oscilloscopes and high order LP filters

[senmeis]

Hi,

An oscilloscope can be roughly seen as a high order LP filter. Questions:

1. Which type of filter, Butterworth, Tscebysceff or Bessel?

2. Can man set the bandwidth of this filter in most cases?

 

[KlausST]

An oscilloscope can be roughly seen as a high order LP filter. Questions:

What? Please explain.

Some have built in filters .. and those filters usually are proprietary. So: RTFM.

Klaus

 

[LvW]

Hi,

An oscilloscope can be roughly seen as a high order LP filter. Questions:

1. Which type of filter, Butterworth, Tscebysceff or Bessel?

2. Can man set the bandwidth of this filter in most cases?

Each electronic device (amplifiers, instruments, filters, control blocks etc.) have an upper operating frequency (physical limit).
Hence, all these devices can - if you want - seen as an overall "lowpass filter".
But it makes no sense to ask "which type of filter ?" because it is an unwanted (not designed) frequency limit.

 

[FvM]

Digital oscilloscopes are often providing filters to reduce bandwidth intentionally. A popular filter characteristic is e.g. 4th order Bessel. Bessel produces only minimal overshoot. High end oscilloscopes can provide additional filters like Butterworth or steep "brick wall", also possibly programmable FIR filter.

Maximal bandwidth of DSO is the superposition of analog amplifier, ADC sampling and digital filter bandwidth. The frequency response is most likely less ideal than at at reduced bandwidth.

 

[senmeis]

Many instruments, such as high-speed scopes and even network analyzers, can be approximated as high order filters with a pole frequency and a filter order.

Taken from this article: https://www.signalintegrityjournal....avoid-gibbs-ringing-artifacts-in-measurements

One of the authors is from Lecroy, an oscilloscope manufacturer.

 

[FvM]

It's not filter order and pole frequency that causes ringing, it's pole location in the complex plane.