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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Hi Julian,<br>
We have experienced this problem as well. We solved it using the following guidelines:<br>
<br>
No metal near the polhemus or any of the receivers/transmitters - you will need to move the setup around the room to find the perfect spot.<br>
Use a wooden or plastic chair<br>
Use plastic or cloth glasses/holder to attach the receiver to the subject<br>
<br>
My system is sensitive to the proximity of the transmitter and the receiver. I use two receivers, #1 is the stylus and #2 is secured to plastic glasses that the subject wears. The transmitter is taped to the back of the chair. If #2 and the transmitter are
too close to each other (i.e. a short person or child), then the measurement are inaccurate. You would have to experiment with different distances that give good results.
<br>
<br>
Hope this helps!<br>
Beth<br>
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<p><font size="1">------------------------------------------------------------------------------------------</font></p>
<p><font size="1">Elizabeth Bock / MEG System Engineer</font></p>
<p><font size="1">McConnell Brain Imaging Centre / Montreal Neurological Institute</font></p>
<p><font size="1">McGill University / </font><font size="1">3801 University St. /
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<div style="direction: ltr;" id="divRpF256871"><font color="#000000" face="Tahoma" size="2"><b>From:</b> fieldtrip-bounces@science.ru.nl [fieldtrip-bounces@science.ru.nl] on behalf of Julian Keil [julian.keil@gmail.com]<br>
<b>Sent:</b> Monday, June 03, 2013 11:14 AM<br>
<b>To:</b> FieldTrip discussion list<br>
<b>Subject:</b> [FieldTrip] Polhemus Patriot<br>
</font><br>
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<div>Dear FieldTrip-Users,
<div><br>
</div>
<div>I have a not really FieldTrip-related question, but maybe one of you can help me anyways.</div>
<div>In our lab, we have a Polhemus Patriot 3D tracking system to acquire electrode positions.</div>
<div>Unfortunately, the recordings are severely distorted in the Z-axis (up-down).</div>
<div>After contacting the Polhemus Support, I got the information, that this is due to metal in the surroundings of the source which distorts the magnetic field.</div>
<div>I tried to get as far away from any metal as possible in our lab (~1.5 m to the walls and floor) but to no avail.</div>
<div><br>
</div>
<div>Now to my question: Has anyone any experience dealing with this? I'm quite puzzled by this as I know plenty of labs use Polhemus trackers, and I'm not sure if our lab is especially metal prone or if I'm missing something.</div>
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<div>Thanks a lot for any help.</div>
<div><br>
</div>
<div>Julian</div>
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<div style="word-wrap:break-word; font-size:12px">********************</div>
<div style="word-wrap:break-word"><b>Dr. Julian Keil</b></div>
<div style="word-wrap:break-word"><b><br>
</b></div>
AG Multisensorische Integration<br>
Psychiatrische Universitätsklinik<br>
der Charité im St. Hedwig-Krankenhaus<br>
Große Hamburger Straße 5-11, Raum E 307<br>
10115 Berlin</div>
<div><br>
Telefon: +49-30-2311-1879<br>
Fax: +49-30-2311-2209 </div>
<div><a href="http://psy-ccm.charite.de/forschung/bildgebung/ag_multisensorische_integration" target="_blank">http://psy-ccm.charite.de/forschung/bildgebung/ag_multisensorische_integration</a></div>
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