Test & Measurement

Oscilloscopes combine multiple built-in instruments

8th September 2017
Mick Elliott

The MDO-2000E Series Oscilloscopes from GW Instek which combine several test instruments in one enclosure are available atSaelig. An actual spectrum analyser is included in the design, not just an FFT calculation to display the frequency domain. The series includes two instrument combinations: MDO-2000EG and MDO-2000EX.

MDO-2000EG models have a built-in true spectrum analyser and a dual channel 25MHz arbitrary waveform generator, while the MDO-2000EX models feature a built-in a true spectrum analyser, an arbitrary waveform generator, a 5,000 count DMM, and a 5V/1A power supply.

The MDO-2000EX provides a space-saving combination of spectrum analyser, DMM and power supply, making it ideal for educational or space-restricted use. The MDO-2000E Series is available in three bandwidths: 70, 100 and 200MHz and in two or four channel models. A conventional digital oscilloscope uses FFT calculations over the entire signal bandwidth up to half the sampling rate.

But inadequate calculation capability means it is impossible to have a signal's detailed frequency information due to the insufficient frequency resolution from the calculation.

In contrast, the MDO-2000E series analyses just a defined signal spectrum of interest to allow engineers to effectively conduct precision signal measurements in the frequency domain.

Users can input specific data of interest regarding the signal: centre frequency, span, and start/stop frequency, similar to a traditional spectrum analyser.

While observing frequency domain display, engineers can observe waveform characteristics which are not easily seen from time domain waveforms, such as the harmonic composition of a waveform and the frequency characteristics of a modulation signal.

Compared with an oscilloscope's FFT, the MDO-2000E series allows engineers to effectively conduct signal measurements both in the time and frequency domains.

Offering an advantage over conventional spectrum analysers, the spectrum function of MDO-2000E series can test signals that are below 9kHz, such as audio and vibration signals.

The MDO-2000E series can also test signals that have a DC component without damaging the instrument. It offers the same capabilities as real-time spectrum analysers, but faster than frequency sweeping.

This is because the oscilloscopes utilise advanced digital circuitry and software to render the frequency display.

Ordinary spectrum analysers process narrow frequency bandwidths which are frequency swept over time.

Thousands of frequency sweeps are collected to form a spectrum. T

he FFT settings of ordinary digital oscilloscopes are dependent on the horizontal scale or sample rate setting, which is totally different from the frequency range setting of the MDO-2000E series.

Most DSOs will have insufficient frequency resolution.

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