Measurement Errors
If a measurement cannot be made the string "9.91E+37 (NaN)" is returned as the measurement result. Negative infinity is reported as −9.9E+37 (−Infinity). Examples that cause this situation to occur include:
- The source signal is not displayed or there is some other settings conflict
- Lack of data
- The signal is clipped
- The requested measurement is not possible (for example, a period measurement on an FFT waveform)
A settings conflict is one reason a measurement cannot be made. A settings conflict occurs when the source signal is not displayed or when there is some other incompatible system setting. Typically, source :DISPlay? queries let you check whether a source is displayed. You can check the error queue for '-221,"Settings conflict"' messages using :SYSTem:ERRor:NEXT? queries. Note that when there is a settings conflict, a measurement command's :STATus? child query will return invalid (INV), and the :STATus:REASon? and :STATus:DETails? child queries will return empty strings.
When source signals are displayed and there are no settings conflicts, use a measurement command's :STATus? child query to determine if a measurement result is correct (CORR). If the measurement result is invalid (INV) or questionable (QUES), use the :STATus:REASon? child query to return a message string that helps to identify the cause. The :STATus:DETails? child query may give more information about the cause. The following table shows some of the common :STATus:REASon? response strings.
| Query Response | Description |
|---|---|
| Measurements | |
| Edge? | The required edge was not found. |
| Voltage? | The requested amplitude was not found. |
| Top = Base | The waveform top and base are equal. |
| Incomplete | The completion criteria has not been met. |
| Clipped Hi | The waveform is clipped at the top of the display. |
| Clipped Low | The waveform is clipped at the bottom of the display. |
| Too Small | The input signal is too small. |
| Lower? | The lower threshold is not on the waveform. |
| Upper? | The upper threshold is not on the waveform. |
| Thresholds? | The upper and lower thresholds are too close. |
| Time? | The requested time is not on the waveform. |
| Time? | The requested time was not found. |
| Left? | The left bounding data point was not found. |
| Right? | The right bounding data point was not found. |
| Top? | The specified eye top is not on the waveform. |
| Base? | The specified eye base is not on the waveform. |
| Eye? | Unable to identify the eye. |
| Crossings? | Not enough crossings were found. |
| No data | Not enough samples have been acquired. |
| Source? | The source waveform is not in the correct format. |
| Jitter? | The jitter is too large. |
| Period? | The measurement period is too small. |
| Transition? | The measurement transition is too small. |
| Width? | The measurement pulse width is too small. |
| Cross? | The crossing is too thin. |
| Dark Level? | The dark level is invalid. |
| Corr Factor? | The Correction Factor is larger than the measured ER. |
| Mismatch | Not all waveforms were acquired simultaneously. |
| Cal Req'd | {0} requires calibration. |
| DFE? | The measurement is not defined for the output of a DFE. |