During product development, the frequency spectra of disturbances need to be measured frequently and compared against the limits set in current product standards. The effectiveness of the instrument's shielding is checked by an EMC engineer. Being able to have the measurement results available quickly streamlines efforts to shield the instrument efficiently and reduces the time to market. The introduction of spectrum measurements based on fast Fourier transform (FFT) – also known as a time domain scan – allows a significant reduction in measurement times without affecting accuracy. The CISPR, the International Special Committee on Radio Interference, has embraced this new technology: As of the publication in June 2010 of Amendment 1 to the third edition of CISPR 16-1-1, the use of FFT-based test instruments is permitted in standard-compliant measurements. Rohde & Schwarz launched with the R&S ESU the world's first commercial EMI test receiver capable of time domain scans. The EMI test receiver family R&S ESR does also supports time-domain scans and delivers even faster measurements. Taking the R&S ESR EMI test receiver as an example, this paper examines a CISPR 16-1-1-compliant test instrument with time domain scanning capabilities. It compares the measurement speed and level measurement accuracy of conventional stepped frequency scanning (the reference) against the speed and accuracy of advanced time-domain scanning. It also contains guidance on making optimum use of time domain scans.