Capacitor numbering
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Capacitor numbering
by TerrySmith » Sun Nov 21, 2004 2:54 pm
Does anyone know of a website on how to read capacitor numbers? :?: :?: I have a pile of ceramic disc caps, and was needing to know what the numbers mean. :help:
T. Smith
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TerrySmith - KT88
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by erichayes » Mon Nov 22, 2004 2:41 am
Hi All,
Ceramic caps (and, recently, orange drop and other plastic caps) use a military protocol for identifying the value, voltage and tolerance...usually.
The first (top) line of data is generally three digits and a letter. The first two digits are the significant figures of the capacitance, and the third is the multiplier. The value will be presented in picofarads. Thus, a reading of 221 would translate to 22 times 10 to the first power, or 220 pF. Conversely, a 104 label would indicate a 10 x 10000 pF or 0.1 µF.
Occasionally manufacturers will label the caps directly in picofarads, and this gets sticky when you're dealing with values between 100 and 820 pF. You don't know if the third digit is significant or a multiplier. When in doubt, measure. There've been several suggestions regarding capacitance checkers and LCR bridges on other threads, and I heartily recommend the purchase of same.
The remaining information is usually tolerance, voltage rating, and themal coefficient.
Tolerance is given as J (±5%), K (±10%) and Z (±20%). No letter indicates ±20% or worse.
Voltage ratings are usually self-explanitory, but if there are no markings, it's fairly safe to asume that the cap is rated at 400V minimum unless it's thin and has high capacitance.
Thermal, or temperature, coefficient is expressed in parts per million, and goes either negative or positive to the basic capacitance specification. Practically speaking, a cap with a N750 designation will decrease slightly in capacitance as its temperature rises. The ideal ceramic cap has a "NP0" spec, which translates to "negative-positive zero" characteristic.
Ceramic caps are great for RF work, but I don't recommend them for audio use unless absolutely necessary. They have a tendency to be microphonic.
Ceramic caps (and, recently, orange drop and other plastic caps) use a military protocol for identifying the value, voltage and tolerance...usually.
The first (top) line of data is generally three digits and a letter. The first two digits are the significant figures of the capacitance, and the third is the multiplier. The value will be presented in picofarads. Thus, a reading of 221 would translate to 22 times 10 to the first power, or 220 pF. Conversely, a 104 label would indicate a 10 x 10000 pF or 0.1 µF.
Occasionally manufacturers will label the caps directly in picofarads, and this gets sticky when you're dealing with values between 100 and 820 pF. You don't know if the third digit is significant or a multiplier. When in doubt, measure. There've been several suggestions regarding capacitance checkers and LCR bridges on other threads, and I heartily recommend the purchase of same.
The remaining information is usually tolerance, voltage rating, and themal coefficient.
Tolerance is given as J (±5%), K (±10%) and Z (±20%). No letter indicates ±20% or worse.
Voltage ratings are usually self-explanitory, but if there are no markings, it's fairly safe to asume that the cap is rated at 400V minimum unless it's thin and has high capacitance.
Thermal, or temperature, coefficient is expressed in parts per million, and goes either negative or positive to the basic capacitance specification. Practically speaking, a cap with a N750 designation will decrease slightly in capacitance as its temperature rises. The ideal ceramic cap has a "NP0" spec, which translates to "negative-positive zero" characteristic.
Ceramic caps are great for RF work, but I don't recommend them for audio use unless absolutely necessary. They have a tendency to be microphonic.
Eric in the Jefferson State
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