Search found 1124 matches

by Coen
Fri Dec 17, 2021 1:28 pm
Forum: EEG data analysis
Topic: Gain and offset for physical values
Replies: 4
Views: 4963

Re: Gain and offset for physical values

The BDF file header defines the gain of each channel with the physical and digital minimum and maximum values. The file format does in principle support minimum and maximum values that are not symmetrical around zero. I am not familiar with the EEGlab routines, but I suspect that the "offset" parame...
by Coen
Thu Dec 16, 2021 2:12 pm
Forum: EEG data analysis
Topic: Gain and offset for physical values
Replies: 4
Views: 4963

Re: Gain and offset for physical values

It is a DC amplifier, data is not high-pass filtered. Offset is simply the low-passed value of the data (cut-off frequency < 1 Hz) ABR (speedmode 9) saves 5 channels in ActiView 813 and 900: 3 DC monopolar (unreferenced) low-frequency channels and 2 AC bipolar (referenced) high-frequency channels. O...
by Coen
Mon Dec 06, 2021 3:29 pm
Forum: BioSemi Software (ActiView executable)
Topic: Problem with ActiView receiving triggers
Replies: 4
Views: 4948

Re: Problem with ActiView receiving triggers

Test with the parallel adapter connected to the USB-receiver, but with the USB-microUSB cable disconnected from the MacBook. All 16 trigger lines should now be Low in ActiView (your screenshot shows lines 1-8 high and 9-16 low). If not, the adapter is not functioning properly and should be replaced....
by Coen
Mon Dec 06, 2021 2:26 pm
Forum: BioSemi Software (ActiView executable)
Topic: Problem with ActiView receiving triggers
Replies: 4
Views: 4948

Re: Problem with ActiView receiving triggers

What are you using to interface the Macbook with the parallel trigger port on the USB-receiver ?

Best regards, Coen (BioSemi)
by Coen
Fri Dec 03, 2021 3:07 pm
Forum: BioSemi Hardware
Topic: Finding GSR input
Replies: 1
Views: 4520

Re: Finding GSR input

If there is no GSR label, then there is no GSR input. Aux3 (unlabeled) is currently not connected. BioSemi can install a GSR input on Aux3.

Best regards, Coen (BioSemi)
by Coen
Tue Nov 16, 2021 6:50 pm
Forum: BioSemi all other topics
Topic: Synchronizing EEG signal with EMG and speech
Replies: 5
Views: 7253

Re: Synchronizing EEG signal with EMG and speech

ActiRead (https://www.biosemi.com/download.htm) is made available complete with LabVIEW source code especially for researchers who want to add special features. You can add a sound output by programming in LabVIEW, as well as changing the ERGO amplitude. Up to 128 EEG channels on 16 kHz are possible...
by Coen
Mon Oct 25, 2021 3:32 pm
Forum: BioSemi Hardware
Topic: Spikes when using response box
Replies: 1
Views: 4804

Re: Spikes when using response box

The voltage switching in the response button boxes may cause very small Common Mode spikes in the EEG signal. Averaging over a lot of sweeps makes the spikes visible (all the small spikes add up, the EEG noise cancels out). Since the spikes are Common Mode, referencing reduces them with a factor of ...
by Coen
Wed Oct 20, 2021 6:56 pm
Forum: EEG data analysis
Topic: 'Common' reference after biosig import of GSR, Resp and Plet
Replies: 3
Views: 4994

Re: 'Common' reference after biosig import of GSR, Resp and Plet

You are correct: referencing should only be applied to the EEG channels, the sensor channels should remain unreferenced (or else the EEG reference is subtracted from the sensor channels).

Best regards, Coen (BioSemi)
by Coen
Mon Oct 18, 2021 2:43 pm
Forum: BioSemi Software (ActiView executable)
Topic: ActiView responding to keyboard commands even when it does not have focus
Replies: 2
Views: 4918

Re: ActiView responding to keyboard commands even when it does not have focus

In the latest 9.00 Windows version of ActiView (put on our website today), I have deleted the arrow Left/Right/Up/Down and Pgup/Pgdn keyboard shortcuts. In LabVIEW 2021, the "key focus" property node does not work for the Menu Ring controls, and therefore I could not get the shortcuts to work fully ...
by Coen
Thu Sep 30, 2021 12:49 pm
Forum: BioSemi Software (LabVIEW programming)
Topic: Correct way to index AUX channels?
Replies: 1
Views: 4493

Re: Correct way to index AUX channels?

The senso signals are sent from the AD-box in a block of 16 channels. Installed sensors generate data on dedicated channels in the block, uninstalled sensors generate flatliners. ActiView processes the 16 channels into 7 sensor channels (displayed and saved to BDF file). Inspect the LabVIEW source c...
by Coen
Fri Sep 24, 2021 11:44 am
Forum: BioSemi Hardware
Topic: CM out of range with more than 64 electrodes
Replies: 3
Views: 6298

Re: CM out of range with more than 64 electrodes

We do not offer a daisy chain option for two 64 channel systems on the same subject.

Best regards, Coen (BioSemi)
by Coen
Wed Sep 22, 2021 9:00 pm
Forum: BioSemi Hardware
Topic: CM out of range with more than 64 electrodes
Replies: 3
Views: 6298

Re: CM out of range with more than 64 electrodes

You can only use the channels that are actually installed in the AD-box. To check: inspect the offsets with no electrodes connected to the AD-box, installed channels are maximally negative, uninstalled channels are zero. You will probably find that only channels 1-64 are installed. In order to use m...
by Coen
Wed Sep 22, 2021 8:58 pm
Forum: BioSemi Hardware
Topic: Combing 10-20 and ABCD electrodes for recording 128 electrodes
Replies: 2
Views: 5547

Re: Combing 10-20 and ABCD electrodes for recording 128 electrodes

You can only use the channels that are actually installed in the AD-box. To check: inspect the offsets with no electrodes connected to the AD-box, installed channels are maximally negative, uninstalled channels are zero. You will probably find that only channels 1-64 are installed. In order to use m...
by Coen
Mon Sep 20, 2021 1:02 pm
Forum: BioSemi Software (ActiView executable)
Topic: the unit of EMG data
Replies: 1
Views: 4536

Re: the unit of EMG data

The scaling of each channel is found in the BDF header, see https://www.biosemi.com/faq/file_format.htm (physical and digital min/max values). The electrode channels are LSB = 31.25 nV (1/32 uV). The scaling in ActiView does not affect the BDF file. All settings in the left sidebar only affect the d...
by Coen
Mon Sep 13, 2021 2:17 pm
Forum: BioSemi Hardware
Topic: Weird noise
Replies: 4
Views: 6591

Re: Weird noise

Determine the frequency of the interference (zoom in, make spectrum), it looks like 50 Hz from the mains supply. Test with electrodes in water. Increase/decrease the area of the included loop between cables of CMS/DRL and other electrodes to determine whether an electric or magnetic field causes the...
by Coen
Sun Sep 12, 2021 9:42 pm
Forum: BioSemi Hardware
Topic: Weird noise
Replies: 4
Views: 6591

Re: Weird noise

Gel bridge between CMS and DRL, see viewtopic.php?f=7&t=810&p=3048

Best regards, Coen (BioSemi)
by Coen
Fri Aug 27, 2021 12:08 pm
Forum: EEG data analysis
Topic: Biosemi data format/Reading .bdf into Matlab
Replies: 9
Views: 27529

Re: Biosemi data format/Reading .bdf into Matlab

Use the digital and physical min/max values in the file header to scale the data, see https://www.biosemi.com/faq/file_format.htm . From the file header, you can conclude that the scaling for the EEG channels is LSB = 31.25 nV (1/32th uV) Using the BDF --> EDF converter to rescale the data is possib...
by Coen
Thu Aug 19, 2021 12:38 pm
Forum: BioSemi Hardware
Topic: Battery Life
Replies: 1
Views: 5192

Re: Battery Life

A 64 channel system should work more than 12 hours on a new battery, and still more than 6 hours on a battery that is a few years old. 2.5 hours is certainly too short, you should replace the internal cells of the battery.

Best regards, Coen (BioSemi)
by Coen
Mon Aug 16, 2021 1:26 pm
Forum: BioSemi Software (ActiView executable)
Topic: Defining in code the number of channels
Replies: 2
Views: 5205

Re: Defining in code the number of channels

The above is in principle possible by modifying the (open source LabVIEW) code of ActiView.

Note that you can save the settings (including TCP/IP selections) in the CFG file.

Best regards, Coen (BioSemi)
by Coen
Mon Jul 26, 2021 2:02 pm
Forum: BioSemi Software (ActiView executable)
Topic: ActiView example client raw data transformation
Replies: 2
Views: 5287

Re: ActiView example client raw data transformation

Each sample is a 24-bit word from the Analog-to Digital converter. Each 24-bit sample is sent as 3 bytes.

TCP blocksize is in samples
Buffersize is in bytes

Best regards, Coen (BioSemi)
by Coen
Thu Jun 24, 2021 1:26 pm
Forum: BioSemi all other topics
Topic: Synchronizing EEG signal with EMG and speech
Replies: 5
Views: 7253

Re: Synchronizing EEG signal with EMG and speech

The ActiveTwo system can measure EEG, EMG (with flat electrodes and headbox, see https://www.biosemi.com/accessoires.htm) and microphone (via ERGO input), all simultaneous, synchronized and up to 16 kHz sample rate. Trying to use other devices for EMG and sound acquisition seems a needless complicat...
by Coen
Wed Jun 16, 2021 5:29 pm
Forum: EEG data analysis
Topic: 1Hz Unexpected Frequency in Signal
Replies: 1
Views: 5123

Re: 1Hz Unexpected Frequency in Signal

"Is it possible that something in the hardware is causing this?"

No, the BioSemi system does not generate any signal of exactly 1 Hz.

Best regards, Coen (BioSemi)
by Coen
Thu Jun 10, 2021 3:27 pm
Forum: BioSemi all other topics
Topic: Strange activity on a single electrode
Replies: 14
Views: 31308

Re: Strange activity on a single electrode

You should indeed first remove the flat/bad channels, and then reference to one or more of the remaining valid channels.

Best regards, Coen (BioSemi)
by Coen
Fri May 07, 2021 11:54 am
Forum: BioSemi Hardware
Topic: Is this the problem of battery?
Replies: 3
Views: 6875

Re: Is this the problem of battery?

You probably left the batteries too long (several months) is a discharged state. Always charge the batteries before storing and recharge them every few months. The cells can sometimes be recovered with a few charge/discharge cycles. If not, then contact your local BioSemi representative for replacem...
by Coen
Thu May 06, 2021 11:59 am
Forum: BioSemi Hardware
Topic: Is this the problem of battery?
Replies: 3
Views: 6875

Re: Is this the problem of battery?

Does the second battery work ?

Check the fuse of the battery. If OK, then replace the internal cells.

Best regards, Coen (BioSemi)
by Coen
Tue Mar 16, 2021 12:50 pm
Forum: BioSemi Software (ActiView executable)
Topic: strange event names of triggers on Actiview
Replies: 5
Views: 8292

Re: strange event names of triggers on Actiview

In analog trigger display mode, you see 16 colored dots/bars, indicating the separate trigger lines (bits). It will probably show that there is something wrong with bit 8 (grey, 2^7 = 128). You did not follow my recommendation to inspect the bits in analog trigger display mode. I cannot further help...
by Coen
Mon Mar 15, 2021 8:36 pm
Forum: BioSemi Software (ActiView executable)
Topic: strange event names of triggers on Actiview
Replies: 5
Views: 8292

Re: strange event names of triggers on Actiview

Inspect in "analog" trigger display mode to see which trigger lines are faulty.

Best regards, Coen
by Coen
Wed Mar 10, 2021 1:26 pm
Forum: EEG data analysis
Topic: Different event codes (triggers) in EEGLAB
Replies: 1
Views: 6173

Re: Different event codes (triggers) in EEGLAB

- Use the ""analog" display mode to inspect the 16 separate trigger lines.
- Use positive logic: pull all 16 lines low between the triggers.
- To see the same numbers as "decimal" display mode: split the 16 trigger bits in two 8-bit groups.

Best regards, Coen (BioSemi)
by Coen
Thu Mar 04, 2021 6:31 pm
Forum: BioSemi all other topics
Topic: Can I change the sampling rate to 1000Hz?
Replies: 1
Views: 5936

Re: Can I change the sampling rate to 1000Hz?

Only integer divisions or multiples of 2048 Hz are possible. Sample-rate are available in powers of 2 from 32 Hz (speedmode 4, decimation = 1/64) to 16384 Hz (speedmode 7, decimation = 1). Note that the analog bandwidth is always approx. 1/5th of the sample-rate (indicated in the right sidebar). For...