Author Topic: Water LEVEL monitoring (i.e. river level)  (Read 6702 times)

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Re: Water LEVEL monitoring (i.e. river level)
« Reply #25 on: November 05, 2015, 04:51:29 PM »
I have completed my research into just the water level monitoring equipment and performed some preliminary experimentation with a bench test set up.

I opted for the Stevens SDX pressure sensor and a Dynisco UPR700 pressure / process Indicator.

SDX 93720-035 sensor (35 foot range with 50ft cable and desiccant cartridge):

UPR700 Monitor/ Processor / Indicator (UPR700-0-0-3)

I already have the UPR700 monitor / indicator ($495 value).  I set this instrument up in a bench test scenario and was able to select the operating min/max pressure range from 0 psi to 35 psi with 0.00 decimal point location.  The PSI reading itself is immaterial, irrelevant and just an arbitrary measurement scale that I will use to scale the output of the Stevens SDX pressure transmitter to. 

The output of the SDX pressure transmitter at atmospheric pressure is 4mA and when submersed in 35 feet of water it will be 20mA.  Therefore, I have scaled and calibrated the input of the UPR700 to be 4.0000 mA = 0.00 psi (corresponding to 0.00 feet of water) and 20.0000 mA = 35.00 psi (corresponding to 35.00 feet of water).  Hence, I will be able to measure the water depth to the nearest 0.01 foot or 0.12 inch throughout the range of 0.00 to 35.00 feet.

I have the SDX transmitter on order ($417).  When it arrives, I can fine calibrate the UPR700 to the sensor by zero/span in a real world environment to take into account any errors in the transmitter itself or in signal excitation and cabling.

I will re-zero the reading with the SDX transmitter connected to the UPR700 with the sensor out of water and then submerse it in a pipe filled to 35 feet of water and span the signal to provide the most accurate reading.

To monitor the river level, I will drive a 1-1/4" to 2" sand point and well pipe into the river bottom right near the river bank with some "breather" vent holes along the length of the pipe to allow water to enter and exit freely with the rise and fall of the river level.

This pipe will be set in a protected area so that river ice and flood debris will not damage the pipe or the sensor and its wiring.

The UPR700 provides linear outputs (voltage or current) which relay the input signal that I can scale and calibrate to retransmit the signal to another device.  I ponder using one of the available "off the shelf" special purpose Davis Instrument sensors. 

Someone mentioned that Davis sensors may have a 4-20mA input to use, which would be great.  However, I only found mention of a 0 -3 volt range input available through my research of Davis Instrument's documentation.  I will have to do further research and investigation on this, but I also have available to me a programmable signal conditioner which I can scale and calibrate to any voltage or current level I require.  Therefore, I can make just about anything work here. 

I am quite pleased with the progress on this project so far.  Although the "real world" implementation will have to wait until spring.  Once I have the actual system installed and calibrated to actual river conditions, then I can turn my attention to actually uploading the data to my Davis Weather station and then broadcasting it out to the internet, too.  I will utilize my winter months to conduct research into how to do these.  I believe that some Raspberrie Pie or Arduino solution will be a part of this project.

I thought some of you might like to hear about my update regarding this DIY project - just for fun.



« Last Edit: November 05, 2015, 06:36:44 PM by ACWxRADAR »

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Re: Water LEVEL monitoring (i.e. river level)
« Reply #26 on: February 12, 2016, 04:17:02 PM »
I just joined the forum because I have been doing exactly the same thing.  I have been running a Maxbotix ultrasonic sensor and an Milone eTape since last spring.  I've been using HOBO data loggers to record the level of a lake.  The goal is to add a second Davis VP2 to capture the data and post it to WeatherLink as we are currently doing with our weather station.  I'm right in the middle of doing this NOW.  As part of this task, I found another devise that measures water level.  It's called AquaPlumb.  According to the manufacturer it can record a maximum water height of 3 meters.  It uses capacitance as a measuring method, so it senses ANY moisture on its' sensing wire.  Therefore it needs to be held vertically in the water column and be somewhat protected from splashing.  That means putting it in a stilling well.  I already have one but can't install it until the lake ice clears.  (I have to work standing in the water.)  I just came in from setting it up in the snow as a test for something else.  The best that I can figure out, after many emails back and forth with Davis, is that I can connect and POWER it from the UV, Solar and Wind Direction ports of an ISS or remote anemometer station.  Right now I am powering it from a HOBO data logger.  More info to follow.

As far as Maxbotix and eTape go, they both have some limitations.  Maxbotix requires a large open space around its' sensing cone or it picks up stray fixed "objects".  Also, I get about 1/2" of noise unless I post process my data.  Finally, there needs to be some correction for the local speed of sound.  (Maxbotix does supply a speed of sound compensation circuit that makes the correction strictly based on air temperature  In general, for water level, that's good enough.)  I'm using it in parallel with the eTape as the eTape cannot be allowed to freeze and I need to know the lake level even when it is frozen. 

The eTape needs to be vented to compensate for changes in atmospheric pressure and is currently only available at a maximum length of 32 inches.  You cannot stack one on top of the other; that is submerge the lower one(s).  All must be vented.  However one of the good things about it is that to the HOBO data loggers, it looks like a thermistor or RTD.  It is strictly a resistance device.  It can be substituted for the wind direction potentiometer in a Davis system or plugged into the solar or UV ports as a variable resistance voltage divider circuit power by the 3V coming from the RJ11 socket.

Right now I shouldn't be posting to this forum as I have other things to do.  But, I felt the need to get some of this information out.  As soon as I have some time, I'll post pictures, sketches, wiring diagrams, data etc. as appropriate.  I'm involved with others who also have a need to record and post water level along with weather data in an inexpensive manner.  I just can't take the time to get into all this right now.