Instrument measurement. Use a multimeter to measure. Connect the probes to the two ends. The one with the larger swing is the correct one. But note that the positive terminal of an analog multimeter should be connected to the negative terminal of the capacitor, and the opposite should be connected to the digital multimeter.
Identify markings. Check the markings on the capacitor sleeve; for example, "+" indicates the positive terminal and "-" indicates the negative terminal.
Shape and color. For through-hole electrolytic capacitors, the longer lead is the positive terminal and the shorter lead is the negative terminal; the color of the casing may also indicate the positive and negative terminals.
Surface mount electrolytic capacitors. They are usually colored on the bottom, typically for the negative terminal.
The above methods can help correctly identify the positive and negative terminals of electrolytic capacitors, thus avoiding damage caused by reverse connection in the circuit.
Distinguishing the positive and negative terminals of an electrolytic capacitor: ① The lead on the side of the capacitor sleeve with a white silver edge and a "一" mark is the negative terminal, and the lead on the other side is the positive terminal; ② For new capacitors, the lead with the longer lead is the positive terminal, and the other lead is the negative terminal.
Distinguishing the positive and negative terminals of a bolt-on electrolytic capacitor: ① The port with a "+" mark on both sides of the white silver edge of the capacitor sleeve is the positive terminal, and the other port is the negative terminal; ② The port with a "one" mark on the white silver edge of the capacitor sleeve is the negative terminal, and the other port is the positive terminal.
The method for determining the positive and negative terminals of an electrolytic capacitor is as follows:
1. Visual identification:
The first method is to check the electrolytic capacitor's tubing. One end of the tubing will have a negative terminal marking printed on it. The other end, however, will not have a positive terminal marking.
The second method is to look at the leads of the electrolytic capacitor. The end with the grid pattern on the lead represents the negative terminal, and the other end represents the positive terminal.
For pin-type electrolytic capacitors, the longer end of the pin is the positive terminal, and the shorter end is the negative terminal.
2. Measurement using instruments:
1. Find a desktop power supply, reduce the voltage, and connect the electrolytic capacitor in parallel at the power supply's output terminal;
2. Turn the capacitor upside down and connect it in parallel, then observe the change in the ammeter reading;
3. When the current is large, it means that the positive and negative terminals of the capacitor are exactly opposite to those of the power supply, which will not damage the capacitor.
Note: Electrolytic capacitors should not be used in AC power circuits, otherwise the capacitors will be damaged.
I. Distinguishing the positive and negative terminals of an electrolytic capacitor
1. Lead-type (wire-type) electrolytic capacitor
There are two methods to identify the positive and negative terminals of a pin-type electrolytic capacitor. For long-legged capacitors, the longer pin is the positive terminal, and the shorter pin is the negative terminal. The second method is to check the negative terminal marking line printed on the capacitor's casing. This marking line is usually white, yellow, or other colors. The side with the negative marking line is the negative terminal, and the other side is the positive terminal.
2. Horn-shaped electrolytic capacitor
Unlike pin-type electrolytic capacitors, horn-shaped electrolytic capacitors do not have pins, so the length of the pins cannot be used to determine their polarity. However, checking the negative terminal markings printed on the capacitor sleeve is still valid. Additionally, you can check for embossing on the terminals in a grid pattern. The side with the embossing is the negative terminal, and the other side is the positive terminal.
II. Distinguishing the positive and negative terminals of surface mount capacitors
Unlike the previous two types of capacitors, surface-mount electrolytic capacitors do not have leads, so the positive and negative terminals cannot be identified by the length of the leads, and they do not have a negative terminal marking line printed on the sleeve. However, surface-mount electrolytic capacitors do have a negative terminal marking printed on the negative terminal side, as shown in the figure below.
III. Distinguishing the Positive and Negative Terminals of Solid-State Capacitors
Solid-state capacitors are further divided into surface-mount solid-state capacitors and through-hole (pin-type) solid-state capacitors. The method for identifying the positive and negative terminals of surface-mount solid-state capacitors is exactly the same as that for surface-mount electrolytic capacitors mentioned earlier; as shown in the diagram below, the red end is the negative terminal.
Through-hole solid capacitors have leads; therefore, in addition to the same method of identifying the positive and negative terminals as surface-mount electrolytic capacitors, another method for identifying the positive and negative terminals of through-hole solid capacitors is to look at the length of the leads. The side with the longer lead is the positive terminal, and the side with the shorter lead is the negative terminal.
How to distinguish the positive and negative terminals of a capacitor
1. Identifying the positive and negative terminals of bolt-type electrolytic capacitors. Bolted aluminum electrolytic capacitors have clear positive and negative markings on the sleeve, with "+" for positive and "-" for negative. Most bolt capacitors also have "+" and "-" markings engraved next to the terminals on the cover plate.
2. Identifying the positive and negative terminals of soldered aluminum electrolytic capacitors. Soldered aluminum electrolytic capacitors, also known as horn capacitors, are currently all marked with a "negative terminal indicator," meaning the solder pin corresponding to the "-" mark on the sleeve is the negative terminal. The positive and negative terminals of soldered electrolytic capacitors are also distinguished on the cover plate, mostly by "embossing" the negative terminal, while some manufacturers directly print "+" and "-" marks on the rivets.
3. Methods for identifying the positive and negative terminals of leaded electrolytic capacitors. Leaded electrolytic capacitors also use a "negative terminal marking," meaning the lead corresponding to the "-" marking on the sleeve is the negative terminal. Another method is by the length of the leads: the longer lead is the positive terminal, and the shorter lead is the negative terminal.
4. How to identify the positive and negative terminals of a surface-mount aluminum electrolytic capacitor. Surface-mount aluminum electrolytic capacitors, also known as chip aluminum electrolytic capacitors, do not have a casing, so the capacitance, voltage, positive and negative terminals are printed on the bottom of the aluminum casing.
Applications of electrolytic capacitors
Polarized electrolytic capacitors are typically used in power supply circuits or intermediate frequency and low frequency circuits for functions such as power filtering, decoupling, signal coupling, time constant setting, and DC blocking. They are generally not suitable for AC power supply circuits. When used as filter capacitors in DC power supply circuits, their anode (positive terminal) should be connected to the positive terminal of the power supply voltage, and their cathode (negative terminal) should be connected to the negative terminal. Reversing these connections will damage the capacitor.
Non-polar electrolytic capacitors are commonly used in speaker crossover circuits, television S-correction circuits, and starting circuits for single-phase motors.
Electrolytic capacitors are widely used in household appliances and various electronic products. They have a wide capacitance range, typically 1~33000μF, and a rated operating voltage range of 6.3~700V. Their drawbacks include dielectric loss, large capacitance error (maximum permissible deviation of +100% and -20%), poor high-temperature resistance, and susceptibility to failure over long storage periods.
To determine the polarity of an electrolytic capacitor, observe the side of the capacitor. A "-" indicates the negative terminal and a "+" indicates the positive terminal. If the capacitor is not marked with polarity, you can also determine it by the length of its leads: the longer lead is the positive terminal and the shorter lead is the negative terminal.
