My apologies for my vague explanations. I am currently strobing a GaAs IR Emitter every 16ms, it has a peak wavelength of 950nm. This is then either reflected, or not, by the base of the turbine, this is then received by a NPN phototransistor, which has daylight filtering, for, the more light this transistor receives, the more current it draws. I was hoping to find a device that would change it transitional state once either it detected difference in pressure/water-flow, reason being, the device could still be in low-power mode, but, i could have this device tied to an interrupt and the device would only come out of low power mode once it detected a change in transition, i.e: HI/LO OR LO/HI, and then strobe the IR emitter, thereby saving on power consumption. To answer some other question, the uP takes 6 clock cycles to wake, i.e: 6us. The uP can be in low power mode, depending on what modules u want active, with the lowest power consumption being 0.1uA @ 3v or 5v. It however still has a management system that awakes if an interrupt is generated. Hence my request for some help on trying to find the sensor mentioned. Thanks.