Search found 1124 matches

by Coen
Mon Nov 20, 2006 11:52 am
Forum: BioSemi all other topics
Topic: principle of functionning
Replies: 2
Views: 8070

Please read the forum and our website, and stop poluting this forum with silly questions.

Regards, Coen (BioSemi)
by Coen
Wed Nov 01, 2006 8:18 pm
Forum: BioSemi Software (ActiView executable)
Topic: Additional Trigger Question
Replies: 6
Views: 12326

On ActiView 5.14 and higher, the function keys F1-F8 are by standard coupled to trigger lines 9-16. A key press makes the respective trigger line high. Make sure that the trigger inputs 9-16 are pulled low at the trigger port of the USB receiver (by connecting pin 9-16 to pin 37). If trigger inputs ...
by Coen
Fri Oct 27, 2006 4:21 pm
Forum: EEG data analysis
Topic: Trigger problems revisited
Replies: 3
Views: 11318

I have a special version of the BDF reader available, which displays the trigger values as arrays of numbers. Please email me directly for such a special version of the BDF reader.

Best regards, Coen (BioSemi)
by Coen
Thu Oct 05, 2006 12:57 pm
Forum: BioSemi Hardware
Topic: Trigger with parallel port
Replies: 1
Views: 5576

You can sent the TTL (0-5V) signals from the parallel port directly to the input pins (pin 1-16) of the trigger port on the USB receiver. Make the ground connection by connecting pin 25 on the parallel port to pin 37 on the trigger port on the USB receiver (see http://www.biosemi.com/faq/trigger_sig...
by Coen
Wed Sep 27, 2006 3:57 pm
Forum: BioSemi Hardware
Topic: passive electrodes
Replies: 4
Views: 9098

I assumed an EIT setup with passive electrodes to inject current, and a separate set of active electrodes to measure the resulting potential distribution. You are correct that our active electrodes cannot be used for current injection. The ActiveTwo inputs can be modified to work with (any) passive ...
by Coen
Tue Sep 26, 2006 10:54 am
Forum: BioSemi Hardware
Topic: passive electrodes
Replies: 4
Views: 9098

What would be the reason that active electrodes cannot be used for Electrical Impedance Tomography ?

Coen (BioSemi)
by Coen
Mon Sep 25, 2006 10:38 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Modifying actiview program: Changing the screen resolution
Replies: 9
Views: 21243

Right click on the graphs, and search for property nodes
by Coen
Mon Sep 25, 2006 5:47 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Modifying actiview program: Changing the screen resolution
Replies: 9
Views: 21243

Did you reduce the size of the offset graphs (controlled by property nodes) ?

Best regards, Coen (BioSemi)
by Coen
Mon Sep 25, 2006 4:53 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Modifying actiview program: Changing the screen resolution
Replies: 9
Views: 21243

The tab size scales automatically to the selected font size of the text on the tabs.

Best regards, Coen (BioSemi)
by Coen
Mon Sep 18, 2006 1:10 pm
Forum: BioSemi Software (ActiView executable)
Topic: Timing accuracy of USB trigger out
Replies: 8
Views: 16640

The "data" input of USB_WRITE is an array of 64 Bytes. The first Byte is used to start/stop the acquisition (00=stop, FF= start). The second and third byte are used to control the outgoing triggers (example: 01 + 00 makes pin 17 High, and 18-31 Low ). The remaining 61 bytes are not used. Best regard...
by Coen
Thu Sep 07, 2006 3:54 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Modifying actiview program: Changing the screen resolution
Replies: 9
Views: 21243

You cannot modify the exe directly. You'll need to have the LabVIEW programming environment installed on your PC (LabVIEW full development version). Open the ActiView LabVIEW library (ActiviewXXX.llb). It is then basically a matter of resizing all front panel controls and indicators. In addition, yo...
by Coen
Thu Aug 24, 2006 8:40 am
Forum: BioSemi Software (ActiView executable)
Topic: No reference or average reference?
Replies: 3
Views: 13857

Dear John, On March 11th, 2004, I have sent the following personal email to to you: [quote]To record 32 pin and 3 EX channels, proceed as follows: 1) In the monopolar tabpage, select channel selection "free choice" 2) In the channels list, select channels 1-32 and EX1, EX2 and EX3, there are now 35 ...
by Coen
Tue Aug 15, 2006 3:01 pm
Forum: BioSemi Hardware
Topic: EEG trigger- rising edge or falling edge?
Replies: 1
Views: 6682

ActiView displays both the rising and falling edges of the triggers. It is instructive to compare the "analog" and "decimal" display formats while the system is running. The recording of triggers in the BDF file is level sensitive, not edge sensitive. For example, bit 0 of the trigger/status channel...
by Coen
Fri Aug 11, 2006 10:55 am
Forum: BioSemi Software (LabVIEW programming)
Topic: how to read filtered signals from BDF reader to Matlab
Replies: 1
Views: 10888

Instead of Matlab, I would recommend to use LabVIEW for further signal processing. You can then build directly on the code used in BDFreader (including the 2nd order Bessel filter if you like). After all, this section of the forum is intended to discus LabVIEW code.

Best regards, Coen (BioSemi)
by Coen
Wed Aug 09, 2006 1:27 pm
Forum: BioSemi Hardware
Topic: Power / CMS in range going off
Replies: 1
Views: 5490

Besides the current limiter in the DRL circuit (which switches off the power supply to the active electrodes is larger then normal leakage currents are detected), the ActiveTwo has a secondary safety circuit which switches off the entire AD-box if faulty voltage levels are detected on the internal s...
by Coen
Thu Aug 03, 2006 11:13 pm
Forum: BioSemi Software (ActiView executable)
Topic: ignoiring channels while recording
Replies: 1
Views: 5781

Display the wanted channel selection in the monopolar chart (use the "free choice" option), then select the "save as monopolar displayed" option in the file dialog.

Best regards, Coen (BioSemi)
by Coen
Thu Aug 03, 2006 11:07 pm
Forum: BioSemi Software (ActiView executable)
Topic: data compression mechanism
Replies: 3
Views: 8330

If you run BDF-todecimatedBDF.exe: make sure you have the LabVIEW run-time-engine version 7.1 properly installed (RTE is freeware, available from ftp://ftp.ni.com/support/labview/windows/runtime/7.1/LVRunTimeEng.exe) If you run BDF-todecimatedBDF.llb: make sure you have LabVIEW 7.1 or higher install...
by Coen
Thu Aug 03, 2006 5:12 pm
Forum: BioSemi Hardware
Topic: Charger
Replies: 1
Views: 5431

The symptoms suggest that there is no power available at the output connector of the wall-adapter. Check with a voltmeter, there should be 9V between the concentric plug poles. No 9V: make sure that the wall outlet is OK (between 100 and 240 VAC). If it is, please sent the wall-adapter to BioSemi fo...
by Coen
Thu Aug 03, 2006 4:07 pm
Forum: BioSemi Software (ActiView executable)
Topic: data compression mechanism
Replies: 3
Views: 8330

The data can be re-sampled to a lower sample rate with the Decimator tool from http://www.biosemi.com/download/BDF-to-decimatedBDF.zip . You will of course reduce the bandwidth of the data (new -3 dB point is at 0.2616 multiplied by the new sample rate), so use the tool wisely. Compression tools lik...
by Coen
Thu Jul 20, 2006 6:18 pm
Forum: BioSemi Software (ActiView executable)
Topic: ActiView finite or continuous acquisition?
Replies: 1
Views: 5893

ActiView certainly supports continuous acquisition of data ActiView reads new data out of the ringbuffer with subvi Act_ring.vi, whether new data is available is decided on the basis of the READ_POINTER function call, and subsequent calculations in subvi Act_Pointer.vi (all within the acquisition Wh...
by Coen
Tue Jul 04, 2006 5:00 pm
Forum: BioSemi Software (ActiView executable)
Topic: Actiview components
Replies: 3
Views: 12200

A trimmed down version in LabVIEW 8.2 is now available from http://www.biosemi.com/download/ActiView603-Light.zip

Best regards, Coen (BioSemi)
by Coen
Fri Jun 23, 2006 12:53 pm
Forum: EEG data analysis
Topic: Reference and averaging
Replies: 1
Views: 6888

So long as you do not perform any artifact rejection, it does not matter whether the referring is done before or after averaging. However, performing artifact rejection on unreferenced (raw) signals will lead to wrong results. So, in practice you should always reference (and filter) the data before ...
by Coen
Thu Jun 01, 2006 2:51 pm
Forum: BioSemi Hardware
Topic: Shielding in EEG
Replies: 8
Views: 21750

IMRR: apply test signal with known voltage across the isolation barrier, and measure the effect on the system's output signal (see http://www.biosemi.com/publications/pdf/Isolation_mode_rejection.pdf) Isolation capacitance: apply (AC) test signal with known voltage across the isolation barrier, and ...
by Coen
Thu May 25, 2006 9:43 pm
Forum: BioSemi Hardware
Topic: Shielding in EEG
Replies: 8
Views: 21750

What exactly do you want to measure: the Isolation Mode Rejection Ratio (IMRR), the isolation capacitance, the breakdown voltage of the isolation, or some other parameter ? If you want to contribute to this forum, I would appreciate it if you would at least put some effort into writing a clear quest...
by Coen
Tue Apr 18, 2006 11:08 pm
Forum: BioSemi Hardware
Topic: Electrode Noise Levels
Replies: 3
Views: 9504

When measured with the electrodes in saline (salt water), the electrode noise is very close to the noise level of the electronic circuitry (a few microvolt peak-to-peak, see specs). Please explain how you have determined the electrode noise when measuring on a subject skin. In other words: which met...
by Coen
Thu Apr 13, 2006 1:15 pm
Forum: BioSemi Software (ActiView executable)
Topic: problem recording data from EXG electrodes while using AIB
Replies: 2
Views: 8309

This is not a known bug. Please test with the latest 5.37 version of ActiView (http://www.biosemi.com/download.htm) 1) Test with a single AD-box on speedmode 4 2) Test with 1 AD-box (speedmode 4) plus AIB (speedmode 8) 3) Test with two AD-boxes (speedmode 0 and speedmode 1) Test with the CMS/DRL and...
by Coen
Thu Mar 23, 2006 3:54 pm
Forum: EEG data analysis
Topic: neuroguide and biosemi
Replies: 1
Views: 7974

Neuroguide list BioSemi BDF as a supported file format on http://www.appliedneuroscience.com/EEG%20Formats.jpg . However, I have not yet heard of customers actually using this combination.

Best regards, Coen (BioSemi)
by Coen
Mon Mar 13, 2006 4:08 pm
Forum: BioSemi all other topics
Topic: BDF structure
Replies: 2
Views: 9734

ActiView writes BDF file with 1 second record length. So, the number of samples in a record is equal to the sampling rate. The number of samples per record is always listed in the file header, see http://www.biosemi.com/faq/file_format.htm

Best regards, Coen (BioSemi)
by Coen
Tue Mar 07, 2006 6:41 pm
Forum: EEG data analysis
Topic: merging BDFs?
Replies: 10
Views: 35400

In principle, merging of two files only involves deleting the header of the second file, adding the data section of the second file to the first file, and adjusting the length field in the header of the first file to the new value (total length of the two files). In LabVIEW, the code will be quite s...
by Coen
Wed Feb 08, 2006 7:36 pm
Forum: EEG data analysis
Topic: Trigger display
Replies: 4
Views: 13979

Unconnected trigger lines are high due to the internal pull-up resistors in the USB receiver. The "baseline correction" described above is a good solution. An alternative is to connect all unused trigger lines to ground (pin 37 on the trigger port). The 16 trigger bits should not be regarded as an a...