The SS495A is an analogue output sensor, there is no need to use a pull-up or pull-down resitor. It you are just counting pulses, it would be better to use the hall effect switch version SS441A device. This will switch high when the magnet passes over the sensor, and then low when it is not. It also has all the hysteresis and Schmitt triggering ciruitry to avoid glitches. I use this device in a tachometer of mine.