JPH039022Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an improvement of a low-voltage penholder-type voltage detector that detects the presence or absence of charge in an electrical object to be tested, such as an electric wire, by bringing its end fitting into contact. It is.

[Conventional technology]

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, as shown in FIG. There was one connected in series between the metal fittings 5. This voltage detector 6 grasps the metal clip 5' portion integrated with the rear end metal fitting 5, brings the tip metal fitting 4 into contact with the electrical object to be tested, and checks whether or not the neon discharge tube 2 is lit. It attempts to detect whether the body is charged or not. 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 in broad daylight.

In addition, in order to clearly notify that dangerous voltage has been detected even when used in broad daylight, a neon discharge tube is used as a voltage detection element, and this discharge current is amplified using a voltage transformer and an amplifier. A danger alarm for high-pressure work that emits a sound is also known (Japanese Utility Model Publication No. 37-23374).

However, since all of the above devices use neon discharge tubes for voltage detection, voltages between 50V and 80V cannot be detected due to the neon discharge tube's principle of not discharging below 80V. Therefore, it cannot detect the voltage to ground of 50V specified in Article 354 of the Industrial Safety and Health Regulations, which is required as a low-voltage voltage detector.

The discharge characteristic of a neon discharge tube is that a discharge current flows in proportion to the extent to which the applied voltage exceeds the discharge starting voltage, and the operating point of the detection circuit such as an amplifier that operates in response to this discharge current is unstable. become.

If a neon discharge tube is left in the dark for a long time, the number of ions in the enclosed gas will decrease and the discharge starting voltage will rise to 2 to 3 times the standard value. does not return to the standard value, resulting in a lack of reliability.

Furthermore, since neon discharge tubes are made of glass, they are susceptible to shock and break easily, resulting in frequent failures.

There were some drawbacks.

As a measure to avoid using a neon discharge tube, as shown in FIG.
Although there is a device that operates the display device 10 with the output of , the operation is unstable as described below and is not suitable for practical use.

In other words, this voltage detector 11 outputs an output to the amplifier 9 by the current flowing from the voltage to be tested 12 to the earth E via the tip fitting 7, the current-limiting voltage resistor 8, the human body's earth resistance Ro and earth capacitance Co. The display device 10 is operated by the output, and the electrical object 12 to be tested is
This detects whether or not the battery 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 object 12 to be tested, the human body's ground resistance Ro, and the ground voltage. It is determined by the value divided by the combined impedance of capacitance Co. However, the ground resistance Ro and ground capacitance Co of the human body vary greatly depending on the usage conditions of the voltage detector 11, ie, the way the voltage detector is held, whether or not gloves are worn, the type of covering, etc. For this reason, even if the voltage to ground 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 lowest 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 Ro and ground capacitance Co. but,
In this case, since the value of the current flowing through the amplifier 9 becomes small, the amplification sensitivity of the amplifier 9 must necessarily be increased. However, when trying to increase the amplification degree of the amplifier 9, an output is generated in the amplifier 9 due to electrostatic induction from a nearby charged object 13 other than the electrical object 12 to be tested, and even though the electrical object 12 to be tested is not charged, it is detected. The disadvantage is that there is a high risk that the appliance will incorrectly display charging status.

As a device that can solve the drawbacks of the above-mentioned devices using neon discharge tubes and devices that use the amplifier itself to detect voltage, there is a device that uses Zener diodes to detect voltage (Japanese Utility Model Application Publication No. 51-31565).
is also known. This energization detector supplies a detection signal from the energization detection terminal to an amplifier consisting of a Darlington connection circuit through a series circuit of a Zener diode and a current limiting resistor, and detects voltage by activating a light emitting diode with the output of the amplifier. This circuit is housed in a synthetic resin case along with a DC power supply, and is constructed to be handy so that an inspector can hold it with one hand.

[The problem that the idea attempts to solve]

The energization detector (voltage detector) using the Zener diode has the following problems.

The Zener diode becomes conductive when the input voltage exceeds a certain breakover voltage, and even when it is conductive, the voltage across it is maintained at this breakover voltage. That is, when the input voltage exceeds the breakover voltage (for example, 40V), the current begins to flow, but only a voltage that exceeds the breakover voltage (for example, 1V when the input voltage is 41V) is supplied to this current-carrying circuit including the amplifier. Then, when this exceeded magnitude exceeds a certain value determined by the amplification factor of the amplifier, etc., a voltage detection output is generated.

That is, the voltage detecting operation voltage of this current detector (voltage detector) is not determined only by the breakover voltage of the Zener diode, but is greatly influenced by the amplification factor of the amplifier.

Therefore, if the amplification factor of the amplifier is small, the operating voltage point of the voltage detector becomes unclear, resulting in a lack of accuracy as a voltage detector. On the other hand, it is possible to increase the amplification factor of the amplifier in order to clarify the operating point.
In this case, erroneous voltage detection outputs are likely to be generated due to induced voltage due to electromagnetic noise or frictional electricity generated when handling the insulating case of the voltage detector.
Furthermore, since the amplification factor of the amplifier fluctuates depending on the ambient temperature and the voltage drop of the power supply battery, there is a problem in that the operating voltage point becomes unstable in these respects as well. Incidentally, since the amplifier of the energization detector using the Zener diode is connected in a Darlington manner, the amplification factor fluctuation due to changes in ambient temperature is particularly large.

In addition, this current detector (voltage detector) cannot detect voltages with a polarity different from the polarity determined by the Zener diode. I had a problem with it being unusable.

The purpose of this invention is to provide a voltage detector that can accurately determine the operating voltage point of the voltage detector without being affected by the amplification factor of the amplifier, and that can safely detect both AC and DC voltages.

[Means to solve the problem]

Therefore, the present invention consists of a pen-shaped insulating container in which a tip fitting such as a pin is implanted at the tip to make contact with the electrical object to be tested, and a light-emitting diode is attached to the middle part so that its light-emitting surface is exposed to the outside. The resistor has a current-limiting withstand voltage resistor and exhibits negative resistance characteristics that are symmetrical in both directions for applied voltages that are higher than the breakover voltage, and exhibits high insulation resistance characteristics for applied voltages that are lower than the breakover voltage. , a diac (DIAC) with a breakover voltage of 50V or less, and a breakover that suddenly rises due to its negative resistance when the positive and negative charging voltage of the electrical object to be tested applied to this diac exceeds the breakover voltage. and an amplifier that receives and amplifies input positive and negative voltages, the voltage detector is connected in series between the tip fitting and the battery case, and the light emitting diode is lit by the output of the amplifier. do.

[Effect]

According to the above configuration, the diac used as the voltage detection element has negative resistance characteristics, so that when the input voltage exceeds the breakover voltage, the resistance value suddenly decreases and the voltage rises rapidly. The operating point of voltage detection is determined only by the breakover voltage when supplied to the amplifier, without being affected by the amplification factor of the amplifier, and due to its bidirectional characteristics, DC and AC voltages of which it is unclear whether they are negative or positive voltages can be used. The minimum detection voltage is extremely stable, as the breakover voltage of a diac is stable and is not affected by ambient temperature or voltage fluctuations of the power supply battery unlike an amplifier. We can provide a highly reliable low voltage pen holder type voltage detector.

〔Example〕

As shown in FIG. 3, a current-limiting withstand voltage resistor 8 is attached to a pin-shaped tip fitting 7 that is brought into contact with the electrical object to be tested.
For example, a DIAC (product name: trigger diode) with a breakover voltage of 50V.
and an amplifier 9 are connected in series, and the output of the amplifier 9 lights up a light emitting diode 10 capable of emitting high-intensity light.

An example of the assembly structure of this voltage detector 14 is shown in FIG. In the figure, 15 is a pen-shaped insulating container, a fountain pen-shaped cylindrical case made of insulation-resistant resin;
7 is a pin-shaped tip fitting that is embedded and fixed at the tip, has a small surface area and is difficult to be guided;
is the current-limiting withstand voltage resistor connected to the tip fitting,
TD is DIAC, 9 is DIAC TD
10 is a light emitting diode that serves as an indicator; 16 is a conductive conductor so that it can be reliably grounded against direct current when held in hand for voltage detection; 17 is a battery, 18 is a metal clip connected to the battery holder, and 19 is an operation test button.

The operation of this voltage detector 14 is as follows.

When the battery case 16 portion at the rear end of the voltage detector 14 is grasped, the ground side of the amplifier 9 is established by the human body's ground resistance Ro and ground capacitance Co. 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 electrical object 12 to be tested charged by positive or negative direct current or alternating current is the result of the current-limiting withstand voltage resistor 8, the diac TD, the internal resistance of the amplifier 9, and the ground impedance of the human body connected in series. applied to the circuit. However, Diazuk
When the TD is in a non-conducting state, its resistance is extremely high compared to other elements, and most of the voltage is applied to this diac TD.
is applied to Then, the presence or absence of charging is determined almost unaffected by the ground impedance of the human body.
In other words, when the positive or negative DC or AC ground voltage of the non-voltage detecting object is even slightly higher than the breakover voltage, the diac TD breaks over, and its negative resistance characteristic causes the resistance value to drop rapidly. Since the voltage that rises to
0 lights up. Furthermore, when the ground voltage of the electrical object to be tested is lower than the breakover voltage, the diac TD maintains a high resistance, so the amplifier 9
No current flows through , so the light emitting diode 10 does not light up. Note that by pressing the operation test button 19 and checking whether the light emitting diode 10 is lit or not, it is easy to check whether the device is operating normally or not, and the battery consumption can be determined based on the brightness at that time.

[Effect of idea]

As explained above, according to this invention, since a diac is used as the voltage detection element, the operating point of the voltage detection can be determined accurately only by the breakover voltage without being affected by the amplification factor of the amplifier. This makes the detection operation extremely stable.
Note that this breakover voltage is not affected by voltage fluctuations in the power supply battery like the amplification factor of an amplifier, and furthermore, the variation of this breakover voltage with respect to the ambient temperature is due to the variation of the amplification factor of the amplifier with the ambient temperature. It is extremely small compared to .

Also, since diacs have bidirectional characteristics, unlike when using Zener diodes, even when the object to be detected is a DC voltage and it is unclear whether it is positive or negative,
Electricity can be detected reliably. Therefore, it satisfies the necessary conditions for a voltage detector used for safety confirmation, that is, it always detects if the object to be detected is charged with either alternating current or positive or negative direct current of a certain voltage or higher.

[Brief explanation of drawings]

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...DIAC, Co...ground capacitance, Ro...ground resistance, 7...metal fittings, 8...
... Current-limiting withstand voltage resistor, 9... Amplifier, 10...
Light emitting diode, 14... voltage detector.

Claims (1)

[Claims for Utility Model Registration] A pen-shaped device with a pin-shaped tip fitting attached to the tip to make contact with the electrical object to be tested, and a light-emitting diode attached to the middle so that its light-emitting surface peeks outward. Inside the insulating container, there is a current-limiting withstand voltage resistor and a resistor that exhibits symmetrical negative resistance characteristics for applied voltages above the breakover voltage, and high insulation resistance characteristics for applied voltages below the breakover voltage. A diac (DIAC) with a breakover voltage of 50 V or less, and a break that suddenly rises due to its negative resistance when the positive and negative charging voltage of the electrical object under test applied to this diac exceeds the breakover voltage. A voltage detector, comprising: an amplifier that receives and amplifies the input of positive and negative voltages; the voltage detector is connected in series between the tip fitting and the battery case; and the light emitting diode is lit by the output of the amplifier.