Type: SystemInt32 The number of samples to read. If you set samplesPerChannel to -1 for a continuous acquisition, the read retrieves all samples available in the buffer at the time of the read. If you set samplesPerChannel to -1 for a finite acquisition, the read behavior is set by the ReadAllAvailableSamples property of the DaqStream you are reading from.
data
Type: NationalInstrumentsAnalogWaveformDouble
An initialized 1D array of
AnalogWaveformTData
that contains the read data. Each element in the array corresponds to a channel in the task. The order of the channels in the array corresponds to the order in which you add the channels to the task or to the order of the channels you specify in
ChannelsToRead.
If the first dimension of data does not match the number of channels; or
If ReallocationPolicy is not ToGrow, and data is not capable of holding the required number of samples.
OutOfMemoryException
There is not enough memory to carry out this operation.
Remarks
If the data buffer is large enough to hold the number of samples requested, this overload attempts to reuse existing
AnalogWaveformTData
objects and their corresponding memory to acquire data. This results in more efficient memory allocation when performing multiple reads with a continuous analog input task.
NI-DAQmx scales the returned data to the units of the measurement, including any custom scaling you apply to the channel. You specify these units with the create channel methods or the
DAQ Assistant.
The data returned from analog waveform reads is affected by the
WaveformAttributeMode
property of the
DaqStream
you are reading from.
NI-DAQmx read and write methods time out after the amount of time specified by the
Timeout
property on the task you are reading from or writing to.