Measurement Selector (MA)

Measure pressure, temperature, humidity, and trace gas levels in moist air internal volumes

• 

Libraries:
Simscape / Foundation Library / Moist Air / Sensors

Description

The Measurement Selector (MA) block lets you access the pressure, temperature, moisture level, and trace gas level measurements inside a block with a finite moist air volume. There is no mass or energy flow through the sensor.

Blocks with a finite moist air volume contain an internal node, which represents the moist air volume inside the component. For a complete list of these blocks, see Blocks with Moist Air Volume. Regular sensors cannot connect to this internal node. Therefore, each of the blocks with a finite moist air volume has a physical signal output port F, which outputs a vector signal containing the pressure (in Pa), temperature (in K), humidity, water droplets mass ratio, and trace gas level measurements inside the component. For more information, see Measuring Moisture and Trace Gas Levels.

Use the Measurement Selector (MA) block to unpack the vector signal and reassign units to pressure and temperature values. Connect the input port F of the Measurement Selector (MA) block to the physical signal output port F of a block with finite internal moist air volume to access the data.

Connect the output ports of the Measurement Selector (MA) block to PS-Simulink Converter blocks to transform the output physical signals into Simulink^® signals, for example, for plotting or additional data processing. Use the Output signal unit parameter of the PS-Simulink Converter blocks connected to ports P and T to reassign units to pressure and temperature values, respectively.

Examples

Vehicle HVAC System

Models moist air flow in a vehicle heating, ventilation, and air conditioning (HVAC) system. The vehicle cabin is represented as a volume of moist air exchanging heat with the external environment. The moist air flows through a recirculation flap, a blower, an evaporator, a blend door, and a heater before returning to the cabin. The recirculation flap selects flow intake from the cabin or from the external environment. The blender door diverts flow around the heater to control the temperature.

• Open Model

Aircraft Environmental Control System

Models an aircraft environmental control system (ECS) that regulates pressure, temperature, humidity, and ozone (O3) to maintain a comfortable and safe cabin environment. Cooling and dehumidification are provided by the air cycle machine (ACM), which operates as an inverse Brayton cycle to remove heat from pressurized hot engine bleed air. Some hot bleed air is mixed directly with the output of the ACM to adjust the temperature. Pressurization is maintained by the outflow valve in the cabin. This model simulates the ECS operating from a hot ground condition to a cold cruise condition and back to a cold ground condition.

• Open Model

Medical Ventilator with Lung Model

Models a positive-pressure medical ventilator system. A preset flow rate is supplied to the patient. The lungs are modeled with the Translational Mechanical Converter (MA), which converts moist air pressure into translational motion. By setting the Interface cross-sectional area to unity, displacement in the mechanical translational network becomes a proxy for volume, force becomes a proxy for pressure, spring constant becomes a proxy for respiratory elastance, and damping coefficient becomes a proxy for respiratory resistance.

• Open Model

Ports

Input

F — Vector physical signal containing pressure, temperature, humidity, and trace gas levels data

physical signal vector

Connect this port to the physical signal output port F of a block with finite internal moist air volume to access the data. Blocks with a finite moist air volume have a physical signal output port F, which outputs a vector signal containing the pressure (in Pa), temperature (in K), humidity, water droplets mass ratio, and trace gas level measurements inside the component. Use the Measurement Selector (MA) block to unpack this vector signal.

Output

P — Pressure measurement, Pa

physical signal

Physical signal output port for pressure measurement.

T — Temperature measurement, K

physical signal

Physical signal output port for temperature measurement.

W — Humidity level measurement, unitless

physical signal

Physical signal output port for humidity level measurement. To select the quantity you want to measure, use the Measured humidity specification parameter.

G — Trace gas level measurement, unitless

physical signal

Physical signal output port for trace gas level measurement. To select the quantity you want to measure, use the Measured trace gas specification parameter.

D — Mass ratio of water droplets to moist air, unitless

physical signal

Physical signal output port for the mass ratio of water droplets to moist air.

Parameters

Measured humidity specification — Select the humidity property to measure

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio

Select the property to measure:

• Relative humidity ― Physical signal port W reports the relative humidity.

• Specific humidity ― Physical signal port W reports the specific humidity.

• Mole fraction ― Physical signal port W reports the water vapor mole fraction.

• Humidity ratio ― Physical signal port W reports the humidity ratio.

Measured trace gas specification — Select the trace gas property to measure

Mass fraction (default) | Mole fraction

Select the property to measure:

• Mass fraction ― Physical signal port G reports the trace gas mass fraction.

• Mole fraction ― Physical signal port G reports the trace gas mole fraction.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2018a

R2024b: Model water droplets suspended in moist air flow

Blocks in the moist air domain can now model water droplets suspended in a moist air flow. To model water droplets, select Enable entrained water droplets in the Moist Air Properties (MA) block connected to your moist air network.