Datasheet

Thursday, 17 July 2003 MiniProject: Design Aspects Colin K McCord
EEE512J2 – Electronic Product Design Page 6 Chapter 2: Fundamentals
Y Input AC
DC
Frequency-compensated
attenuator
Y Amplifier
Y Shift
Y Deflection
Stage
Trigger
pickoff amp
CRT
CRT Y
Deflection
plates
CRT X
Deflection
plates
Sweep gate
logic
Sweep
(time base)
generator
X Deflection
Stage
X
Shift
int
ext
Trigger
Input
Trigger
Selector
Trigger
Level
Trigger +/-
Polarity
Auto -
Brightline
Circuit
Blanking
Amplifier
To CRT
Grid 1
X Input Sweep Speed Setting
Figure 2.4b. Block diagram of a basic CRT oscilloscope; similar to a traditional analogue ECG display
2.5. Digital Sampling
Digital sampling requires an ADC (analogue-to-digital converter) to converter analogue voltages to binary
representation. The sampling rate specifies the number of samples taken per second. Figure 2.5a
demonstrates clearly how an analogue waveform is digitally sampled and displayed onto the screen (LCD,
Computer Monitor, or a CRT using a DAC etc…).
50Hz sine-wave, sampled at 500Hz (x10)
-10
-6
-2
2
6
10
Volts
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10
0
1
2
3
4
5
6
7
8
9
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
Array containing ADC readings at each sample point
Draw Waveform using Pulse Interpolator (join the dots)
-10
-6
-2
2
6
10
Volts
Figure 2.5a. Example showing how a sine-wave is digitally sampled