# Command: voltmeter

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Name:

    voltmeter - Device to record membrane potential from neurons.

Synopsis:

    voltmeter Create

Examples:

      SLI ] /iaf_cond_alpha Create /n Set
      SLI ] /voltmeter Create /vm Set
      SLI ] vm << /interval 0.5 >> SetStatus
      SLI ] vm n Connect
      SLI ] 10 Simulate
      SLI ] vm /events get info
      --------------------------------------------------
      Name	 Type	 Value
      --------------------------------------------------
      senders	 intvectortype
      times	 doublevectortype
      V_m	 doublevectortype
      --------------------------------------------------
      Total number of entries: 3

Description:

      A voltmeter records the membrane potential (V_m) of connected nodes
      to memory, file or stdout.

      By default, voltmeters 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,
      which contains membrane potential as vector /V_m and pertaining
      times as vector /times and node GIDs as /senders, if /withtime and
      /withgid are set, respectively.

      Accumulator mode:
      Voltmeter 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 parameter can be set in the status dictionary:
      interval	 double	- Recording interval in ms

Sends:

    DataLoggingRequest

Remarks:

     	- The voltmeter model is implemented as a multimeter preconfigured to
      record /V_m.
     	- The set of variables to record and the recording interval must be set
      BEFORE the voltmeter is connected to any node, and cannot be changed
      afterwards.
     	- A voltmeter cannot be frozen.
     	- If you record with voltmeter 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 voltmeter with frozen nodes.

SeeAlso:

- Device
- RecordingDevice
- multimeter

Source:

    /opt/conda/conda-bld/nest_1510213973486/work/nest-2.14.0/models/modelsmodule.cpp

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