Non-contact measurement & inspection

An acoustic camera with 32 microphones would be able to detect that leak, but the signal-to-noise ratio is still too poor to hear anything quieter.

Look but Don’t touch

In contrast, a camera with 124 microphones can pick up both the

16.5 kHz leak and one that is 18.5 kHz, making it easy to detect, locate, and quantify the small leak.

Sound Detection Range

Adding just the right number of microphones to an acoustic imaging camera can also improve the chances of picking up very quiet noises from a long distance. This is especially important when inspecting high- voltage systems, which requires a safe distance from the energised equipment. The force of a sound signal drops significantly as one moves further away from its source. The solution is to increase the number of microphones: quadrupling the number of microphones essentially doubles the sound detection range.

Microphone Placement

The placement of microphones on an acoustic camera factors into how the camera determines the direction and location of sounds. The camera collects data from each microphone, measures the timing and phase differences in the signals, and calculates the source location. These microphones need to be grouped closely together to ensure they collect enough data on sound waves to correctly determine from what direction they originated.

Microphone Performance

Just like frequency, there is a sweet spot for how many microphones an acoustic imager hosts. A potential downside of too many microphones is each requires processing power to convert audio data signals into images—so adding too many has diminishing returns. Some manufacturers balance this by reducing the resolution of the acoustic image pixels, or “sound” pixels, but this will affect the camera’s overall performance. It's important to have enough sound pixels to detect corona and partial discharge reliably from a distance and pinpoint its exact source. With 124 microphones and advanced processing power, the FLIR

Si124 provides industry-leading detection sensitivity, excellent acoustic image resolution and a great range.

Intelligent Analytics

The final features to consider are the computing power and analytics provided by the acoustic imaging camera and any companion software. A camera such as the FLIR Si124 offers on-camera analytics, easy-to- understand reporting, and predictive analysis using an AI/web tool. An inspector can classify leak severity, perform leak cost analysis, and partial discharge pattern analysis in real-time during a survey. Once the survey is complete, the inspector only needs to connect to their Wi-Fi network to automatically upload images to the FLIR Acoustic Camera Viewer for further, cloud-based analytics. This includes calculating the estimated yearly energy expense caused by compressed air or vacuum leaks and determining whether a partial discharge issue will require service or replacement. The Viewer can also be used to create reports to share with a maintenance team or client.

FLIR Systems Instrumentation Monthly March 2021

portfolio, able to measure a wide range of continuous, web-fed or cut-to-length materials down to a resolution of 4 µm. The innovative SICK SPEETEC combines unprecedented affordability


with precision surface measurement for process control and quality inspection tasks, useful for industries as diverse as printing, textiles, tyre manufacture or building materials production. The Class 1 eye-safe infra- red laser eliminates the need for special guarding or safety measures required by many conventional velocimeters. The SPEETEC uses the Laser Doppler principle to work at speeds

between 0.1 and 10 m/s to measure directly on the material surface with an accuracy of 0.1 per cent, and a repeatability of 0.05 per cent. Typically, Return on Investment can be achieved in under 12 months, according to Darren Pratt, SICK’s UK product manager for motion control sensors. “The performance and affordability of the SICK SPEETEC will

come as a surprise to many machine builders and end-users,” he says. “It therefore promises new automation opportunities, as well as process improvements by achieving higher levels of measurement accuracy and throughput speeds which were not possible previously. “The SPEETEC’s non-contact measurement principle means it can

be used where a measuring wheel in contact with the substrate would never have produced completely reliable results. There’s no danger of damage to the material, important, for example for delicate, smooth or soft materials such as extrusions or textiles. “There is no need for any marks or scales on the material itself.

What’s more, unlike a measuring wheel which can wear over time due to abrasion with the material surface, the SPEETEC’s non- contact measurement function cannot be impaired in this way, so maintenance and downtime is reduced.” Product testing and field trials have already shown the SICK

SPEETEC to be reliable even when measuring materials with challenging, highly reflective, dark-black or uneven surfaces. SICK also expects to see it being installed to increase process speeds in applications where rotary encoders or measuring wheels would be prone to inaccuracy due to slippage of the material. The SPEETEC is easy to mount due to its generous mounting

tolerances and compact design. The rugged aluminium housing, measures just 140mm x 95mm x 32.5mm. The SICK SPEETEC can be set up in a matter of minutes and does not require any supplementary electronics to process the signal output. The Laser Doppler measurement is automatically converted onboard the sensor into TTL/HTL signals identical to those of an incremental encoder, so that they can be easily integrated into the machine control system.


ith the SPEETEC non-contact sensor for speed and length measurement, SICK has added a compact, affordable, eye-safe laser surface motion sensor to its

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