What is Dual Trace Oscilloscope : Working & Its Applications

The ancient approach of developing the picture of a signal is a more complicated and burdensome procedure. Through this procedure, the calculation of current and voltage values of a revolving rotor at specific positions related to the rotor axis and in regard to calculations using a galvanometer becomes more tedious. Making this process so streamlined, there arrives a device called Oscilloscope which was invented during the period 1920s. There are many types and classifications of these oscilloscopes and the one type which we are going to discuss today is Dual Trace Oscilloscope.

What is Dual Trace Oscilloscope?

The basic dual trace oscilloscope definition is that a single electron wave creates two traces where the beam undergoes deflection through two individual sources. The production of each trace has their own individual methods where those are chopped and alternate approaches. These two approaches are considered as two modes of operation of dual trace oscilloscope.

This device is generally used to evaluate the voltage levels of various electronic circuits, whereas the concurrent initiation of each sweep in the device is somewhat complicated. So, to make this process easy dual-trace oscilloscope is used where it generates two traces through one electron beam.


This section displays the block diagram of the dual trace oscilloscope and also explains how this device works. In the above-shown block diagram image of the device, it has two separate input channels which are named A and B. These inputs are individually given to the attenuator and the preamplifier phases. And the outputs from these sections are then given as input to the provided electronic switch.

Dual Trace Oscilloscope Block Diagram
Dual Trace Oscilloscope Block Diagram

Through this electronic switch, only one channel is passed to the perpendicular amplifier section. This device also consists of a trigger selection switch where this allows the triggering of the circuit either with the external signal or with the A or B channels.

And then the signal that is received from the horizontal amplifier section is provided as input to the electric switch using sweep generator or through channel B. With this, the vertical and horizontal signals those are from channels A and B are fed to the CRT for the working of the oscilloscope. This is termed as the “X-Y approach” and allows for precise X-Y measurements.

The dual-trace oscilloscope working can be explained in two methods where one is Alternate mode and the other is Chopped mode.

Alternate Mode Dual Trace Oscilloscope Working Principle

In the alternate mode, the device allows the connection between channels in an alternate method. The switching of A and B channels occurs at the starting position of every impending sweep. In addition, there will be synchronization for the sweep and switching rates and this synchronization directs to spot traces in every sweep in both the channels.

This means that in the initial sweep, there will be a trace of A and then there will be a trace of B. The transition in the switch between two channels happens during the flyback sweep period. During this time, the electron beam is not visible and because of this, there will be a transition. This alternate mode of operation in the oscilloscope device permits the maintenance of the exact phase relationship between the two channels.

Working in Alternate Mode
Working in Alternate Mode

Whereas the drawback of this method is that the display exhibits the incidence of both signals at various time instances. And this scenario is not suitable for the exhibition of signals that have a minimal frequency. The output through this operation is shown as below:

Chopped Mode Dual Trace Oscilloscope Working Principle

In the chopped mode, just in the time period of a single sweep, there will be switching of channels many times. The switching process is so fast that even for a minimal section, there exists a display. In this mode, the electric switch is operated at a frequency range of nearly 100KHz – 500KHz. This frequency is not based on the sweep generator frequency.

So, even minimal segments of both the channels will be in connection to the amplifier in a constant approach. In the condition that the chopping speed is more than that of the horizontal sweep rate, then there happens merging of the chopped section, and this forms originally provided channels signal at the oscilloscope display. Whereas, when the chopping speed is less than that of the horizontal sweep rate, then it directs to signal discontinuity. The output wave of chopped mode is shown as follows:

Working in Chop Mode
Working in Chop Mode

So, this the detailed dual trace oscilloscope working.


While choosing the dual-trace oscilloscope, there are few specifications to be considered and those are:

  • The operating temperature: 50 to 400C
  • Deflection accuracy is ±5 %
  • Chopping frequency is nearly 120KHz
  • The phase shift is nearly 3 to10 kHz
  • Preciseness is ±5 %

Applications of Dual Trace Oscilloscope

The applications of dual trace oscilloscope include the following.

  • It is used for assessment of the performance of the system
  • Evaluate the signals generated by the function generators
  • To assess the issues, those happen in electrical and electro-optical systems
  • Check the reaction of silicon, avalanche photodiode

This is the detailed concept of a dual trace oscilloscope. Here the article gives a clear explanation of the device working, functional diagram, operating principle, two operational modes, and applications.