Vacuum
Theory
Thermal mass flow measurement
Thermal Mass Flow Meters and Controllers make use of the heat conductivity of fluids (gases or liquids) to determine mass flow.
Coriolis mass flow measuring principle
A Mass Flow Meter operating on the "Coriolis principle" contains a vibrating tube in which a fluid flow causes changes in frequency, phase shift or amplitude, proportional to the mass flow.
Pressure measurement
The Bronkhorst High-Tech EL-PRESS pressure sensor is a piezo resistive bridge on the surface of a silicon chip.
Mass flow controller (MFC) theory
In the case of mass flow control, the output signal is continuously compared with a setpoint signal from a voltage source. Any deviations between setpoint signal and measured signal are translated into a solenoid control valve adjustment until the two signals are identical.
Theory and advantages of 'CEM' Vapour Control
The vapour generation system consists of a liquid flow controller, an MFC for carrier gas, a temperature Controlled-Evaporation-Mixing device (CEM) and a power supply / readout / control unit.
Volume Flow versus Mass Flow
The ranges of Bronkhorst's thermal mass flow meters / controllers for gases are specified in such units as ln/min, sccm or m3n/h. These units look like volumetric units, but in truth they are expressions of Mass Flow. What is the story behind this?
