Diagnose a Broken Electrode (with pictures!)?

smcphers · Post by **smcphers** » Tue Mar 03, 2009 9:17 pm

Hello all,

I was wondering if anyone could offer a diagnosis or prognosis for a misbehaving electrode. One of our pin-type electrodes has recently gone on the fritz. It will operate normally sometimes but there will be long periods of time during which it will behave erratically. I know it's impossible to give any judgment without more information so I captured some screen shots of the aberrant activity:

http://bieegl.net/electrode/P10Capture1.png
http://bieegl.net/electrode/P10Capture2.png
http://bieegl.net/electrode/P10Capture3.png

What does this say about the health of the electrode?

Thanks in advance!

terracop · Post by **terracop** » Tue Mar 03, 2009 10:05 pm

Have you tried to click the links? They are not active. Without photos - just assumptions....
Pin broken? As long as there is a signal - fine. Wire broken? Send it back...

smcphers · Post by **smcphers** » Wed Mar 04, 2009 8:36 pm

Sorry, the links were fine from within our network, I didn't realize they would be unreachable outside of it. I've updated the links so you should be able to see the screen captures

terracop · Post by **terracop** » Thu Mar 05, 2009 10:10 pm

Thank you, looks like the electrode is really broken or it has no contact (possible as well...)
I searched the forum and couldn't find any information about how to measure (e.g. a voltmeter or similar) an electrode when it is broken. If this is due to a broken wire which gives contact somtimes and sometimes not...it might be hard to find out...exchanging one electrode seems to be impossible so you might just send the whole cap back sadly with the instruction to exchange this particular electrode...unless Biosemi has a better idea to identify the source of the problem...

Post by **Coen** » Fri Mar 06, 2009 11:16 am

The signal trace suggest a bad contact between electrode tip and skin (not enough gel in the holder). The electrode itself is most probably OK. A defect electrode (broken wire) will trigger the safety circuits, and signal on all electrodes will be lost (blue light flickering). Another possibility is a polluted electrode tip which may cause high levels of noise (tip is polluted with traces of metal other than silver)

Test the electrode set in salt water as described in the manual. This will show whether the electrode is functional (offset within normal range) and generates a normal noise level.

Best regards, Coen (BioSemi)