Flow Measurement & Control

A rotameter is a flow measurement device used for measuring the flow rate of a fluid (liquid or gas) passing through an enlarged vertical pipe (typically a cone-shaped tube). It operates on the variable area principle, where the position of a float within the tube directly indicates the flow rate.
• Simple, robust, and cost-effective.
• Do not require electrical power (in their mechanical version).
• Ideal for low flow rates and fixed installations

Laminar mass flow meters calculate mass flow by measuring the pressure drop across laminar flow elements.
Operating Principle
These flow meters are equipped with a laminar restriction element through which the fluid flows in a laminar regime. When the gas passes through this element:
• a pressure drop occurs between the inlet and outlet of the laminar element,
• this pressure drop is proportional to the volumetric flow rate in the laminar regime,
• knowing the temperature and pressure of the gas, the mass flow rate can be calculated accurately.
Advantages
• Very good accuracy even at low flow rates,
• Fast and linear response in the laminar regime,
• Low sensitivity to gas composition (if properly calibrated).

Thermal mass flow meters utilize the thermal properties of gases to directly measure the mass flow rate of a gaseous fluid.
• Direct measurement of mass flow (no need to correct for temperature or pressure).
• Ideal for pure gases.
• Very few moving parts → reduced maintenance.

Laminar liquid flow controllers are designed to ensure precise and stable regulation of the volumetric flow rate of liquids.
They operate based on the principle of laminar fluid dynamics: when the liquid flows through a laminar flow element (usually a calibrated channel or tube), a pressure drop occurs between the inlet and the outlet of this element.
This pressure drop is proportional to the flow rate of the liquid. By measuring this pressure drop, the controller can:
• Calculate the flow rate in real time
• Compare the actual flow rate to the desired flow rate
• Actively adjust a valve or actuator to maintain the target flow rate

These controllers regulate the mass flow rate by measuring the pressure drop (or pressure loss) of the gas through a laminar restriction element, also known as a laminar flow element.

Advantages
• High accuracy in mass flow measurement.
• Fast response time, suitable for dynamic processes.
• Less sensitive to temperature and pressure variations compared to volumetric systems.

Typical Applications
• Research laboratories in chemistry or physics.
• Industrial process control involving gases.
• Calibration and standardization systems.

Thermal mass flow controllers operate by measuring the amount of heat absorbed or carried away by a flowing gas. This principle relies on the specific heat capacity of the gas—that is, the amount of energy required to increase its temperature. By monitoring the temperature change within a heated flow, these devices can accurately calculate and control the mass flow rate, independently of ambient pressure or temperature.

Variable area flow meters (also called rotameters) with a needle valve added at the inlet or outlet. They operate by allowing a float to move freely within a conical tube, where the float’s equilibrium height is proportional to the volumetric flow rate.