Decoding Capacitor Number Marking to get the capacitance value is a must for electrical circuit designers. It also helps in replacing the capacitor with exact alternate while repairing a PCB. This post will teach you how to decode capacitor number markings with suitable example and that too with simple and easy to remember steps.
How to Decode Capacitor Number Marking
Mostly, ceramic capacitors come under this category. In normal practice, Ceramic capacitor has a three digit code value on its body. Kindly note that the decoded value of a Ceramic capacitor is always measured in Pico farad (pF).
Example of a Capacitor
Now, let’s take an example to understand it more easily. Suppose, we have to decode the capacitance value of the below mentioned capacitor.
Step 1 – First Two Digits of Capacitor Number
The three digit code of the capacitor is 681J. Here, The first 2 digit code gives us the starting capacitance value of the capacitor.
Thus, we can easily identify now that in case of capacitor 681J, the first two digit 68 means “the capacitor has starting capacitance value of 68”.
Step 2 – Third Digit of Capacitor Number
The third digit says how many zeros we have to add in it to get the actual capacitance value.
Here in the given example, the third digit 1 means “the number of zeroes behind 68 will be one” i.e . the capacitance value will be 690 pF.
Step 3 – Fourth letter of Capacitor Number
If there is a letter code after three digits, it denotes the tolerance value of the capacitor. If there is no letter code, then the tolerance value is unknown.
Now , the tolerance as per the letter code is as tabulated below:
Thus, we can easily identify now that in case of capacitor 681J, the last letter code J means “the capacitor has a tolerance limit of ± 5 %.
Coming to the conclusion, we can now easily decode capacitor marking (number) of most of the capacitors. Here, capacitor 681J means “it has a capacitance value of 680pF ± 5% tolerance.
In some case, we will see only a decimal value written on it. Suppose the decimal value written on the body of a capacitor is 0.01. Then this is the capacitance value in pico Farad. We do not have to convert it.