The calorimetric measuring method is based on a mechanically protected built-in sensor element being electrically heated. The mass flow rate, standard flow velocity and standard flow rate are determined as a result of the emerging thermal flow on the on-flowing gas.
On account of this measuring principle, working temperature and pressure of the medium have no detrimental effect on the measurement values. As thermal mass flow is about calorimetric measuring, only the property data of the gas components is critical.
An advantage of these sensors for measuring mass flow is the negligible pressure drop and they are also suitable for measuring consumption of compressed air and other gases, thus determining standard flow rate or mass flow rate of the gas components.
Thermal mass flowmeters of a certain design are perfect for precise measuring of low flow velocities (laminar flow) with long-term stability.
Examples of application include measuring laminar flow in clean rooms or machines, in fan/filter units; flow measurement in production facilities in the pharmaceutical, food processing and semiconductor industries; monitoring flow in gloveboxes and insulators as well as the velocity rate of sedimentation in spray booths.
Compressed air, natural gas and other gas mediums are expensive sources of energy. Considerable cost savings can be achieved by detecting and eliminating pipe leakages and performance control of compressors. Thermal flow sensors have no moving parts, are accurate, robust and maintenance-free. With their turndown ratio of 1:1000, flow rates from leakage flows to maximal withdrawal of gas can be measured reliably, even with a working pressure of up to 50 bar. Various output signals such as 4-20 mA, quantity pulse or M-Bus are available for rendering and processing consumption quantity measurements of natural gas, propane, butane, LPG, compressed air, CDA, etc.
Höntzsch calorimetric flow meters are well suited for various applications in explosive atmospheres (ATEX, CSA) and have proved invaluable in fixed and portable measuring of landfill gas quantities. These also reliably measure the ever-decreasing gas flow rate on completed landfill sites.
Thermal mass flow meters can be used in the most varied of applications in which standard flow rate measurements are required.
Additional fields of application for these thermal mass flow sensors for measuring flow rate in clean gases are fixed or portable consumption measurement in air, compressed air, landfill gas, nitrogen (N2), natural gas, propane (C3H8), methane (CH4), butane (C4H10), argon (Ar), helium (He2), carbon dioxide (CO2), hydrogen (H), sulphur hexafluoride (SF6), ethane (E2H2), etc. For gas flow proportional measuring and standard flow velocities from 0.8 to 200 m/s as well as standard volume flow from 0.04 m³/h with a time constant of just 1 s.
Höntzsch calorimetric flow meters for measuring mass flow are available as insertion probes for installation in pipelines with an inside diameter of 25 mm or as measuring tubes with an inside diameter from 8 mm.