June 23, 2023
The Low Voltage Electroscopic Pen is a safety aid commonly used by electricians to check whether conductors are charged below 500V or enclosures of various electrical equipment.
How can you work without a low-voltage electroscope pen? But did you know that low voltage tester has many magical functions besides detecting presence of voltage in line.
5 tips on how to skillfully use electroscope pen, turning a novice electrician into a master.
1. AC and DC rating
The electric pen distinguishes between alternating and direct current, alternating current is bright, direct current is dark.
The whole body of AC neon tube is bright, and one end of DC neon tube is bright.
First of all, let readers know that before using a low-voltage pen-electrometer, it must be tested on a confirmed charged body; it must not be used until electroscope handle has been confirmed to be in good working order. When distinguishing between AC and DC, it is best to make a comparison of "two powers" so that it is obvious. When measuring alternating current, both ends of neon tube light up simultaneously, and when measuring direct current, only one end of neon tube shines extremely brightly.
2. Evaluation of DC positive and negative poles
The electric pen detects positive and negative poles, and neon tube needs to be watched closely,
The bright front end is negative pole and bright back end is positive pole.
The front end of neon tube refers to tip of electroscope pen, and rear end of neon tube refers to end of hand. The bright front end is negative pole, and opposite is positive. pole. When checking, you should pay attention: supply voltage is 110V and higher, if a person is isolated from ground, then with one hand he touches any pole of power source, and with other hand he holds a measuring pen, metal tip of pen touches other pole of power source under test and front end of neon tube If rear end of neon tube is bright, power supply being tested is positive. This is based on principle of unidirectional DC current flow and electrons flow from negative to positive.
3. Judging whether a DC power supply is grounded or not, and difference between positive and negative ground
Substation constant current ratio, electric pen does not light up when touched,
If light is close to pen tip, there is a ground fault at positive pole
The DC ratio of power plants and substations is isolated from ground. When a person stands on ground and touches positive or negative pole with an electroscope, neon tube should not light up. If it lights up, then withDC system There is a grounding phenomenon; if light is at end closest to pen tip, it is a positive ground; if light is at end closest to finger, it is a negative ground.
4. Evaluation of one and other phase
To assess similarity and difference between two lines, hold a pen in each hand
Two legs are isolated from ground, and two handles touch main line,
Looking at pen with eyes, it is different if it is not bright.
When doing this test, remember that two legs must be insulated from ground. Since most of our country is powered by 380/220V, and neutral point of transformer is usually directly grounded, so when doing test, human body must be isolated from ground to avoid looping, to avoid misjudgment; The bright display is same, so only one is visible.
5. Evaluation of grounding fault of phase wire of a three-phase three-wire power supply line 380/220 V
Three-phase line of star connection method, electric handle touches two lights;
The rest have low brightness, phase wire is grounded;
If there is almost no light, there is a short to metal ground.
The secondary winding of a power transformer is usually connected in shape of a Y. In a three-phase three-wire system where neutral point is not earthed, when touching three-phase wires with an electric test pen, two of them are slightly brighter than usual, and other If brightness is weaker at root, then it is grounded phase line with weak brightness, but it is not too serious, if two are very bright, and remaining one is almost invisible, it means that this phase line has a short to metal ground. If light is close to end of finger, ground fault is at negative pole.
An unexpectedly small electroscopic pen can do so many tricks. As long as we use it flexibly during normal times, work efficiency can be doubled.
Finally, I still want to remind everyone to use electroscope pen correctly to avoid electric shock.
Use an electric pen to test electricity to prevent electric shock and ensure safety.
Touch metal tip at end of pen and never touch electrical connector.
Do not use pen body if it is broken, and do not replace resistor at will.
Keep dry and clean, do not touch high voltage.