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Did you use the unreferenced (raw) signals as basis of your analysis ? The correlation is a measure for the amount of Common Mode in the signals. The CMS/DRL loop becomes less effective at higher frequencies (the loop amplification decreases proportionally to the frequency). So, it is to be expected...

The program reads (variable) parts of the ringbuffer. The data remains available in the ringbuffer until overwritten by new data (when the "clock" has made a full round). The convertxxx vi's are used to adjust the program to the version (Mk1 or Mk2) and sample rate (speedmode) of the connected AD-bo...

Act_Pointer.vi determines whether new data is available in the ringbuffer. If not enough new data is available, the program waits. If enough new data is available, the program reads a new block of data from the ringbuffer.

Best regards, Coen (BioSemi)

The USB_WRITE call is used for two functions: - start and stop acquisition, 1st byte of the 64 byte array is used, in LabVIEW, I used the values 1 and 0 to start/stop the acquisition (actually, only the LSB of the byte is read by the USB receiver to start and stop) - sent output triggers to the trig...

The usual cause for a wrong file size in the header is that the recording was not stopped normally (but instead by a PC crash, full harddisk, etc.). If the file is basically correct, and the problem is just in the header, then you can repair the file with the tool available from http://www.biosemi.c...

If the optical link light remains off, then I suggest to replace the optical fiber.

The flashing USB light indicates that the communication between PC and receiver works.

Best regards, Coen (BioSemi)

f nothing has been changed to the PC and AD-box (speedmode ?), then the USB cable and optical cable are the prime suspects. - Is the "optical link" light on the USB receiver on to indicate that data is received ? - What happens with the "USB link" light on the receiver when acquisition is started ? ...

As far as I know, the basic ActiView code can be used. However, the problem with LabVIEW RT is that it needs to run on dedicated real time (National Instruments) hardware. An interface between the ActiveTwo and this special real time hardware is not available at the moment. An option (using our stan...

A new version of the zip file (same name, now 3.7 Mb) is available on the same link as above, the full source code is now added to the zip. Follow the "Triggers Boolean" output array from subvi "TrigProcess.vi", and you'll find an added USB_WRITE function call (lower right section of the main diagra...

Old electrodes may produce more (low frequency) noise than newer ones. Electrode wear cannot significantly influence signal amplitude. You can easily check this with a "two bucket test", as described in the guidelines for use of the ActiveTwo system. In other words: you may encounter differences in ...

Save only the relevant channels to file (do not save "flat" channels), and reduce the sample rate for just enough analog bandwidth (but not more).

Best regards, Coen (BioSemi)

I don't know an "official" coordinate. However, the coordinates of the nose can be quite easily extrapolated from the existing ones. The azimuth is surely 90 degrees (same as Fpz, Fz, etc), the inclination should be something around 138 degrees (Fpz is on 92, arc length from nose to Fpz is approx eq...

A special version of ActiView is ready for download from http://www.biosemi.com/download/ActiView606-Lores.zip . This version routes the response signals from input trigger lines 9 and 10 to trigger output lines 1 and 2 (pin 17 and 18, see http://www.biosemi.com/faq/trigger_signals.htm). Please note...

Why is the value not possible ? Why should the values be 0,10 ? If you claim that there is an error, than please provide a justification for your claim.

The polar coordinates are given in degrees, and used successfully by hundreds of our customers.

Coen (BioSemi)

The answer is above, ActiView should be reprogrammed to sent out triggers, and a special cable should be constructed.

Best regards, Coen

The provided response box connect to the AD-box. The triggers are directly available in ActiView. Make sure you have set the CFG to see the triggers. The trigger cable is not involved.

I was referring to sending triggers from the acquisition PC to output trigger lines.

Best regards, Coen (BioSemi)

The LabVIEW code of ActiView Light (http://www.biosemi.com/download/ActiView604-Light.zip) shows an example of how to sent codes to trigger port (15 lines available). You will have to make the appropriate cable yourself according to the information on http://www.biosemi.com/faq/trigger_signals.htm B...

When water or gel enters the electrode, they will stop working, and they won't work again (blue light keeps blinking). Problems with leaking electrode have never been reported to us. A possible cause is pollution of the Ag-AgCl tips with traces of non-silver metal. However, the low frequency noise w...

The artefacts in your file ("bump" on most channels from t=76 to t=80) look like slow waves due to sweating, as discussed in thread viewtopic.php?t=28.

Best regards, Coen (BioSemi)

The trigger lengths values refers to the trigger signals coupled to the trigger port on the USB receiver.

When triggers are controlled with the function keys, the line remains high approximately as long as the key is pressed.

Best regards, Coen (BioSemi)

If you could record previously with many headcap channels, then there should be no problem at all with recording just the 8 EXG electrodes. You will just need the separate CMS/DRL lead (connection to the front panel of the AD-box).

Best regards, Coen (BioSemi)

In general, you can check your referencing step because the reference trace should be flat after referencing (everything zero, no noise). In your example, the EXG5 trace should be flat after referencing all channels to EXG5. The CMS/DRL loop cancels out after referencing In general, the reference ch...

A ringbuffer overflow means that the PC is not able to keep up with the incoming data stream. Basically, the problem can only be solved with a faster processor in your acquisition PC A CMS and DRL electrodes is always necessary, also if you only use the flat electrodes (EX inputs). The ringbuffer ov...

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...

With the Jazz enabled (output trigger is 16 High), the special Jazz version of the USB receiver adds 4 extra channels to the data stream. Inspect the LabVIEW code of the subvi named Act_Jazz.vi to learn about how the Jazz information is embedded in the 4 extra channels (it's quite complex). With the...

The trigger cables as currently delivered by BioSemi already have triggers 9-16 grounded (connected to pin 37). This is not true for our older cables (delivered before 2007), were triggers 9-16 are floating (and pulled high by the pull-ups in the receiver). The change of the 24-bit value in the firs...

The connection of pin 9-16 to pin 37 is indeed done by soldering a short wire. The pin layout can for example be found on http://pinouts.ru/connector/37_pin_D-SU ... ctor.shtml (pin 1 is also seen inside the connector).

Best regards, Coen (BioSemi)

There are no technical problems at all with using a duplex version of the optical fiber. In addition, the most duplex cables are easily split into two separate cables (we have actually done this ourselves during supply problems of the single optical fibers).

Best regards, Coen (BioSemi)

ActiView uses a fixed record length of 1 second for the BDF files. However, changing the open-source LabVIEW code yourself to achieve a different record should not present too much problems.

What would be the advantage of a different record length ?

Best regards, Coen (BioSemi)

Test the system with the electrodes in salt water as described in the manual, and discuss the results with BioSemi directly. An AD-box problem is very unlikely.

Best regards, Coen (BioSemi)