Output signal attributes, including width, dimensionality, sample time, and complex signal flag


Signal Attributes


The Probe block outputs selected information about the signal on its input. The block can output the input signal's width, dimensionality, sample time, and a flag indicating whether the input is a complex-valued signal. The block has one input port. The number of output ports depends on the information that you select for probing, that is, signal dimensionality, sample time, and/or complex signal flag. Each probed value is output as a separate signal on a separate output port. The block accepts real or complex-valued signals of any built-in data type. It outputs signals of type double. During simulation, the block icon displays the probed data.

Data Type Support

The Probe block accepts signals of the following data types:

  • Floating point

  • Built-in integer

  • Fixed point

  • Boolean

  • Enumerated (input only)

  • Bus object

For more information, see Data Types Supported by Simulink in the Simulink® documentation.

You can use an array of buses as an input signal to a Probe block. For details about defining and using an array of buses, see Combine Buses into an Array of Buses.


Probe width

Select to output the width, or number of elements, of the probed signal.

Probe sample time

Select to output the sample time of the probed signal. The output is a two-element vector that specifies the period and offset of the sample time, respectively. See Specify Sample Time for more information.

Detect complex signal

Select to output 1 if the probed signal is complex; otherwise, 0.

Probe signal dimensions

Select to output the dimensions of the probed signal.


The Probe block ignores the Data type override setting of the Fixed-Point Tool.

Data type for width

Select the output data type for the width information.

Data type for sample time

Select the output data type for the sample time information.

Data type for signal complexity

Select the output data type for the complexity information.

Data type for signal dimensions

Select the output data type for the dimensions information.


For Data type for width, Data type for sample time, and Data type for signal dimensions, the Boolean data type is not supported. Furthermore, if you select Same as input in any of these drop-down lists, and the block’s input signal data type is Boolean, when you simulate your model, you see an error.


The sldemo_fuelsys model shows how you can use the Probe block.

In the fuel_rate_control/validate_sample_time subsystem, the Probe block determines the sample time of the input signal to verify that it matches the assumed value of the design:

For more information, see the model description.


Data Types

Double | Single | Boolean | Base Integer | Fixed-Point | Enumerated | Bus

Sample Time

Inherited from driving block

Direct Feedthrough


Multidimensional Signals


Variable-Size Signals


Zero-Crossing Detection


Code Generation


Introduced before R2006a

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