AnalogInput

Prerequisites:

  • bonsai DAQmx Library
  • NI DAQmx driver from the NI website

Category: Source

Brief: Generates a sequence of voltage measurements from one or more DAQmx analog input channels

Properties:

  • ActiveEdge(NationalInstruments.DAQmx.SampleClockActiveEdge) - the edges (Rising or Falling) of the NI-DAQmx device's sample clock signal used for sample acquisition
  • BufferSize (int) - the number of samples acquired in a single hardware buffer; the upper limit of the buffer (FIFO - 'first-in, first-out') depends on the DAQ board; if set to 0, acquisition is timed by the hardware without a buffer
  • Channels (System.Collections.ObjectModel.Collection<Bonsai.DAQmx.AnalogInputChannelConfiguration>) - all analog input channels to acquire voltage samples from, specified by adding channels in the AnalogInputChannelConfiguration Collection Editor and setting its parameters as appropriate:
    • PhysicalChannel - the physical analog input channel on the board, selected from the drop-down list once the device is connected
    • ChannelName - can be anything
    • MaximumValue - maximum voltage value expected in measurements, not to be confused with device range; limiting the input to as small a range as appropriate can improve measurement precision
    • MinimumValue - minimum voltage value expected in measurements, analogous to MaximumValue
    • TerminalConfiguration - input terminal configuration as appropriate for the particular device; for more information about the options (Differential, Pseudodifferential, Rse, Nrse) see the NI website
    • VoltageUnits - the units used to return voltage measurement from the channel; for more information about the options (Volts, FromCustomScale, FromTeds), see the NI website
  • SampleMode (NationalInstruments.DAQmx.SampleQuantityMode) - specifies whether samples are acquired until the task is stopped (SampleContinuous) or a specific number of samples, set by BufferSize, is reached (FiniteSamples)
  • SampleRate (double) - sampling rate in samples per second. It should be greater than twice the highest frequency component expected in the measured signal, respecting the Nyquist Sampling Theorem. The upper limit depends of the DAQ board.
  • SamplesPerRead (int) - the number of samples bonsai tries to read at any time; the default value of -1 means that all available data, set by BufferSize, are acquired; positive values smaller than BufferSize means that data from the hardware buffer are read more often
  • SignalSource (string) - source terminal of the clock; if not specified, the internal clock of the device will be used

Output (OpenCV.Net.Mat):

  • IsInvalid (bool)
  • ElementType (int)
  • Size (OpenCV.Net.Size)
    • Width (int)
    • Height (int)
  • Rows (int)
  • Cols (int)
  • Step (int)
  • Depth (OpenCV.Net.Depth)
  • Channels (int)
  • ElementSize (int)
  • Data (System.IntPtr)
  • IsClosed (bool)
tip

To avoid missing data due to subscription delays, this node should be initialised before any nodes whose output AnalogInput is supposed to acquire. For example, if the output of AnalogOutput is fed back into AnalogInput, the latter should be placed higher in the workflow than the former.

tip

Write data to file using MatrixWriter

caution

Runtime Error: Device cannot be accessed

Most likely happens because the NI-DAQmx device is not connected/powered. Several other possible reasons and remedies are listed in the bonsai error message.

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