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We have seen this problem with a few USB cards (particular with VIA chipsets). The problem can be solved by installing a Windows patch from http://support.microsoft.com/?kbid=822603, followed by un upgrade of the receiver firmware with the special utility available from http://www.biosemi.com/downlo...

The best Common Mode rejection is achieved for electrodes close to the CMS electrode. So, in your application, the best location of the CMS electrode would be the back of the head. The DRL electrode can be located anywhere on the body. In practice, the location of the CMS and DRL electrodes is not v...

You can modify the electrode labels and start/stop code by opening the CFG file with a simple text editor (Notepad or Wordpad). When editing the labels, be sure to not change the keys (section before the "=" sign). Also leave the number of keys intact. The labels can be up to 16 characters long. The...

We use a constant, alternating current via a pair of standard passive Ag-AgCl electrodes (1 microamp, 512 Hz). To determine the GSR response, the ActiveTwo measures the voltage drop between the two electrodes. Our ActiView acquisition software presents the GSR data in Ohm. Best regards, Coen (BioSemi)

There are indeed further time lags in the USB link. First, the transfer between Receiver and PC ringbuffer occurs in bursts of 64 kByte. This leads to a timing jitter of approx. 30 msec. Second, the receiver contains an additional FIFO buffer to handle interrupt latencies. The FIFO handles hick-ups ...

It would be best to base everything on National Instruments real-time hardware. Interface to the PXI hardware can be done with a National Instruments PCI 6533 digital I/O card, our old style receiver (http://www.biosemi.com/products_activeone.htm), and ActiView 4.09 (http://www.biosemi.com/download_...

Latencies in the order of a few msec is what we would expect as an optimum. Because of the Windows OS, and the USB driver layers, it is impossible to have more accurate control over the trigger timing. The only way to improve on this would be to change to a real-time operating system. Best regards, ...

We use 24-bit sigma-delta analog-to digital-converters (each channels has its own converter), with the preamp gain set for a Least Significant Bit value of 1/32th uV (31.25 nV). This means an input range from +262 mV to -262 mV (+/- 2^23*31.25 nV). More on this topic is found on http://www.biosemi.c...

The best way to connect electrodes to a signal source is to use a bucket with salt water. Use a non-metal bucket (plastic or glass) to prevent pollution of the electrodes with strange metal ions. We have found no adverse effect from using simple tab water and household salt. The concentration is not...

This is not a bug, but a feature which was included in version 3.44 and higher, after suggestions by several customers. Two reserved trigger codes can be used to press/release the Pause button. This allows the starting/stopping of streaming data to file to be controlled by the stimulation setup. The...

The connection of triggers to the ActiveTwo receiver is described on http://www.biosemi.com/faq/trigger_signals.htm

The pin layout of a cable for an interface with E-prime is found on http://www.biosemi.com/faq/presentation.htm

Best regards, Coen (BioSemi)

A Faraday cage is used to achieve two things: elimination of interference currents in the electrode wires, and elimination of interference current in the ground electrode (DRL electrode in case of the ActiveTwo). Both mechanisms cause 50 Hz noise in the data, it is anything but a black art, as you c...

The [save] section at the end of the CFG contains the selector settings in the file initialization popup window. So, by changing these settings, you can select which channels are saved: Subset: setting 0 (all available channels) to 8 (save as monopolar displayed) Touchproofs: 0 (do not save touchpro...

The CFG can be edited in two ways: 1) Run ActiView, and from the "about" tabpage, save a new CFG. All current settings of the controls are then stored into the new cfg (except for the contols on the "average" tabpage", they will be added to the CFG in the next 5.17 version). 2) Open the CFG in Wordp...

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