uxcell 1/4" Hall Effect Water Flow Sensor Switch Flowmeter Counter Fluid Meter DC5V 0.15-1.5L/min SEN-HW06K

This flow meter is built well and has not leaked thus far. Like any of the many other hall effect flow meters out there, this is not a "plug and play" solution for measuring flow rate. For use with an Arduino, some coding is necessary in order to use this device. I was able to calibrate this device by taking a known weight of distilled water and letting it flow through the device due to gravity into an empty beaker while counting each "pulse" from the device using one of the digital pins on an Arduino. I made sure that no air was in any of the lines or inside the impeller while running the test, and I stopped the flow before air entered any of the lines. Once stopped, I weighed the leftover water and through subtraction found the exact amount of water that had flowed through the device. This gave a factor of 0.211 mL per pulse from the device, meaning for every time the hall effect sensor changed state from high to low (or vice versa) 0.211 mL of distilled water had moved through it. This can be used to measure flow rate of a liquid- in my case I am counting the pulses in a loop and then once a second has passed I multiply the "mL per pulse" by the number of pulses recorded over that second (pulses per second) which gives mL per second.

bought for a flow monitor on a custom RODI manager, sadly I had some bugs I thought were code but were actually that the pulsed output of this device was able to swing WILDLY onder the weak field of a motor that drew 30w to boost pressureI had to move from a 4-inch distance to over 12 inches of distance behind a steel bladder tank just to stop the ghost flow reading, and it still randomly gets a few extra pulses(likely from power line stabilitythey really should have used a stronger pullup internally with teh hall-effect sensor simply grounding the signal locally with a local bypass capacitor given the leads are so thinotherwise works perfectly fine once you realize the pulses are about 1 per 0.2ml(not documented, shame on seller, had to find out from a reviewer) and it is inductively sensitive

I contacted the manufacturer - the Q value is 76 = i.e., F=76Q +/- 10%.