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Neil I'd be surprised if there was a solution to this. You are measuring small voltages across a resistance in the presence of an electromagnetic field which is bound to induce voltages. It's not helped by the fact that the phone is moveable and so, by the inverse square law, you can get very large electric fields. ECG monitoring equipment goes to very extreme lengths to reduce the effects of interference but they essentially identify the erroneous beats & throw them away! It's different when you want each event to matter. The MDA investigations into EM interference considered that a short disturbance of a trace was of little consequence as long as the system recovered afterwards. Unless there is an EMG system that is built to survive surgical diathermy??!! I have a contact who is using Cyberlink - I'll ask him about his experience of interference. It might be worth putting your query out on the general medical physics or physiological measurement lists for a more informed view than mine. Barry Taylor, Clinical Scientist Bioengineering Department Tulley Medical Physics Building, Hull Royal Infirmary Anlaby Road, Hull HU3 2JZ Tel 01482 675928, fax 01482 675750 > ---------- > From: Neil Gregory[SMTP:[log in to unmask]] > Reply To: A discussion list for Assistive Technology professionals. > Sent: 09 April 2002 16:18 > To: [log in to unmask] > Subject: EMG and mobile phones > > Dear All, > > I was using a surface EMG system that showed the EMG trace on the screen. > The system I use has a peak detection of 400uV and the signals I was > getting were about 5-10uV. The client's relative received a call on their > mobile phone during the assessment and this severely interfered with the > EMG signal. I had used skin preparation, good electrodes, good signal to > noise ratio reduction in the pre-amplifier, fibre optic link to the PC and > the phone was about 2 meters away. This would render the system useless > during a mobile phone call. > > I have tested this again at work and get interference during a call at > about 1 metre (presumably different signal strengths). Has anybody else > observed this phenomenon or does anybody have advise about this. Obviously > I will ask people not to have mobile phones on when within the same room > as the EMG equipment. > > Thanks, > > Neil Gregory > Clinical Engineer > Access to Communication and Technology > West Midlands Rehabilitation Centre, England > [log in to unmask] > Tel. UK +44 (0)121-627 8235 > Fax. UK +44 (0)121-627 8892 > > This e-mail contains proprietary information some or all of which may be > legally privileged. It is for the intended recipient only. If an > addressing or transmission error has misdirected this e-mail, please > notify the author by replying to this e-mail. If you are not the intended > recipient you must not use, disclose, distribute, copy, print, or rely on > this e-mail. >