How does a test pen work?
Electricity pen test luminous principle is that there is a certain potential difference between the charged body and the earth, when the potential difference exceeds a certain value, the neon bubble will be luminous, below a certain value, it does not emit light. Ordinary low-voltage power test pen voltage measurement range is generally 60 - 500v, below 60v neon bubble may not glow. Higher than 500V, can not be tested with a low-voltage pen, otherwise the insulation breakdown will occur, resulting in the risk of human electric shock.
When the handheld electric pen standing on a stool or other insulator to test the firewire, the large current will pass through the electric pen internal large resistance buck resistor bar into a weak small current, and then through the neon bulb, the human body, the discharge of the surrounding environment, at this time, neon bulbs will be glowing. However, the human body at this time will not have the danger of electric shock.
Zero line somewhere disconnected, the stylus neon tube why glow
Because the zero line is short-circuited, but the fire wire is connected, the electrically charged body, the test pen, the human body and the earth to form a circuit, so the test pen in the neon bubble will glow. Measurement of the firewire, the firewire and the ground between the voltage U = 220V or so, the human body resistance is generally very small.
Usually only a few hundred to a few thousand ohms, and the internal resistance of the stylus is usually a few megohms or so, the current through the stylus is very small, usually less than 1 milliamps, such a small current through the human body, there is no harm to the human body, and such a small current through the stylus neon bubbles, neon bulbs will be glowing.
The role of the test pen:
Role 1: check the electricity, touch the object with the metal head, glowing is the object charged, not glowing is not charged.
Role 2: can be used for low-voltage phase verification, measuring the line between any wire whether the same phase or different phase.
Role 3: Can be used to distinguish between alternating current and direct current. In the test with the stylus, if the stylus neon bubble in the two poles are glowing, is the alternating current; if only one of the two poles is glowing, is the direct current.
Role 4: can determine the positive and negative poles of DC. Will be connected to the stylus in the DC circuit test, neon bubble light up the pole is the negative pole, does not light up the pole is positive.
Role 5: can be used to determine whether the DC ground. In the DC system insulated to ground, can stand on the ground with a stylus contact DC system in the positive or negative pole, if the stylus neon bubble does not light, there is no grounding phenomenon. If the neon bubble is bright, it shows that there is a grounding phenomenon, and its bright such as the tip of the pen, then the positive pole is grounded. If the light is at the end of the finger, it is negative grounding.
