Basic Maintenance Electrician Technology

Author: Editor-in-Chief: Bian Meng
Publisher:
Publish Date: 2000-04-01
Features:
Section: Chapter Common Tools, Measuring Instruments, and Meters - Training Requirements
Section Common Tools and Measuring Instruments and Maintenance
1. Voltage Tester
A voltage tester is an auxiliary safety tool used to check whether low-voltage conductors and the shells of electrical equipment are live. The voltage range detected by a voltage tester is 60 to 500V. Voltage testers are often designed in pen-like structures, with metal probes at the front, followed by a neon bulb, a safety resistor, and a spring inside. The spring contacts the metal part at the back, and when using it, the hand should touch that metal part.
The working principle of a voltage tester is that when holding it to test a live object, the live object, the tester, and the human body form a circuit to the ground (even if wearing insulated shoes or standing on an insulating material, it is considered a circuit because the leakage current of the insulating material is sufficient to cause the neon bulb to glow). As long as the potential difference between the live object and the ground exceeds a certain value (usually 60V or higher), the voltage tester will emit a glow; otherwise, it will not. If the voltage is alternating current, both electrodes of the neon bulb will glow, while for direct current, only one electrode will glow.
When using a voltage tester, the following points should be noted:
1) Before using the voltage tester, it is essential to check whether the neon bulb in it can glow normally on a live power supply.
2) Insulated shoes should generally be worn when using a voltage tester.
3) When testing in bright light, the glow of the neon bulb may be difficult to see. In this case, it is necessary to avoid light and test carefully.
4) When testing, avoid touching both metal probes to live objects at the same time, or touching a live object and the metal casing simultaneously, to prevent phase-to-phase and phase-to-ground short circuits.
5) Some equipment, especially testing instruments, may become charged by induction during operation. Using a voltage tester to test may indicate a live condition, but it does not necessarily pose a risk of electric shock. In such cases, other methods (e.g., using a multimeter to measure) must be used to determine whether the equipment is truly live or only induced.
6) For live objects with a safety voltage of 36V or below, the voltage tester is often ineffective.
7) The metal probes of voltage testers are often made in the shape of a screwdriver and can only withstand very small torques. Special care should be taken when using them to avoid damage.
2. Screwdrivers
Screwdrivers are also known as screwdrivers, open-end wrenches, or twist drivers. They can be divided into two types based on the shape of their heads: flat-head and cross-head. They can also be divided into two types based on the material of their handles: wooden handles and plastic handles. Plastic handles have better insulation properties and are suitable for electricians.
Flat-head screwdrivers are used to tighten or remove slotted screws and wood screws. Their specifications are indicated by the length of the body excluding the handle, with common lengths of 100mm, 150mm, 200mm, 300mm, and 400mm.
Cross-head screwdrivers are specifically designed for tightening or removing cross-slotted screws and wood screws. Their specifications are indicated by the body length and the cross-slot specification number. The cross-slot specifications have four types:
- Type I is suitable for screw diameters of 2 to 2.5mm.
- Type II is for 3 to 5mm.
- Type III is for 6 to 8mm.
- Type IV is for 10 to 12mm.
A multi-purpose screwdriver is a combination tool with detachable handle and body parts. It comes with three different sizes of flat-head body parts, two specifications (Type I and Type II) of cross-head body parts, and one drill bit. When the drill bit is installed, it can be used to pre-drill holes for wood screws. It has a plastic handle with a structure similar to a voltage tester, so it can also be used as a voltage tester. Its specifications are indicated by the total length, with only one size of 230mm currently available.
When using screwdrivers, the following points should be noted:
1) Electricians should not use screwdrivers with metal rods extending directly to the top of the handle, as this can easily cause electric shock accidents during use.
2) When tightening or removing live screws with a screwdriver, the hand should not touch the metal rod of the screwdriver to avoid electric shock accidents.
3) To prevent the metal rod of the screwdriver from touching the skin or nearby live objects, an insulating tube should be worn on the metal rod.