, since the measurement can be made only by the current flowing through the coupling capacitance formed by the conductor to be measured and the detection probe, the oscillator for flowing the current as in the conventional example is not necessary, so that the circuit becomes unnecessary. There is also an effect that the configuration is simple and that even a circuit under test having high impedance can be accurately measured.

According to a second aspect of the present invention, there is provided a non-contact voltage measuring device for measuring a voltage applied to a conductor in a non-contact manner, the non-contact voltage measuring device being arranged so that a coupling capacitance is formed between the conductor and the conductor. The detection probe, at least two capacitors 13 and 14 having different capacitance values, and these capacitors 13 and 1
Selection means 15 for selectively connecting 4 between the detection probe and the common potential point, and the detection probe and the capacitors 13, 1
4 and a high input impedance amplifier 2 to which the voltage at the connection point with 4 is input, and the capacitor 1 is selected by the selecting means 15.
One of 3, 14 is selectively connected between the detection probe and the common potential point, the value of the coupling capacitance Cx is obtained from the value of the output voltage of the high input impedance amplifier 2 at that time, and the coupling capacitance Cx The value is used to measure the voltage applied to the conductor. Non-contact measurement is possible without breaking the insulation.

Since the voltage can be measured in a non-contact manner without breaking the insulation, there is an effect that the voltage can be easily measured. Further, it is not necessary to expose the conductor portion, and since the detection probe has a small coupling capacitance, the current that flows is very small, so there is little risk of electric shock, and there is the effect that measurement can be performed safely.

Further, since the measurement can be made only by the current flowing through the coupling capacitance formed by the conductor to be measured and the detection probe, the oscillator for flowing the current as in the conventional example becomes unnecessary, so that the circuit becomes unnecessary. There is also an effect that the configuration is simple and that even a circuit under test having high impedance can be accurately measured.

According to the invention of claim 3, in the invention of claim 2, a bootstrap circuit is used as the high input impedance amplifier 2. There is an effect that a high input impedance amplifier can be easily configured.

According to a fourth aspect of the present invention, there is provided a non-contact voltage measuring device for measuring a voltage applied to a conductor in a non-contact manner, the non-contact voltage measuring device being arranged so that a coupling capacitance is formed between the conductor and the conductor. The detection probe, at least two capacitors 13 and 14 having different capacitance values, selection means 15 for selectively connecting the capacitors 13 and 14 to a common potential point with the detection probe, and the detection probe and the capacitors 13 and 14. An A / D converter 4 for converting the voltage applied to the voltage-divided conductor into a digital signal, an arithmetic unit 5 to which the output of the A / D converter 4 is input, and an output of the arithmetic unit 5 are input The display unit 6 is provided, and the calculation unit 5 calculates the coupling capacitance C from the input value.
The value of x is obtained, and the voltage applied to the conductor is obtained from this value and displayed on the display unit 6. Non-contact measurement is possible without breaking the insulation.

Since the voltage can be measured in a non-contact manner without breaking the insulation, there is an effect that the voltage can be easily measured. Further, it is not necessary to expose the conductor portion, and since the detection probe has a small coupling capacitance, the current that flows is very small, so there is little risk of electric shock, and there is the effect that measurement can be performed safely.

Further, since the measurement can be performed only by the current flowing through the coupling capacitance formed by the conductor to be measured and the detection probe, the oscillator for flowing the current as in the conventional example is not required, so that the circuit is not necessary. There is also an effect that the configuration is simple and that even a circuit under test having high impedance can be accurately measured.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a table showing the measurement results of one example of the present invention.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional non-contact voltmeter.

FIG. 5 is a configuration diagram of a detection probe.

FIG. 6 is a diagram for explaining the operating principle of a conventional non-contact voltmeter.

[Explanation of symbols]

1 Input section 12 coupling capacity 13, 14 capacitors 15 switch 2 Bootstrap circuit 3 input circuits 4 A / D converter 5 computing section 6 Display

Claims (4)

[Claims] 1. A non-contact voltage measuring method for measuring a voltage applied to a conductor in a non-contact manner, wherein a detection section probe is arranged so as to form a coupling capacitance with the conductor, and is common to the detection probe. A capacitor is connected between the potential point and the capacitor and the coupling capacitance to divide the voltage applied to the conductor, and the divided voltage is detected to change the value of the capacitor. The contactless voltage measuring method is characterized in that the coupling capacitance is obtained from the value of the divided voltage at that time, and the voltage applied to the conductor is obtained from the value of the coupling capacitance. 2. A non-contact voltage measuring device for measuring a voltage applied to a conductor in a non-contact manner, the detection probe being arranged so as to form a coupling capacitance with the conductor, and at least having a different capacitance value. Two capacitors, selection means for selectively connecting these capacitors between the detection probe and the common potential point, and a high input impedance amplifier to which the voltage at the connection point between the detection probe and the capacitor is input And one of the capacitors is selectively connected between the detection probe and a common potential point by the selection means, and the coupling capacitance of the high input impedance amplifier is then calculated from the value of the output voltage of the high input impedance amplifier at that time. A non-contact voltage measuring device, wherein a value is obtained, and the voltage applied to the conductor is calculated using this coupling capacitance value. 3. The high input impedance amplifier,
The non-contact voltage measuring device according to claim 2, wherein a bootstrap circuit is used. 4. A non-contact voltage measuring device for measuring a voltage applied to a conductor in a non-contact manner, wherein at least a detection probe arranged to form a coupling capacitance with the conductor has a different capacitance value. Two capacitors, a selection means for selectively connecting the capacitors between the detection probe and the common potential point, and a voltage applied to the conductor divided by the detection probe and the capacitor as a digital signal. An A / D converter for converting to
The arithmetic unit has an arithmetic unit to which the output of the A / D converter is input and a display unit to which the output of the arithmetic unit is input. The arithmetic unit obtains the value of the coupling capacitance from the input value, A non-contact voltage measuring device, characterized in that the voltage applied to the conductor is obtained from the value of the coupling capacitance and displayed on the display unit.