How to use a multimeter to detect the quality of capacitors
Capacitors, commonly referred to as capacitors, have the ability to hold charges and are represented by the letter C. Definition 1: A capacitor, as the name suggests, is a 'container for storing electricity' and a device that holds an electric charge. English name: capacitor. Capacitors are one of the widely used electronic components in electronic devices, widely used in circuit isolation, coupling, bypass, filtering, tuning circuits, energy conversion, control, and other aspects. Definition 2: A capacitor is composed of any two conductors (including wires) that are insulated from each other and located very close to each other.
Capacitors are different from capacitors. Capacitance is a fundamental physical quantity, with the symbol C and the unit F (Farads).
General formula C=Q/U for parallel plate capacitors: Inter plate electric field strength E=U/d, capacitor capacitance determination formula C=ε S/4 π kd
With the rapid development of electronic information technology, the updating speed of digital electronic products is getting faster and faster. The production and sales of consumer electronic products, mainly flat panel TVs (LCD and PDP), laptops, digital cameras, etc., continue to grow, driving the growth of the capacitor industry. And it has driven the development of related materials and equipment industries, making China a major producer of capacitors worldwide.
1. Detection of fixed capacitors
A detects small capacitors below 10pF
Due to the small capacity of fixed capacitors below 10PF, using a multimeter for measurement can only qualitatively check for leakage, internal short circuits, or breakdown phenomena. When measuring, a multimeter with R × 10k range can be used, and two probes can be connected to either pin of the capacitor. The resistance value should be infinite. If the resistance value (pointer swinging to the right) is zero, it indicates that the capacitor is damaged by leakage or internal breakdown.
B detects whether there is charging phenomenon in the fixed capacitor of 10PF~0.01 μ F, and then judges its quality.
The multimeter is set to R × 1k gear. The beta values of both transistors are above 100, and the penetration current should be small. 3DG6 and other models of silicon triodes can be used to form composite transistors. The red and black probes of the multimeter are respectively connected to the emitter e and collector c of the composite tube. Due to the amplification effect of the composite transistor, the charging and discharging process of the measured capacitor is amplified, which increases the amplitude of the multimeter pointer and facilitates observation. It should be noted that during testing, especially when measuring capacitors with smaller capacities, the pins of the tested capacitor should be repeatedly switched to contact points A and B in order to clearly see the swing of the multimeter pointer.
For fixed capacitors above 0.01 μ F, the R × 10k range of a multimeter can be used to directly test whether the capacitor has a charging process and whether there is an internal short circuit or leakage. The capacitance of the capacitor can be estimated based on the amplitude of the pointer swinging to the right.
