A monitor of incident beam data. It is similar to the :ref:`NXdata` groups containing monitor data and its associated dimension scale, e.g. time_of_flight or wavelength in pulsed neutron instruments. However, it may also include integrals, or scalar monitor counts, which are often used in both in both pulsed and steady-state instrumentation. Count to a preset value based on either clock time (timer) or received monitor counts (monitor). Starting time of measurement Ending time of measurement preset value for time or monitor Distance of monitor from sample Range (X-axis, Time-of-flight, etc.) over which the integral was calculated Nominal reading to be used for normalisation purposes. Total integral monitor counts Time variation of monitor counts Time-of-flight Monitor efficiency Monitor data The rank (``dataRank``) of the ``data`` must satisfy ``1 <= dataRank <= NX_MAXRANK=32``. At least one ``dim`` must have length ``n``. Proportion of incident beam sampled by the monitor (0<x<1) Geometry of the monitor Elapsed actual counting time, can be an array of size ``np`` when scanning. This is not the difference of the calendar time but the time the instrument was really counting, without pauses or times lost due beam unavailability