Role of Delay Line in CRO and Its Function | New Topic

In this note, we are going to know about some important Role of Delay Line in CRO and Its definition, purpose, diagram, and Functions. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.

Author Name: Arun Paul.

What is Delay Line in CRO?

A Delay Line in a Cathode Ray Oscilloscope (CRO) is an electrical circuit that delays the input signal by a brief amount of time before it reaches the vertical deflection plates. This delay gives the oscilloscope’s trigger circuit ample time to process and stabilize the signal before it appears on the screen.

There are two types of delay in CRO

1. Lumped Parameter Delay Line: This circuit is created by using inductors and capacitors.
2. Distributed Parameter Delay Line: This circuit is created by using coaxial cables.

Use of Delay Line in CRO

• When a signal is applied to the CRO, the trigger circuit detects and stabilizes the waveform before displaying it. Without a delay line, some of the signal would be lost during the process.
• The delay guarantees that even the start of the waveform is shown on the screen, preventing the loss of critical signal information.
• A delay line allows users to fully evaluate the waveform’s leading edge, which is critical for accurate measurements.

Delay Line in CRO with Diagram

Here is the circuit diagram of delay line in CRO with neat sketches –

Role of Delay Line in CRO

The above figure indicates the signal’s amplitude about the time and the relative position of the sweep generator output signal. The diagram indicates that when the delay line is not used, the first part of the signal is lost, and just a portion of the signal is displayed. To compensate for this disadvantage, the signal is not applied directly to the vertical plates but rather through a delay line circuit, as illustrated in figure.

This gives time for the sweep to commence at the horizontal plates before the signal has reached the vertical plates. The trigger pulse is picked off at a moment t₀ after the signal has passed through the main amplifier. The sweep generator sends the sweep to the horizontal amplifier, and the sweep begins at the HDP at time t₀ + 80 ns. As a result, the sweep begins on time, with the signal arriving at the VDP at t₀+200ns.

Function of Delay Line in CRO

There are lots of functions of delay line in CRO or delay line function in CRO to ensure accurate waveform display and measurement –

1. Ensure Complete Waveform Display
2. Improve Triggering Accuracy
3. Allow Precise Time Measurements
4. Prevents loss of critical signal information
5. Improve performance in high frequency measurement