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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...

http://psychophysiology.cpmc.columbia.e ... e/PolyRex/

Best regards, Coen (BioSemi)

A basic BDF file reader is provided on http://www.biosemi.com/download/BDFReader.zip

Best regards, Coen (BioSemi)

We do not see commercial advantages in making the driver code available to the public.

Best regards, Coen (BioSemi)

Please refer to the LabVIEW code of the cropper and decimater tools as an example of how to modify BDF files afterwards. In addition, study how ActiView adds the "start epoch" trigger bit to the BDF file. Combining these code examples should solve your problem.

Best regards, Coen (BioSemi)

For feedback applications, I recommend to eliminate the TCP/IP transfer from your loop. To keep delays to a minimum, is best to work in LabVIEW directly on the acquisition PC. Learning the LabVIEW language and working on the basis of the existing ActiView code is a quicker route to success than deve...

It is quite normal to see delays in the order of 100 ms between the events in the real world and the display on the client PC. Actually, this is what you expect: data acquisition via USB on a Windows PC causes delays of a few tens of msec, while the TCP/IP file transfer between two Windows PCs add a...

Do you have access to the source code of the EDF --> proprietary_format converter ? If yes, then I would recommend to modify your converter to read BDF directly. Because BDF is just a 24-bit version of EDF, this would probably take just a few simple modification of the code. Currently, I do not have...

With BioSemi active electrodes, it is not necessary to reduce the impedances by scrubbing. The signal quality is optimal without any skin preparation.

Best regards, Coen (BioSemi)

An application to reduce the number of channels in a BDF file is best based on the LabVIEW code of the filecropper (http://www.biosemi.com/download/Cropper.zip).

Best regards, Coen (BioSemi)

The EX inputs can only be used with our active electrodes. For the connection of a strain gage, we offer our miniature zero-drift preamp (can be located closed to the strain gages for minimal influence of connection cables), in combination with an Ergo input (via a free Aux connector), please refer ...

All controls located in the left sidebar only influence the displayed data, they do not influence the data to file. The data to file is controlled by controls in the right sidebar, and by the selections in the file dialog. So, the reference selection does indeed not influence the data to file. The i...

The channel numbers versus cap layout are shown here: http://www.biosemi.com/headcap.htm, coordinates are available here: http://www.biosemi.com/download/Cap_coords_all.xls With the 32-channel cap, it is best to load the 10-20system32+8.cfg provided on the software CD (or on http://www.biosemi.com/d...

Use the "free choice" channel selection option to display only the 8 EX channels in the monopolar chart. In the file popup menu, choose the option "save as monopolar displayed" and uncheck the other options. The right sidebar will then show that 8+1 channels are being saved in the BDF file (8 EX cha...

The Aux ports can be used for a range of sensors. The Aux ports are configured for particular sensors, so no general characteristics can be given. If you have not purchased additional sensors with your system, then the Aux ports are left unwired. All channels (electrodes and extra sensors) in the Ac...

By converting from 24-bit BDF to 16-bit EDF, you loose a certain amount of low-frequency information in the the data. The original BDF file shows data recorded with a true DC amplifier. The EDF conversion shows the data as if it was recorded with an AC amplifier (amplifier with high-pass filter). Pl...

ActiView Light saved in LabVIEW 8.0 can be downloaded from http://www.biosemi.com/tmp

Best regards, Coen (BioSemi)

The client code is available from http://www.biosemi.com/download/ActiveTwoClient_4.zip

(32+8+status) means: 32 headcap channels plus 8 EX (flat electrode) channels, plus the extra channel for trigger and system status bits. So, a total of 41 channels.

Best regards, Coen (BioSemi)

Using the LabVIEW client as example and basis for further development is the best route. Several customers have successfully copied the client in another programming language, using the LabVIEW code as an example. Basically, the client receives data in packages with a size displayed in ActiView. For...

ActiView 5.35 and higher automatically configures itself according to the version of the GSR circuit. The display in nanoSiemens indicates that your particular AD-box has the new 16 Hz version of the GSR circuit, and not the older 512 Hz version (which would show a display in Ohm). Therefore, you sh...

You are right, the current Client exe still uses RTE 7.1

I will put a version compiled in LabVIEW 8.2 on our website during the coming days. Sorry for the inconvenience.

Best regards, Coen (BioSemi)

The updated tools are now available for download from our website, see http://www.biosemi.com/new.htm . Please let me know if any problem remains.

Best regards, Coen (BioSemi)

The current file tools (compiled in LabVIEW 7.1) are not able to process the BDF files beyond the 2 GB point. I have new versions ready compiled in LabVIEW 8.2 (which works with 64 bit array indexes), and these can handle much larger file lengths. The new tools will be put on our website during the ...

ActiView only separates the triggers into two bytes for display purposes; the 16 trigger lines are always stored as in the BDF file as 16 independent bits (see http://www.biosemi.com/faq/trigger_signals.htm) The analog trigger display mode shows all the 16 lines as colored bars. Displaying the trigg...

ActiView does not offer an option for high-pass filtering the data before saving to file. Their is not need for high-pass filtering, because the 24-bit BDF file format allows to save the full sample words as they are generated by the analog-to-digital converters. You can apply any high-pass filterin...

We are the experts on the ADCs and opamps used in the ActiveTwo, and we are quite familiar with what is available from different manufacturers. Please feel free to post you specific questions here. I cannot promise that we will reveal all details (competitors may read this forum too), but as you can...

Your question probably arises from the recent trend among several of our competitors to rely on sub-suppliers for hardware development and production. BioSemi have always taken a different route. All ActiveTwo hardware (the complete chain from active electrodes to USB interface) and the complete Act...

The ActiveTwo system uses DC coupled amplifiers, no high-pass filters are applied. The high dynamic range of the used 24-bit ADCs allowed elimination of all coupling capacitors from the design. So, the above statement is correct: the lowest resolvable frequency is only limited by the duration of the...

In the ActiveTwo, the-3dB point is at approx 1/5th of the sample rate, also see http://www.biosemi.com/faq/adjust_filter.htm. For a selected sample-rate, the ActiView software displays the cutoff frequency in the right sidebar. Competing systems with a 24-bit ADC show exactly the same low-pass respo...

There is a distribution of electrical potentials across the head. However, we can only measure potential DIFFERENCES. So, you can not speak about "a signal at Cz" or " a "signal on the ear". You can only speak of a signal (voltage) between Cz and the ear. ActiveTwo measures the voltages of all elect...