The EMI-DSA800 option provides a Quasi-Peak detector and EMI filter (200Hz, 9kHz, 120kHz, -6dB bandwidth). Quasi-Peak detection is a weighted form of peak detection. For each data point, the detector detects the peaks within the specified time interval, weights the peaks detected using a circuit with specified charge and discharge characteristics, as well as the display time constant specified in the CISPR Publication 16 standards, and displays the result. By default, the instrument uses a Gaussian filter and will switch to the EMI filter automatically when the Quasi-Peak detector is selected. Press 'BW/Det' at the front panel. Then, press 'Det Type' to select Quasi-Peak detector. At this point, the instrument automatically changes the filter type to EMI and the 'Filter Type' menu is grayed out and disabled. The DSA800-EMI option is used in electromagnetic interference tests. Each licence contains a unique product key. The product key is used to generate a software licence code that must be entered into your instrument. To generate a Rigol software licence code using your Rigol product key, please see HERE. Installed software licence codes are permanent - They are unaffected by Rigol firmware updates. For further information, please click on the 'DOCUMENTS, SOFTWARE & VIDEOS' tab, above.