2018-02-14 at 8:45 AM #3976
I will be deploying a network of about 15-20 wireless sensors small to medium sized streams. They will be outfitted with Decagon CTD, a DO sensor, and a pH sensor. These will connect to a SODAQ mbili with a GPRSbee. I’m trying to finalize my installation method and would appreciate any advice and pictures of other folks’s in-stream setup. The sites will range in the degree of urbanization. My hope is some will be secured to bridges but most will have to be secured in-stream somehow. Currently I am thinking securing the sensors to rebar or angle iron in the stream and the datalogger and solar panel on fence posts/angle iron on the stream bank. How have folks dealt with securing the wires? At some of our sites I’m worried there will be several yards between the sensor and data logger as I don’t want the datalogger deployed in stream. Any pictures are much appreciated.
2018-02-15 at 2:56 PM #4135
Installation is what the systems needed to be built for, as it brings it all together.
I’ve been building and testing equipment for deployment in small to mediums sized streams in N California, and occasionally been out with the Hydrologists that will later on be doing the stream rating curves.
My part has been to build the equipment and test in a safe location – in the industry we call it “staging the equipment”.
It’s so much easier to verify the equipment works and is reliable by first building it in a safe location, letting it soak for a couple of days, with all the tools and cellular connectivity.
For the location in the stream bed, its best to do a survey – geographical and RF – go there with a cellphone on the network you are going to use, and then see if there is a signal.
There are cell phone Apps that will help track the strength of a signal on a network as you move around. I have eneded up with two phones for ATT 2G and ATT 3G network to map where the 2G network had been removed.
If you are looking to deploy a 2G network, know when it is likely to be sunsetted – I even here ATT 3G sunset dates are being mentioned.
For the cellular providers, rural areas have a different cellular network installation criteria than urban networks
For the geographical instream locaiton – I imagine you are looking for a reliable place to be able to measure amongst other items stream flow. For that the hydrologists I’ve been out with look for a pool with a stable down stream riffle. The down stream riffle defines the ability to do the rating curve.
One aspect of the measurement location is that the measured depth is often impacted by the diurnal temperature cycle of the water, so its valuable also to have a temperature sensor on the depth measurement.
If you aren’t likely to be doing stream flow rating curves, it does make the installation location easier.
Perhaps people who have experience of the Decagon CTD can comment on what they have found is optimial for it – as the EC may require water flowing round it to be useful.
So on the one hand for the sensor its valuable to have a pool with a stable stream, and the RF needs to be able to find the cellular network signal – the cellular radio horizon. Cellular radio signals don’t go through the earth very well. In N california we tend to have deep ravines for the streams, and its very tricky. For other locations maybe the geography is kinder.
Then we measure the difference between the inpool measurement position and where the logger is going to – this is the length of waterproof line that sensor needs to have.
Typically we are then going to mount the logger/battery housing on a pole/tree/fence above the flood line – with a reasonable solar aspect, and run a flexible conduit down to the stream side. Sometimes this has been 100′.
The sensors cable needs to pull through the protective conduit. So the protectective conduit inner diameter must be able to take the maximium dia of the sensor cable bundle.
Typically we use a plumbers pull line, and have to figure out how to carefully attach the cable bundle (including sensors) to the plull line.
Its conceivable, depending on the sensor cable lengths that you could put one environmental housing for the sensor termination and venting, and then run a 2nd extension cable to different location where the logger/RF signal/solar panel are optimal. Then there needs to be infield cable connections.
For fixing in the stream, I recommend the active part of the measurement sensor should be kept 6″ below the surface level for where flow measurements are being made. Typically sensors don’t know where the 0 water level is (they are typically a pressure sensor of some sort), and the least accurate part of measuring is close to 0.
The hydrologists I’ve worked with have fixed the sensors firmly in the stream on roots of trees, or with a rebar post. Equally important is then the flexible conduit is well tied down, and prevented from oscillating, when water flows across it.
Finally when its all installed, its valuable to have a way of verifying that the data is flowing through to the final destination – which typically is by bringing up the website on a cellphone and checking that its reported in at least once.
All cable entries to the enclosures benefit from good down ward drip line practises.
Well hope this is useful, and good luck – send some pictures of your locations. 🙂
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