River water level

[Bern1937]

WATER HEIGHT ? --- Looking at using an ultrasonic system (WINGONEER DC 5V Waterproof Ultrasonic Distance Sensor system ) and mounting the sensor on a post overlooking the river. I will use the waterproof sensor. Take the echo return time signal and use it to start and stop a counter. (Digiten 4 digit LED counter panel meter. ) Looking at the LTC6900 to create about a 5.6 KC time base for measuring the distance in feet. --- A couple questions: Can I extend the cable between the control module and the sensor to 250 feet? If so can I use multi conductor cable, or would the sensor need to have coax? What kind of stability is reasonable to expect using these parts and overall method? Any thoughts and/or other ideas? How about a better way? Comments ? – Thanks

 

[Nigel Goodwin]

I would say not - the obvious way would be to have a micro-controller do the counting, and send the data back down the wires as a serial data stream - you could power it up the same cable as well. It would probably be wise to take multiple readings, and send the average back as water is rarely flat.

I seem to recall that existing water height systems measure the height in a tube, in order to reduce the surface movement of the water.

It's an EXTREMELY common operation, measuring water height (or depth) through a fixed size channel, in order to monitor the amount of water in the local river system - the data is usually sent back wirelessly, and I'd like to imagine that it's all powered by a small water turbine (but I've no actual knowledge of that).

 

[Beau Schwabe]

Instead of measuring the height of water in a tube, measure the pressure in a "sealed" tube (at the top).

 

[Nigel Goodwin]

Interestingly, after posting yesterday, I did a little googling - and there's a site that lists all the UK river monitoring sites - and the ones I know anbout are listed on it. There's 48 in Derbyshire where I live, and you can check the river levels and flooding risks.

Not a problem where I live, as I'm fairly high up

 

[dr pepper]

Measuring the distance from above and taking an average with a micro is a good way to go.
Or maybe a non contact capacitive probe in the water.
I played around with the idea of a time delay reflectometer for measuring levels, just with a piece of uninsulated wire, but soon found the development time was way more than I was prepared to do.
If you want to transmit a digital signal 250 foot, and your not using a micro that can error detect then I'd suggest to use some 50ohm coax and impedance match it either end.