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Analog Input (Single Sample)

Acquire single sample from multiple analog channels of data acquisition device

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  • Analog Input (Single Sample) block

Libraries:
Data Acquisition Toolbox

Description

The Analog Input (Single Sample) block opens, initializes, configures, and controls an analog data acquisition device. The opening, initialization, and configuration of the device occur once at the start of the model execution. The block acquires a single sample every time step, synchronously from the device, during the model run time.

The block has no input ports. It has one or more output ports, depending on the configuration you choose in its dialog box.

Use the Analog Input (Single Sample) block to incorporate live measured data into Simulink® for:

  • System characterization

  • Algorithm verification

  • System and algorithm modeling

  • Model and design validation

  • Controller design

Analog input acquisition is done synchronously, according to the following diagram.

Timing of synchronous analog input

At the first time step (T1), data is acquired from the selected hardware channels. The simulation does not continue until data is read from all channels.

Notes

To use this block, you need both Data Acquisition Toolbox™ and Simulink software.

Some devices are not supported by the Simulink blocks in Data Acquisition Toolbox. To see if your device supports Simulink, refer to Supported Hardware.

You can use Analog Input (Single Sample) block only with devices that support single sample acquisition. If the device does not support single sample acquisition, the model generates an error. To acquire data from devices that do not support acquisition of a single sample (such as devices designed for sound and vibration), use the Analog Input block.

Other Supported Features

  • If you have DSP System Toolbox™, you can use this block for signal applications.

  • This block supports the use of text accelerator mode, but not Rapid Accelerator or code generation.

  • The block supports the use of model referencing, so that your model can include other Simulink models as modular components.

For more information on these features, see the Simulink documentation.

Ports

Output

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Acquired analog input data, returned as doubles. If using only one output port for all channels, the output is an array of data. If using a port for each channel, each scan results in a single value on each port. Multiple ports are named by channel names or device specified channel IDs.

Data Types: double

Timestamp of scan, returned as a double. This port is available when you check the Output timestamp parameter.

Data Types: double

Parameters

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Use the Block Parameters dialog box to select your device and to set other configuration options.

The device from which you want to acquire data. The items in the list vary, depending on which devices you have connected to your system. Devices in the list are specified by adaptor or vendor name and unique device ID, followed by the model name of the device, for example, ni Dev1 (USB-6255). The first available device is selected by default. A CompactDAQ chassis would be shown as a single device identified by vendor name, chassis ID, and chassis model; for example, ni cDAQ2 (cDAQ-9172).

Device channel selection and configuration table. The channel configuration table lists the hardware channels of your device, and lets you select and configure them. Specify which channels to acquire data from (by default all the channels are selected). The following parameters are specified for each selected channel:

Channel ID — Hardware channel ID specified by the device. The Channel ID column is read-only, and the parameters are defined when the device is selected.

Name — Channel name. By default the table displays any names provided by the hardware, but you can edit the names. For example, if the device is a sound card with two channels, you can name them Left and Right.

Module — Device ID the channel belongs to. The Module column is read-only. If a CompactDAQ chassis is selected, it shows the ID of the CompactDAQ module which the channel belongs to; otherwise the ID of the device.

Measurement Type — Measurement type of the channel. This block supports only voltage measurement types. (For other measurement types, use a DataAcquisition object in MATLAB®.)

Input Range — Input ranges available for each channel supported by the hardware, defined when a device is selected.

Terminal Configuration — Specifies the hardware terminal configuration, such as single-ended, differential, etc. The terminal configuration options are defined by the capabilities of the selected channel.

Coupling — Hardware coupling configuration, such as AC or DC. The coupling type is defined when a device is selected.

Number of output data ports, specified as:

1 for all channels — Outputs the acquired data from a single port as a 1-by-N vector with a length equal to the number of channels selected.

1 per channel — Outputs the acquired data from N ports, where N is equal to the number of selected channels. Each port output is a 1-by-1 double. For naming, each output port uses the channel name if one was specified, otherwise the channel ID, for example, ai0.

Specifies the sample time of the block during the simulation. This is the rate at which the block is executed during simulation. The default value is 1 (simulation seconds). For more information, see Timing in Hardware Interface Models and What Is Sample Time? (Simulink).

Select this option to output the absolute timestamp of the scan. This option adds a new output port to the block. The data type of this port is double (datenum), which corresponds to a serial date number. You can convert the datenum into a datetime value with the datetime function.

Version History

Introduced in R2016b

See Also

Blocks