Fig. 1 - Various capacitors - how to read correctly |
Submultiples
A pF (picofarad) is the smallest submultiple that exists to "practically" indicate capacity. I say practical because there are still smaller submultiples, SI Prefixes (International System of Units)
(deci, centi, milli, micro, nano, pico, femto, atto, zepto and yocto), but they are not used in electronics. 1 picofarad is 1,000,000 (1 million) times less than 1 microfarad (μF).
Halfway between picofarad and microfarad there is another sub-multiple called nanofarad widely used and it is 1000 times larger than 1 picofarad and 1000 times smaller than 1 microfarad.
Typical Capacitor Values
For capacitors facing between 1pF to 1μF (almost all capacitors except for electrolytic), reference values are indicated with a three-digit number followed by a letter.
The first two digits indicate the starting number, while the third digit represents the number of zeros that must be added to the starting number to get the ending value.
The result obtained is necessary to consider it in picofarad.
Examples of encodings
Let's use it as an example; 4 types of captions written on the capacitors, as shown in Figure 3 below.
Figure 2 - Capacitor with only capacitance captions |
104 - Which is its capacitance in pF, and without any further information.
Figure 3 - Capacitor with voltage and capacitance value captions |
104 - What is its value in pF
The capacitor in Figure 4, we can see in the description the set of 3 numbers "104", which represents the reading in Picofarad, followed by the letter "J", representing Tolerance, and the set of three numbers "250" represent the working voltage followed by the letter "V", which is the working voltage indication.
Figure 4 - Capacitor with capacitance, tolerance, voltage captions |
J - It's the tolerance
250V - Is the working voltage.
Figure 5 - Capacitor with maximum voltage, capacitance, tolerance |
104 - What is your capacitance in pF
J - It's your tolerance
Let's Practice:
Practical reading of the Polyester Capacitor
- The first two initial 2A digits refer to Maximum Voltage, we can use the complete EIA table codes that indicate the maximum capacitors work voltages in direct voltage (DC).
0G = 4VDC | 0L = 5.5VDC | 0J = 6.3VDC |
1A = 10VDC | 1C = 16VDC | 1E = 25VDC |
1H = 50VDC | 1J = 63VDC | 1K = 80VDC |
2A = 100VDC | 2Q = 110VDC | 2B = 125VDC |
2C = 160VDC | 2Z = 180VDC | 2D = 200VDC |
2P = 220VDC | 2E = 250VDC | 2F = 315VDC |
2V = 350VDC | 2G = 400VDC | 2W = 450VDC |
2H = 500VDC | 2J = 630VDC | 3A = 1000VDC |
- The next three digits refer to its capacitance, in the case as already exemplified 104 = 10 + 4 zeros, which is equal to 100,000pF = 100nF.
- The last digit is the Letter "J", right after the three digits, determines the tolerance of the component.
It is interesting to note the fact that some letters correspond to "asymmetric tolerances", such as "P", that is, the component may have a capacity greater than indicated, but not less.
This type of tolerance is used with "filter" capacitors, where a value possibly higher than indicated does not minimize circuit operation, as we can see in the EIA table below.
EIA Table of Code Working Tolerance Indicators of a Capacitor
- B = ± 0.10pF
- C = ± 0.25pF
- D = ± 0.5pF
- E = ± 0.5%
- F = ± 1%
- G = ± 2%
- H = ± 3%
- J = ± 5%
- K = ± 10%
- M = ± 20%
- N = ± 30%
- P = ± +100%, - 0%
- Z = ± +80%, - 20%
Dimensions of a Voltage-Based Capacitor
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