Dual Trace Oscilloscope Block Diagram – Explain | New Topic

In this note, we are going to know about Dual Trace Oscilloscope or Dual Trace CRO Block Diagram. Also about its function, working principle, advantages, and disadvantages as well. Welcome to Poly Notes Hub, a leading destination for engineering notes.

Author Name: Arun Paul.

What is Dual Trace Oscilloscope or Dual Trace CRO?

A Dual Trace CRO is a more advanced Cathode Ray Oscilloscope (CRO) that can display two distinct signals at the same time. This makes it especially useful in applications that need waveform comparisons, such as electronic circuit examination and troubleshooting.

A Dual Trace CRO is a valuable tool for electrical engineers and researchers since it allows them to examine and compare two signals at the same time. While it has several drawbacks, it remains a useful tool for analog circuit analysis and signal diagnostics.

Function of Dual Trace Oscilloscope

• The bandwidth ranges from few Hz to MHz.
• There are two independent input channel (Channel A and Channel B).
• The time base range is adjustable. Typically from nanoseconds to few milliseconds.
• There are various types of triggering options like internal, external, TV triggering etc.
• The input impedance is usually 1MΩ with a capacitance of around 20pF.
• It requires 220V AC power supply or can be battery operated for portable one.

Dual Trace Oscilloscope Block Diagram

Here is the block diagram of the dual trace oscilloscope –

• Input Channels: The CRO can receive two different impulses because it has two separate input terminals. These signals are then treated independently using preamplifiers and attenuators.
• Preamplifier and Attenuators: Each channel includes a pre-amplifier to increase signal strength and an attenuator to reduce signal amplitude as needed. This ensures that the input signals fall within a quantifiable range.
• Delay Line: The delay line significantly retards the signal before it reaches the vertical amplifier. This guarantees that the triggering circuit stabilizes the waveform and avoids distortion when displayed.
• Electronic Switch: This switch switches between Channel A and Channel B depending on the mode selected. There are two types of switching mode, Alternate Mode and Chop Mode.
• Vertical Amplifier: This amplifier strengthens the signal before sending it to the vertical deflection plates (VDP), which govern the vertical movement of the beam on the CRT screen.
• X-Y Mode Selector: Allows the CRO to operate in X-Y mode, which sends one signal to the X-axis and another to the Y-axis. This is handy for calculating phase difference and Lissajous figures.
• Trigger Switch: The trigger circuit keeps the waveform display stable by synchronizing the input signal with the sweep generator.
• Sweep Generator: Creates a time basis signal that governs the travel of the electron beam across the screen from left to right.
• Horizontal Amplifier: amplifies the sweep signal before transferring it to the horizontal deflection plates (HDP), which control the beam’s horizontal mobility.
• Cathode Ray Tube: The processed signals are shown as waveforms on the CRT screen, indicating voltage fluctuations over time.

Dual Trace Oscilloscope Working Principle

The Dual Trace CRO processes two different input signals separately using pre-amplifiers and attenuators. The signals are then routed into an electrical switch, which alternates between the two signals depending on the mode (Alternate or Chop). The signals are amplified and delivered to the CRT’s vertical and horizontal deflection plates, where they appear as waveforms on the screen.

Dual Trace CRO Advantages

Here are the advantages of dual trace cathode ray oscilloscope –

• It can display two waveforms at one time.
• It provides accurate measurement.
• Provides alternative and chop modes to suit both high and low frequency transmissions.
• Used in communication systems, medical devices, power electronics, and research laboratories.
• Enables stable waveform display, increasing analysis efficiency.

Dual Trace CRO Disadvantages

Here are the disadvantages of dual trace cathode ray oscilloscope –

• A maximum of two signals can be displayed at the same time.
• At higher frequencies, the chopped display may cause artifacts or distortions.
• Modern digital storage oscilloscopes (DSOs) provide increased accuracy and storage capacity.
• Dual trace CROs are larger and more energy-intensive than digital counterparts.
• It lacks advanced automated functions present in DSOs.