Objectives
- To measure the Resistance of a resistor by using Color Coding Method.
- To measure the voltage and Current by using Digital Power Supply and Multimeter.
Resistors regulate the amount of current flowing in an
electronic circuit. Resistors present a resistance, or impedance, to the
electrical circuit and reduce the amount of current that is allowed to flow.
Resistors are utilized for simple signal conditioning and to protect active
electronic devices that could be damaged by receiving excess current. Resistors
must be properly sized and intact to perform these functions. Use these tips to
learn how to test resistors.
The electronic color code is used to
indicate the values or ratings of electronic components, usually for resistors, but
also for capacitors, inductors, diodes and others.
The
colored bands on a resistor can tell you everything you need to know about its
value and tolerance, as long as you understand how to read them. The
order in which the colors are arranged is very important, and each value of
resistor has its own unique combination.
|
Black
|
Brown
|
Red
|
Orange
|
Yellow
|
Green
|
Blue
|
Violet
|
Grey
|
White
|
|
0
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
|
S no.
|
Color
|
Tolerance
|
|
1
|
Gold
|
5%
|
|
2
|
Silver
|
10%
|
|
3
|
No band
|
20%
|
Figure 1
Here is an example that shows how the table and resistor
shown above can be used to figure out a resistor value by proving that
yellow-violet-brown is really 470 Ω:
- The first stripe is yellow, which means the leftmost digit is a 4.
- The second stripe is violet, which means the next digit is a 7.
- The third stripe is brown. Since brown is 1, it means add one zero to the right of the first two digits.
Yellow=4, Violet=7, Brown(Multiplier)=10
Gold(Tolerance)=+-5%
Resistance of the resistor = 470 Ω
Although the first two bands are
fairly straightforward, the third and fourth bands might require a bit more
explanation.
The color of the band determines the power of 10 you need to
multiply the first two resistor digits by. For example, an orange third band
with a digit value of 3 would indicate a multiplier of 103,
though you can also just think of this as telling you to “stick 3 zeros on the
end".
Example:
Brown-black-orange resistor.
- Brown = 1, black = 0, orange multiplier = 103
10 x 103 = 10000,
which is the same as 10 + three zeros = 10000.
The fourth color band indicates the resistor's tolerance.
Tolerance is the percentage of error in the resistor's resistance, or how much
more or less you can expect a resistor's actual measured resistance to be from
its stated resistance. A gold tolerance band is 5% tolerance, silver is
10%, and no band at all would mean a 20% tolerance.
For example:
A 220 Ω resistor has a silver tolerance band.
- Tolerance = value of resistor x value of tolerance band = 220 Ω x 10% = 22 Ω
220 Ω stated resistance +/- 22 Ω
tolerance means that the resistor could range in actual value from as much as
242 Ω to as little as 198 Ω.
|
S no
|
1st
band
|
2nd
band
|
3rd
band
|
4th
band
|
r (Ω)
|
rang of r_(Ω)
|
r(Ω) dmm
|
error
|
|
1
|
Red=2
|
Violet=7
|
Red=
|
Gold=
|
2700
|
2560-2835
|
2640
|
|
|
2
|
Red=2
|
Red=2
|
Red=
|
Gold=
|
2200
|
2090-2310
|
2230
|
|
|
3
|
Brown=1
|
Black=0
|
Red=
|
Gold=
|
1000
|
950-1050
|
981
|
|
|
4
|
Red=2
|
Black=0
|
Orange=
|
Gold=
|
20000
|
1900-2100
|
19500
|
|
|
5
|
Brown=1
|
Black=0
|
Brown=10
|
Gold=
|
100
|
95-105
|
98
|
|
Definition:
Power
applications that use digitally managed and digitally controlled solutions to
provide configuration, monitoring, feedback and supervisory or control
functions which extend to full loop control using digital hardware and software
algorithms.
Figure 2
Definition:
A digital
multimeter (DMM) is a test tool used to measure two or more electrical
values—principally voltage (volts), current (amps) and resistance (ohms). It is
a standard diagnostic tool for technicians in the electrical/electronic
industries.
Figure 3
A multimeter generally, has three parts:
- Display
- Selection Knob
- Ports
- Sometimes, it also has buttons in it.
The display usually
has four digits and the ability to display a negative sign. A few multimeters
have illuminated displays for better viewing in low light situations.
The selection
knob allows the user to set the multimeter to read different things
such as milliamps (mA) of current, voltage (V)
and resistance (Ω).
Two probes are
plugged into two of the ports on the front of the unit. COM stands
for common and is almost always connected to Ground or ‘-’ of a circuit.
The COM probe is conventionally black but there is no
difference between the red probe and black probe other than color. 10A is
the special port used when measuring large currents (greater than 200mA). mAVΩ is
the port that the red probe is conventionally plugged in to. This port allows
the measurement of current (up to 200mA), voltage (V), and resistance (Ω). The
probes have a banana type
connector on the end that plugs into the multimeter. Any probe with a banana
plug will work with this meter. This allows for different types of
probes to be used.
For Voltage measurement, we connect the
cold or negative terminal of the digital power supply with the same terminal of
the digital multimeter and similarly, we connect the positive terminals.
For the current measurement, first we
calculate the power supply value from the digital power supply and then we
calculate the current from the formula:
v=i/r
We can find the value
of the Resistance of the power
supply, by the help of using DMM.
Then we calculate the value from the DMM and compare it with
the values given on the digital multimeter and we find out the error.
Error% =
|
s.no
|
power supply
|
DMM
|
error
|
|
1
|
15
|
15
|
|
|
2
|
5
|
5.22
|
|
|
3
|
-15
|
-15.1
|
|
|
s.no
|
power supply
|
DMM
|
error
|
|
1
|
15
|
15
|
|
|
2
|
5
|
5.22
|
|
|
3
|
-15
|
-15.1
|
|
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