Hi,
I have been reading through all the posts here regarding the lead off, both DC and AC in ADS1298 without finding sufficient help. I have managed to get DC lead off to work but not the AC lead off and this is where my problem is.
For simplicity, I am simply using a differential input IN1P and IN1N on one ADS1298 to see if I can get the AC lead-off to work.
I have set Lead-Off Control Register to 0b00010001, i.e. AC lead-off detection at Fdr/4, 6nA and Pull-up/pull-down resistor mode.
I have set the LOFF_SENSP and N registers to 0xFF (although I'm not sure if that is necessary?)
I have set Configuration Register 3 to 0b01000010 but it's not clear if the RLD is needed for this setup?
My Fdr is 2 kHz
I have a 200k ohm resistor connected over IN1P and IN1N on my ADS1298 and I simultaneously have an oscilloscope (1M input impedance) accross the resistor. I am, so far, not able to see any voltage oscillation at 500 Hz as I would have expected and I can therefore not verify that my AC lead-off is working (just noise of 10-15 mVpp). Not even by using the FFT settings on the oscilloscope can I see any tone at 500 Hz. How can I verify that the ADS1298 is indeed generating the 500 Hz current pulses?
Am I missing some other register settings needed for the AC lead-off to work?
p.s. I have already read the "Understanding Lead-off..... application note".
Best regards,
Saevar
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