Using a digital multimeter to measure the DC multiples of transistors
A transistor has two PN junctions, similar to the unidirectional conductivity of a diode. When using a multimeter to detect a transistor, it can be viewed as two diodes with a common base, while an NPN type can be considered as a common cathode dual diode.
Of course, the transistor is not a simple structure as shown in the figure, as it has a current amplification effect, which is significantly different from the finished common anode (or cathode) diode sold in the market. The latter is a diode with two common anodes (or cathodes) and no current amplification capability. In engineering practice, a digital multimeter "diode" is often used to measure the two PN junctions of the transistor, and the type of transistor is determined based on the value displayed on the LCD
The steps to determine the type of transistor using a digital multimeter: Currently, there are common anode and common cathode diodes on the market. Although the above testing methods can determine the internal diodes of the device, they cannot be determined as transistors. Therefore, using this method cannot determine that a 3-pin component containing two PN junctions must be a transistor. Kind reminder: In the above steps to determine the type of transistor, the silicon transistor should be between 500~700, and the germanium transistor should be between 200~300. This value represents the forward conduction voltage of the PN junction inside the transistor, measured in mV.
Measure the DC multiplier of a transistor using a digital multimeter:
Although the above testing methods and steps can determine whether a transistor is PNP or NPN, they cannot determine which is the collector and which is the emitter. By using the "hFE" function of the digital multimeter, while measuring the DC amplification factor of the transistor, the names of each pin can be determined, which can be described as "killing two birds with one stone". The common small signal transistors S8050 and S8550, S1815 and 1015 are paired transistors, respectively. The method for measuring the DC amplification factor is very simple: ① Turn the rotary dial to the "hFE" position; ② Insert the transistor correctly into the socket next to the "hFE" gear, and the LCD reading will be the DC amplification factor: the β value of the transistor. It should be pointed out that there are currently two main schools of transistor pin sorting in the world: one is Meixu; The other is Japanese style sorting. For low-power transistors, the order of the three pins of the transistor is e-b-c, and the Japanese order is e-c-b. Regardless of the sorting, when the transistor pin is facing down and the text face is facing the viewer, the left pin is the e-pin.
