Which is better - an AC or DC triboelectric bag leak detection system?

Posted by Earl Parker on Jan 19, 2017 11:00:00 AM

What Does It All Mean

When considering a triboelectric bag leak detection system OEMs, sales reps, and other re-sellers may throw a number of seemingly confusing technical specs at the project engineer. One that frequently gets cited is whether the unit processes an AC signal or a DC signal. Often this is even touted as an advantage over other makes and models.  But not much explanation accompanies these claims as to the difference between the AC or DC signal, or why it even matters. So we often field questions from visitors to our site who have noted the various technical specifications of our units, as well as read much in our blog about our our Unified AC/DC signal processing technology.

But what is the difference between triboelectric systems that use AC and those that use DC? And what benefit does AC/DC unified technology provide? Lets take a look at the differences and highlight what one is used over the other. 

Superior Signal Vs. Adaptability to Harsher Conditions

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In the beginning when Auburn patented and developed the first generation of triboelectric bag leak detection systems all of the systems exclusively used the DC signal spectrum.

When particles impact the probe it generates a DC signal measured in pico amps. This signal is the most consistent and reliable and requires no amplification. It is also very linear, robust and easy to detect, transmit and process into a usable form for both emissions and flow monitoring applications.  

However, this DC signal begins to fade under certain conditions, particularly if buildup develops on the probe. Based on a significant amount of application experience we know that this is sometimes an issue with applications involving high moisture contents or exceptionally “sticky” dusts. Once a significant layer of dust builds up on the surface of the probe, the signal generated by impact to the probe weakens and eventually becomes unusable. It also can be affected by applications where condensed moisture is present in the gas stream, causing high signals that mask the particulate, leading to a false signal. 

Competitive Opportunity Born of Application Requirement

This application issue turned out to be good news for potential competitors seeking to develop alternatives to Auburn's systems. AC signal technology, also developed by Auburn, was deployed as a means to overcome challenges in applications where conditions interfered with the DC signal. This approach was later exploited by competitors as a way to get around the original DC patent.  Particles passing nearby the insulated probe (but not making contact with it) creates an AC signal using an induced triboelectric effect. The AC Signal is not as linear as DC signal, and it requires additional amplification and processing before it can be used. As such, without proper processing and other high quality installation and electrical components the AC is subject to false readings. However, product buildup causes much less interference with the generation of the AC signal. Jacketing or coating the probe with a proper insulative layer  helps overcome the issues caused by material buildup. The jacket protects the probe from the buildup of material or the presence of condensed moisture allowing the AC signal to continue to be detected. 

How Auburn’s Unified Technology Combines Benefits of Both DC and AC Signal

Long ago we recognized the benefits of both DC and AC signal spectrums and began developing technology to combine both into our detection technology. The result was the Auburn TRIBO.dsp (unified signal processing) series, which makes use of both DC and AC signals. This innovative approach required significant R&D to overcome signal processing complications. The eventual result was an award winning solution which combines the advantages of both spectra without the drawbacks of using just one over the other. This contrasts with many other triboelectric bag leak detection system manufacturers that continue to use only the AC signal spectrum for their units. When combined with cheaper electronics these units often suffer from poor signal quality, false readings and early failure (especially when compared with some of our units which have been in service for decades and continue to function properly). 

To learn more about how Auburn’s unified triboelectric detection systems can help your facility improve its emissions monitoring and compliance efforts please contact us today for a free consultation!

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Topics: Triboelectric Detection, Particulate Monitoring, Process Control