Double Beam Oscilloscope
Jun 27, 2015
Double Beam Oscilloscope
Multi-Input OscilloscopeOscilloscopes can have multiple input and display facilities.
The most common one is of-TWO INPUTS.
Single beam oscilloscopeDouble beam oscilloscope
There are primary two types of multi input oscilloscope
How a double beam oscilloscope looks like
The double beam analog oscilloscope can display two signals simultaneously.
A special dual beam CRT generates and deflects two beams separately.
Unlike an ordinary Dual trace oscilloscope which time shared a single electron beam, thus loosing about 50% of each signal, a dual beam oscilloscope simultaneously produced two separate electron beams capturing the entirely of both signals.
Also Dual trace oscilloscope cannot capture two fast transient events, as it cannot switch quickly enough between traces.so to avoid these problems Dual Beam Oscilloscope is used.
Dual Beam Oscilloscope
constructionThe dual beam oscilloscope has two separate electron beams and therefore two completely separate vertical channels.each channel consists of a preamplifier and attenuator.
There is single set of horizontal plates and single time base circuit.
The sweep generator drives the horizontal amplifier which in turn drives the plates.
The horizontal plates sweep both the beams across the screen at the same rate.
AttenuatorAnd
preamplifier
AttenuatorAnd
Preamplifier
Delay line
Vertical amplifier
Trigger
Vertical amplifier
Delay line
Trigger Sweep generator
Sweep generator
Horizontal amplifier
Horizontal amplifier
Vertical deflection plate
Vertical deflection plate
Horizontal deflection plate
Channel A
Channel B
External
Line
Dual Beam Oscilloscope with independent time base
Horizontal amplifier
Main vertical
amplifier
Main vertical
amplifier
Delay line
Delay line
Sweep generator
Trigger circuit
Preamplifier and
attenuator
Preamplifier and
attenuator
Signal A
Signal B
Two sets of Y-deflection plates
X deflection plates
line
Dual beam oscilloscope with common time base
SB
Exit
There are two methods of used for generating the two electron beams within the CRT.
1) Double gun tube
2) Split beam
Modes of operation:
A. Double gun tube: method allows the brightness and focus of each beam to be controlled separately but it is bulkier than a split beam.
B. Split beam : In this method a single electron gun is used.
A horizontal splitter plate is placed between the last anode and the Y deflection plate.
This plate is held at the same potential as the anode, and it goes along the length of tube,between the two vertical deflection plates which isolates the channels.
Disadvantages:
This arrangement has half the brightness of single beam.
The two display may have noticeably different brightness .
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