I have a package of 10 inductors, all of which are supposed to be 22µH, but they all have "220" printed on the case. It does not seem right when I compare to an otherwise identical (same type) inductor with an inductance of 3.3µH, which has "3R3" printed on it. Is it just odd ordering or am I missing something? Inductor is an SDR0604 type.
There are two ways of marking parts...
A Three digit code for values from 10 and up
X Y Z X - First digit Y - Second digit Z - Power of ten 220 would be 22 = 22 x 10^0 (1) 221 would be 220 = 22 x 10^1 (10) 222 would be 2,200 = 22 x 10^2 (100) 223 would be 22,000 = 22 x 10^3 (1000)
The Minimum for this coding would be 100 = 10 x 10^0 and the Maximum would be 999 = 99,000,000,000 = 99 x 10^9 (1,000,000,000)
For values under 10
you use a character to replace the decimal point
e.g. 3R3 = 3.3 R33 = 0.33
R is used for Ohms.
For resistors the value is usually in Ohms For Capacitors the value is usually in pico farads
e.g. a Capacitor marked 103 would be 103 pF = 10 x 10^3 (1000) pF = 10nF = 0.01uF
For Inductors the value is usually in micro henrys e.g. a Inductor marked 220 woulf be 22uH = 22 x 10^0 (1) uH
The part marked 3R3 is a 3.3 ohm resistor as R is used on resistors.
Panasonic SM inductors use R in the part marking (for example, 2R6 corresponds to the 2.6 microhenry part on the specified datasheet).