Hi Ali, Happy New Year! JP6 can only be used to provide a DC voltage to the BIAS electrode. There are no electrode signals included in the feedback path, which are needed to sense the common-mode voltage on the electrode inputs and derive the appropriate cancellation signal. The BIAS amplifier will sense the individual electrode inputs as you set the corresponding BIAS_SENSP/N bits to 1. Right now you only have IN2N selected. Is this one of your electrode inputs? You don't have to select every electrode that you use, but you may experiement with selecting more than one. How are you measuring the 50-Hz noise? Are you collecting and analyzing data or just probing the inputs? Scope probes can introduce a lot of extra noise as well, so it's best to just short the electrodes together (inputs and BIAS) and look at the noise in an FFT or histogram. Also, remember that you won't completely eliminate this noise, even with proper common-mode cancellation. I would start with all BIAS_SENSx bits set to 0 and fix the mid-supply voltage problem first. Remember that you are using bipolar supplies (+/-2.5 V), so mid-supply will be close to GND (0 V). One side of R8 is connected to the BIAS amplifier inverting input (BIASINV). This node is a virtual short to the amplifier's non-inverting input, which is conneted to the internal mid-supply BIASREF voltage. Check out this application note: Improving CMRR with RLD: Best Regards,
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