JPH0628748U - Non-contact AC voltmeter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a non-contact AC voltmeter for measuring AC voltage on the wire coating. [Structure] The non-contact AC voltmeter includes a pickup 1 covering a coating 7 of an AC commercial line 6, a shield 2 covering the pickup 1, and two resistors 3 and 4 connected in series between the pickup 1 and ground. And an operational amplifier 5 whose input side is connected to the connection point 8 of the two resistors 3 and 4 and whose output side is connected to the shield 2 and whose amplification degree is equal to the reciprocal of the voltage division ratio of the two resistors 3 and 4. The output of the amplifier 5 is the measurement point.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an AC voltmeter.

[0002]

[Prior art]

 Conventionally, AC commercial voltage has been measured using a transformer (Fig. 3) or a resistor (Fig. 4).

[0003]

[Problems to be solved by the device]

 All of the above-mentioned conventional AC voltage measuring methods have a problem in safety because they connect a transformer or a resistor to the AC commercial voltage line.

An object of the present invention is to provide a non-contact AC voltmeter that measures an AC voltage over a wire coating.

[0005]

[Means for Solving the Problems]

 The non-contact AC voltmeter of the present invention comprises a pickup covering a coating of an AC voltage line, a shield covering the pickup, two resistors connected in series between the pickup and ground, and two input sides of the two resistors. The operational amplifier is connected to the connection point of the resistor, the output side is connected to the shield, and the multiplication factor is equal to the reciprocal of the voltage division ratio of the two resistors.

[0006]

[Action]

 Since the AC voltage is measured from the wire coating, it is highly safe.

[0007]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a non-contact AC voltmeter according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram thereof.

A pickup 1 is covered on the coating 7 of the _AC commercial line 6 (AC voltage V _AC ) and a shield 2 is covered on the pickup 1. A resistor 3 and a resistor 4 are connected in series with each other between the pickup 1 and the ground. The input side of the operational amplifier 5 is connected to the connection point of the resistors 3 and 4, and the output side of the operational amplifier 5 is connected to the shield 2. Here, the apparent capacitance between the AC commercial line 6 and the pickup 1 is C ₁ , the apparent capacitance between the pick-up 1 and the shield 2 is C ₂ , and the capacitance between the shield 2 and the ground is C ₃ . The resistance values of the resistors 3 and 4 are R ₁ and R ₂ , respectively. The potential V ₂ at the connection point 8 of the resistors 3 and 4 _{V 2 = {R 2 / (} R 1 + R 2)} × V AC = ATT × V AC However, ATT≡R ₂ / in (R ₁ + R ₂₎ is there. Here, the amplification degree of the operational amplifier 5 is set to 1 / ATT. Was although I, the output voltage V ₃ of the operational amplifier 5 is _{V 3 = V 2 × (1} / ATT) = ATT × V AC × (1 / ATT) = V AC. Since the potential V ₁ = V ₃ of the pickup 1, the capacitance C ₂ between the pickup 1 and the shield ₂ is apparently absent. Therefore, the AC voltage V _AC can be accurately measured from the output voltage V ₃ of the operational amplifier 5.

[0010]

[Effect of device]

 As described above, the present invention has an effect that the AC voltage can be safely measured by non-contactly measuring the AC voltage using the pickup, the shield, the resistor, and the operational amplifier.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a non-contact AC voltmeter according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the non-contact AC voltmeter of FIG.

FIG. 3 is a diagram showing an example of a conventional method of measuring an AC voltage.

FIG. 4 is a diagram showing an example of a conventional method of measuring an AC voltage.

[Explanation of symbols]

1 pickup 2 shield 3,4 resistance 5 operational amplifier 6 AC commercial line 7 coating 8 connection point between resistance 3 and resistance 4 V _AC AC voltage R ₁ , R ₂ resistance values V ₁ , V ₂ , V ₃ voltage C ₁ , C ₂ , C ₃ capacity

Claims (1)

[Scope of utility model registration request] 1. A pickup covering an AC voltage line, a shield covering the pickup, two resistors connected in series between the pickup and ground, and an input side at a connection point of the two resistors. Connected,
An output amplifier connected to the shield and having an amplification degree equal to the reciprocal of the voltage division ratio of the two resistors;
A non-contact AC voltmeter whose output is the measurement point of the operational amplifier.