looking for a sensor to check the water level in a bathtub and send one type of pulse for higher and a different for lower water levels...any ideas?

[magdalen]

the level should have a two inch tolerance (for moving water). Thought about a sensor "strip" but could not find any info online

[PdB]

An alternative solution for your kind of application is one that is not in, but on the outside of the bathtub. We did some experimenting a bit some years ago with non-contact level-sensors that were used on a non-metal waste-water tank aboard small vessels. As you can imagine, offshore the rocking and shaking of water is there all the time.
We ended up designing a prototype sensor by adding signal processing in a micro-controller.
It outputs an RS-232 and TTL signal, and we are still looking for a interested commercial partner.

Patrick de Boevere
Serenity systems design

[AVR]

Consider looking at the sensors used by RV manufacturers on their potable water and waste holding tanks. These sensors are just bare contacts that "short" when sequentially submerged by changing water levels. There is a "sending unit" that controls the voltage (very low) and conditions the returning signals for output to an annunciator panel in the RV. You would need three (minimum) contacts so that the system could interpret the difference between the two sensor levels of interest. This is a somewhat "crude or brute force approach"; however, it is rugged, cheap, and easy to use; else , they would not be used in a production line item. You could use a voltage divider on the output of one sensor in order to distinguish sensor outputs.