Command: multimeter


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

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.


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

Hans Ekkehard Plesser


multimeter Create


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
g_in doublevectortype
senders intvectortype
times doublevectortype
t_ref_remaining doublevectortype
V_m doublevectortype
Total number of entries: 6


- 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
- 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.