# 3.3.1.32. NXmonitor¶

**Status**:

base class, extends NXobject

**Description**:

A monitor of incident beam data.

It is similar to the 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.

**Symbols**:

No symbol table

**Groups cited**:

**Structure**:

@default: (optional) NX_CHARDeclares which child group contains a path leading to a NXdata group.

It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion.

mode: (optional) NX_CHARCount to a preset value based on either clock time (timer) or received monitor counts (monitor).

Any of these values:

`monitor`

|`timer`

start_time: (optional) NX_DATE_TIMEStarting time of measurement

end_time: (optional) NX_DATE_TIMEEnding time of measurement

preset: (optional) NX_NUMBER {units=NX_ANY}preset value for time or monitor

distance: (optional) NX_FLOAT {units=NX_LENGTH}Distance of monitor from sample

range[2]: (optional) NX_FLOAT {units=NX_ANY}Range (X-axis, Time-of-flight, etc.) over which the integral was calculated

nominal: (optional) NX_NUMBER {units=NX_ANY}Nominal reading to be used for normalisation purposes.

integral: (optional) NX_NUMBER {units=NX_ANY}Total integral monitor counts

type: (optional) NX_CHARAny of these values:

`Fission Chamber`

|`Scintillator`

time_of_flight[ref(efficiency)]: (optional) NX_FLOAT {units=NX_TIME_OF_FLIGHT}Time-of-flight

efficiency[ref(i)]: (optional) NX_NUMBER {units=NX_DIMENSIONLESS}Monitor efficiency

data[n]: (optional) NX_NUMBER {units=NX_ANY}Monitor data

sampled_fraction: (optional) NX_FLOAT {units=NX_DIMENSIONLESS}Proportion of incident beam sampled by the monitor (0<x<1)

count_time: (optional) NX_FLOAT {units=NX_TIME}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

integral_log: (optional) NXlogTime variation of monitor counts

GEOMETRY: (optional) NXgeometryGeometry of the monitor

## Hypertext Anchors¶

Table of hypertext anchors for all groups, fields, attributes, and links defined in this class.

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