Field Test:
They are multiplying:
The build 20th of January 2021:
Improvements since the DN50 build: Internal battery housing, on/off switch, aviation connector, DN80 sensor, detachable sensor pole.
Here is one of the earlier designs using an DN50 sensor.
I have switched to using a DN80 sensor, I have created a new Arduino housing that now has an on/off switch, an aviation connector for the main cable and internal battery housing. I'm working to change the firmware to read MPS instead of Km/H.
After that I will do some tweaking comparing the readings with a purpose build flow meter to increase the accuracy. If all of these steps go as planned then I will complete the build instructions and finish this project.
I worked with the good folks at Colorado State University's Hydraulics Lab (https://hydraulicslab.engr.colostate.edu/) on the calibration of a series of flow velocity sensors including the DN-80 sensor used for this project. We ran their fume from near-still water conditions up to 0.4 m/s flow rate and hung a Marsh McBirney flow meter along with the DN80 for an open channel calibration. The lowest stream velocity the DN-80 could record using a 5 sec integration time was 0.025 m/s but above that limit, a linear regression between the DN80 and MM estimates had an r2 of 0.9955, with a bias of -0.004 m/s and RMSE (aka standard deviation of residuals) of 0.009 m/s. Will try to get larger range of observations in the future but this is a very good start, IMHO. Photo of DN80 in the flume is at
https://photos.app.goo.gl/iHZ2Cd89UM8E9uDn9