Hi All,
Iam using three ADS1299 in daisy chain mode to acquire 24 Channel EEG. My EEG Recording is all perfect and I want to measure Impedance of electrode of all INP channels. To Achieve this I set the register settings as shown below . My sampling Rate Is 250SPS with 24x gain.
I need to measure Impedance only one time before the EEG Recording starts. To calculate the impedance How many samples or how many seconds of data do I need ?
WREG(CONFIG1, 0b10110110);
WREG(LOFF, 0b00000010); // IMPEDANCE CHECK 6 nA CURRENT // 31.2 HZ CURRENT SIGNAL
WREG(LOFF_SENSP, 0b11111111); // IMPEDANCE CHECK FOR +VE CHANNEL
WREG(LOFF_SENSN, 0b111111111); // IMPEDANCE CHECK FOR -VE CHANNEL
WREG(CONFIG3, 0b11101100);
WREG(BIAS_SENSP, 0b11111111);
WREG(BIAS_SENSN, 0b11111111);
WREG(MISC1, 0b00000000); // open SRB1 Switch
I've externally connected the -ve inputs of all channels to the REF Electrode in my PCB, so SRB1 connection dosen't matter in my case.
I've attached the text file which has the data of the channel . . During this data I had INP electrode at O2, REF at INN & BIAS ELECTRODE attached to the body.
How do I calculate the impedance from the acquired data?eeg24channel2gnd28.txt