Weird GSR data
Posted: Sat Jul 23, 2011 1:32 pm
I have a BioSemi Active Two Mk2 box (checked against serial key) and 16 Hz excitation current (check by GSR unit displayed in ActiView).
I together with a colegue we wrote an acquisition program for GSR values. Can you help me decipher what is going on with my values from the ringbuffer please.
The most natural looking value in the ringbuffer is e.g. 48439296.
That makes it in binary 10111000110010000000000000. After dividing 48439296 by 256 to get rid of the additionally inserted zero LSB; we have 189216, that is, 101110001100100000.
So my 24 bit Integer is 189216.I found in one thread that this value is stored in the ringbuffer as scaled nanoSiemens with a factor of 31.25 nS, so that makes it 189216 * 31.25 or 5913000 nS
To sum it all up
32bit Integer: 48439296
24bit Integer: 189216
GSR value: 5913000 nS = 5913 uS
Please correct me if I’m wrong up until now.
Back to the question, why do the values jump between positive and negative values?
Here’s an exempt from the value list:
Sync: -256 gv: 4666uS
Sync: -256 gv: 4937uS
Sync: -256 gv: 5358uS
Sync: -256 gv: 5612uS
Sync: -256 gv: 5600uS
Sync: -256 gv: 5533uS
Sync: -256 gv: 5653uS
Sync: -256 gv: 5997uS
Sync: -256 gv: 6127uS
Sync: -256 gv: 6036uS
Sync: -256 gv: 5913uS
Sync: -256 gv: 6001uS
Sync: -256 gv: 6282uS
Sync: -256 gv: 6374uS
Sync: -256 gv: 6245uS
Sync: -256 gv: 6098uS
Sync: -256 gv: 3200uS <- this is where data get's corrupted
Sync: -256 gv: 963uS
Sync: -256 gv: -16uS
Sync: -256 gv: -829uS
Sync: -256 gv: -1461uS
Sync: -256 gv: -1758uS
Sync: -256 gv: -1796uS
Sync: -256 gv: -1955uS
Sync: -256 gv: -2288uS
Sync: -256 gv: -2599uS
Sync: -256 gv: -2676uS
Sync: -256 gv: -2530uS
Sync: -256 gv: -2578uS
Sync: -256 gv: -2843uS
Sync: -256 gv: -3074uS
Sync: -256 gv: -3080uS
Sync: -256 gv: -2889uS
Sync: -256 gv: -2884uS
Sync: -256 gv: -3104uS
Sync: -256 gv: -3295uS
Sync: -256 gv: -3267uS
Sync: -256 gv: -1855uS
Sync: -256 gv: 1874uS
Sync: -256 gv: 2988uS
Sync: -256 gv: 3572uS
Sync: -256 gv: 4157uS
Sync: -256 gv: 4774uS
Sync: -256 gv: 5097uS <- this is where we get back to the normal values
Sync: -256 gv: 5144uS
Sync: -256 gv: 5174uS
Sync: -256 gv: 5397uS
Sync: -256 gv: 5763uS
Sync: -256 gv: 5902uS
Sync: -256 gv: 5795uS
I together with a colegue we wrote an acquisition program for GSR values. Can you help me decipher what is going on with my values from the ringbuffer please.
The most natural looking value in the ringbuffer is e.g. 48439296.
That makes it in binary 10111000110010000000000000. After dividing 48439296 by 256 to get rid of the additionally inserted zero LSB; we have 189216, that is, 101110001100100000.
So my 24 bit Integer is 189216.I found in one thread that this value is stored in the ringbuffer as scaled nanoSiemens with a factor of 31.25 nS, so that makes it 189216 * 31.25 or 5913000 nS
To sum it all up
32bit Integer: 48439296
24bit Integer: 189216
GSR value: 5913000 nS = 5913 uS
Please correct me if I’m wrong up until now.
Back to the question, why do the values jump between positive and negative values?
Here’s an exempt from the value list:
Sync: -256 gv: 4666uS
Sync: -256 gv: 4937uS
Sync: -256 gv: 5358uS
Sync: -256 gv: 5612uS
Sync: -256 gv: 5600uS
Sync: -256 gv: 5533uS
Sync: -256 gv: 5653uS
Sync: -256 gv: 5997uS
Sync: -256 gv: 6127uS
Sync: -256 gv: 6036uS
Sync: -256 gv: 5913uS
Sync: -256 gv: 6001uS
Sync: -256 gv: 6282uS
Sync: -256 gv: 6374uS
Sync: -256 gv: 6245uS
Sync: -256 gv: 6098uS
Sync: -256 gv: 3200uS <- this is where data get's corrupted
Sync: -256 gv: 963uS
Sync: -256 gv: -16uS
Sync: -256 gv: -829uS
Sync: -256 gv: -1461uS
Sync: -256 gv: -1758uS
Sync: -256 gv: -1796uS
Sync: -256 gv: -1955uS
Sync: -256 gv: -2288uS
Sync: -256 gv: -2599uS
Sync: -256 gv: -2676uS
Sync: -256 gv: -2530uS
Sync: -256 gv: -2578uS
Sync: -256 gv: -2843uS
Sync: -256 gv: -3074uS
Sync: -256 gv: -3080uS
Sync: -256 gv: -2889uS
Sync: -256 gv: -2884uS
Sync: -256 gv: -3104uS
Sync: -256 gv: -3295uS
Sync: -256 gv: -3267uS
Sync: -256 gv: -1855uS
Sync: -256 gv: 1874uS
Sync: -256 gv: 2988uS
Sync: -256 gv: 3572uS
Sync: -256 gv: 4157uS
Sync: -256 gv: 4774uS
Sync: -256 gv: 5097uS <- this is where we get back to the normal values
Sync: -256 gv: 5144uS
Sync: -256 gv: 5174uS
Sync: -256 gv: 5397uS
Sync: -256 gv: 5763uS
Sync: -256 gv: 5902uS
Sync: -256 gv: 5795uS