This model outputs the relative humidity of the fluid flowing
from port_a to port_b. The sensor is
ideal, i.e., it does not influence the fluid.
Note that this sensor can only be used with media that contain
the variable phi, which is typically the case for
moist air models.
If the parameter tau is non-zero, then its output
is computed using a first order differential equation. Setting
tau=0 is not recommend. See Annex60.Fluid.Sensors.UsersGuide
for an explanation.
quantity attribute for mass fraction
variables.tauInv since this now exists in
Annex60.Fluid.Sensors.BaseClasses.PartialDynamicFlowSensor.
This is for #372.