<html><head><base href="x-msg://10/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Dear all,<div><br></div><div>thank you very much for your input.</div><div>I'll have to experiment a bit more with the distance to the walls (which probably contain metal) and the chair.</div><div>Thank you also for the idea with the second sensor, I hadn't tried this before.</div><div><br></div><div>Best,</div><div><br></div><div>Julian</div><div><br></div><div><div><div>Am 05.06.2013 um 17:53 schrieb Elizabeth Anne Bock, Ms:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div ocsi="0" fpstyle="1" style="word-wrap: break-word; "><div style="direction: ltr; font-family: Tahoma; color: rgb(0, 0, 0); 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><div><br><div style="font-family: Tahoma; font-size: 13px; "><div style="font-family: Tahoma; font-size: 13px; "><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">------------------------------------------------------------------------------------------</font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">Elizabeth Bock / MEG System Engineer</font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">McConnell Brain Imaging Centre / Montreal Neurological Institute</font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">McGill University /<span class="Apple-converted-space"> </span></font><font size="1">3801 University St. /<span class="Apple-converted-space"> </span></font><font size="1">Montreal, QC H3A 2B4</font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1"><br></font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">Office: 514.398.3706<span class="Apple-converted-space"> </span><br></font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">MEG Lab: 514.398.6056</font></div><div style="margin-top: 0px; margin-bottom: 0px; "><font size="1">Mobile: 514.718.6342</font></div></div></div></div><div style="font-family: 'Times New Roman'; color: rgb(0, 0, 0); font-size: 16px; "><hr tabindex="-1"><div id="divRpF256871" style="direction: ltr; "><font color="#000000" face="Tahoma" size="2"><b>From:</b><span class="Apple-converted-space"> </span><a href="mailto:fieldtrip-bounces@science.ru.nl">fieldtrip-bounces@science.ru.nl</a><span class="Apple-converted-space"> </span>[<a href="mailto:fieldtrip-bounces@science.ru.nl">fieldtrip-bounces@science.ru.nl</a>] on behalf of Julian Keil [<a href="mailto:julian.keil@gmail.com">julian.keil@gmail.com</a>]<br><b>Sent:</b><span class="Apple-converted-space"> </span>Monday, June 03, 2013 11:14 AM<br><b>To:</b><span class="Apple-converted-space"> </span>FieldTrip discussion list<br><b>Subject:</b><span class="Apple-converted-space"> </span>[FieldTrip] Polhemus Patriot<br></font><br></div><div></div><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><div><br></div><div>Thanks a lot for any help.</div><div><br></div><div>Julian</div><div><br></div><div><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; font-size: medium; "><div><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></span></div><br></div></div></div>_______________________________________________<br>fieldtrip mailing list<br><a href="mailto:fieldtrip@donders.ru.nl">fieldtrip@donders.ru.nl</a><br><a href="http://mailman.science.ru.nl/mailman/listinfo/fieldtrip">http://mailman.science.ru.nl/mailman/listinfo/fieldtrip</a></div></span></blockquote></div><br></div></body></html>