Wireless Delsys Trigno System: In-line hardware high-pass filter

[Gustavo Sandri Heidner]

Greetings,
I've recently heard from a peer that the Delsys system operates with an HPF of 20 Hz. If this is the case, the data acquired wouldn't be suitable for a EEG-EMG coherence analysis in the 4-30 Hz threshold.
I've tried to search for this mention in the documentation, but there's nothing there. This also comes as a surprise to me, because why would the system just have an embedded filter that cuts those frequencies out. My first guess is because it transmits the information over WiFi, but I am not 100% sure.
Can anyone confirm or disprove this?
Many thanks.

[John Letizi]

Re: Wireless Delsys Trigno System: In-line hardware high-pass filter

Hello Gustavo,

Some of our Trigno EMG sensors use a HPF with a corner frequency of 20 Hz, because any motion artifacts will tend to contaminate EMG signals at lower frequencies (<20 Hz). This engineering decision was motivated by this publication, published in the Journal of Biomechanics, which shows that the 20 Hz corner frequency provides an optimal compromise between noise rejection and EMG signal loss.

We do have two sensor models, the Trigno Flex & soon-to-be-released Trigno Avanti sensors, which have two EMG signal bandwidths for users to choose from (20-450 Hz or 10-850 Hz). These sensors may be better suited for your coherence studies if you're interested in beta band activity (15-30 Hz). All Trigno sensors are interchangeable, so these could be easily added to your existing system.

I'll be happy to answer any additional questions you may have; feel free to email me directly at jletizi@delsys.com, or call my direct line at 508-545-8237. I look forward to speaking with you!

Best Regards,

John Letizi
Research Engineer
Delsys, Inc.