At 08:09 AM 02/21/07, you wrote: >I have a very small capacitor labeled 103. Is this a .0001uf/100pf? >Thanks for the help. > >Laryn K8TVZ
From a web page I'm working on for the constructions projects page at repeater-builder... Here's some cut and paste text... In the past, capacitors have been marked in a variety of ways and have included the disastrous decimal point and sometimes lots of zeros. If you have ever tried to decide if a mark on a capacitor is a decimal point or a spot of dirt, you know what I mean. I don't know why folks use a decimal point in such a vital place. This is done to save space on the bodies that are getting smaller and smaller. This capacitor code works similarly to the resistor color code. You may have a capacitor that has 104J printed on it. Often it will also have 100V printed below it. The 104 represents the capacitor value, the J represents the tolerance, and the 100V tells us it is rated for 100 volts. The 3-digit code does away with the decimal point and uses either a number or letter instead. There are two forms of the 3-digit code. One uses three digits and the other uses two digits and a letter. To read the capacitor value, take the first two digits as the first and second significant digits. The third digit is a multiplier. Usually, this multiplier is the number of zeros to add after the first two digits. However table 1 below shows that there are a couple of exceptions. The resulting value you get is in picofarads which you can then convert to microfarads if necessary. Using table 1 below, the 104J capacitor identifier breaks into a 104 portion and a J portion. The 104 decodes to 100,000pF, or a .1µF capacitor (1,000,000 pF = 1uF). Refer to table 2 and you will see that the J tells us the tolerance is 5%. This means the actual capacitor value can vary +/-5% from its value of .1µF. (You might want to copy the two tables below onto a 3x5 card and tape it to the side of your capacitor parts bin) Table 1: Multiplier Code Third Digit Multiplier (multiply the first 2 digits by this number) If you want to know where to start when memorizing the table, start with: 100 = 10 plus no zeros or 10picofarads, 0.01nanofarad, or .00001uf 101 = 10 plus one zeros or 100picofarads, 0.1nanofarad, or .0001uf 102 = 10 plus two zeros or 1, 000picofarads, 1nanofarad, or .001uf 103 = 10 plus three zeros or 10,000 pF, 10 nanofarads or 0.01 uF. 104 = 10 plus 4 zeros or 100,000pF or 100n. or 0.1 uF 105 = 10 plus 5 zeros or 1,000,000pF or 1,000n. or 1 uF 106 or 107 Not used 108 multiply times 0.01 - i.e. a 108 capacitor is a 0.1pf (yep,a 1/10 pf) 109 multiply times 0.1 - i.e. a 109 capacitor is a 1pf Table 2: Tolerance Code Letter Tolerance B +/- 0.10% C +/- 0.25% D +/- 0.5% E +/- 0.5% F +/- 1% G +/- 2% H +/- 3% J +/- 5% K +/- 10% M +/- 20% N +/- 0.05% P +100% ,-0% Z +80%, -20% Is should be obvious that a "P" or "Z" rating might be ok for a power supply ripple filter,but not for a resonant circuit. Mike WA6ILQ
