Raw data sequence numbers, millivolt range samples
Hi, I'm looking at the raw data files and have a question. I expected to see time stamps or sequential numbering but I see the following with the left column being repeat time over and over. Its this data not time based but instead represents sequential snapshot of 30 frequencies every 1/250 of a second? If not, what do these negative integers represent? I'm trying to plot this in excel to do some analysis and charting.
%OpenBCI Raw EEG Data % %Sample Rate = 250.0 Hz %First Column = SampleIndex %Other Columns = EEG data in microvolts
-29, 8081.03, -865.44, 19319.28, 31468.30, 4714.09, 36761.35, -587.38, 26779.51
-28, 7641.59, -845.37, 18335.31, 29751.33, 4410.33, 34759.82, -586.38, 25320.54
-27, 11011.34, -1218.13, 26441.22, 42836.22, 6349.84, 50050.63, -838.01, 36456.92
-26, 11253.32, -1239.29, 27008.26, 43812.66, 6513.92, 51190.20, -847.11, 37284.79
-25, 8650.79, -943.85, 20747.91, 33684.50, 5021.52, 39353.35, -641.34, 28665.91
-24, 7839.11, -858.66, 18819.74, 30543.50, 4541.02, 35679.64, -587.60, 25991.48
-23, 9083.59, -988.33, 21808.86, 35371.27, 5258.18, 41330.65, -674.69, 30106.37
-22, 9370.79, -1021.45, 22475.91, 36478.40, 5420.41, 42621.87, -699.86, 31046.37
-21, 8285.79, -904.84, 19865.83, 32214.38, 4782.71, 37647.51, -621.60, 27421.97
-20, 7669.91, -839.35, 18382.90, 29819.39, 4430.27, 34849.56, -573.88, 25382.28
-19, 7913.70, -873.89, 18990.96, 30806.51, 4576.32, 36001.14, -589.77, 26218.50
-18, 7970.50, -873.06, 19110.25, 31023.08, 4608.30, 36247.33, -596.34, 26399.82
-17, 7534.79, -829.74, 18101.85, 29343.43, 4341.69, 34289.47, -572.54, 24970.43
-16, 7067.73, -779.76, 16950.02, 27509.54, 4085.27, 32144.98, -534.47, 23408.91
-15, 6720.05, -744.63, 16135.54, 26167.65, 3879.57, 30575.26, -508.90, 22270.78
-14, 6573.11, -718.56, 15760.03, 25569.88, 3804.15, 29875.92, -488.54, 21763.80
-13, 6354.24, -697.91, 15231.15, 24721.16, 3670.22, 28886.25, -478.80, 21041.08
-12, 6094.00, -660.34, 14592.02, 23707.84, 3529.72, 27698.05, -451.57, 20178.93
-11, 5942.61, -658.82, 14268.30, 23129.65, 3429.47, 27033.92, -450.92, 19693.38
-10, 5895.92, -637.14, 14126.64, 22906.45, 3399.97, 26767.42, -442.90, 19495.70
-9, 5690.13, -619.81, 13647.84, 22128.83, 3282.73, 25862.98, -432.44, 18841.65
-8, 5397.81, -581.77, 12929.97, 20992.73, 3125.47, 24533.52, -406.00, 17870.22
-7, 5238.02, -580.68, 12572.52, 20387.65, 3022.58, 23823.58, -404.10, 17351.32
-6, 5049.71, -570.26, 12130.45, 19676.98, 2920.08, 22988.65, -384.58, 16741.30
-5, 4790.45, -521.67, 11467.76, 18610.87, 2772.38, 21739.91, -355.71, 15830.26
-4, 4611.03, -507.74, 11054.19, 17935.57, 2661.62, 20955.25, -352.49, 15258.26
-3, 4572.52, -496.63, 10968.67, 17785.75, 2636.48, 20777.11, -352.38, 15126.72
-2, 4449.96, -484.76, 10687.80, 17343.10, 2570.50, 20260.56, -343.50, 14752.26
-1, 4205.75, -465.65, 10115.62, 16417.35, 2436.12, 19175.96, -322.87, 13964.38
0, 4023.65, -449.52, 9686.17, 15717.07, 2335.71, 18357.08, -308.95, 13369.87
%OpenBCI Raw EEG Data % %Sample Rate = 250.0 Hz %First Column = SampleIndex %Other Columns = EEG data in microvolts
-29, 8081.03, -865.44, 19319.28, 31468.30, 4714.09, 36761.35, -587.38, 26779.51
-28, 7641.59, -845.37, 18335.31, 29751.33, 4410.33, 34759.82, -586.38, 25320.54
-27, 11011.34, -1218.13, 26441.22, 42836.22, 6349.84, 50050.63, -838.01, 36456.92
-26, 11253.32, -1239.29, 27008.26, 43812.66, 6513.92, 51190.20, -847.11, 37284.79
-25, 8650.79, -943.85, 20747.91, 33684.50, 5021.52, 39353.35, -641.34, 28665.91
-24, 7839.11, -858.66, 18819.74, 30543.50, 4541.02, 35679.64, -587.60, 25991.48
-23, 9083.59, -988.33, 21808.86, 35371.27, 5258.18, 41330.65, -674.69, 30106.37
-22, 9370.79, -1021.45, 22475.91, 36478.40, 5420.41, 42621.87, -699.86, 31046.37
-21, 8285.79, -904.84, 19865.83, 32214.38, 4782.71, 37647.51, -621.60, 27421.97
-20, 7669.91, -839.35, 18382.90, 29819.39, 4430.27, 34849.56, -573.88, 25382.28
-19, 7913.70, -873.89, 18990.96, 30806.51, 4576.32, 36001.14, -589.77, 26218.50
-18, 7970.50, -873.06, 19110.25, 31023.08, 4608.30, 36247.33, -596.34, 26399.82
-17, 7534.79, -829.74, 18101.85, 29343.43, 4341.69, 34289.47, -572.54, 24970.43
-16, 7067.73, -779.76, 16950.02, 27509.54, 4085.27, 32144.98, -534.47, 23408.91
-15, 6720.05, -744.63, 16135.54, 26167.65, 3879.57, 30575.26, -508.90, 22270.78
-14, 6573.11, -718.56, 15760.03, 25569.88, 3804.15, 29875.92, -488.54, 21763.80
-13, 6354.24, -697.91, 15231.15, 24721.16, 3670.22, 28886.25, -478.80, 21041.08
-12, 6094.00, -660.34, 14592.02, 23707.84, 3529.72, 27698.05, -451.57, 20178.93
-11, 5942.61, -658.82, 14268.30, 23129.65, 3429.47, 27033.92, -450.92, 19693.38
-10, 5895.92, -637.14, 14126.64, 22906.45, 3399.97, 26767.42, -442.90, 19495.70
-9, 5690.13, -619.81, 13647.84, 22128.83, 3282.73, 25862.98, -432.44, 18841.65
-8, 5397.81, -581.77, 12929.97, 20992.73, 3125.47, 24533.52, -406.00, 17870.22
-7, 5238.02, -580.68, 12572.52, 20387.65, 3022.58, 23823.58, -404.10, 17351.32
-6, 5049.71, -570.26, 12130.45, 19676.98, 2920.08, 22988.65, -384.58, 16741.30
-5, 4790.45, -521.67, 11467.76, 18610.87, 2772.38, 21739.91, -355.71, 15830.26
-4, 4611.03, -507.74, 11054.19, 17935.57, 2661.62, 20955.25, -352.49, 15258.26
-3, 4572.52, -496.63, 10968.67, 17785.75, 2636.48, 20777.11, -352.38, 15126.72
-2, 4449.96, -484.76, 10687.80, 17343.10, 2570.50, 20260.56, -343.50, 14752.26
-1, 4205.75, -465.65, 10115.62, 16417.35, 2436.12, 19175.96, -322.87, 13964.38
0, 4023.65, -449.52, 9686.17, 15717.07, 2335.71, 18357.08, -308.95, 13369.87
Comments
As far as the large positive or negative microvolt values, see,
http://openbci.com/forum/index.php?p=/discussion/201/large-millivolt-data-values-dc-offset
Note that on that post the author shows a modified CSV file with a millisecond timer as the first column. He changed the source to do that. (Just to see how consistent the clock values were at reception time. Which as expected are nominally [1/250 =] 4 milliseconds apart.)
William