Component labeling and identification

A bit of history about capacitor identification:

Back in the early days of electronics capacitors in radio electronics were primarily in microfarads or micromicrofarads. This was labeled as mf or uf, and mmf or uuf. Some in the early days didn't like the mmf/uuf designation so they stayed with mf/uf and used a lot of zeros.

Example: a 27pf was 0.000027uf. This was a nightmare in drawing schematics.

The lower case "u" was used because the Greek "" was impossible on a typewriter. The uuf was still harder and cumbersome so sometime in the mid-70's the "pico" prefix replaced the mmf/uuf.

Example: 47uuf became 47pf

As miniaturization took place in the early 80's parts became smaller and identification needed to follow suit. Engineers started to use "nano" to shorten identification. A 0.001uf (or 1000pf) was too long so it became 1nf.

Still a problem surfaced when a 0.0015uf (1500pf) became 1.5 nf. Why? Decimal points on very small components would seem to disappear. Also a photocopy of a photocopy would fade out the decimal point. Further generations of photocopies either made all decimal points disappear or many dots appear all over the page due to laser drum imperfections and you couldn't tell what was and what was not a decimal point.

Years ago the Europeans started to replace the decimal point with the alpha designator so a 1.5nf became 1n5 or 1N5.

Caution should be noted on some capacitors because many manufacturers used a three digit number instead of the "European" standard. As an example, a capacitor that is marked 100 was 10pf. 470 was not 470pf but 47pf. A 470pf became 471. The "1" designated the multiplier or how many zeroes after the two significant digits. So a 472 was a 4700pf. A 103 is a 0.01uf. A 105 is a 1uf. The Europeans were ahead of the time and confusion could have been averted if the manufacturers followed the contemporary format. Instead of 4700pf only three digits would be needed so it would be 4N7. Examples of other designations follow.

The decimal point is replaced with the unit multiplier/identifier.

The "R", "K" and "M" denote resistors. "R" for units of resistance, "K" for thousands of ohms, and "M" for millions of ohms.

The "N", "P" and "U" denote capacitors. "N" for nano farads, "P" for pico farads, and the "U" for micro farads. Unofficially, the "F" can be used to identify farads within certain limits.

Unofficially, the "Z" or the "V" can denote zener diodes.

Below are some examples of component identification:

4K7    4.7K or 4,700 ohms

12R    12 ohms

R33    0.33 ohms

M56    560,000 ohms

K12    120 ohms

82K    82,000 ohms

2M2    2,200,000 ohms

10M    10,000,000 ohms

1R5    1.5 ohms

N10    100 pf

1U0    1 uf

473   0.047uf (if a capacitor)

473   47,000 ohms (if a resistor)

105   1,000,000 ohms (if a resistor)

3P3    3.3 pf

15P    15 pf

P47    0.47 pf

1P5    1.5pf

1N5    .0015uf

1N0    .001uf or 1000pf

10U    10 mf

U33    0.33 uf

F10    0.1 farads or 100,000 uf

3N3    0.0033 uf

20N    0.02 uf 

22N  0.022uf

5Z1    5.1 volt zener or,
5V1    5.1 volt zener