Multimeter on the hfe, PNP, NPN, are what it means
HFE is triode DC current amplification factor abbreviation, is the triode current amplification; PNP and NPN is on behalf of two types of triode.
Triode conduction IE = (amplification +1)*IB and ICB has nothing to do with, ICB = 0 ICB>0, there may be a problem with the triode, so the triode in normal operation, regardless of whether it is working in the amplification or saturation zone ICB = 0. When UEB>0.7V (silicon) (germanium 0.2V), RC/RB < amplification, the triode is working in the saturation zone, and vice versa, work in the amplification zone. In the amplification area.
The difference between a PNP-type triode and an NPN-type triode is that the direction of the two PN junctions is not the same.
PNP is a common cathode, that is, the two PN junction N junction connected to do as the base, the other two P junctions were done collector and emitter; circuit diagrams are marked as the arrow inward triode; NPN is the opposite.
The number of display digits of a digital multimeter is usually 3 1/2 digits to 8 1/2 digits. There are two principles for determining the number of display digits of a digital instrument: first, the number of digits that can display all the digits from 0-9 is a whole number;
The second is that the fraction of the value of the maximum display value of the highest digit as the numerator, with full scale when the count value of 2000, which indicates that the instrument has three integer bits, and the fraction of the numerator is 1, the denominator is 2, so it is called the 3 1/2 bits, read as "three and a half", and the highest bit can only display 0 or 1 (0 is usually not displayed). The highest bit can only display 0 or 1 (0 is usually not displayed).
3 2/3 bit (read as "three and two-thirds bit") digital multimeter can only display the highest bit 0 ~ 2 of the number, so the maximum display value of ± 2999. In the same case, it is higher than 3 1/2 bit digital multimeter limit of 50%, especially in the measurement of 380V AC voltage is very valuable.
Popular digital multimeter generally belongs to 3 1/2 bit display handheld multimeter, 4 1/2, 5 1/2 bit (6 bit below) digital multimeter is divided into handheld, desktop two kinds. 6 1/2 bit above most of the digital multimeter belongs to the desktop.
