# 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.

Common Reasons for INV or QUES Status
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.