If code is 3r9 then r is an indicator of values less than 10pf and has nothing to do with resistance.
Ceramic capacitor marking reader.
682k is 6 8 nf 10 tolerance.
I have always been unaware of the markings on a disc ceramic capacitor such as j m and other symbols.
Some small capacitance capacitors can be marked with an r between numbers.
Reading values printed on electrolytic capacitors is easy digits on ceramic capacitors need to know some theory.
Unlike resistors capacitors use a wide variety of codes to describe their characteristics.
The top 683 marking indicates the capacitance value which is 68 000 picofarads pf.
For beginners some values might prove confusing.
Values with the letter capital k represents 10 tolerance.
Often the value may be given in picofarads.
Physically small capacitors are especially difficult to read due to the limited space available for printing.
The markings on a ceramic capacitor are more concise in nature since it is smaller in size as compared to electrolytic capacitors.
823k is 82 nf 10 tolerance.
Like resistors has some coding which needs to decipher printed digits on ceramic capacitors also needs deciphering.
There are three exceptions for the last digit.
The above image shows a mylar film capacitor.
American technical ceramics corp.
Ceramic capacitors are generally smaller than types like electrolytic capacitors and therefore the markings need to be more concise.
My article on ceramic disc capacitor values might help with the tolerance letters.
Thus for such concise markings many different types of schemes or solutions are adopted.
Atc provides component and custom integrated packaging solutions for the rf microwave and telecommunications industries atc designs develops manufactures and markets multilayer capacitors single layer capacitors resistive products inductors and custom thin film products for rf microwave and millimeter wave applications.
Here is how to read ceramic capacitor values.
Some capacitors are only marked as 0 1 or 0 01 mostly in these cases the values are given in uf.
Example 103k is a 10 nf capacitor with a 10 tolerance.
A variety of schemes may be used.
7 is not.
Npo type capacitors are frequently used for precision timing filtering frequency setting and tuning circuits.
Has a very low dissipation factor and are very stable over wide variations in temperature frequency voltage and time.
The value of the capacitor is indicated in picofarads.
3r9 would be 3 9pf.
To get this value you multiply the leading digits 68 in this case by 10 raised to the power of the last digit 3 and the result is the capacitance in picofarads in this case we get 68x10 3 pf.