Acoustic Ultrasound Technology

At the most basic level, an ultrasound listening device (ULD) converts ultrasound into the audible range, delivering that demodulated signal into a head set.

Like most ultrasound detectors, CTRL’s sensors are tuned to a narrow frequency centered on a 40 kilohertz (kHz) signal, which is approximately 20kHz beyond the human auditory range. At such a high frequency, sound is highly localized to its source, which makes ultrasound detection a valuable tool “honing in” to listen directly to a specific component’s operating conditions. For example, a contact sensor can be used to listen to the internal friction created by a single motor bearing as it rotates, without being affected by the operation of other nearby components. That data can then be captured by software, added to a trend, and analyzed for a significant change in condition over time.

In addition to monitoring the condition of rotating components, ultrasound detection equipment can be used to hear other internal changes in any mechanical, hydraulic, or fluid delivery system. And because ultrasound technology does not detect any sound in the audible range, it can also be used in very noisy industrial environments to detect airborne ultrasound created by pneumatic leakage or electrical faults. In any environment, competing ultrasound in the 40 kHz range can mask ultrasonic events with a particularly low amplitude — for instance, the quiet friction of a slow-moving bearing or a small, lightly pressurized steam leak. Unfortunately, most ultrasound sensors on the market today use a method of demodulation that generates their own ultrasound, intrinsic to the operation of the sensors themselves. This results in a constant, underlying “white noise” that can be heard in an operator’s head set or seen on a waveform generator.

CTRL sensors are built on a unique, enhanced IP to shift ultrasonic frequency into the audible range, producing the highest signal-to-noise ratio of any ultrasound detector on the market.

In the example to the right, four ultrasound sensors record the operation of the same steam trap at the same time. The top waveform was recorded by a CTRL sensor. Notice the relatively quiet baseline. The other three waveforms were. Recorded by three different competitive sensors. Notice the underlying “white noise,” created by the sensors themselves.

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