Datalogging O2 signal

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My question is, what should a good O2 sensor look like under normal cruising? I've got one that likes to be the exact opposite of the other when one is reading .97 volts the other will read .02 and than they start cycling. Before i pay out for a new O2 sensor I'd like to make sure the rear is reading right, or wrong. At around $100 a shot I'd like to replace only the bad one, and not both.

At idle they both read .00 and .01 but than when i'm driving i get different readings from them. I've tried disabling one of them with the logger and the readings don't really change(at idle of course) cause i don't feel like driving around even while cruising to test this out. And with the wide range of readings i'm getting, i'm not sure which one i can trust to be right.