Multifunctional electronic induction test pen
Aiming at the shortcomings of most neon bulb test pens that cannot distinguish between DC power supply and single function, the author has made a multi-functional electronic induction test pen. Its circuit schematic diagram and printed board diagram are shown in Figure 1 and Figure 2 respectively. The pen has the following functions:
1. It can detect whether the fuse, inductor, coil, resistor, etc. are open;
2. Able to judge whether the capacitance of 100pF~1pF is good or bad;
3. Be able to judge the quality of low-power silicon-electrode tubes and silicon triodes
4. No contact test is required when testing AC power above 220V. Instead, it can be judged whether it is live wire or neutral wire by induction; 5. Contact measurement can be performed on DC power below 400V.
How to use the electric pen:
1. Detection of AC power supply: put the probe of the electric pen close to the socket of the power supply or the power cord. The red and green light-emitting diodes on the electric pen are all on. The higher the detected voltage, the farther the distance between the probe of the electric pen and the power source under test will be.
2. Detection of DC power supply (below 400V): Touch the probe of the electric pen to the DC power supply under test, and touch the "ground" of the device with the other hand. At this time, if it is red, the LED lights up. Indicates that the power supply under test is "positive". Otherwise, it is "negative". Note that the power supply without an isolation transformer cannot touch the "ground" by hand.
3. Detection of fuses, resistors, etc.: one hand holds one end of the conductor to be tested, while the other hand touches the "A" point of the electric pen, and at the same time touches the probe to the other end of the conductor to be tested, at this time the red light is on, indicating The conductor under test is not broken.
4. Capacitor measurement: hold one pin of the capacitor under test with one hand, and touch the "A" point of the electric pen with the other hand. At the same time, touch the probe to the other pin of the capacitor under test. If the red light is on , and then slowly turn off, indicating that the measured capacitor is good. For capacitors below 100pF, only whether it is short-circuited. For capacitors above 1μF, only whether it is open-circuited can be tested.
5. Measurement of low-power silicon diodes and silicon triodes: hold one pin of the diode with one hand, and touch the "A" point with the other hand, and at the same time, touch the probe to the other pin of the diode under test. The light is on. It means that the pin contacted by the probe is the negative pole of the diode. In the same way, according to the principle that the triode has two PN junctions, it is convenient to measure the low-power silicon triode. In addition, according to the principle of AC induction, the test pen can also conveniently measure the breakpoint of the electric blanket.
