BioSemi.nl

Hi.

In my program, I need to check if biosemi is switched off. What should be the return value if it is not turned on? My codes did a USB_WRITE(handle, usbdata). But that doesnt seem to be the correct way to do it as it always return 0 regardless if biosemi is switched on/off.

Thanks.

Hi.

Data channels captured off biosemi can be read correctly by dividing the values 256.(?)

How about GSR, ERG, Plet, and temp? If I read the values off the 24 bit bdf file, how do I arrive at the right values for GSR, ERG, resp, and plet, temp?

Many thanks.
Marc

Could you recommend a base line correction method?

Hi. What should be the raw voltage range we expect to see when using Biosemi to record EEG? We recorded some EEG signals in a bdf file. When we open this raw bdf file (raw = no processing done), we see that some channels' voltages fall in the positive microvolt values, while some channels fall in th...

Thanks. I read it but dont quite get it. How do I translate it into 3D coordinates? For example, FP1 is -92 and -72. What would it be in 3D coordinate? Any pointer?

Hi.

Does anyone has the location file for the 64 bit EEG electrodes?
Basically, I need to know the exact coordinates that biosemi use for the headcap. XY coordinate or polar coordinates.

Thanks.
marc

Hi. Is there a way we could do real time power spectral analysis with activeview? if not, what do people use to do real time analysis with biosemi hardware? By realtime I mean, to see the frequency spectrum in real time. I dont mean to just view the eeg signals but to actually apply some analysis me...

Nothing to conclude. Just want to make a comparison on the sensitivity of this device with other devices that we may want to use in the lab.

Hi coen.
What is the maximum voltage output we can expect from the photosensor? and the minimum detectable voltage (or light intensity input)?

Hi.

I checked the forum but couldnt find info on how to interpret the battery signal so we can make sense of how much battery left in our program. Any advise please.

Many thanks again.
M

Thanks Coen.

Could you advise how to "additional processing" the BATT so we can know how much battery left?

The buffer width is 4 bytes wide. Would the diff. between the sync word FFFFFF00 and -1 FFFFFFFF be sufficient enough to distinguish them? Or I'm missing something?

Thanks Paul and Coen. I've followed your cues and taken the advise to adjust the programs. I did not use READ_Pointer and our buffer size remain at 32MB and not exact multiples of 282. So far the data is as good as what you'll get from labview. One thing to note is that there seems to be delay in ei...

Thanks Paul. Our data seems alright except for the sensor channels. Out of the 282 data, does index 258-265 correspond to EXG1-8? And how do we map the rest of the 16 channels to GSR1,2;ERG1,2;RESP;PLET;TEMP? Which index corresponds to these 7 of them? And where do the rest of the unmapped channels ...

Thanks Paul for the info. 1. If the update is every 64 msec, that means, for a throughput rate of 1732608/sec, 110886.912 bytes = 27721.728 long words = 98 blocks of 282 data, are already available and waiting? Would this delay be a problem? 2. We observed that when we call READ_POINTER, the functio...

Many thanks again. I have this call to -> READ_POINTER(theHandle, &lPointer). When I read the content of this lPointer, the values start from 0, then 131072, 262144, 393216 etc. The increment is always by 131072. Question is, this does not look like the insertion index, i.e. a byte offset between 0 ...

Thanks Coen.

3*2048*282 = 1732608. Is this the exact number that the '1.5Mbytes' refer to? If not, could you provide a more precise number for this 1.5M?

Cheers.

According to the info I read, the throughput remains constant at 1.5 MByte per second for Active2 system. So, at 2048 Hz, there are 282 samples. That would mean a total of 2048*282*4 bytes which is 2310144. That is above the 1.5Mbytes per sec throughput rate. Could someone please enlighten? Thank you.

Specifically, the "screen" we're referring to is LCD screens. Thanks.

Hi. Is there anywhere we could get the specifications of the Photo sensor? Primarily, we like to measure the flicker frequency of our stimuli on screen. Would like to know how sensitive is this Photo sensor and the range in which it will normally function and any other environmental requirement for ...

Thank you!!

Thank you Paul. It helps a great deal. Where would I begin the extraction point? I dumped the memory after I called read pointer for several seconds. I received output that is of this pattern - 19D57A00 00000000 00000000 FFFFFF00 8900FF00 0A19FB00 EF3AF600 7E9EBE00 7E951900 7E9CD400 7EABAD00 FFECC80...

Thanks Coen. If we were to not use labview, which in the case for our research, we have specific needs that is best addressed with our own development, could you kindly share on the first question and enlighten a little more on the answer? Here's the question again - If we were to *not* do with doub...

Thanks! 1. If we were to *not* do with double buffer like activeview, but to read direct, am I right to say that we should read 282 32 bit words for each sample from the read pointer? 2. If so, can we assume that ringbuffer pointer is sequential? That is, it gets incremented by this sample size for ...

Hi. Using speed mode 4, the # of channels is 256 @ 2048Hz. I read from the old threads that there is 282 buffered channel. A bit confused here. What's the new additional channels for and where are they from? So, if I were to read from active 2 hardware directly using my program, should I bother with...

How about how much to read? Is it fixed or varies for each iteration? In either case, how and who decide how much to read?

Thank you.

Hi. I'm reading the Act_Pointer.vi block diagram. A simple question. The quotient and remainder on the left (buffer pointer / 4. The very first input to the while loop), according to the context help, there is supposed to be 2 output. But I'm seeing 1 output only. Could someone explain? Also, as I r...