# Command: multimeter

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Name:

    multimeter - Device to record analog data from neurons.

Synopsis:

    multimeter Create

Examples:

      SLI ] /iaf_cond_alpha Create /n Set
      SLI ] n /recordables get ==
      [/V_m /g_ex /g_in /t_ref_remaining]
      SLI ] /multimeter Create /mm Set
      SLI ] mm << /interval 0.5 /record_from [/V_m /g_ex /g_in] >> SetStatus
      SLI ] mm n Connect
      SLI ] 10 Simulate
      SLI ] mm /events get info
      --------------------------------------------------
      Name	 Type	 Value
      --------------------------------------------------
      g_ex	 doublevectortype   <doublevectortype>
      g_in	 doublevectortype   <doublevectortype>
      senders	 intvectortype	 <intvectortype>
      times	 doublevectortype   <doublevectortype>
      t_ref_remaining	 doublevectortype   <doublevectortype>
      V_m	 doublevectortype   <doublevectortype>
      rate	 doublevectortype   <doublevectortype>
      --------------------------------------------------
      Total number of entries: 6

Description:

      A multimeter records a user-defined set of state variables from connected nodes
      to memory, file or stdout.

      The multimeter must be configured with the list of variables to record
      from, otherwise it will not record anything. The /recordables property
      of a neuron model shows which quantities can be recorded with a multimeter.
      A single multimeter should only record from neurons of the same basic
      type (e.g. /iaf_cond_alpha and any user-defined models derived from it
      using CopyModel). If the defaults or status dictionary of a model neuron
      does not contain a /recordables entry, it is not ready for use with
      multimeter.

      By default, multimeters record values once per ms. Set the parameter /interval
      to change this. The recording interval cannot be smaller than the resolution.

      Results are returned in the /events entry of the status dictionary. For
      each recorded quantity, a vector of doubles is returned. The vector has the
      same name as the /recordable. If /withtime is set, times are given in the
      /times vector in /events.

      Accumulator mode:
      Multimeter can operate in accumulator mode. In this case, values for all
      recorded variables are added across all recorded nodes (but kept separate in
      time). This can be useful to record average membrane potential in a population.

      To activate accumulator mode, either set /to_accumulator to true, or set
      /record_to [ /accumulator ].  In accumulator mode, you cannot record to file,
      to memory, to screen, with GID or with weight. You must activate accumulator
      mode before simulating. Accumulator data is never written to file. You must
      extract it from the device using GetStatus.

Parameters:

      The following parameters can be set in the status dictionary:
      interval	 double	- Recording interval in ms
      record_from  array 	- Array containing the names of variables to record
      from, obtained from the /recordables entry of the
      model from which one wants to record

Sends:

    DataLoggingRequest

Remarks:

     	- The set of variables to record and the recording interval must be set
      BEFORE the multimeter is connected to any node, and cannot be changed
      afterwards.
     	- A multimeter cannot be frozen.
     	- If you record with multimeter in accumulator mode and some of the nodes
      you record from are frozen and others are not, data will only be collected
      from the unfrozen nodes. Most likely, this will lead to confusing results,
      so you should not use multimeter with frozen nodes.

Author:

    Hans Ekkehard Plesser, Barna Zajzon (added offset support March 2017)

FirstVersion:

    2009-04-01

SeeAlso:

- Device
- RecordingDevice

Source:

    /opt/conda/conda-bld/nest_1524088722951/work/nest-2.14.0/models/multimeter.h

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