Overview
Unlike Simulink signals, which are essentially unitless,
physical signals can have units associated with them. You specify
the units along with the parameter values in the block dialogs, and Simscape unit
manager performs the necessary unit conversion operations when solving
a physical network. Simscape blocks support standard measurement
systems. The default block units are meter-kilogram-second or MKS
(SI).
Simscape software comes with a library of standard units,
and you can define additional units as needed (see Unit Definitions). You can use these
units in your block diagrams:
To specify the units of an input physical signal,
type a unit name, or a mathematical expression with unit names, in
the Input signal unit field of the Simulink-PS Converter block dialog. You
can also select a unit from a drop-down list, which is prepopulated
with some common input units. Signal units that you specify in a Simulink-PS
Converter block must match the input type expected by the Simscape block
connected to it. For example, when you provide the input signal for
an Ideal Angular Velocity Source block, specify angular velocity units,
such as rad/s or rpm, in the
Simulink-PS Converter block, or leave it unitless. If you leave the
block unitless, with the Input signal unit parameter
set to 1, then the physical signal units are inferred
from the destination block.
Simscape block dialogs have drop-down combo boxes
of units next to a parameter value, letting you either select a unit
from the drop-down list, or type a unit name (or a mathematical expression
with unit names) directly into the box. These drop-down lists are
automatically populated by those units that are commensurate with
the unit of the parameter, based on the current list of unit definitions.
For example, if a parameter is specified, by default, with the units
of meters per second, m/s, the drop-down list of
units contains commensurate units, such as mm/s, in/s, fps (feet
per second), fpm (feet per minute), and so on,
including any other linear velocity units currently defined in your
unit registry.
To specify the units of an output physical signal,
type a unit name, or a mathematical expression with unit names, in
the Output signal unit field of the PS-Simulink Converter block dialog. You
can also select a unit from a drop-down list, which is prepopulated
with some common output units. The system compares the units you specified
with the actual units of the input physical signal coming into the
converter block and applies a gain equal to the conversion factor
before outputting the Simulink signal. The default value is 1,
which means that the unit is not specified. If you do not specify
a unit, or if the unit matches the actual units of the input physical
signal, no gain is applied.
For more information, see Specifying Units in Block Dialogs.
 | Working with Physical Units | | Unit Definitions |  |
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