How Do I Read an Ac Capacitor Rating?

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Unlike resistors, capacitors use a wide variety of codes to draw their characteristics. Physically small capacitors are especially difficult to read, due to the limited space available for press. The data in this commodity should help you read near all modern consumer capacitors. Don't be surprised if your information is printed in a different order than the 1 described here, or if voltage and tolerance info is missing from your capacitor. For many low-voltage DIY circuits, the but information you demand is the capacitance.

1. one

   Know the units of measurement. The base unit of capacitance is the farad (F). This value is much besides large for ordinary circuits, then household capacitors are labeled with one of the post-obit units:^{[1] [2]}

   • 1 µF, uF, or mF = 1 microfarad = 10^-6 farads. (Careful — in other contexts, mF is the official abbreviation for millifarads, or 10^-3 farads.)
   • one nF = ane nanofarad = 10^-ix farads.
   • ane pF, mmF, or uuF = i picofarad = 1 micromicrofarad = 10^-12 farads.

2. two

   Read the capacitance value. Well-nigh large capacitors have a capacitance value written on the side. Slight variations are common, so await for the value that almost closely matches the units higher up. You lot may need to adjust for the following:

   • Ignore majuscule letters in the units. For instance, "MF" is simply a variation on "mf." (It is definitely not a megafarad, even though this is the official SI abbreviation.)
   • Don't become thrown past "fd." This is just another abbreviation for farad. For example, "mmfd" is the same equally "mmf."
   • Beware single-letter markings such equally "475m," commonly plant on smaller capacitors.^[3] See below for instructions.

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3. 3

   Look for a tolerance value. Some capacitors list a tolerance, or the maximum expected range in capacitance compared to its listed value. This isn't of import in all circuits, but yous may need to pay attention to this if yous crave a precise capacitor value. For example, a capacitor labeled "6000uF +50%/-70%" could actually have a capacitance equally high as 6000uF + (6000 * 0.5) = 9000uF, or as low as 6000 uF - (6000uF * 0.vii) = 1800uF.

   • If there is no percent listed, expect for a single alphabetic character after the capacitance value or on its own line. This may be code for a tolerance value, described below.

4. 4

   Check the voltage rating. If there is room on the body of the capacitor, the manufacturer usually lists voltage as a number followed by a V, VDC, VDCW, or WV (for "Working Voltage").^[4] This is the maximum voltage the capacitor is designed to handle.

   • 1 kV = ane,000 volts.
   • Meet below if yous doubtable your capacitor uses a code for voltage (a unmarried alphabetic character or one digit and one alphabetic character). If there is no symbol at all, reserve the cap for low-voltage circuits only.
   • If you are building an AC circuit, look for a capacitor rated specifically for VAC. Do not apply a DC capacitor unless you lot take an in-depth knowledge of how to convert the voltage rating, and how to use that type of capacitor safely in Air conditioning applications.^[5]

5. 5

   Look for a + or - sign. If y'all encounter 1 of these side by side to a final, the capacitor is polarized. Make sure to connect the capacitor'south + end to the positive side of the circuit, or the capacitor could eventually cause a brusk or even explode.^[6] If at that place is no + or -, you can orient the capacitor either fashion.

   • Some capacitors use a colored bar or a ring-shaped depression to show polarity. Traditionally, this marker designates the - cease on an aluminum electrolytic capacitor (which are unremarkably shaped like tin cans). On tantalum electrolytic capacitors (which are very small), this marker designates the + end.^[7] (Disregard the bar if it contradicts a + or - sign, or if it is on a not-electrolytic capacitor.)

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1. 1

   Write down the first ii digits of the capacitance. Older capacitors are less anticipated, simply almost all modern examples use the Eia standard lawmaking when the capacitor is too small to write out the capacitance in total. To start, write downwards the commencement 2 digits, so decide what to do side by side based on your code:^[8]

   • If your code starts with exactly ii digits followed by a letter (e.1000. 44M), the first two digits are the full capacitance lawmaking. Skip downwardly to finding units.
   • If ane of the showtime ii characters is a letter, skip down to letter systems.
   • If the first three characters are all numbers, continue to the adjacent step.

2. two

   Apply the third digit as a zero multiplier. The three-digit capacitance code works every bit follows:

   • If the tertiary digit is 0 through 6, add that many zeroes to the finish of the number. (For case, 453 → 45 x 10³ → 45,000.)
   • If the tertiary digit is 8, multiply by 0.01. (e.thou. 278 → 27 x 0.01 → 0.27)
   • If the third digit is ix, multiply by 0.1. (e.g. 309 → 30 x 0.1 → three.0)

3. 3

   Work out the capacitance units from context . The smallest capacitors (fabricated from ceramic, film, or tantalum) use units of picofarads (pF), equal to 10^-12 farads. Larger capacitors (the cylindrical aluminum electrolyte blazon or the double-layer type) employ units of microfarads (uF or µF), equal to 10^-vi farads.^[nine]

   • A capacitor may overrule this by adding a unit after information technology (p for picofarad, northward for nanofarad, or u for microfarad). All the same, if there is only one letter of the alphabet subsequently the code, this is usually the tolerance code, not the unit. (P and Due north are uncommon tolerance codes, simply they do exist.)

4. four

   Read codes that comprise messages instead . If your lawmaking includes a letter as one of the first two characters, there are three possibilities:

   • If the letter is an R, supersede it with a decimal point to get the capacitance in pF. For case, 4R1 means a capacitance of iv.1pF.^[10]
   • If the letter is p, n, or u, this tells you lot the units (pico-, nano-, or microfarad). Replace this letter with a decimal betoken. For example, n61 means 0.61 nF, and 5u2 means 5.2 uF.^[eleven]
   • A code similar "1A253" is really two codes. 1A tells you lot the voltage, and 253 tells you lot the capacitance as described above.^[12]

5. 5

   Read the tolerance code on ceramic capacitors. Ceramic capacitors, which are usually tiny "pancakes" with ii pins, typically listing the tolerance value as i letter immediately after the three-digit capacitance value. This letter of the alphabet represents the tolerance of the capacitor, meaning how close the actual value of the capacitor can be expected to be to the indicated value of the capacitor. If precision is important in your circuit, translate this code every bit follows:^[13]

   • B = ± 0.1 pF.
   • C = ± 0.25 pF.
   • D = ± 0.5 pF for capacitors rated below 10 pF, or ± 0.v% for capacitors to a higher place ten pF.
   • F = ± 1 pF or ± ane% (same system every bit D higher up).
   • M = ± 2 pF or ± 2% (see above).
   • J = ± five%.
   • Thou = ± ten%.
   • 1000 = ± 20%.
   • Z = +80% / -20% (If you meet no tolerance listed, presume this as the worst case scenario.^[14] )

6. half dozen

   Read letter-number-alphabetic character tolerance values. Many types of capacitors correspond the tolerance with a more detailed three-symbol organisation. Interpret this every bit follows:^[15]

   • The beginning symbol shows minimum temperature. Z = 10ºC, Y = -30ºC, X = -55ºC.
   • The second symbol shows maximum temperature. 2 = 45ºC, four = 65ºC, 5 = 85ºC, six = 105ºC, 7 = 125ºC.
   • The third symbol shows variation in capacitance across this temperature range. This ranges from the most precise, A = ±1.0%, to the to the lowest degree precise, V = +22.0%/-82%. R, one of the most mutual symbols, represents a variation of ±15%.^[16]

7. seven

   Interpret voltage codes . Yous tin expect up the Environmental impact assessment voltage chart for a full list, but most capacitors employ i of the post-obit common codes for maximum voltage (values given for DC capacitors just):^[17]

   • 0J = 6.3V
   • 1A = 10V
   • 1C = 16V
   • 1E = 25V
   • 1H = 50V
   • 2A = 100V
   • 2nd = 200V
   • 2E = 250V
   • One letter codes are abbreviations of 1 of the common values above. If multiple values could apply (such every bit 1A or 2A), yous'll need to work it out from context.
   • For an judge of other, less common codes, await at the start digit. 0 covers values less than ten; one goes from ten to 99; 2 goes from 100 to 999; and and so on.

8. viii

   Await up other systems. Sometime capacitors or capacitors made for specialist use may use different systems. These are not included in this article, but yous tin can use this hints to guide your further research:

   • If the capacitor has ane long lawmaking beginning with "CM" or "DM," look up the U.S. military capacitor chart.
   • If there is no code but a serial of colored bands or dots, look up the capacitor color code.^[eighteen]

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• Ever mensurate the capacitance if you aren't able to read the information on the capacitor.

• The capacitor tin also list information on operating voltages. The capacitor should support a college voltage than the circuit you lot use information technology in; otherwise, it may break down (possibly explode) under functioning

• 1,000,000 picoFarads (pF) equals one microFarad (µF). Many common capacitor values are near this crossover area and could be ordinarily referred to using either unit designation. For example, a 10,000 pF cap is more than commonly referred to every bit 0.01 uF.

• Although you can't determine capacitance past the shape and size lonely, yous can guess at a rough range based on how the capacitor is being used:

  • The largest capacitors in a television monitor are in the power supply. Each one can have a capacitance as high as 400 to ane,000 µF, which tin can exist lethal if handled incorrectly.^{[19] [20]}
  • The large capacitors in an antiquarian radio typically range from ane-200 µF.^[21]
  • Ceramic capacitors are ordinarily smaller than your pollex and attach to the circuit with two pins. Used in many applications, they typically range from 1 nF to ane µF, and occasionally up to 100 µF.^[22]

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• Be very careful when handling large capacitors, which can hold a lethal amount of energy when charged. Ever make certain to discharge them first by using an advisable resistor. Never short excursion them, every bit this could cause an explosion.

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About This Article

Article Summary X

To read a large capacitor, kickoff observe the capacitance value, which will be a number or a number range most commonly followed past µF, M, or FD. Then look for a tolerance value, typically listed every bit a percentage. Next, check the voltage rating, which is usually listed as a number followed by the messages V, VDC, VDCW, or WV. Finally, see if your capacitor is polarized by looking for plus or minus signs next to its terminals, which betoken that it is. For more on reading capacitors, including how to read compact capacitor codes, scroll down!

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