Why does the zero line of the measuring pen not emit light
Not only is there current passing through, but it is also equal in magnitude to the current in the live wire, because the zero wire is connected in series with the live wire and the consumer, and the current in the series circuit is equal everywhere. Don't believe it, just use an ammeter to measure it. As for why it cannot be measured with a measuring pen, it is simple because the measuring pen is used to distinguish between the live wire and the zero wire, or to determine whether a conductor is connected to the live wire, and cannot determine whether there is current. When the metal body of the stylus tip contacts the live wire or a conductor connected to the live wire, a circuit is formed from the live wire through the stylus, the human body, and the ground. Because there is a 220V voltage between the live wire and the ground, a weak current flows from the live wire through the stylus and the human body to the ground. The neon tube of the stylus emits light, but it is not the same as the current in the live wire. When the metal body of the stylus tip contacts the zero line, there is no voltage between the zero line and the ground, so no current flows through the stylus, and the neon tube of the stylus does not emit light.
What is the working principle of an electric pen for detecting luminescence
The principle of electropen detection for luminescence is that there is a certain potential difference between the charged object and the earth. When the potential difference exceeds a certain value, the neon bubble will emit light, and if it falls below a certain value, it will not emit light. The voltage measurement range of an ordinary low-voltage test pen is generally between 60-500V, and neon bubbles below 60V may not emit light. When the voltage is higher than 500V, it is not possible to use a low-voltage test pen for testing, otherwise insulation breakdown may occur, causing a risk of electric shock to the human body.
When standing on a stool or other insulator with a handheld electric pen to test the live wire, the large current will pass through the high resistance voltage reducing resistance rod inside the pen and become a weak small current. Then, it will pass through the neon bubble and the human body to discharge the surrounding environment. At this time, the neon bubble will emit light. However, there is no risk of electric shock in the human body at this time.
The function of the test pen:
Function 1: Electricity testing, using a metal head to touch an object. If it emits light, the object will be charged, and if it does not emit light, it will not be charged.
Function 2: It can be used for low-voltage nuclear phase measurement to determine whether any wires in the circuit are in phase or out of phase.
Function 3: It can be used to distinguish between alternating current and direct current. When using a test pen for testing, if both poles in the neon bubble of the test pen emit light, it is an alternating current; If only one of the two poles emits light, it is direct current.
Function 4: It can determine the positive and negative poles of direct current. Connect the test pen to a DC circuit for testing, and the electrode with the neon bubble shining is the negative electrode, while the electrode without the neon bubble shining is the positive electrode.
Function 5: It can be used to determine whether the DC is grounded. In a DC system with insulation to ground, standing on the ground can be used to contact the positive or negative poles of the DC system with a measuring pen. If the neon bubble of the measuring pen is not lit, there is no grounding phenomenon. If the neon bubble lights up, it indicates grounding. If it lights up at the tip of the pen, it indicates positive grounding. If it shines on the finger end, it is negative grounding.
