Electronic Measurements - EE251 Lectures

(1)

EE251 Lectures

Electronic Measurements

Section 05

(2)

Electrical & Computer

Engineering King Abdulaziz University

Slide 2

Measurements

• How to measure voltage?

• How to measure current?

• How to measure resistance?

• How to view a signal?

(3)

Slide 3

Bread Boards

• A board with spring contact holes to hold components; no soldering is required

• Holes of each row are internally connected

(4)

Slide 4

Example

(5)

Slide 5

Example

(6)

Slide 6

Rules

• Study Circuit

• Collect all components

• Start at the middle

• Power must be off

• Careful with sensitive components

• Nice wiring

(7)

Slide 7

Bad Example

(8)

Slide 8

Measuring Volt

• Measure the voltage drop on R 22

(9)

Slide 9

Measuring Current

• Measure the current through R 22

(10)

Slide 10

Measuring Resistance

• Measure the resistance of R 22

(11)

Slide 11

Oscilloscopes

Karl Ferdinand Braun (1897)

Cathode Ray Tube

(12)

Slide 12

Oscilloscopes

(13)

Slide 13

Selection Criteria

• Analog vs. Digital

– Digital: Sample and Hold

• Bandwidth, Sampling Rate, Resolution (Accuracy) – 5x the maximum signal frequency

• Number of Channels – 2-4 for correlations

• Memory Depth – Recording Time

• Triggering Capability

– Display Signal after Trigger

• Display Capability

– phase shift, rise time, fall time

– delay, pulse width, duty cycle, frequency and period

• Analysis Capabilities

– Math, FFT

(14)

Slide 14

CAD Simulators (Demo)

(15)

Slide 15

Example

+ −

+

+ +

−

3 2

: I 1 I I

KCL = +

0 12

4 5

0 5

6 5

. : 1

2 2

3

3 1

= +

+

−

= +

+

−

I I

I

KVL I I mA

mA I

5 . 116

4 . 36

9 . 152

3 2 1

=

⇒

(16)

Slide 16

Simulation

mA I

5 . 116

4 . 36

9 . 152

3 2 1

=

(17)

Slide 17

Non-Ideal Instruments

voltmeter ammeter

L

M R

R >> r m << R L

(18)

Slide 18

Measurement Error

3.00V

4.50V 10MΩ

4.498V

10MΩ

(19)

Slide 19

Range Extension

• A voltmeter of maximum range of 50V

– Can it read 100V safely?

• Voltage Divider

 

 



 +

×

=

M g

meter R

v R

V 1

 

 



 +

×

=

M g

meter

R

er R

er 1

(20)

Slide 20

Non-Ideal OSX (Harmonics)