CounterMultiChannelReader.MemoryOptimizedReadMultiSampleDouble Method (Int32, Double[,], ReallocationPolicy, Int32)
- Updated2023-02-21
- 2 minute(s) read
CounterMultiChannelReaderMemoryOptimizedReadMultiSampleDouble Method (Int32, Double, ReallocationPolicy, Int32)
Reads one or more Double samples from one or more
CIChannel
objects in a task.
Namespace: NationalInstruments.DAQmx
Assembly: NationalInstruments.DAQmx (in NationalInstruments.DAQmx.dll) Version: 20.7.40.49302
Syntax
public double[,] MemoryOptimizedReadMultiSampleDouble( int samplesPerChannel, ref double[,] data, ReallocationPolicy policy, out int actualNumberOfSamplesPerChannelRead )
Public Function MemoryOptimizedReadMultiSampleDouble ( samplesPerChannel As Integer, ByRef data As Double(,), policy As ReallocationPolicy, <OutAttribute> ByRef actualNumberOfSamplesPerChannelRead As Integer ) As Double(,)
Parameters
- samplesPerChannel
- 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: SystemDouble
An initialized 2D array of Double samples that contains the read data. Each element in the first dimension of the array corresponds to a channel in the task. Each element in the second dimension of the array corresponds to a sample from each of the channels. 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. - policy
- Type: NationalInstruments.DAQmxReallocationPolicy
Dictates the reallocation behavior of the read operation. Refer to ReallocationPolicy for more information. - actualNumberOfSamplesPerChannelRead
- Type: SystemInt32
The actual number of samples per channel read. This is useful when the reading operation yields fewer samples than the actual length of data.
Return Value
Type: DoubleA reference to the data parameter containing samples from the task.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentException |
|
| DaqException | The NI-DAQmx driver returned an error during the asynchronous operation. |
| 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 memory allocated from the array 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.
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.
Refer to NI-DAQmx Readers and Writers for more information about memory limitations in NI-DAQmx read methods.