Auto Test Pen, also called auto test pen, test light in jargon, is a circuit testing tool commonly used by auto electricians in automotive electrical equipment installation, circuit modification and maintenance activities. It is used to detect whether the measured point in the car circuit is electric, accurate measurement also needs to use a multimeter.
The working principle of a car measuring electric pen
● When the nib and clip of the automobile measuring pen are connected with the positive electrode of DC12V at one end and the negative electrode of DC12V at the other end, the indicator light will be on.
● If the light bulb as the indicator, the car test pen in use when there is no positive and negative points, as long as there is 12V voltage between the nib and the clip, the bulb will be bright.
● If the light emitting diode as the indicator light, because the rated voltage of the light emitting diode is low, must be used in series resistance.
If there are two light-emitting diodes in reverse parallel, there is no positive or negative polarity in the use of the automobile measuring pen.
If there is only one light-emitting diode, the car test pen in use when there is a positive and negative polarity, the reverse use of light-emitting diode is not bright.
The use and experience of automobile Electric Test Pen
1.
A few industry terms first:
DC12V positive terminal, called fire line;
The car test pen clamp to the metal frame, called the iron;
The clip of the car measuring pen is clamped to the DC12V positive terminal, which is called the fire line.
2.
The metal frame of most vehicles is connected with the negative electrode of the battery. When this kind of vehicle is tested with iron, if the measured point has electricity, the indicator light will be on.
The metal frame of a small number of vehicles is connected with the positive electrode of the battery. When this kind of vehicle is tested with iron, if the measured point is conduction with the negative electrode, the indicator light will be on.
The specific circuit test method should be selected in combination with the automobile circuit.
3.
If the exposed metal tip of the automobile measuring pen is too long, it can be wrapped with electrical tape to avoid touching other circuits during the test, causing test errors or short circuit faults.
4.
When testing, try to use the nib to measure the joint. If you need to find the line, you can connect a small wallpaper knife on the tip of the pen, and use the blade to gently cut the wire skin and connect it to the metal wire for measurement. After the measurement is completed, be sure to wrap electrical tape around the wire break.
5.
Because the automobile measuring electropen can only be used to measure the automobile power system and electrical control system, can not be used to measure the electronic control system, so it is particularly important to make a correct judgment on the function of the wire. These two systems can be distinguished in several ways.
Wire thickness: Electrical control system wire is very thin.
Classification of vehicles: American and German cars adopt more electronic control systems.
The price of the vehicle: The higher the price of the car, the more electronic control systems are used.
6.
Order of measurement:
No power. ACC, ON, start.
No power: live wire;
ACC: ACC line;
ON: oil pump line, turn signal, brake light, ceiling light, central lock, horn;
Start: Start line.
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