This model outputs the density of the fluid flowing from
port_a to port_b.
The sensor is ideal, i.e., it does not influence the fluid. 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 IBPSA.Fluid.Sensors.UsersGuide
for an explanation.
tauInv since this now exists in
IBPSA.Fluid.Sensors.BaseClasses.PartialDynamicFlowSensor. This
is for #372.Modelica.Fluid.