- Flow Averaging Tube – FAT Probe: Utilize a single thermal mass sensor within a tube featuring multiple drilled holes, allowing for flow averaging across various points. This design reduces the need for long straight pipe runs and is ideal for installations with space constraints.
- Multipoint Sensors on a Single Insertion Probe: Incorporate multiple sensors (typically 3 or 4) along a single probe, providing enhanced resolution over single-point sensors. These are suitable for applications with higher temperatures (above 250–300°F) where FAT probes may not perform optimally.
- Multiple Single-Point Transmitters Averaged Together: Involve installing several single-point sensors at different insertion points, with their outputs averaged to obtain a comprehensive flow profile. This approach is beneficial when a single probe is impractical due to pipe size or configuration.
As pipe sizes get larger single point solutions become less and less practical due to their straight runs requirements. Using any type of multipoint solution will help reduce the required straight run because the measurement will no longer rely on a single reference point which requires fully developed flow. However, the quality of the measurement will go up as users add additional sensing points. In this article, we will explore the following options: FAT Probe options, multipoint model with multiple sensors, and a multipoint model with multiple insertion points.
Using a FAT Probe for Applications with Installation Constraints
EPI offers 3 types of “multipoint” solutions. Our premier multipoint solution is our Flow Averaging Tube which uses one thermal mass sensor and up to dozens of drilled holes in the tube that act as the sensing points. These can act as a single probe or as multiple probes for larger diameter ducts and extra short straight runs. The FAT probe does have smaller ports than the standard single point transmitter and can be subject to plugging in dirty service. A simple purge option can help reduce that issue.
For example, the Master-Touch 9700MP HAZ FAT averaging flow tubes are ideal for usage in hazardous areas. These thermal mass flow meters are an indispensable piece of equipment to provide you with precise and dependable flow measurement. Offering an Inline style thermal mass flow design that features the sensing elements openly mounted on the flow suction, these flow meters, from EPI, are available in sizes from 2″ pipe through to 4″ pipe and can be provided with flanged end arrangements if necessary.
Multiple Sensors on a Single Insertion Probe
The second type of multipoint sensor that EPI offers features multiple sensors along a single insertion probe (usually 3 or 4). This offers much better resolution than a single point sensor, but far less than a FAT probe. The multipoint is useful for high temperature applications that exceed the performance recommendations of the FAT probe (about 250-300˚F).
Single Point Transmitter Across Multiple Insertion Points
A third type of multipoint offering is a standard single point transmitter averaged together over multiple insertion points. Think of this as a solution for where a single probe will not be practical.
In summary, we usually look towards our FAT probe first when multipoint sensing is beneficial, but also remember there are a few other multipoint options as well.
