On Monday, 1 May 2017 12:26:09 BST Terry Coles wrote:
> Has anyone ever done anything like this? Ideally, for level, an ultrasonic
> sensor with a good level of water resistance would be ideal (it won't be
> immersed, but it will be exposed to rain, mist etc). The capacitive sensor
> requires RF, which brings it's own issues and the other types may provide
> readings that are too coarse to monitor rate of change of level.
>
> I haven't found anything much yet that will give us flow measurement in a
> 'river'. The commercial types tend to be fairly cheap but designed to go
> into pipes. However, we should be able to come up with something using
> hall effect sensors, so I'm more interested in level at the moment.
>
> Any ideas, links to projects that have done this?
A quick update on this:
As I mentioned at last night's meeting, we are currently considering a solution
based on
measuring the air pressure in a pipe that is connected to the bottom of the
butt. Obviously
when the tank is empty the sensor will measure 0 kPa (as compared to the
atmosphere)
and when it is full it will measure the pressure due to the height of the water
column,
which I calculate to be up to 15 kPa in a 200 litre butt.
Also, someone on the Raspberry Pi Forums has suggested using a load cell to
weigh the
butts. I'm still looking at that.
Both solutions are based on the 'strain gauge' type of sensor, so the output
voltage tends
to be rather low (typically less than 30 mV). This would require us to design
some low
noise circuits to amplify the signal to the level where it can be converted to
digital for the
Pi to process.
--
Terry Coles
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