Search found 1129 matches

by Coen
Mon Jul 15, 2024 6:03 pm
Forum: BioSemi Software (ActiView executable)
Topic: Detailed review on the concept of offset?
Replies: 4
Views: 439

Re: Detailed review on the concept of offset?

Google on "opamp buffer output impedance". With active electrodes, the electrode impedances in the interference paper (Ze in Fig. 1) are reduced from tens of kOhm to less than an Ohm, and the magnitude of interference is reduced with the same ratio.

Best regards, Coen (BioSemi)
by Coen
Fri Jul 12, 2024 7:15 pm
Forum: BioSemi Software (ActiView executable)
Topic: Detailed review on the concept of offset?
Replies: 4
Views: 439

Re: Detailed review on the concept of offset?

1. What is the definition of offset? The electrode-gel-skin interface forms a galvanic half-cell. The half-cell potential is determined by the electrode metal. The offset voltage is the potential difference between two of these half-cells. When the electrodes are identical (same metal and perfectly ...
by Coen
Fri Jun 07, 2024 2:36 pm
Forum: BioSemi all other topics
Topic: Modify ActiView Configuration
Replies: 1
Views: 843

Re: Modify ActiView Configuration

The above is not a standard option in ActiView that can be enabled with a CFG setting. Bipolar display for all channels would require changing the (open source LabVIEW) source code.

Best regards, Coen (BioSemi)
by Coen
Thu May 30, 2024 1:38 pm
Forum: EEG data analysis
Topic: Seeking help with CMS and DRL location with EEGLAB
Replies: 2
Views: 1109

Re: Seeking help with CMS and DRL location with EEGLAB

Reference the data. After referencing, the locations of CMS and DRL are not relevant anymore.

Best regards, Coen (BioSemi)
by Coen
Sat Mar 09, 2024 5:48 pm
Forum: BioSemi Software (ActiView executable)
Topic: Event Related Average module
Replies: 4
Views: 9950

Re: Event Related Average module

That depends on whether the evoked responses also alternate in polarity. With ABR for example, that's not the case (so the noise trace still shows the noise).

Best regards, Coen (BioSemi)
by Coen
Fri Mar 08, 2024 7:23 pm
Forum: BioSemi Hardware
Topic: Active Two Questions (CM. ABR, etc.)
Replies: 4
Views: 5279

Re: Active Two Questions (CM. ABR, etc.)

The trigger port needs TTL level signals. In order to connect an audio line signal, you will need to convert to TTL with a comparator and flip-flop. The accuracy of trigger timing is one sample length, see https://www.biosemi.com/faq/review_trigger_timing.htm

Best regards, Coen
by Coen
Fri Mar 08, 2024 1:56 pm
Forum: BioSemi Hardware
Topic: Active Two Questions (CM. ABR, etc.)
Replies: 4
Views: 5279

Re: Active Two Questions (CM. ABR, etc.)

It is a custom made system for 16+3 channel ECG (LA RA LL is the Wilson Central Terminal). It is probably something like 20 years old. Please email the serial number to info@biosemi.com, and I can check which upgrades are still possible. Soundcard to trigger interface can be done with the ERGO-OPTIC...
by Coen
Wed Feb 14, 2024 2:42 pm
Forum: BioSemi Software (ActiView executable)
Topic: Editing 32-channels in default.cfg
Replies: 3
Views: 3337

Re: Editing 32-channels in default.cfg

Do not edit CFGs in Notepad.

Open ActiView, set the controls according to your preferences, make a short data file, select the "about" tabpage and save your front-panel settings in a new CFG.

Best regards, Coen (BioSemi)
by Coen
Wed Feb 14, 2024 2:37 pm
Forum: BioSemi all other topics
Topic: Use few electrodes than64
Replies: 2
Views: 4679

Re: Use few electrodes than64

No, best regards, Coen (BioSemi)
by Coen
Tue Nov 07, 2023 2:47 pm
Forum: BioSemi Hardware
Topic: Biosemi simultaneous Biopac
Replies: 1
Views: 5759

Re: Biosemi simultaneous Biopac

Why don't you measure simultaneous EEG and ECG (extra TP-flat electrodes) with the BioSemi system ?

Best regards, Coen (BioSemi)
by Coen
Tue Oct 31, 2023 3:11 pm
Forum: EEG data analysis
Topic: How Can I Verify That ActiveTwo USB-Receiver 5.1 Is Receiving Triggers from PsychoPy 3?
Replies: 4
Views: 7790

Re: How Can I Verify That ActiveTwo USB-Receiver 5.1 Is Receiving Triggers from PsychoPy 3?

Select the "analog" trigger format and trigger line 1-16 are displayed as colored dots/bars. Select the "decimal" trigger format and the triggers are displayed as two groups of 8 bit numbers.
by Coen
Fri Oct 20, 2023 12:52 pm
Forum: BioSemi all other topics
Topic: ActiView TCP server
Replies: 11
Views: 19026

Re: ActiView TCP server

Filtering the TCP outputs is not a standard option in ActiView, it is only possible by modifying the (open source LabVIEW) code. You could consider programming a simple low pass in you C++ client. High frequency interference on the photo sensor signal is usually caused by 100 Hz fluctuating light fr...
by Coen
Tue Oct 10, 2023 7:32 pm
Forum: BioSemi Hardware
Topic: Sending triggers from Response Switch through parallel port to psychopy
Replies: 3
Views: 7679

Re: Sending triggers from Response Switch through parallel port to psychopy

You have to make a suitable cable to route pins 17+18 of the USB-receiver to readable pins of the psychopy PC.

Best regards, Coen (BioSemi)
by Coen
Tue Oct 03, 2023 5:37 pm
Forum: BioSemi all other topics
Topic: ActiView TCP server
Replies: 11
Views: 19026

Re: ActiView TCP server

The timing across the channels is only determined by the sampling moments. All ADCs (EEG and sensors) in the AD-box sample at the same moment, controlled by the same clock pulse (sampling is synchronous within 10 picosecond). The trigger channel is added in the USB-receiver with a precision of one s...
by Coen
Mon Sep 25, 2023 4:00 pm
Forum: BioSemi all other topics
Topic: Trouble with repairing BDF file
Replies: 8
Views: 11429

Re: Trouble with repairing BDF file

We have inspected the file, all the data (not just the triggers) is corrupted after 1960 seconds (total file is 4576 sec). In an Hex-file-editor, we can see that after 1960 seconds the data is from an Excel file. It looks like hard disk problems, but how this could happen without error popups is puz...
by Coen
Mon Sep 25, 2023 3:29 pm
Forum: BioSemi all other topics
Topic: ActiView TCP server
Replies: 11
Views: 19026

Re: ActiView TCP server

The photosensor does not output negative values. You can connect a signal generator to the ERGO (see https://www.biosemi.nl/forum/viewtopic.php?f=1&t=931&p=2854 ). Even easier is to connect a potentiometer (approx. 10k linear) between pin 1 and 3 with the wiper to pin 4 and pin 5 to pin 2 (ERGO will...
by Coen
Mon Sep 25, 2023 2:38 pm
Forum: BioSemi all other topics
Topic: Trouble with repairing BDF file
Replies: 8
Views: 11429

Re: Trouble with repairing BDF file

It appeared that the header and part of the data at the beginning of the file were missing (we have no idea how the file could get corrupted like this, we have never seen anything similar). We could repair the file by stripping the begin of the file until the start of a whole 1 sec data block, addin...
by Coen
Thu Sep 21, 2023 9:41 pm
Forum: BioSemi Hardware
Topic: Sending triggers from Response Switch through parallel port to psychopy
Replies: 3
Views: 7679

Re: Sending triggers from Response Switch through parallel port to psychopy

With "RespSwitch=1" in the CFG, the button triggers are available on pins 17 and 18 of the trigger port on the USB-receiver, see https://www.biosemi.com/faq/trigger_signals.htm . I understand that you acquire the psychopy triggers with the AIB. Why don't you connect the psychopy triggers directly to...
by Coen
Thu Sep 21, 2023 2:32 pm
Forum: BioSemi all other topics
Topic: Trouble with repairing BDF file
Replies: 8
Views: 11429

Re: Trouble with repairing BDF file

The first bytes of the header are already corrupted, and it looks like a lot of fields have been overwritten with zero's. We have only seen things like that when a computer crashes during recording (although usually in such cases only the file length field is wrong and can be easily repaired). Pleas...
by Coen
Thu Sep 21, 2023 2:03 pm
Forum: BioSemi Software (ActiView executable)
Topic: Acquisition software SDK support for ARM platforms
Replies: 1
Views: 7573

Re: Acquisition software SDK support for ARM platforms

The ARM processor is not supported by BioSemi. The driver source code is proprietary and not made available to BioSemi users. The best way to proceed is to set up an extra thread in (open source LabVIEW) ActiView to read data from the ringbuffer (example code is available). The extra thread runs par...
by Coen
Wed Sep 20, 2023 9:16 pm
Forum: BioSemi Software (ActiView executable)
Topic: EEG and posturography collection
Replies: 1
Views: 5100

Re: EEG and posturography collection

It is possible to start recording with a TTL pulse, see https://www.biosemi.nl/forum/viewtopic.php?f=2&t=711&p=2174 . However, this is not precise enough and not sufficient for synchronization. For synchronization, TTL timing pulses should be sent from BioSemi to posturography (similar to https://ww...
by Coen
Thu Sep 14, 2023 2:18 pm
Forum: BioSemi Software (ActiView executable)
Topic: strange artifact across all sites in EEG
Replies: 2
Views: 5728

Re: strange artifact across all sites in EEG

60 Hz in a shielded booth means interference by magnetic field. Bundle and twist the electrode wires to minimize enclosed loops.

Best regards, Coen (BioSemi)
by Coen
Thu Sep 14, 2023 2:13 pm
Forum: BioSemi all other topics
Topic: Trouble with repairing BDF file
Replies: 8
Views: 11429

Re: Trouble with repairing BDF file

It looks like most of the header is zero. It is unlikely that this is a BDF file generated by ActiView. Which error message does ActiRead display ?

Best regards, Coen (BioSemi)
by Coen
Thu Sep 07, 2023 1:42 pm
Forum: BioSemi all other topics
Topic: ActiView TCP server
Replies: 11
Views: 19026

Re: ActiView TCP server

The above is correct. The ADCs output 24-bit data words. The USB-receiver convert these words into 32 bit integers by just adding a least significant zero byte. ActiView processes these 32-bit integers, but only the 3 most significant bytes are streamed to BDF file and sent via TCP/IP. The only proc...
by Coen
Wed Sep 06, 2023 5:40 pm
Forum: BioSemi all other topics
Topic: ActiView TCP server
Replies: 11
Views: 19026

Re: ActiView TCP server

What is sent by TCP/IP are the 3 most significant bytes of a signed 32 bit integer. The client should again construct the signed 32 bit integer from these 3 bytes (add a zero least significant byte). The MSB of the most significant byte is the sign bit.

Best regards, Coen (BioSemi)