The structure and application analysis of the test pencil
Measuring the structure and performance of the electric pen
The structure of the traditional measuring pen is composed of several parts such as a metal pen tip, a voltage limiting resistor, a neon tube, and a metal body at the end of the pen. Its working principle is very simple. When the metal pen tip of the electric test pen is in contact with the power line of the object under test, the electric test pen will form a complete current path. The current passes through the pen tip, resistor, neon tube, pen tail metal, and human body. , The ground returns to the power ground of the object under test. During this period, the current after passing through the resistance becomes weak, and when it flows through the neon tube, it will make the neon tube glow and will not cause electric shock to the human body.
Now the new type of test pencil is a digital display test pencil, which can directly display the value of the voltage of the measured object, and has high sensitivity and accuracy, and is widely used in the fields of various electrical appliances and circuit measurements. For example, the AX-988 inductive digital display electric pen, a rectangular miniature liquid crystal display is designed and placed on the top of the pen to display the voltage value. Breakpoint measurement button, a self-test indicator LED red light-emitting tube is set at the tip of the pen. Self-inspection is required before operating the test pen. Touch the thumb of the finger to the sensor and breakpoint measurement button, and the little finger bulges out the tip of the test pen. If the red LED light-emitting tube lights up, it proves that the function of the test pen is normal. In addition to the measuring point function of the traditional electric pen, this new type of electric pen can also read 12V, 36V, 55V, 110Y, and 220V voltage values through the display screen, which can easily detect wire breakage, battery voltage capacity, and capacitors. performance, polarity of electronic components, etc.
There are two operable function buttons on the body of the AX-988 inductive digital test pen. One is the DIKECT button, also called the direct measurement button, which is used when the tip of the pen touches the line directly. First lightly touch the direct contact button, and then use the metal pen tip of the electric test pen to touch the object that needs to be detected by the circuit. The electric test pen can display five levels of voltage values: 12v, 36V, 55V, 110Y, and 220V. The other button is the INDUCTANCE button, which is the induction and breakpoint measurement button. Lightly touch the sensor, breakpoint measurement button, when the metal tip of the test pen is close to the object to be detected, if the high voltage symbol appears on the display screen, it means that the object under test is charged with AC. When using the test pen to measure the wire at the disconnection point, lightly touch the sensor and breakpoint measurement button, the metal tip of the test pen is close to the insulating outer layer of the tested wire, if the tested wire is somewhere, the high voltage symbol on the display will disappear , then say
It indicates that there is a line disconnection at this point.
Application of test pencil
When detecting AC voltage, you need to lightly touch the direct measurement button of the test pen with your thumb, touch the tip of the pen to the wire of the power supply under test or insert the tip of the pen into the inside of the power socket under test. If the red LED light-emitting tube lights up, the liquid crystal display will display the reading, indicating that one end of the tested wire is the phase wire of the power supply, the current working voltage is 220V, and the other wire without voltage reading is the neutral wire of the power supply.
When measuring the break point of the live wire, lightly touch the sensor and break point measurement button with the thumb, and the metal tip of the test pen touches the insulating outer layer of the tested wire. When the wire is energized, the display will display a high-voltage symbol. Move the tester lightly. If the high-voltage symbol on the display disappears somewhere in the tested wire, it means that there is a disconnection at that point.
When measuring the disconnection of the uncharged wire, lightly touch the sensing and power-off measurement button with the thumb, touch one end of the wire to be tested with the other finger, and touch the other end of the wire to be tested with the metal pen tip. If the LED light tube is shining, then It means that there is no open circuit in the wire. If the LED light-emitting tube does not light up, it means that there is at least one open circuit in the wire.
When using the galvanic pen to detect the battery energy, first use the mobile phone to detect the positive electrode of the battery, then use the thumb to lightly touch the sensor, power-off measurement button, and then use the tip of the galvanic pen to touch the negative electrode of the battery. If the LED lamp flashes and then turns off when the metal pen tip touches the negative electrode of the battery, it can be estimated that there is a certain voltage in the battery. If the metal pen tip touches the negative electrode of the battery, the LED lamp is always on If it does not turn off, it means that the energy in the battery has been basically exhausted.
When measuring the performance of an electrodeless capacitor, first touch the lead pin of the capacitor with your finger, touch the metal pen tip of the electric pen to the other lead pin of the capacitor, and lightly touch the sensor and breakpoint measurement button with your thumb to see if the LED light-emitting tube is First light up and then slowly turn off, then exchange the lead pin touched by the finger with the lead pin touched by the metal pen tip, and also lightly touch the sensor and power-off measurement button with the thumb to see if the LED light-emitting tube lights up first and then Slowly turn off. If the LED light-emitting tube lights up first and then goes out slowly in the two tests, it means that there is no fault in the capacitor, otherwise, it means that there is an open circuit or short circuit inside the capacitor.
Compared with the traditional test pencil, the new digital display induction test pencil has a wider range of applications and has a digital display function. However, it is necessary to prevent the digital display electric test pen from falling or other damages, so as to prevent the display screen or internal electronic components of the digital display electric induction test pen from being damaged, resulting in inaccurate electric measurement. In addition, the battery in the pen should be replaced in time, so as to avoid the problem caused by the battery.
