Why do I get a Meas Uncal message when I select either the Quasi-Peak or EMI Average detector for taking a full band sweep with the MXE EMI Receiver?
When trying to take full band sweeps with one of the EMI detectors (Quasi-Peak, EMI Average, CISPR RMS Average) you will most likely notice that the Meas Uncal message will be displayed and the Sweep or Scan time will be 4 ks. With the instrument in either the Spectrum Analyzer mode or the EMI Receiver mode Frequency Scan measurement with the default Smooth Scan Type selected the sweeptime rules of the instrument dictate the speed at which it can sweep. With an EMI detector that is going to be much slower than with conventional detectors; so slow that the maximum sweeptime of the instrument (4 ks) can easily be reached. When the instrument calculates a needed scan time that is greater than the maximum scan time of the instrument the Meas Uncal message is displayed.
If you need to run a full scan with one of the EMI detectors you can do so in the EMI Receiver mode using the Discrete (Stepped) Scan Type. You can select this under the Meas Setup, More, Scan Type menu. This will allow for any scan or dwell time desired without getting a Meas Uncal message. If you run a full band scan of this type expect the overall scan time to be lengthy.
While many of the emissions standards state that the frequency band of interest must be measured with one or more of the EMI detectors they also usually state that it is understood that a peak detector measurement will always be greater than any of these, so scans can be performed with the peak detector and only suspect signals found with this would need to be measured with the specified EMI detector. This is mainly because the EMI detectors are very slow, and taking scans with them can be impractical at times if not impossible.