An averaging pitot tube is an insertion differential-pressure meter that improves on the simple pitot by sensing the flow at several points across the pipe rather than just one. A bar spans the bore with multiple upstream-facing ports, and the pressures they see are averaged inside the probe to produce a single, more representative impact pressure. That averaging is the whole point, because it makes the measurement far less dependent on exactly where in the velocity profile the probe sits. The result is a low-cost, very low-pressure-loss meter that can be hot-tapped into a live line, of which the Annubar is the best-known example.
Averaging Pitot Tube in one line: An averaging pitot tube is a probe spanning the pipe with several sensing ports that average the velocity profile to give a stable differential pressure between the impact and static readings. It converts that differential to flow with a flow coefficient, offering very low permanent pressure loss and easy insertion, unlike a single-point pitot that samples only one location.
A basic pitot tube has one forward-facing hole that senses the impact, or total, pressure of the flow at a single point, and one static port. The difference between them is the dynamic pressure, from which velocity is derived. The trouble is that a single point sees only one thread of the velocity profile, so the reading depends heavily on exactly where the probe tip sits and on how developed the flow is. Move the tip, add an upstream elbow, or let the profile skew, and the single-point pitot's number shifts even at constant flow.
The averaging pitot addresses this by running a bar across the full pipe diameter with several impact ports distributed along its upstream face. Each port senses the local impact pressure at its position in the profile, and the internal geometry of the probe combines those pressures into a single averaged high-side signal. A separate downstream or side port provides the low-side, static-like reference. Because the high side now reflects several points rather than one, the differential represents the average velocity across the pipe far better than a single-point device can.
That averaging translates directly into tolerance for imperfect installation. An averaging pitot is less sensitive to modest upstream disturbances and to precise insertion depth than a single-point pitot, because a skew that raises the pressure at one port tends to lower it at another. It still benefits from reasonable straight run and correct orientation, but it forgives the kind of profile distortion that makes a single-point pitot unreliable. Like every DP meter, its output follows the square-root law, scaled by a flow coefficient specific to the probe's shape and blockage.
The averaging pitot's standout advantage is how little it disturbs the flow. It is a slender bar rather than a plate or a throat, so it blocks only a small fraction of the pipe and its permanent pressure loss is very low compared with an orifice, nozzle, or venturi. On large ducts and lines where pumping or compression energy is a real operating cost, that near-negligible pressure penalty is a strong argument, and it lets the same technology scale to big pipes cheaply since only the bar length changes.
Because it is an insertion device, an averaging pitot can be fitted through a small tap and, in many designs, installed or withdrawn on a live, pressurized line through an isolation valve using a hot-tap procedure. That makes it inexpensive to add to an existing line and serviceable without a shutdown, the same access advantages that draw operators to insertion meters generally. The measurement point costs a fraction of a full-bore meter, especially on large diameters.
The main weakness is plugging. The sensing ports are small holes, and in dirty, wet, or condensing gas they can foul, drip, or block, which corrupts the averaged pressure and therefore the flow reading. Some designs mitigate this with self-cleaning port geometry, purge connections, or a shape that resists deposit buildup, but averaging pitots are fundamentally happier in clean, dry service than in streams heavy with liquids or particulate. Where fouling is a concern, port plugging is the failure mode to design against and to watch for.
Annubar is a well-known brand name that has become nearly synonymous with the averaging pitot tube, much as some other trademarks stand in for a whole class of device. An Annubar is an averaging pitot: a bar with multiple sensing ports and a shaped cross-section engineered to give a stable, well-characterized flow coefficient across a range of conditions. When engineers say Annubar in the field they almost always mean an averaging pitot tube, and the terms are used interchangeably in practice even though one is a product family and the other is the generic technology.
In a monitoring scheme the averaging pitot behaves like any DP meter, which makes it easy to integrate. A differential transmitter, plus static pressure and temperature for gas density correction, feeds an RTU or flow computer that extracts the square root and reports a corrected rate, and a cloud platform such as Merobix reads the flow and the raw differential back over Modbus or DNP3 to trend and alarm. The very low pressure loss makes these meters common on large flare, fuel-gas, and utility headers across a field.
Given the plugging risk, historized data is the practical safeguard for averaging pitots on remote sites. A differential that slowly falls toward zero or goes suspiciously flat at steady flow is a classic signature of fouled or blocked sensing ports rather than a real drop in flow, and catching that pattern on a dashboard lets an operator schedule a purge or cleaning before the record is corrupted. Remote alarming on a stale or out-of-range differential turns a low-maintenance, low-loss meter into a trustworthy one on unmanned lines where port fouling would otherwise go undetected.
A standard pitot tube senses impact pressure at a single point, so its reading depends heavily on probe position and the shape of the velocity profile. An averaging pitot spans the pipe with several sensing ports and averages the pressures across the profile, giving a differential that represents the mean velocity far more reliably. The averaging design is much more tolerant of imperfect insertion and modest upstream disturbances.
Yes. Annubar is a widely used brand name for an averaging pitot tube, and the term has become a common generic label for the technology. An Annubar is a bar with multiple sensing ports and a shaped profile that gives it a stable flow coefficient, which is exactly what defines an averaging pitot. Engineers use the two terms interchangeably in the field.
Its main weakness is that the small sensing ports can plug in dirty, wet, or condensing service, which corrupts the averaged pressure and the resulting flow reading. It performs best in clean, dry flow, and in fouling conditions it needs self-cleaning port designs, purge connections, or regular attention. Watching the differential for a slow decline toward zero at steady flow helps catch port plugging early.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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