standard oxigen sensor range goes up to 1,5 volts, so if you use a a\f ratio monito, iw will always show rich, because they are made for oxigen sensors going from 0 to 1 v
you will need an aftermarket universal o2 sensor to have a better reading.
but again a wideband kit is the best way to check a\f ratio...
commercial air fuel meter are not so accurate