Extending air ultrasonic measurement to 30 m
The BBDM-21KR30M is an air-coupled ultrasonic distance transducer with a 21 kHz center frequency and a reference range of 1.0 to 30 m. It can be evaluated for large-tank level monitoring, industrial distance measurement, collision avoidance, area monitoring and long-range target detection.
At distances approaching 30 m, adequate echo margin depends on more than the nominal range. Target area and orientation, airborne attenuation, temperature gradients, mounting alignment and receiver design all influence whether the return signal can be separated from noise and unwanted reflections.
Technical specifications
| Parameter | Specification |
|---|---|
| Model | BBDM-21KR30M |
| Center frequency | 21 kHz +/-5% |
| Recommended range | 1.0-30 m |
| Minimum impedance | 1,100 ohm +/-20% |
| Capacitance | 11,000 pF +/-20% at 1 kHz |
| Operating voltage | Peak voltage below 1,500 Vpp |
| Operating temperature | -40 to +80 degrees C |
| Pressure rating | Up to 3 kgf or 0.3 MPa |
| Beam characteristic | -3 dB half-power angle: 13 degrees +/-10% |
| Housing material | PTFE |
| Protection rating | IP68 |
| Weight | 1,020 g +/-5% |
Echo margin and vessel layout
The 13-degree half-power angle must be kept clear of fill pipes, reinforcement, wall transitions and other structures that may create an earlier return. The 1 m lower end of the reference range also matters when defining the highest measurable level.
Electrical matching
The assembly weighs 1.02 kg. The drive and receive circuit should be matched to the stated impedance, capacitance and peak-voltage limit.