JPH0142051Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a penholder-type voltage detector that detects whether or not an electrical object to be tested, such as an electric wire, is charged by bringing its end fitting into contact.

Generally, when working on electrical equipment, it is important to detect whether or not electric wires, electrical equipment, etc. are charged, for work safety, finding faults in electrical equipment, etc. Conventionally, as a voltage detector for detecting this, a neon discharge tube 2 and a current-limiting voltage resistor 3 are housed in an insulating cylinder 1, as shown in FIG.
There was one connected in series between the front end fitting 4 and the rear end fitting 5. This voltage detector 6 is used by grasping the metal clip 5' part integrated with the rear end metal fitting 5 and bringing the tip metal fitting 4 into contact with the electrical object to be tested.
It attempts to detect whether the electrical object to be tested is charged or not by looking at whether or not it is lit. This is an attempt to light up the neon discharge tube 3 by the current flowing from the electrical object to be tested to the ground through the ground resistance and ground capacitance generated when the human body grips the metal clip 5'. However, since the light emitted is weak, it is extremely difficult to confirm whether it is lit in bright places such as daytime or afternoon. Also,
Voltages up to around 50V must be detected as dangerous voltages, but since neon discharge tubes have the characteristic of not discharging below 80V, voltages between 50V and 80V cannot be detected, which satisfies the performance as a voltage detector. I couldn't do it. Furthermore, since neon discharge tubes are made of glass, they have the drawback of being weak against shock, easily broken, and prone to failure. Therefore, by improving this drawback, the second
As shown in the figure, there is one in which an amplifier 9 is connected to the end fitting 7 via a current-limiting withstand voltage resistor 8, and the output of the amplifier 9 is used to operate a display 10. This voltage detector 11 consists of a voltage detector 12, a metal tip 7, a current-limiting withstand voltage resistor 8, and a human body's ground resistance R ₀
The current flowing to the earth E through the ground capacitance C ₀ causes the amplifier 9 to generate an output, and the output operates the display 10 to detect whether or not the electrical body 12 to be tested is charged. As is clear from this operating principle, the magnitude of the current input to the amplifier 9 is determined by the current withstand voltage resistor 8, which limits the ground voltage of the electrical body 12 to be tested, and the human body's ground resistance _R0. It is determined by the value divided by the combined impedance of ground capacitance C ₀ . However, the ground resistance R ₀ and ground capacitance C ₀ of the human body vary greatly depending on the usage conditions of the voltage detector 11 , ie, how the voltage detector is held, whether gloves are worn, the type of footwear, etc. For this reason, even if the ground voltage is the same, the current input to the amplifier 9 varies, and the detection operation may or may not be performed. In other words, the minimum voltage that the voltage detector 11 can detect varies greatly depending on the conditions of use, and this instability poses a problem when using this voltage detector. In order to eliminate this instability, it is conceivable to make the value of the current-limiting withstand voltage resistor 8 very large to reduce the influence of changes in the human body's ground resistance R ₀ and ground capacitance C ₀ . However, in this case, since the value of the current flowing through the amplifier 9 becomes small, the amplification sensitivity must necessarily be increased. However, when trying to increase the amplification degree of amplifier 9,
An output is generated in the amplifier 9 by electrostatic induction from a nearby charged body 13 other than the electrical object 12 to be tested, and the electrical object 12 to be tested is
The disadvantage is that there is a high risk that the voltage detector will erroneously indicate charging when the battery is not charged.

Furthermore, when designing an amplifier used for this purpose and trying to store it in a small carrying case, such as a fountain pen-shaped cylindrical case, the mounting space for the power switch and the mounting structure for the power supply battery become problems. Become. In other words, in normal amplifiers, operating current flows even when there is no human input signal, so it is necessary to install a power switch to shut off the power when not in use, which increases the installation space and reduces battery life if you forget to turn off the power switch. wear-out accidents are likely to occur. In addition, in a voltage detector, grounding is performed by grasping the rear end metal fitting and using the human body's ground resistance and ground capacitance, but it is recommended to use this rear end metal fitting as a battery storage case for structural reasons and for convenience in putting in and taking out batteries. It's advantageous. However, in ordinary amplifiers, one end of the input side cannot be directly coupled to the power supply, so this cannot be achieved, and this has been an obstacle to miniaturization.

Therefore, in view of the above-mentioned conventional drawbacks, and in order to improve and eliminate this, the present invention exhibits bidirectional symmetrical negative resistance characteristics for applied voltages above the breakover voltage, and exhibits bidirectional symmetrical negative resistance characteristics for applied voltages below the breakover voltage. By interposing a semiconductor element for voltage level detection, such as a bidirectional diode (trigger diode) with high insulation resistance characteristics, in the front stage of the amplifier, the minimum detection voltage is stabilized, and after detection starts, the amplifier It is an object of the present invention to provide an amplifier that can provide sufficient current and is suitable for an electroscope.

That is, as shown in FIG.
A voltage level detection semiconductor element TD such as a trigger diode having a breakover voltage of 50 V, for example, and an amplifier A to be described later are connected in series, and the output of the amplifier A lights up the display 10, for example, a light emitting diode. did. Next, to explain the configuration of amplifier A, _R1 is a voltage detection resistor inserted between input terminal A and ground of the amplifier, and _Tr1 is a resistor with an emitter connected to input terminal A and a base connected to ground. The first transistor, Tr ₂ , is the second transistor whose base is connected to the input terminal A and the emitter is connected to the earth terminal. R ₂ and R ₃ are resistors, which are connected in series to form a voltage dividing resistor R' A current supplied from one end C is supplied to the first transistor Tr ₁ and the second transistor Tr ₂ from the connection point D and the other end E. Tr ₃ is the first stage transistor of the buffer circuit B for amplifying the voltage generated at the connection point N of the voltage dividing resistor R' and driving the display 10, and has the opposite polarity to the previous stage transistors Tr ₁ and Tr ₂ . are used. Tr ₄ is the output stage transistor of the same buffer circuit B, R ₄ and R ₅ are voltage dividing resistors, C ₁ is a smoothing capacitor, R ₆ is a resistor for limiting the display current, 16 is a rear end metal fitting, and 17 is a rear end. A power battery has one electrode connected to the end fitting, 18 is a metal clip connected to the rear end fitting, 19 is an operation test switch, and _R7 is a resistor for limiting the operation test current.

Further, an example of the assembly structure of this voltage detector 14 is shown in FIG. In the figure, 15 is a fountain pen-shaped cylindrical case made of insulating resin, 7 is a tip fitting embedded in the tip, 8 is a current-limiting withstand voltage resistor connected to the tip fitting, and TD is A semiconductor element for voltage level detection, 9 an amplifier, 10 a light emitting diode serving as an indicator, 16 a rear end metal fitting serving as a battery storage section, 17 a power source battery, 18 a metal clip coupled to the battery storage section, 19 is an operation test switch.

The operation of this voltage detector 14 is as follows. When the rear end of the voltage detector 14 is grasped, the earth side B of the amplifier A is grounded by the human body's ground resistance R ₀ and ground capacitance C ₀ . Here, the tip metal fitting 7 of the voltage detector 14 is brought into contact with the voltage object 12 to be tested. Then, the ground voltage of the charged electric object 12 to the ground changes between the current-limiting withstand voltage resistor 8 and the voltage level detection semiconductor element.
It is applied to a series circuit of TD, the voltage detection resistor R ₁ of amplifier A, and the ground impedance of the human body. However, in the non-conducting state, the voltage level detection semiconductor element TD has an extremely high resistance compared to other elements, and most of the voltage is applied to the voltage level detection semiconductor element TD. Then, the presence or absence of charging is determined almost unaffected by the human body's impedance to ground. In other words, when the ground voltage of the electrical object to be tested is higher than the breakover voltage, the voltage level detection semiconductor element TD breaks over and becomes conductive, so the voltage detection resistor of amplifier A
A current flows through _R1 , and its amplified output lights up the light emitting diode 10, which is an indicator. In addition, when the ground voltage of the electrical object under test is lower than the breakover voltage, the voltage level detection semiconductor element
Since TD maintains a high resistance, no current flows through the voltage detection resistor _R1 of the amplifier A, and therefore the light emitting diode 10 serving as the indicator does not light up. The operation of the amplifier A when detecting the state of charge will be described in detail as follows.

First, consider a case where the electrical object 12 to be tested is charged to a positive voltage exceeding the breakover voltage. At this time, the voltage level detection semiconductor element TD becomes conductive.
Apply current to the voltage detection resistor _R1 and apply a positive voltage to input terminal A. Then, the first transistor Tr ₁ is non-conductive, and current flows from the base to the emitter of the second transistor Tr ₂ , making the second transistor Tr ₂ conductive. Then, since the potential at the connection point N of the voltage dividing resistor R' falls, the first stage transistor Tr ₃ of the buffer circuit B becomes conductive, and at the same time, the output stage transistor Tr ₄ also becomes conductive, and the display 10 turns on to indicate charging state detection. do. In addition, when the electric body 12 to be tested is charged to a voltage exceeding the breakover voltage, the second transistor Tr ₂ is non-conductive and the first transistor Tr ₁ is conductive, and the voltage dividing resistor R' is The potential at the connection point D is lowered, the buffer circuit B is operated in the same manner as described above, and the display 10 is turned on to detect the state of charge. With such an operation, it is possible to detect whether the electric body 12 to be tested is charged with an alternating current voltage or charged with a positive or negative direct current voltage. In addition, this circuit uses a voltage detection resistor R ₁ inserted between the input terminal A and earth ground.
The structure is such that when no current flows into the circuit, no current flows from the power supply battery 17 into the circuit. When the tip fitting 7 is not brought into contact with a charged object, no current flows and the power battery 17 is not consumed at all. Therefore, the power switch can be omitted, the voltage detector can be made more compact, and there is no risk of battery consumption caused by forgetting to turn off the power switch. Moreover, the power supply battery 17 has a structure in which one electrode is directly connected to the rear end metal fitting 16 and the metal clip 18, which is a grounding part A. For this reason, as shown in FIG. 4, it is possible to construct the rear end fitting 16 itself as a battery storage part by integrating the power contact and the metal lid 16', so that it can be easily inserted and removed from the rear end. can. In addition, press the operation test switch 19 and turn on the power battery 17.
By connecting the input terminal A of the amplifier A through the current limiting resistor _R7 , and checking whether the light emitting diode 10 is lit or not, you can easily check whether it is operating normally or not. Therefore, you can know the battery consumption. Further, although the display described above uses a light emitting diode, a display element such as a liquid crystal or an acoustic display means such as a speaker may be used.

As explained above, according to this invention, the minimum detection voltage can be set by the breakover voltage of the semiconductor element for voltage level detection such as a trigger diode, and after breakdown, the resistance of the semiconductor element for voltage level detection can be set. Since the current is extremely low and sufficient current can be supplied to the amplifier, there is no need for the amplifier to have a voltage level detection function and a high amplification function, and its detection operation becomes extremely stable. In addition, no operating current flows when the amplifier is not detected, and one electrode of the power battery is directly connected to the ground of the amplifier, so a power switch is not required and the rear end bracket can also be used as a battery storage case. Therefore, an extremely compact voltage detector can be provided. Furthermore, in this invention, since a semiconductor element is used for voltage level detection, the breakover voltage can be arbitrarily selected from a low voltage range to 80 V or less, which could not be detected using conventional neon discharge tubes. It can also detect low voltages, eliminating the fragility of neon discharge tubes. Furthermore, since we used a light emitting diode as an indicator,
It becomes a high-brightness, easy-to-read voltage detector.

[Brief explanation of the drawing]

Figure 1 is a side view of a conventional voltage detector using a neon discharge tube, Figure 2 is a block diagram of a conventional voltage detector using an amplifier, and Figure 3 is an embodiment of the voltage detector of the present invention. FIG. 4 is a side view showing the assembled structure of the voltage detector shown in FIG. 3. TD...Semiconductor element for voltage level detection, A...
Amplifier, R ₁ ... Voltage detection resistor, R' ... Voltage dividing resistor, Tr ₁ ... First transistor, Tr ₂ ... Second transistor, B ... Buffer circuit, Tr ₃
...First stage transistor, Tr ₄ ...Output stage transistor, R ₀ ...Resistance to ground, C ₀ ...Capacitance to ground,
A...Input terminal, B...Ground, D...Connection point of the voltage dividing resistor, E...Other end of the voltage dividing resistor, 7...Tip fitting, 8...Resistor for current limiting withstand voltage, 10... ...Indicator (light-emitting diode), 14 ...Voltage detector, 16...Rear end metal fitting, 17...Power battery, 18...Metal clip.

Claims (1)

[Scope of utility model registration request] The tip of the metal fitting that comes into contact with the electrical object to be tested is equipped with a current-limiting withstand voltage resistor, which exhibits bidirectional symmetrical negative resistance characteristics for applied voltages that are above the breakover voltage, and for applied voltages that are below the breakover voltage. is inserted between the input terminal and ground in a voltage detector in which a voltage level detection semiconductor element with high insulation resistance characteristics and an amplifier are connected in series, and the display is operated by the output of the amplifier. A voltage detection resistor, a first transistor whose emitter is connected to the input terminal and whose base is connected to ground, a second transistor whose base is connected to the input terminal and whose emitter is connected to ground, and two resistors. A voltage dividing resistor is configured by directly connecting the resistors, and supplies the power supply voltage from one end and the connection point thereof to the respective collectors of the first and second transistors. A voltage detector characterized in that the amplifier is constituted by a buffer circuit for obtaining a drive output and a battery having one electrode connected to ground.