What’s the Difference Between Digitizers and Oscilloscopes for Wideband Measurements? (.PDF Download)

We live in a time of significant technology disruption. Emerging applications in wireless communications are trending to wider bandwidths, as well as higher frequencies, denser modulation schemes, multiple channels, and more data to manage. To measure wideband signals, engineers typically use oscilloscopes and digitizers that utilize analog-to-digital converter (ADC) technology for waveform acquisition. In some cases, these instruments are used interchangeably for waveform analysis. 

However, despite the many similarities, it’s important to understand that oscilloscopes and digitizers differ significantly, with each optimized for different target applications. For example, oscilloscopes normally come with a large front-panel display and keyboard for quick visualization of time-variant waveforms. Some instrument vendors promote an oscilloscope as a digitizer or a digitizer as an oscilloscope.  This can cause confusion. This article describes the key attributes to consider when selecting a digitizer or oscilloscope for your next wideband measurement solution.

Resolution and Dynamic Range 

Both digitizers and oscilloscopes use ADCs to acquire the waveform data. The ADC samples the input voltages and generates a binary representation of the voltages levels. A good measure of the dynamic range is the effective number of bits (ENOB).  ENOB is the effective bit resolution when noise and distortion are considered.  It accurately reflects the broadband noise as it appears in frequency- or time-domain measurements. 

ENOB = (SINAD – 1.76) / 6.02

SINAD (signal-to-noise and distortion ratio) is a measure of the signal quality. The ADC resolution impacts this, but other factors are involved as well.