Basic instruments
Function generator: use high Z
Oscilloscope
DC power supply: V-limit, I-limit
Digital multimeter:
V-meter:
R = “huge”
0.0V
V
Connect in
parallel
20A mA
I-meter
V/:
R = “0”
0.0mA
20A mA
A
Connect in
series
V/:
How to read the value of a resistor?
22 ohm
470 x 0.1
From http://www.token.com.tw/resistor/resistor-color-code.htm
1 0 00
1 0 0 0
1k resistor:
or
What resistor value is
(a)
(b)
When I = 0 at a point
1. Infinite R before and/or after that point
Î simply disconnected.
2. No voltage difference between 2 points
I=0
Vin
R2
Vout = I R1
R1
= Vin
R1
R1 + R2
A more practical way to measure Rth
Rth
Vth
Rth
V
Vth
Rth
Vth
R
V
measures Vth
Insert R and infer Rth
from new Vout
e.g. if insert R = 50:,
Vout drops by ½, what
is Rth?
5k
A
5V
3k
3V
What are VA and VB?
B
Equivalent circuit:
6k
5V