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# Resistance Measurement

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```Understanding the
Resistor Color Code
Dr. Deb Hall
Electronics Engineering
Technology
Valencia Community College
Resistor Color Code
п‚® Manufacturers
typically use a color
band system known as the resistor color
code
п‚® Within this power point, you will learn
how to identify the nominal resistance
and the tolerance of a resistor
Resistor Color Code
п‚®
The power rating is not indicated in the
resistor color code and must be determined
by experience using the physical size of the
resistor as a guide.
п‚®
For resistors with п‚±5% or п‚±10% tolerance, the
color code consists of 4 color bands.
п‚®
For resistors with п‚±1% or п‚±2% tolerance, the
color code consists of 5 bands.
4-Band Resistors
The resistor nominal value is encoded in the color code in
Powers of Ten Notation. The template for determining the
nominal value and tolerance of a resistor with 4 color bands is
given below:
1st Band =
1st Significant Digit
2nd Band =
2nd Significant Digit
3rd Band =
Multiplier
4th Band =
Tolerance
___ ___ п‚ґ 10 п‚ѕп‚ѕ пЃ— п‚± ____ %
How do we know which color corresponds
to which number?
Answer: Using the Resistor Color Code Table
Example 1. Determine the nominal resistance value and the
tolerance for the resistor shown below.
Solution:
Brown =1 Black =0 Red =2
Gold = п‚±5%
2
п‚ѕп‚ѕ
1
0
5 %
___ ___ п‚ґ 10
пЃ— п‚± ____
Nominal value = 10п‚ґ102пЃ—
= 1,000пЃ—
Tolerance = п‚±5%.
п‚®
п‚®
п‚®
It is typical to express the resistance value in:
kпЃ— if the resistance п‚і 1,000пЃ—
MпЃ— if the resistance п‚і 1,000,000пЃ—.
To convert from пЃ— to kпЃ—, пЃ— to MпЃ—, or vice-versa, use the table
below:
In the previous example we would say the resistor has a
nominal value of: 1,000пЃ—
пЂЅ 1kпЃ—
1,000
Example 2. a) Determine the nominal value and tolerance for the
resistor below.
b) What is the minimum resistance value this resistor
can actually have?
c) What is the maximum resistance value this resistor
can actually have?
Solution:
Yellow =4
Violet =7
4 ___
7 п‚ґ 10
___
Orange =3
3
п‚ѕп‚ѕ
Gold = п‚±5%
5 %
пЃ— п‚± ____
Resistor nominal value = 47п‚ґ103пЃ—
= 47,000пЃ—
= 47kпЃ—.
Tolerance = п‚±5%
Solution: continued
п‚®
Minimum resistance value:
Multiply the nominal value by the tolerance and then subtract
this from the nominal value:
пЂЅ 47kпЃ— пЂ­ 47kпЃ— * 0.05
пЂЅ 47kпЃ— пЂ­ 2.35kпЃ—
пЂЅ 44.65kпЃ—
п‚®
Maximum resistance value:
Multiply the nominal value by the tolerance and then add this to
the nominal value:
пЂЅ 47kпЃ— пЂ« 47kпЃ— * 0.05
пЂЅ 47kпЃ— пЂ« 2.35kпЃ—
пЂЅ 49.35kпЃ—
Example 3. a) Determine the nominal value and tolerance for the
resistor below.
b) What is the minimum resistance value this resistor
can actually have?
c) What is the maximum resistance value this resistor
can actually have?
Solution:
Orange =3 White =9
3 ___
9 п‚ґ 10
___
Green =5
5
п‚ѕп‚ѕ
Silver = п‚±10%
10 %
пЃ— п‚± ____
Resistor nominal value = 39п‚ґ105пЃ—
= 3,900,000пЃ—
= 3.9MпЃ—.
Tolerance = п‚±10%
Solution: continued
п‚®
Minimum resistance value:
nominal value вЂ“ nominal value * tolerance:
пЂЅ 3.9 MпЃ— пЂ­ 3.9 MпЃ— * 0.1
пЂЅ 3.9 MпЃ— пЂ­ 0.39MпЃ—
пЂЅ 3.51MпЃ—
п‚®
Maximum resistance value:
nominal value + nominal value * tolerance:
пЂЅ 3.9 MпЃ— пЂ« 3.9 MпЃ— * 0.1
пЂЅ 3.9 MпЃ— пЂ« 0.39MпЃ—
пЂЅ 4.29MпЃ—
5-Band Resistors
п‚®
For resistors with п‚±1% or п‚±2% tolerance, the color code consists
of 5 bands.
п‚®
The template for 5-band resistors is:
1st Band =
1st Significant
Digit
2nd Band =
2nd Significant
Digit
3rd Band =
3rd Significant
Digit
4th Band =
Multiplier
5th Band =
Tolerance
___ ___ ___ п‚ґ 10 п‚ѕп‚ѕ пЃ— п‚± ____ %
Example 4. Determine the nominal resistance and tolerance for
the resistor shown below.
Solution:
Brown = 1
Black =0
Black = 0
Brown = 1
Red = п‚± 2%
1
1 ___
0 ___
0 п‚ґ 10 п‚ѕп‚ѕ
2 %
___
пЃ— п‚± ____
Resistor nominal value = 100п‚ґ101пЃ—
= 1,000пЃ—
= 1kпЃ—.
Tolerance = п‚±2%
Example 5. Determine the nominal resistance and tolerance for
the resistor shown below.
Blue = 6
Solution:
Gray = 8
Black = 0
Orange = 3
Brown = п‚± 1%
3
6 ___
8 ___
0 п‚ґ 10 п‚ѕп‚ѕ
1 %
___
пЃ— п‚± ____
Resistor nominal value = 680п‚ґ103пЃ—
= 680,000пЃ—
= 680kпЃ—.
Tolerance = п‚±1%
Which side of a resistor do I
п‚®
A question that often arises when reading the color
code of real resistors is: how do I determine which
side of a resistor do I read from?
п‚®
For 4-band resistors a gold or silver band is always
the last band.
п‚®
If the resistor has 5 bands or if there is no tolerance
band (п‚±20%), then the first band is the one located
Converting the Nominal Resistance and
Tolerance into the Color Code
We are given the nominal value and the tolerance and we
have to come up with the color code.
4-Band Resistors
1.
Resistors with п‚±5% and п‚±10% Tolerance will have 4-bands
2.
Convert nominal value to ohms (пЃ—)
3.
1st digit (from left to right) of nominal value = 1st color band
4.
2nd digit of nominal value = 2nd band
5.
Number of zeros remaining = 3rd (multiplier) band
6.
Tolerance = 4th band
Example 6. Specify the color code of a resistor with nominal value
of 27kпЃ— and a tolerance of п‚±10%.
Solution:
1) Since resistor Tolerance = п‚±10% it will have 4-bands.
2) Convert the nominal resistance value to пЃ— from kпЃ—.
27,000 пЃ—
Red = 2
Violet = 7
Orange = 3
п‚±10%
Example 7. Specify the color code of a resistor with nominal value
of 1.5kпЃ— and a tolerance of п‚±5%.
Solution:
1) Since resistor Tolerance = п‚±5% it will have 4-bands.
2) Convert the nominal resistance value to пЃ— from kпЃ—.
1,500 пЃ—
Brown = 1
Green = 5
Red = 2
п‚±5%
Converting the Nominal Resistance and
Tolerance into the Color Code
5-Band Resistors
1.
Resistors with п‚±1% and п‚±2% Tolerance will have 5-bands
2.
Convert nominal value to ohms (пЃ—)
3.
1st digit (from left to right) of nominal value = 1st color band
4.
2nd digit of nominal value = 2nd band
5.
3rd digit of nominal value = 3rd band
6.
Number of zeros remaining = 4th (multiplier) band
7.
Tolerance = 5th band
Example 8. Specify the color code of a resistor with nominal value
of 2.5MпЃ— and a tolerance of п‚±1%.
Solution:
1) Since resistor Tolerance = п‚±1% it will have 5-bands.
2) Convert the nominal resistance value to пЃ— from MпЃ—.
2,500,000пЃ—
Red = 2
Green = 5
Black = 0
Yellow = 4
п‚±1%
Congratulations!
You now know how to work
with the resistor color code
ItвЂ™s that simple!
```
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