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Re: High Water Recorder

PostPosted: Mar 31, 2008 4:26 pm
by ggpab
Just did some calculations on the Sensus Pro memory to see how long they could collect data for. The webpage says they can log 1500 hours at 10 second interval. That equals 540 000 total observations. (Probably they are rounding down from 524 288 since that is the closest base 2 number.)

So - at 15 minute intervals = 14.9 YEARS!
Or - at 5 minute intervals = 4.99 years.

I suspect the battery is going to die way before you hit the memory limit. I have no idea if it is possible to recover the data once the battery dies since these are sealed units.

Re: High Water Recorder

PostPosted: Mar 31, 2008 5:13 pm
by Spike
At Carroll Cave in Missouri we deployed a Hobo pressuretransducer to measure stage height of Thunder River. While a bit pricey at $500 plus software and some additional hardware, we are getting a measurement every 15 min with temp changes. The nice thing about recorders is that you can see not just how high the water got, but how long it took to decline. I nice thing to know if you think you might have to wait out a flood beyond a sump. Attaced is a simple graph of some data.


Re: High Water Recorder

PostPosted: Mar 31, 2008 5:22 pm
by cavemanjonny
ggpab wrote:Several excellent low tech options made, but if you factor in your time and gas, then consider the scientific $125 solution.

Luckily I live close enough to the cave that I could write my bike there in about 15 minutes. Although I'd look pretty goofy all geared up riding through downtown Chattanooga :-).

I looked at the specs on the webpage you listed, and it mentioned that the datalogger turns on once it's been submerged under 3 feet of water. Unfortunately, the passage I have in mind is probably not even 2 feet tall, so it doesn't sound like it would ever log anything at all!

Re: High Water Recorder

PostPosted: Mar 31, 2008 5:24 pm
by cavemanjonny
Hmmm, anyone have any dataloggers they'd like to loan out :grin: ? Maybe I can convince my school to buy one!

Re: High Water Recorder

PostPosted: Mar 31, 2008 5:25 pm
by wyandottecaver
A few observations:

depending on the humidity and/or "drippiness" of the cave, chalk and other substances affected by moisture may not perform as you intend. In measuring max water heights in a infrequently flooded hibernacula passage golf balls were placed at various levels (there were lots of ledges, but you could use chopped down styrofoam cups mounted to a stick) as the water rose the golf balls were displaced.(number the balls in case they get re-deposited) Note that neither this nor many other methods might be feasible in heavily visited areas where "tampering" might occur.

Re: High Water Recorder

PostPosted: Mar 31, 2008 6:19 pm
by robcountess
I thought about this problem for a few minutes during class while the lecturer droned on, and came up with a few ideas.

I assume what you are worried about is the high water level between visits, sure you love to have depth vs time data but that's a bit more involved.

I'll draw them at home and post them

Re: High Water Recorder

PostPosted: Mar 31, 2008 7:14 pm
by Teresa
High water recorders are easy. They are called cork tubes.

A tall narrow (hopefully transparent or translucent tube) is firmly attached to the place you want to record the stage. A bit of ground up cork is put in the bottom. By looking at water lines of other floods, you can get an idea how long a tube you need. Make sure the tube is a bit taller than you think the water will get. Look at pages 18 and 19, for detailed instructions how to make this device, called a crest gage. Doesn't take more than about $10-15 of materials

The ones I've seen aren't this elaborate. They consisted of a burnt out 6 or 8 ft. office fluorescent tube, with the top end cut off smoothly with a glaziers tool, and a bunch of little holes carefully drilled in the base. Dump in ground cork. Set tube into flooding area, calibrated for elevation, but with the cork dry. Go away. Wait for rain. Come back. Look at the tube with a flashlight and see how high the water got by the cork ring sticking inside the tube, by measuring the tube.

I know, rube goldberg science. But it works! Needless to say, a glass tube would need to be securely anchored and out of the main flow of the water. This is best accomplished by wrapping the tube in used bubble wrap, and securing the bubble wrap to itself and to the cave with duct tape. As members of the SCA know, you can't hurt much, not yourself or a sword, with it wrapped in bubblewrap and duct tape. You just need to unwrap the bubblewrap before reading the tube. Disclaimer: This invention preceeded Beekman's World by several decades, and I've actually seen one in use on a spring.

Re: High Water Recorder

PostPosted: Mar 31, 2008 8:24 pm
by tncaver
Johnny Prouty wrote: "You guys are amazing! What are your thoughts on cold fusion?"

I suggest 1 million lightning bugs in a clear trash bag smashed with Gallager's big wooden mallet. :laughing:

You know I'm kidding right?

Re: High Water Recorder

PostPosted: Mar 31, 2008 8:55 pm
by Ralph E. Powers
jprouty wrote:
Phil Winkler wrote:Jonny, you can also buy water detecting paste that changes color when water touches it. You could anchor a yard stick or something in the passage, slather on the paste and badda-bing.... It is normally used to detect water bottoms in fuel storage tanks.

Yet another great idea. I could use chalk on a yard stick and the paste on a yard stick, to compare the methods as well! You guys are geniuses!

Oh hush you're making us blush.

Re: High Water Recorder

PostPosted: Mar 31, 2008 9:45 pm
by cavemanjonny
Teresa wrote:As members of the SCA know, you can't hurt much, not yourself or a sword, with it wrapped in bubblewrap and duct tape.

Wow, SCA, that's too awesome for words! Maybe I could make a big cardboard shield to deflect the brunt of the water. I might even be able to to convince a faux-dwarf to guard the devices, so that wayfaring spelunkers don't steal them, thinking they're giant glowsticks.

Re: High Water Recorder

PostPosted: Apr 2, 2008 5:15 am
by Leclused
You can make a Bilborupt yourselfs :-)

This is a home made and cheap high water measuring tool. This is used already in several caves in Begium and France.

I think it was used the first time in the cave "Rupt des puits" in France

An example + info of how it looks like can be found here.


Sc Avalon - Belgium

Re: High Water Recorder

PostPosted: Apr 2, 2008 4:10 pm
by wyandottecaver
hey.. its my golfball idea only using tennis balls and a metal rod. I had to guesstimate which links were pictures since I dont read french :)

Re: High Water Recorder

PostPosted: Oct 8, 2008 8:23 am
by ggpab
Hi Jonny,

The Sensus units are fundamentally pressure and temperature loggers. You can use the software provided to change the 'start pressure' at a value less than barometric pressure and then it the unit will log continuously in or out of the water regardless. You can tell when it was submerged since the pressure jumps significantly and the temperature most likely also changes significantly.

If you do get some of these, or any pressure transducer of any sort, be sure to know where the holes are that allow the pressure change to be measured on a membrane (or bi-metalic stric, or whatever the device). You may need to use some Saran Wrap / cling film / other to make sure you do not get mud in the holes since you won't get any data after that.