New Gear Arriaval: Keysight DSOX3024T

A good oscilloscope is always the basic equipment for a system designer. I have been looking for a suitable oscilloscope for a long time. Keysight DSOX3024T is my final choice.

Why DSOX3024T?

  1. The 200MHz bandwidth (and 5GSa/s) is suitable for most applications. I am not going to design IC, the target is circuit board. So, 200MHz is quite enough.
  2. Rich software options. I also purchased the full set software options such as 8 digit counter in order to fine-tune crystal compensation.
  3. The touch control feature make it much easy to operate. Especially, the feature to find the specific area of captured waveform.
  4. The price is acceptable.
  5. The machine can also be upgraded to 1GHz bandwidth. I don't purchase the upgrade option right now. But I know I  have the option if I need it someday.
The only issue is the noise produced by cooling fan. It is annoying, but acceptable. Maybe it is because my working environment is so quiet and I also want to enjoy high quality music while working.

How to choose the right bandwidth for your oscilloscope?

Now, how do I know that 200MHz bandwidth is enough for my applications? Well, to understand the requirement of bandwidth, we need to know what is the most important signal to measure in the target system? Usually we have to measure the clock and data signals. But the fact is, it is not the highest clock/data frequency determines the required bandwidth, it is the transition (rising/falling) time needs to be observed.

According to Dr. Howard W. Johnson "High-Speed Digital Design - A Handbook of Black Magic", the knee frequency is 0.4/rising-time if 20%-80% threshold is used.

    f_knee = 0.4/t_rise

If we want to measure the rising edge of 3 ns then the knee frequency will be 133MHz. And then the required  bandwidth will be 1.3*f_knee = 173MHz. The rule is:

    bandwidth = 1.0*f_knee for 20% timing accuracy
    bnadwidth = 1.3*f_knee for 10% timing accuracy
    bandwidth = 1.9*f_knee for 3% timing accuracy

Most microprocessors have specified the rising time with few nano seconds. For example, MSP432 has specified the digital I/O port with maximum rising time of 3 ns (3V) and 8 ns (1.62V). So, 200MHz bandwidth will be probably enough to design applications with MSP432.

This is why and how I choose 200MHz. DSOX3024T can be upgraded to 1GHz bandwidth if I need to measure signals with higher frequency in the future.

In summary, DSOX3024T is a really good oscilloscope for my applications.