[aprssig] water level gauge for APRS

Mon Aug 22 00:52:38 EDT 2016

I wasn't gonna' jump in here, and didn't read all the posts, so this may be moot/unimportant, but.... just some thoughts, not necessarily in any order or relevance.

 After thinking them, I think directly sensing the level is better than Steve's pressure technique.

There is a USGS creek sensing station at the inlet to Wonder Lake, Illinois where I live.  It has a rain guage and senses creek level and flow.  I often thought I'd call to find out how they measure creek depth.  I know the flow rate is a calculation.
 http://waterdata.usgs.gov/usa/nwis/uv?05548105 
And another down stream of the lake:
 http://waterdata.usgs.gov/il/nwis/uv?site_no=05548280 
Interesting to watch and compare with my rain guage.

Air in a pipe closed at the top disolves slowly under pressure. If the bottom of the pipe is always submerged, this slowly reduces the pressure at the top making it slowly say there is no water in the pipe.  The vertical water-hammer cushions in home plumbing fill with water over time and must be drained.

Steve's Pressure-pipe measures the water head outside the pipe PLUS atmospheric pressure changes.  If the pipe opens to air on the bottom periodically, this tracks out.  But when it storms, the pressure is low, right?   Then it will rise after the storm, right? 
Then, as the creeks drain, the flooding begins as the parometer is rising after the storm.  So, this will make the water pressure in the pipe rise (once the bottom of the pipe is sealed with the flood level) more than the water alone due to the rising barometer adding to the head.  This shows higher water than actual, not a show stopper depending on what you're trying to do. 

A search shows that the Barometer in the US varies as much as 7.6% max.  Assuming 5% is more typical short-term, this is a 1.6 foot water-head variation due only to barometer. (5% of 32 feet for 14.7 psi, one atm)

My son was doing some pressure measurements and used ultrasonic depth sensors in vertical pipes connected to the system under test. This was more lab measurement and they were $$n.

Another idea I tried long ago was to reflect a laser off a surface and by the changing angle of the reflection, the distance can be inferred. 

If you modulate the laser with a tone, the phase shift of the tome shows the delay and distance.  By setting up a delay time/ period-type measurement, picking the clock freq., you can make it read digitally in any units desired.

You can also put something like a float ball in a pipe, instead of just the water level, for some other type of depth sensing.

A photo sensor of choice may provide an indication of the reflected intensity variatin with distance to the float.

You may be able to slope the pipe for a greater distance-to-surface change.

Or, turn the pipe into a organ pipe and blow air across it and measure the frequency as the level changes the pipe length.

Just some thoughts for the DIYer.

You can tell I needed a break from some other busy work... (:-)

-- 
 Cheers, Steve Noskowicz
 Science & Technical Advisor
 http://www.challengerillinois.org/

 ......................................
 On Sun, Oct 4, 2015 at
 11:53 PM, Steve Dimse <steve at dimse.com>
 wrote:

 > TO make a flood gage, it would seem that a simply
 pressure sensor like we use for atomosphere for balloon
 payloads would work.

 > Just put it inside a pipe with a cap on the top and
 open on the bottom.  Then the pressure will vary with the
 height of the water.  Connect this to the analog input of
 an APRS tracker and you have a flood gage.  Calibate it
 with some testing and done...

 >

 you'd have to worry about temperature, and the chamber
 would have to be perfectly and permanently sealed. There is
 an easier way.

 It never got much traction, but there is a commercial
 product

 http://floodadvisor.com/produc
 ts.php

 that is apparently still for sale, and includes integrated
 TNC and radio, runs for a year on a lantern battery. Their
 non-ham product uses satellite reporting. At this time there
 are just two stations still using the ham version, you can
 see the data at

 http://www.findu.com/cgi-bin/f
 loodadvisor.cgi

 I have one at my house, but never did replace the battery
 when it died.

 This uses an ultrasonic sensor that measures the water level
 inside a PVC pipe, open (copper screen) at the bottom and
 with a tiny vent hole at the top. I don't know what
 sensor it uses, but in other projects I've used this
 sensor with good results,

 http://www.ebay.com/itm/Ultras
 onic-Module-Distance-Measuring -Transducer-Sensor-Perfect-
 Waterproof-/321714364470?hash= item4ae7aba036

 send it a 5v trigger signal, and get back a pulse whose
 length is proportional to distance, easy to measure with a
 pic or arduino. There is a non-waterproof version for less
 than $2 for inside use too.

 If you develop something, please consider sending with the
 flood advisor protocol so it is parsed by findU, then you
 will have graphing available for no extra effort.

 K2GE-7>APFG21,WB2SNN-15*,WIDE2 -1,qAR,KC2YYW-1:=4026.04N/
 07421.51Ww>T+057F-030V062 FloodAdvisor -30

 the data is temp, height*10, voltage*10, and at the end an
 optional sequence number.

 Steve K4HG

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