These capacitors include both aluminum and tantalum electrolytics. They are manufactured by an electrochemical formation of an oxide film onto a metal (aluminum or tantalum) surface. The metal on which the oxide film is formed serves as the anode or positive terminal, the oxide film acts as the dielectric, and a conducting liquid or gel acts as the cathode or negative terminal. Tantalum electrolytic capacitors have larger capacitance per volume ratios when compared with aluminum electrolytic. A majority of electrolytic capacitors are polarized. Electrolytic capacitors, when compared with non electrolytic capacitors, typically have greater capacitances but have poor tolerances (as large as +/- 100 percent for aluminum and about +/- 5 to +/-20 percent for tantalum), bad temperature stability, high leakage, and short lives. Capacitances range from about 1 uF to 1 F for aluminum and 0.001 to 1000 uF for tantalum, with maximum voltage ratings from 6 to 450 V.
This type is very popular non polarized capacitor that is small and inexpensive but has poor temperature stability and poor accuracy. It contains a ceramic dielectric and a phenolic coating. It is often used for bypass and coupling applications. Tolerances range from +/-5 to +/-100 percent, while capacitances range from 1 pf to 2.2 uF, with maximum voltage rating from 3 V to 6 kV.
This type is a very popular non polarized capacitor that is reliable, inexpensive, and has low leakage current but poor temperature stability. Capacitances range from 0.001 to 10 uF, with voltage ratings from 50 to 600 V.
This type is an extremely accurate device with very low leakage currents. It is constructed with alternate layers of metal foil and mica insulation, stacked and encapsulated. These capacitors have small capacitances and are often used in high frequency circuits (eg. : RF circuits). They are very stable under variable voltage and temperature conditions. Tolerances range from +/-0.25 to +/-5 percent. Capacitances range from 1 pf to 0.01 uF, with maximum voltage ratings from 100 V to 2.5 kV.
Other kinds of capacitors include paper, polystyrene, polycarbonate, polyester, glass, and oil capacitors, their characteristics are covered in table below :
Variable capacitors are devices that can be made to change capacitance values with the twist of a knob. These devices come in either air variable or trimmer forms. Air variable capacitors consist of 2 sets of aluminum plates (stator and rotor) that mesh together but do not touch. Rotating the rotor plates with respect to the stator varies the capacitor's effective plate surface area, thus changing the capacitance. Air variable capacitors typically are mounted on panels and are used in frequently adjusted tuning applications (eg. : fine tuning fixed frequency communications receivers, crystal frequency adjustments, adjusting filter characteristics). Trimmers may use a mica, air, ceramic, or glass dielectric and may use either a pair of rotating plates or a compression like mechanism that forces the plates closer together.
Reading capacitors labels is tricky business. Each family of capacitors uses its own unique labeling system. Some system are easy to understand, whereas others make use of misleading letters and symbols. The best way to configure out what a capacitors label means is to first figure out what family the capacitor belongs to. After that, try seeing if the capacitor label follows one of the convention like these :
Capacitors with small capacitances (less than 0.01 uF) do not pose much danger to humans. However, when the capacitances start exceeding 0.1 uF, touching capacitor leads can be a shocking experience. For example, large electrolytic capacitors found in television sets and photoflashes can store a lethal charge. As a rule, never touch the leads of large capacitors. If in question, discharge the capacitor by shorting the leads together with a screwdriver tip before handling it.
For JIS (Japan Industrial Standard), Korea, Taiwan
HJ Serie :
- HJA type; dielectric substans is polyester film with aluminum foil electrode, color : green
- HJT type; dielectric substans is polyester film with tin foil electrode, color : brown
- Temperature ranges : -40 o C to +85 o C
- Voltage range : 1H code = 50 V, 2H = 500 V, 2A = 100 V, 2D = 200 V, 2G = 400 V
- Capacitance standard value : 0.001 to 0.47 uF
- Tolerance : J = 5 %, K = 10 %, M = 20 %
- Breakdown Voltage = 2.5 times voltage level for 1 to 5 seconds
- Isolation resistance = 20000 MOhm at 20 o C
- Dissipation factor : max 1 % at 1 kHz
- Pin connection : copper covered with tin
Standard Value Table :
- Range Value = 0.001 to 6.8 uF
- Tolerance = 10 % to 20 %
- Capacitance range = E - 12
- Voltage Range = 100 V to 630 V
- VR (ac) at 50~60 Hz = 63 V to 220 V
- Test Voltage = 1.6 times VR
- Temperature Range = -40 o C to +100 o C
- Dissipation Factor at 10 kHz = less than 150 x 10 - 4
Isolation Resistance at 20 o C, C = 0.033 uF, R = 30000 MOhm (*), C = 0.33 uF, RC (MOhm x uF) = 10000 s, (*) Acception for 100 V version = R = 15000 MOhm, RC = 5000 s
Standard Value Table :
COLOR VALUE MULTIPLIER TOLERANCE VOLTAGE Black 0 1 20 % Brown 1 10 100 V Red 2 100 250 V Orange 3 1000 Yellow 4 10000 400 V Green 5 100000 Blue 6 630 V Violet 7 Grey 8 White 9 10 %
Plastic metal alloy capacitors (like MK capacitors) can self recovery after breakdown. Very thin metal layer coat to plastic foil about 0.02 to 0.05 um. The arc with rise at breakdown will evaporate metal layer at the point without damage the dielectric. This happened for less then 10 usec. Capacitance lost can be disparage. Metal layer constructed to cylinder type or flat or arranged to stack. Metal syringe method that used to connect the wires guaranted all the roll are connected. That was made the MK capacitors had low inductance and low losses characteristic.
DIN Code :
M = Metal layer ---------- M K S K = Plastic -----------------------| | * Third is the dielectric types : -----| S = Polystyrene (MKS = MKY) P = Polyprophylene (MKP) C = Polycarbonate (MKC = MKM) T = Polythereftalate (MKT = MKH) U = Cellulose Acetate (MKU = MKL)