This sensor sits in line with your water line and contains a pinwheel sensor to measure how much liquid has moved through it. There's an integrated magnetic hall effect sensor that outputs an electrical pulse with every revolution. The hall effect sensor is sealed from the water pipe and allows the sensor to stay safe and dry. The sensor comes with three wires: red (5-24VDC power), black (ground) and yellow (Hall effect pulse output). By counting the pulses from the output of the sensor, you can easily calculate water flow. Each pulse is approximately 2.25 milliliters. Note this isn't a precision sensor, and the pulse rate does vary a bit depending on the flow rate, fluid pressure and sensor orientation. It will need careful calibration if better than 10% precision is required. However, its great for basic measurement tasks!

This IR reflective sensor utilizes a TCRT5000 to detect color and distance. It emits IR and then detects if it receives the echo. This sensor is often used in line following robots, auto data logging on utility meters, because this module can sense if a surface is white or black. The measuring distance range from 1mm to 8mm, and the central point is about 2.5mm. There is also an on-board potentiometer to adjust the sensitivity. The infrared diode will emmitting the infrared continutelly when the module connect to the power, when the emitted infrared light has not been reflected or the strength is not big enough,the triode will in the off state, at this time, D0 output logic LOW and the signal indicate LED off. Application Idea Rainfall detecting Liquid leakage Tank overflow detector Features Supply Voltage: 3.3V~5V Detect distance: 1mm-8mm Digital Outputs HIGH when objects detected On-board indicator LED to show the results On-board potentiometer to adjust the sensitivity On-board LM393 chip

40KHz Ultrasonic Transducer Transmitter and Receiver Pair. These transducers are very useful in making various sensors for detecting obstacles and measuring distances. Features Use for motion or distance sensing Frequency: 40kHz ±1.0kHz Aluminum case Capacitance: 2000pF ±20% Transmitter: bandwidth 5.0kHz/100dB, sound pressure level 112dB/40 ±1.0kHz Receiver: bandwidth 5.0kHz @ -75dB, min. sensitivity 67dB/40 ±1.0kHz (0dB vs. 1V µbar) R=3.9k. Lead length/spacing: 0.28" Case size: 0.30"H x 0.43" Dia.