Variable PIR Sensor

I'm working on my first Max/MSP project for a sound art installation, and so far everything is going great. For one portion of the patch, I would like to have PIR sensors dictate the frequency of some recordings, but I'm not getting any variable numbers from the sensor. Does any one know if the PIR sensors are able to output variable data, or just high and low?

I saw a video of a PIR sensor outputting variable data on a graph, but now I can't find it, of course, so it must be doable, right?

Thanks!

I think you might mean the video that Jeri Ellsworth made: The PIR Sensor - Motion Activated Art - YouTube