E12 Resistors

[SkrillBill]

Little confused on this, probably because i'm over thinking it. In the E12 series, there are 12 values. My understanding thus far is you multiply those valuee by 10 (up to roughly 10⁶). Is this correct for calculating ohm values of the e12 series?

eg,
1.2 * 10 = 12;
1.2 * 100 = 120
1.2 * 1000= 1.2k
1.2 * 10000 = 12k
...
1.2 * 1000000 = 1,200k

[Twoflower]

The E-Series are based on the number of resistors (or capacitors) within a decade: For E12 it is

1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2

Those strange looking numbers are based on the allowed tolerances for the resistors.  For E12 the tolerance is 10%. Any resistor value can vary +/-10%. So a 1.0Ohm resistor with +10% tolerance would be 1.1Ohm. A 1.2Ohm resistor with -10% would be 1.08Ohm. This is actually used while manufacturing: The manufacturer can measure the resistor and identify which value should be printed on it. No resistor is wasted because each measured resistor value will end up in one of the buckets.

Now this 12 values can be multiplied by any 10-based exponent. So you can have a E12 resistor with 3.3Ohm, a 47kOhm 180MOhm (rather high, not impossible but very uncommon).

[SkrillBill]

The E-Series are based on the number of resistors (or capacitors) within a decade: For E12 it is

1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2

Those strange looking numbers are based on the allowed tolerances for the resistors.  For E12 the tolerance is 10%. Any resistor value can vary +/-10%. So a 1.0Ohm resistor with +10% tolerance would be 1.1Ohm. A 1.2Ohm resistor with -10% would be 1.08Ohm. This is actually used while manufacturing: The manufacturer can measure the resistor and identify which value should be printed on it. No resistor is wasted because each measured resistor value will end up in one of the buckets.

Now this 12 values can be multiplied by any 10-based exponent. So you can have a E12 resistor with 3.3Ohm, a 47kOhm 180MOhm (rather high, not impossible but very uncommon).

I got that the values were the values within each decade(which i assume are 10,100,1000,...1,000,000). I wasn't sure if you just simply multipllied each value by the decade to get the actual resistance of a resistor. Trying to order bulk resistors, prior to writing this post i hadn't found a kit.. but i have now found a kit. However i still wish to understand a little more so i thank you for your post.

[Twoflower]

OK, I wasn't sure what your question was.

But you're right. You just multiply the 'base' E12-Value with the multiplier. This multiplier looks like 10^x (or 10 to the power of x); with any x. So x could be also -3: That would be a multiplier of 0.001. Such small values, or even smaller, are often used for capacitors as they're using the same E series style.

[JacobPilsen]

Wikipedia: Preferred number

[Zero999]

Any E24 resistor value can be made from two E12 values, in series or parallel. Again, the numbers in the table, linked below, can be multiplied or divided by a factor of ten.

[Brumby]

The En series values are based on multiples of the nth root of 10

For E12 these are:	10, 12, 15, 18, 22, 26, 32, 38, 46, 56, 68, 83, 100 (Start of next decade)
which have become:	10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82, 100

 
Each subsequent value is a little over 21% higher than the previous value.  This results in a straight line when mapped out on a logarithmic scale and reaches the next decade in 12 steps.  When reading a through-hole resistor with 3 value bands, you take the first and second one to create the numbers above (exactly those numbers) and then you multiply that by the power of 10 given by the third band.

This process is the basically same with any other E series.

Edit: Qualified resistor as a 'through-gole'

[Twoflower]

@Hero999: Yes you could do this. But as the tolerances on lesser E series are bigger than on higher ones you don't gain much. As said a E12 12Ohm resistor can be anywhere between 10.8Ohm (-10%) and 13.2Ohm (+10%). This would be in the range of a E24 resistor of 11Ohm, 12Ohm and 13Ohm. Each of the E12 resistors could be any of three E24 resistor values.

@Brumby: Didn't know that. If I remember my teacher told me that was because of the tolerances. But your explanation make more sense. Doing the right math it will probably show that both approaches are identical.

[floobydust]

I tried to use math to calculate [/url=https://en.wikipedia.org/wiki/E-series_of_preferred_numbers]EIA[/url] (IEC 60063) resistor values.
It did not work for me. Found out a few EIA sequence values are oddball or "fudged", I think from history going back to 1952.

Everyone just uses an array populated with the exact values.

[Benta]

The E3, E6, E12 and E24 series you unfortunately need to know by heart.
E48, E96 and E192 can be calculated from:

10^[N/M]

Where M is 48, 96 or 192 according to the series, and N is an integer 0...[M-1]