Part 2 - RoadTest the InfiniiVision 1000 X-Series Oscilloscope DSOX1102G

Part 2 RoadTest the InfiniiVision 1000 X-Series Oscilloscope  DSOX1102GDSOX1102G

In part 2 I am planning to use the Keysight  DSOX1102GDSOX1102G oscilloscope to measure various characteristics of electric signals My focus will be on evaluating how easy would be for a student to learn how to use the control panel of this oscilloscope and how to use the built-in measurement functions of the  DSOX1102GDSOX1102G oscilloscope

First I would like to summarize how I accessed the measurement panel of the  DSOX1102GDSOX1102G oscilloscope

I started by pressing the measure button on the front panel:

Then I pressed the measurement type key on the right side of the display screen:

Pressing the type key opened the measurement selection window on the screen, as shown in the above picture.  I then selected the measurement by rotating the “Entry” knob on the right side next to the screen:

To activate a measurement I pressed on the “Entry” knob, and the corresponding measurement was displayed at the bottom of the screen.  Here is an example of rise time measurement on a screen captured using the“save to USB function of the  DSOX1102GDSOX1102G oscilloscope

I like the cursors that are automatically displayed when selecting the rise time measurement because they show how rise time is measured on the waveform.   This is a good feature for learning and I think it is beneficial to entry level students.

Here is an example of fall time measurement on the same waveform:

Other characteristics that define a square wave signal like this are pulse width and duty cycle. Each can be measured on positive pulse or on the negative pulse, like I am showing in the following screenshot:

Notice that the duty cycle is not 50% as “ideally” expected.  In this case the positive pulse is longer than the negative pulse, resulting in 55% duty cycle as referred to the positive pulse.  55% added up with 45% duty cycle referred to the negative pulse results in 100% as expected based on the duty cycle definition.  Duty cycle is reflected in pulse width as measured by  DSOX1102GDSOX1102G as 284ns for positive pulse and 232ns on negative pulse   The ratio should correlate with the duty cycle: 284/(284+232) = 0.55 or 55%.

DSOX1102GDSOX1102Gcan also measure the delay between two pulses   Here is an example of delay from one rising edge of channel 1 signal (yellow) to the next rising edge of channel 2 signal (green):

Notice at the bottom of the screen the visual representation of what this delay value means (yellow rising edge to green rising edge). 

Another measurement related to delay is phase difference.  The phase of these two signals is measured as 155 degrees, as shown in the picture below:

The delay and phase are related and part of the relationship is also the period of the signal.  In the following picture I show these three quantities measured on the two waveforms:

So the 220ns delay and the 513ns period mean that the delay represents 220ns/513ns = 0.429 of the period, which considering that the period can be viewed as 360 degree represents 0.429*360degrees = 154 degree phase shift.  This is the value of the phase shift measured by the  DSOX1102GDSOX1102G oscilloscope as shown in the picture above

Another group of measurements relates to signal integrity.  In the following picture I am showing the overshoot of a square waveform rising edge measured with the  DSOX1102GDSOX1102G oscilloscope

Notice the cursors that are automatically displayed when selecting this measure function.  Theses cursors show how the overshoot has been measured, in this case from the top level of the waveform to the peak level.  The overshoot value is displayed at the bottom.  Similarly, the overshoot of the falling edge can be measured, like I am showing in the picture below:

Another characteristic of this waveform that I measured is the preshoot, as I am showing in the next picture:

The preshoot depends on multiple factors, and usually it has a more dominant negative peak right before the rising edge (we cannot see this in the picture above because the driving circuit did not have that type of preshoot).  The peak to peak value of this waveform (with ringing) is shown in the picture below:

This is different that the amplitude measurement, which I am showing in the next picture:

So far I was measuring time domain characteristics of the waveforms.  The same waveforms can be characterized in frequency domain.  The Keysight  DSOX1102GDSOX1102G oscilloscope has the possibility of analyzing signals in frequency domain through a built-in Fast Fourier Transform(FFT function   In the following screenshot I am showing a 2MHz square wave signal displayed on the  DSOX1102GDSOX1102G oscilloscope in time domain(green waveform and in frequency domain(white trace  

To further relate the time domain and frequency domain representation of this waveform, I have used the built-in cursor function to measure the characteristics of the FFT waveform.  I am showing these characteristics in the following screenshot with my annotations in pink color:

We can see the fundamental component located at 2MHz (this is the frequency of the square wave signal shown in the time domain waveform in the previous picture) and odd harmonics at 6MHz, 10MHz, and 14MHz, … (odd harmonics continue beyond the measurement interval). There are also parasitic spurs superimposed to these expected spectral components.  Since rectangular signals are typically used in communication interfaces (like microprocessors, systems-on-chip, peripheral modules, and various interface signals between them) the parasitic spurs translate into timing jitter, which may degrade the performance or generate failures.

In the following picture I am showing the FFT transform of a sinusoidal signal with my annotations in color pink:

We can see the fundamental component located at 2MHz and no harmonics, which ideally is expected from a sinusoidal signal.  There are some parasitic spurs caused by non-ideal frequency generator.  When we design or troubleshoot a circuit these parasitic spurs distort the signals and degrade the performance of our projects.  Since they cannot be visually noticed on the time domain waveform this built-in FFT function in the Keysight  DSOX1102GDSOX1102G oscilloscope is a great tool that can be used to identify the root cause of signals distortion.

This concludes the second part of my road test evaluation of the Keysight InfiniiVision  DSOX1102GDSOX1102G oscilloscope   I will come back with new results as soon as I complete more evaluation work.

Best Wishes to Everyone,

Cosmin