Search found 1124 matches

by Coen
Fri Apr 11, 2008 1:39 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Datafeed with or without gaps?
Replies: 4
Views: 22525

The 2D output arrays from Downtsample-5th.vi have a constant number of rows (number of channels, dependent on the speedmode), and a variable number of columns (successive samples, amount of samples in an array depends on the value of the "display block size", which is constantly adjusted according t...
by Coen
Fri Apr 04, 2008 1:14 pm
Forum: BioSemi Hardware
Topic: additional sensors
Replies: 1
Views: 4764

The unit and scaling for each channel is listed in the BDF file header, see http://www.biosemi.com/faq/file_format.htm. Not all review programs may read and display this information properly (and may plot everything as uV instead of Siemens, degree Celsius, etc). Operation of the temperature sensor ...
by Coen
Fri Apr 04, 2008 12:35 pm
Forum: BioSemi all other topics
Topic: BDF Byte Reading c#
Replies: 8
Views: 15479

LSB of the 24-bit value is 31.25 nV, or 1/32th uV. For the I32 (extra least significant byte added), division by an additional factor of 256 is necessary.

Best regards, Coen (BioSemi)
by Coen
Fri Mar 07, 2008 6:57 pm
Forum: BioSemi Hardware
Topic: Dry electrodes
Replies: 1
Views: 5296

by Coen
Tue Mar 04, 2008 4:38 pm
Forum: BioSemi Software (ActiView executable)
Topic: ActiView Lite
Replies: 1
Views: 5453

Please read http://www.biosemi.nl/forum/viewtopic.php?t=65 ActiView Light only contains the basic acquisition code, the output is a 2D array of ADC values (rows are channels, columns are successive samples). You can use this array as input for your own signal processing code. Standard ActiView has t...
by Coen
Thu Feb 28, 2008 4:30 pm
Forum: BioSemi Hardware
Topic: Signal Quality Changing over Time: CM rejection problem?
Replies: 1
Views: 5331

I would initially suspect the DRL needle (stainless steel can be a problematic electrode material). I would recommend to use a normal surface electrode for the DRL (preferable Ag-AgCl). By the way, the DRL does not have to be located on the right leg, a location near the CMS is fine (but keep the di...
by Coen
Tue Jan 22, 2008 5:09 pm
Forum: BioSemi Software (ActiView executable)
Topic: using an old version of Actiview
Replies: 1
Views: 5708

The new system is a Mk2, whereas the old system was probably a Mk1 (also http://www.biosemi.nl/forum/viewtopic.php?t=270). The difference between Mk1 and Mk2 is the number of channels in each speedmode, see http://www.biosemi.com/faq/adjust_samplerate.htm and http://www.biosemi.com/faq/make_own_acqu...
by Coen
Tue Jan 22, 2008 12:50 pm
Forum: BioSemi all other topics
Topic: BDF Byte Reading c#
Replies: 8
Views: 15479

by Coen
Mon Jan 21, 2008 4:18 pm
Forum: BioSemi all other topics
Topic: BDF Byte Reading c#
Replies: 8
Views: 15479

The answers is found in the LabVIEW code of the BDF reader. Add an extra least significant (zero) byte to generate an I32. In your example you will then have 00000000 00101000 10111110 11111111, with a value -8580096. Divide this by 8192 (256*32) to convert to uV. So, the first value is -1047.375 uV...
by Coen
Wed Jan 16, 2008 1:03 pm
Forum: BioSemi Hardware
Topic: Elec. ref. for one biosemi system multiple participants
Replies: 1
Views: 5702

It is not possible to measure two subjects simultaneously with only one AD-box. However, the ActiveTwo system offers the unique option to measure up to four subjects simultaneously with daisy-changed AD-boxes (each subject has its own AD-box). Information is found on http://www.biosemi.com/new.htm, ...
by Coen
Fri Jan 11, 2008 7:31 pm
Forum: BioSemi Hardware
Topic: GSR electrodes and signals
Replies: 7
Views: 16922

For the (old) 512 Hz version, the unit is Ohm, and the value in the BDF file is scaled as LSB = 0.03125 Ohm For the (new) 16 Hz version, the unit is nanoSiemens (0.001 uS), and the value in the BDF file is scaled as LSB = 0.03125 nanoSiemens ActiView cannot generate negative values (either Ohm or na...
by Coen
Fri Jan 11, 2008 7:03 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Datafeed with or without gaps?
Replies: 4
Views: 22525

The AD-box always sends all samples to the PC, and the PC processes all samples. If for some reason, ActiView cannot keep up with the incoming data-stream, an error is detected and the program stops with a popup message. So, the data in the BDF file always contains ALL samples, you can be 100% sure ...
by Coen
Fri Dec 14, 2007 12:55 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: How is averaging computed?
Replies: 1
Views: 18887

When a selected trigger is detected, the program starts filling the average buffer (green case 1). When the buffer contains all the points for the selected sweep length, a new average results is calculated and plot to screen (green case 4).

Best regards, Coen (BioSemi)
by Coen
Mon Dec 10, 2007 1:52 pm
Forum: BioSemi Hardware
Topic: Actiview USB drops least significant bit of trigger
Replies: 8
Views: 13217

The table in the FAQ on our website means to say:

Pin 1 Pres: Not Connected
Pin 2 Pres - Pin 1 Bio
Pin 3 Pres - Pin 2 Bio
...
Pin 8 Pres - Pin 7 Bio
Pin 9 Pres - Pin 8 Bio
Pin 25 Pres - Pin 37 Bio

Best regards, Coen (BioSemi)
by Coen
Fri Dec 07, 2007 1:21 pm
Forum: BioSemi Hardware
Topic: Actiview USB drops least significant bit of trigger
Replies: 8
Views: 13217

May be obvious, but have you checked continuity of the cable ?

Best regards, Coen
by Coen
Tue Dec 04, 2007 1:28 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Data timestamping & Running two VIs concurrently
Replies: 5
Views: 25053

Thanks for the feedback. Just one further remark: I forgot to extra emphasize to use global variables, and not local variables, to communicate between the parallel while loops. A pair of local variables is basically the same as a connection wire in the diagram. So, when write data to a local variabl...
by Coen
Fri Nov 30, 2007 7:40 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: change left sidebar
Replies: 1
Views: 18539

The left sidebar (which is actually a tab control with the tabs not visible), is coupled to the main tab control at two places in the diagram: - Orange state 0, find the relevant code by right-clicking on the left sidebar outline, and select Find --> Local Variables (controls the left sidebar during...
by Coen
Thu Nov 29, 2007 6:24 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Data timestamping & Running two VIs concurrently
Replies: 5
Views: 25053

Right-click problem: the VI should be stopped (CTRL+.) and in Edit Mode (CTRL+M) First, make sure that the ActiView VI is not running by pressing the red square on the About tabpage (or the "Edit" button in the Light version), or use CTRL+. (Control plus Dot). The toolbar should show up on top of th...
by Coen
Thu Nov 29, 2007 5:26 pm
Forum: BioSemi Software (ActiView executable)
Topic: Actiview display settings
Replies: 1
Views: 5843

The plot color cannot be changed in the current executable versions, you will have to make the changes in LabVIEW (right-click on the chart --> show legend --> right-click on trace icon --> select color, or better use a property node with "active plot" and "plot color" and change the color by connec...
by Coen
Wed Nov 28, 2007 7:37 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Data timestamping & Running two VIs concurrently
Replies: 5
Views: 25053

Because Windows is not a real-time operating system, it is not possible to accurately time stamp the data within ActiView. Proper time stamping can only be archived in hardware, for example by using the trigger port on the USB receiver. LabVIEW allows multi-threading. You can run your additional VIs...
by Coen
Mon Nov 26, 2007 1:04 pm
Forum: BioSemi Hardware
Topic: Actiview USB drops least significant bit of trigger
Replies: 8
Views: 13217

Test the trigger input of the USB receiver by connecting Pin 1 (trigger 1) with Pin 37 (ground). Trig 1 should go Low when the connection is made. Without this connection, Trig 1 is High because of the internal pull-up. Use the "analog" trigger display mode.

Best regards, Coen (BioSemi)
by Coen
Fri Nov 23, 2007 2:55 pm
Forum: BioSemi Software (ActiView executable)
Topic: Actiview configuration
Replies: 1
Views: 6323

The hardware sampling rate can be adjusted with the speedmode switch (rotary switch on the front-panel of the AD-box). Use the settings 4.5,6 or 7, see http://www.biosemi.com/faq/adjust_samplerate.htm). The sample rate can then be further reduced in software by using the "decimation" selector in the...
by Coen
Fri Nov 02, 2007 3:36 pm
Forum: BioSemi Software (ActiView executable)
Topic: Labview_DLL
Replies: 6
Views: 11516

I didn't mean to say that your question was inappropriate. I just wanted to express my view on your plan to develop a Matlab alternative for our LabVIEW solution. There may well be others here on the forum who don't agree with me. In other words, I tried to stir up the discussion a bit, and I am eag...
by Coen
Fri Nov 02, 2007 1:19 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Adding additional features
Replies: 2
Views: 20628

Please read viewtopic.php?t=65&highlight=labview

Start with inspecting the "Light" version, the code shows the basic setup quite clearly. Please don't hesitate to post or email specific questions.

Best regards, Coen (BioSemi)
by Coen
Fri Nov 02, 2007 12:03 pm
Forum: BioSemi Software (ActiView executable)
Topic: Labview_DLL
Replies: 6
Views: 11516

BioSemi only supports programming in LabVIEW, because we are convinced that LabVIEW currently the is the best and most versatile programming environment for the acquisition and analysis of electro-physiological data. BioSemi has adopted an open-source policy, and encourages customers to developed La...
by Coen
Wed Oct 17, 2007 2:32 pm
Forum: BioSemi Hardware
Topic: How can I make my own acquisition software ? details
Replies: 3
Views: 7803

The above is valid for our Mk1 systems (delivered until August 2005), the current Mk2 systems do indeed have extra channels. Meanwhile, the FAQ has been updated, and the figures for both Mk1 and Mk2 are listed, see http://www.biosemi.com/faq/make_own_acquisition_software.htm). To check whether your ...
by Coen
Fri Oct 05, 2007 5:23 pm
Forum: BioSemi all other topics
Topic: TCP/IP processing
Replies: 2
Views: 8943

The LSB of the 24-bit word is scaled at 1/32th uV. So, a value of 8388607 (2^23-1) is equal to 262144 uV.

Note: on systems for ECG applications, the LSB is scaled at 1/8th uV (check the BDF header)

Best regards, Coen (BioSemi)
by Coen
Tue Oct 02, 2007 7:31 pm
Forum: BioSemi Software (ActiView executable)
Topic: Ring buffer - how to increase the number of samples
Replies: 1
Views: 6752

Both approaches are possible. - Example of defining a new buffer can be found in the full standard version of ActiView. A (double) buffer is used to store the 1 second blocks saved to the BDF file, and another buffer is used to calculate the online average (ERP). - Instead of reading small blocks of...
by Coen
Mon Oct 01, 2007 3:33 pm
Forum: EEG data analysis
Topic: Mark I or Mark II?
Replies: 1
Views: 7151

If the Serial Number starts with ADC4 to ADC11, then it's a Mark 1. If the Serial Number starts with ADC12, then it's a Mark 2. Alternatively, you can check the indicator on the "About ActiView" tabpage in ActiView. With the system running (it is not necessary to connect electrodes), the software sh...
by Coen
Thu Sep 27, 2007 4:39 pm
Forum: BioSemi Hardware
Topic: noise level at electrodes immersed in water
Replies: 1
Views: 5447

Noise should be below 10-20 uV peak-to-peak (0.1 - 100 Hz bandwidth). - the pellets have to soak for 5-10 minutes before noise and offsets have stabilized to low values. - use a sufficient amount of salt in the water (without salt, higher noise levels may be encountered), ras a rule of the thump use...