Download ENGR 101 The Resistor Color Code Measuring Resistance

ENGR 101
The Resistor Color Code
Digit Color Mnemonic Mult. # of Zeros
black
0
bold
1
0
1 brown beautiful
10
1
red
2
roses
100
2
3 orange occupy
1,000
3
4 yellow
your
10,000
4
green
5
garden
100,000
5
blue
6
but
1,000,000
6
7 violet
violets 10,000,000
7
gray
8
grow
9 white
wild
silver
0.01 -2
gold
0.1 -1
Introduction to Electrical Engineering
Session 2
Outline
Measuring Resistance
Measuring Voltage
Measuring Current
Measuring Resistance
1.00%
2.00%
0.50%
0.25%
0.10%
0.05%
10.00%
5.00%
1st digit
tolerance
2nd digit
multiplier
2, 5, and 10% tolearnce
resistors have 4 bands as
shown. 1% and smaller
have 5 bands with 3
digits before the mult.
20% resistors have no
tolerance band.
2
Measuring Resistance
An ohmmeter is used to measure a resistance.
Resistor
Ohmmeter
Make sure that the multimeter is configured as an
ohmmeter.
Tol.
Ω
Never try to measure the resistance of a resistor in a
live circuit. (At best you'll get an incorrect reading,
at worst you'll damage the meter.)
Don't try to measure the resistance of a resistor while
it is connected in a dead circuit. (You can possibly
get an incorrect reading.) Disconnect at least one
side of the resistor.
3
4
Measuring Voltage
Measuring Voltage
Resistor
A voltmeter is used to measure voltage.
+
Battery
-
Voltage is always measured between two points
(across a voltage supply or resistor or between any
two points in a circuit).
VAB
red
Resistor
+
-
B
black
Voltage measurements do not require that any
component in the circuit be disconnected.
Voltmeter
A
Make sure that the multimeter is configured as either
a DC or AC voltmeter.
Voltmeters act like open circuits (large resistances).
5
6
Measuring Current
Measuring Current
Resistor
An ammeter is used to measure current.
Make sure that the multimeter is configured as either
a DC or AC ammeter.
+
Battery
-
Current is always measured at a single point.
Current measurements require that the circuit be
broken at a point in order to insert the ammeter.
Resistor
7
I
red
+
Current Direction
An ammeter acts like a short circuit (very small
resistance). Never place an ammeter directly between
the terminals of a voltage source.
Ammeter
-
black
8