- Double Beam Oscilloscope Definition: A double beam oscilloscope uses two electron beams to display signals on a single screen simultaneously.
- Construction: It has two separate vertical channels with individual attenuators and pre-amplifiers for each beam.
- Time Base Circuits: These oscilloscopes can have common or independent time base circuits, allowing different sweep rates.
- Split Beam Method: In this method, a single electron gun is used, but the beam is split into two, resulting in reduced brightness.
- Dual Beam vs. Dual Trace: Dual beam oscilloscopes use two electron guns, while dual trace oscilloscopes split a single beam, affecting their ability to capture fast events and their brightness.
The dual beam oscilloscope emits two electron beams that are displayed simultaneously on a single scope, which could be individually or jointly controlled. The construction and working of the dual beam oscilloscope are completely different from dual trace oscilloscope. The tubes are more complicated to build, and the whole thing is more expensive.
A special type of double beam oscilloscope can display two electron beams by either generating or deflecting them. Nowadays, double beam oscilloscopes are outdated because digital oscilloscopes perform this function more efficiently without needing a dual-beam display. Digital oscilloscopes capture a single electron beam and split it into multiple channels.
Construction of Double Beam Oscilloscope
There are two individual vertical input channels for the two electron beams from different sources. Each channel has its own attenuator and pre-amplifier, allowing independent control of each beam’s amplitude.
The two channels can have either common or independent time base circuits for different sweep rates. Each beam passes through its own channel for vertical deflection before crossing a single set of horizontal plates. A sweep generator drives the horizontal amplifier, providing a common horizontal deflection for both beams across the screen.
A dual beam oscilloscope generates two electron beams within the cathode ray tube using either a double electron gun tube or a split beam method. Each beam’s brightness and focus are controlled separately. However, using two tubes increases the oscilloscope’s size and weight, making it bulky.
The other method is the split beam tube, which uses a single electron gun. A horizontal splitter plate between the Y deflection plate and the last anode isolates the two channels. The potential of the splitter plate is the same as the last anode. Since the single beam is split into two, the resulting beams are only half as bright as the original. This is a disadvantage at high frequencies. To improve brightness, two sources can be used in the last anode instead of one.
Difference between Dual Beam and Dual Trace Oscilloscope
The dual beam oscilloscope has two different electron gun which passes through two completely separate vertical channels, where as dual trace oscilloscope has single electron beam which get split into two and passes through two separate channels.
Dual trace CRO cannot switch quickly between the traces so it cannot capture two fast transient events whereas dual beam CRO there is no question of switching.
The brightness of the two displayed beam has drastically different as it operated at widely spaced sweep speeds. On the other hand, dual trace brightness of the resultant display is same.
The brightness of the displayed beam of the dual trace is half of the brightness of dual beam CRO.
