Support Center: Guides & FAQs

Insertion type flow meters, such as thermal mass flow meters and pitot tube flow meters, can be used in different pipe sizes without needing new calibration because they are designed to measure the flow of fluid within a pipe without being affected by the size or shape of the pipe. Both these types of flow meters measure the velocity of fluid, which is then paired with the cross-sectional area of the pipe to calculate the volume flow.

A thermal mass flow meter works by measuring the temperature difference across a heated sensor element inserted into the pipe. The flow of fluid through the pipe causes heat to be transferred from the sensor element to the fluid. By measuring the heat transfer, the flow rate of the fluid can be determined by using the fluid’s thermal properties and the known cross-sectional area of the pipe.

A pitot tube flow meter works by measuring the pressure difference across a tube that is inserted into the pipe. The tube is positioned so that the fluid flows around it and creates a pressure difference across the tube, which is proportional to the fluid velocity. By measuring the pressure difference, the flow rate of the fluid can be determined by using the fluid’s velocity and the known cross-sectional area of the pipe.

In both cases, the measuring principle is based on the determination of the fluid velocity in the pipe, which is then paired with the pipe cross-section, results in the volume flow, which is independent of the pipe size. This is the reason why these types of flow meters can be used in different pipe sizes without the need for new calibration.

• The sensor may be incorrectly installed — for example, not centered or installed at the wrong depth.
• The wrong gas type, flow units, or reference conditions may be selected in the settings.
• The inner pipe diameter might be entered incorrectly in the software.
• The sensor technology may not be suitable for the current application (e.g., thermal mass sensors in very humid environments).
• There may not be enough straight pipe before or after the sensor, causing turbulent flow.

• Verify the sensor is properly centered in the pipe and installed at the recommended depth and orientation.
• Check the gas type, measurement units, and reference pressure/temperature conditions in the S4C-FS software.
• Enter the correct inner pipe diameter to ensure proper flow calculation.
• Make sure the sensor technology is appropriate for the gas conditions (e.g., avoid thermal mass sensors where liquid water may be present).
• Install the sensor with adequate straight pipe lengths before and after, as specified in the manual.