Beam angle decides what an ultrasonic sensor detects and what it ignores — here’s what sets it, the narrow-versus-wide tradeoff, and how to choose the right beam for your design.
KEY ANSWERS AT A GLANCE
What is beam angle? The angular width of the cone of sound a transducer projects, stated in degrees. •
What sets it? Mainly operating frequency and transducer face size — higher frequencies and larger faces produce narrower beams.
Is a narrow or wide beam better? Neither — a narrow beam concentrates energy and rejects clutter; a wide beam covers more area but picks up surroundings.
Can you narrow the beam? Yes — raise the frequency, enlarge the face, or add an acoustic horn (about 2 degrees on a Series 600).
Why does a sensor see false targets? A too-wide beam, side lobes, or excess gain; run the minimum gain that reliably detects the target
What is beam angle in an ultrasonic sensor?
Beam angle is the angular width of the cone of sound an ultrasonic transducer projects, usually stated in degrees. A transducer doesn’t emit sound in a straight pencil line or radiate in every direction — it sends out a main lobe of energy that is strongest along its axis and tapers toward the edges. Beam angle specifies how wide that cone is.
A useful way to picture it is a flashlight. A narrow beam is a spotlight: bright, far-reaching, and something you have to aim. A wide beam is a floodlight: broad coverage, but less reach and less selectivity. The transducer radiates a fixed amount of acoustic energy either way — beam angle decides whether that energy is concentrated into a tight cone or spread across a wide one.
What determines an ultrasonic sensor’s beam angle?
An ultrasonic sensor’s beam angle is set mainly by the operating frequency and the size of the transducer face. For a given face, a higher frequency (shorter wavelength) produces a narrower beam, and a larger face narrows it further. The frequency relationship is visible across transducer types: a roughly 120 kHz unit runs about a 10-degree beam, while a roughly 200 kHz unit narrows to about 7 degrees.
In SensComp’s electrostatic ultrasonic transducers, the concentric grooves machined into the backplate exist primarily to shape the beam — beam geometry is engineered into the transducer, not just a byproduct of its size.
Two caveats are worth carrying into any design. A published beam angle describes the main cone, typically measured to the points where intensity drops to half its on-axis peak, so real acoustic energy still exists outside the rated cone. And the main lobe is usually surrounded by weaker side lobes. The number on the datasheet is the headline, not the whole story.
Is a narrow or wide ultrasonic beam better?
Neither is universally better — a narrow beam and a wide beam are tuned for different jobs. A narrow beam concentrates acoustic energy, which strengthens the on-axis signal and effective reach, rejects off-axis clutter, and resolves small or closely spaced targets. A wide beam covers more area and tolerates misalignment and target movement, but it picks up walls, floors, and adjacent objects, and spreads its energy so returns are weaker.
The table below summarizes the tradeoff.
|
Factor |
Narrow Beam |
Wide Beam |
|---|---|---|
|
Coverage area |
Small, focused cone |
Broad — covers more of the scene |
|
On-axis reach and signal strength |
Higher — energy concentrated on axis |
Lower — energy spread over a wider area |
|
Clutter and off-axis rejection |
Strong — ignores walls, floors, adjacent objects |
Weak — picks up surrounding surfaces |
|
Tolerance to misalignment or target movement |
Low — must be aimed precisely |
High — forgiving of position changes |
|
Resolving small or closely spaced targets |
Better angular resolution |
Poorer — targets blur together |
|
Typical use |
Targeting one object, tank level, a clearance gate |
Presence or zone detection, lane coverage, moving targets |
Why does beam angle cause false readings or missed detections?
A mismatched beam angle is a common cause of both false targets and missed detections. Too wide, and the beam reaches the tank wall, the floor under a conveyor, or an object in the next lane, returning off-axis echoes that read as phantom targets or noisy data. Too narrow, and a perfectly aimed beam loses a target the moment it tilts, shifts, or moves, opening coverage gaps that don’t appear on the bench.
Gain makes the problem worse in a way that catches people out. Turning up receiver gain to reach a soft or distant target also raises sensitivity to the beam’s edges and side lobes, so the sensor effectively hears wider than its rated cone and starts flagging clutter as targets. Electrostatic ultrasonic transducers have approximately 40 dB greater receive sensitivity than comparable piezoelectric ultrasonic transducers, so they can often detect a difficult target at lower gain — keeping side-lobe false targets down instead of trading them for reach.
How do you change an ultrasonic sensor’s beam angle?
You change beam angle by selecting a different transducer, adding an acoustic horn, or shifting the operating frequency. SensComp’s electrostatic ultrasonic transducers offer several beam options: the Series 600 transducer projects a focused beam of approximately 15 degrees; the 9000 Series uses an asymmetrical pattern of roughly 15 degrees in one plane and 40 degrees in the other, for wide lane or shelf coverage that still rejects the floor and ceiling. An acoustical horn can also be added: a Series 600 fitted with a horn, sourced separately, narrows to about 2 degrees for pinpoint measurement.
Frequency is the other lever. Because electrostatic ultrasonic transducers are broadband — usable from roughly 20 to 100 kHz and optimized near 50 kHz — a custom design has room to shift frequency, with higher frequencies tightening the beam and lower frequencies favoring range and penetration. It’s a deliberate design choice, not a default to assume.
How do you choose the right beam angle for your application?
Choose beam angle by asking two questions before range or accuracy: what is the smallest or most off-axis target you must detect, and what nearby surfaces must the sensor ignore? A fixed, well-located target favors a narrow beam; a target that moves or varies in position favors a wider beam or an asymmetrical fan pattern. A few practical points carry the choice into the field:
- Aim and mount a narrow beam precisely; for a wide beam, account for everything else in the cone — walls, floor, fixtures, passing traffic.
- Run the minimum gain that reliably detects the target, to limit side-lobe false targets.
- Remember the rated cone isn’t a hard wall: a strong reflector just outside it can still return an echo.
- Whatever beam you choose, you can implement it at the transducer, ranging-module, or integrated-sensor level.
Because electrostatic ultrasonic transducers hold frequency and gain stable from -40°C to +85°C, the beam geometry you characterize on the bench doesn’t wander with temperature the way a resonant piezoelectric ultrasonic transducer’s can.
Frequently Asked Questions
Beam angle is the angular width of the cone of sound a transducer projects, usually stated in degrees. The transducer radiates a main lobe strongest along its axis that tapers toward the edges, and beam angle describes how wide that cone is. A narrow beam concentrates energy and rejects clutter; a wide beam covers more area but picks up more surroundings.
Yes. For a given transducer face, a higher operating frequency (shorter wavelength) produces a narrower beam. As an illustration, a roughly 120 kHz transducer runs about a 10-degree beam while a roughly 200 kHz transducer narrows to about 7 degrees. A larger transducer face also narrows the beam.
The SensComp Series 600 electrostatic ultrasonic transducer projects a focused beam of approximately 15 degrees. For wider coverage, the 9000 Series uses an asymmetrical pattern of roughly 15 degrees in one plane and 40 degrees in the other. For a much tighter beam, a Series 600 fitted with an acoustical horn can be narrowed to about 2 degrees.
Off-axis false targets usually come from a beam that is too wide for the application, from the weaker side lobes that surround the main beam, or from excessive receiver gain. Raising gain increases sensitivity to the beam’s edges and side lobes, so the sensor effectively hears wider than its rated cone. Running the minimum gain that reliably detects the real target, and choosing a beam angle matched to the target, both reduce these false readings.
Yes. The main ways are to raise the operating frequency, increase the transducer face size, or add an acoustical horn, which is sourced separately. A SensComp Series 600 transducer fitted with a horn, for example, can be narrowed to about 2 degrees. Because electrostatic ultrasonic transducers are broadband (roughly 20 to 100 kHz), a custom design has room to shift frequency to tune the beam.
Specifying an ultrasonic sensor and not sure which beam fits?
Contact us for help, or compare beam angle, sensitivity, and range across SensComp’s electrostatic ultrasonic transducers and ranging modules:: See all products.