Test-and-Measurement » CMU200: Troubleshooting Invalid Number of Samples

CMU200: Troubleshooting Invalid Number of Samples

cmu200 test equipment power measurement rf measurements error

This issue is frequently encountered when running tests with the Rohde & Schwarz CMU200 communication test set. A typical example is when performing burst power measurements in EGPRS, which can lead to an invalid number of samples being reported by the CMU200.

This problem often arises during Power vs. Time measurements when the burst power measurement exceeds the power mask limits configured in the CMU200 for the specific wireless standard being tested (e.g., GSM, LTE).

Here’s a breakdown of what NAN and INV mean in this context, as observed directly from the CMU200:

Understanding NAN and INV Errors

Indication typeDescription
NANNAN stands for “Not A Number” and signifies missing data within a frame. This occurs when data within a frame or slot isn’t fully acquired, leading to some data being absent. This can happen if the data is corrupted or not completely filled in by lower layers that CMU200 is expecting.
INV (Invalid)“Invalid number of samples returned” or “invalid parameter” is displayed by the CMU200 when a limit check fails. This is often seen during spectrum mask measurements when the measured value falls outside the predefined limits. In some cases, not setting a tolerance for the limit check condition can also result in an INVALID error.