Difference between revisions of "Thaw probe design"
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=== Introduction === | === Introduction === | ||
| − | WERC uses thaw probes to measure active layer depth in summer / fall and sometimes snow depth in winter. The directions that follow are pretty much the current procedure. | + | [[Image:Thawprobe1.jpg|right|400px]] |
| + | WERC uses thaw probes to measure active layer depth in summer / fall and sometimes snow depth in winter. The directions that follow are pretty much the current procedure. | ||
The thaw probe is normally a fiberglass or steel T-handled probe 3 to 6 feet in length. I (Bob Busey) go back and forth in preference. There are pros and cons for each. The Fiberglass probe is lighter but sometimes feels dangerously bendy. The main knock on the steel probe is that sometimes the pointed tip falls off, which creates and error in the graduated marks and makes it harder to stick into the ground. Also, the handle can unscrew at inconvenient times. So, on the whole I prefer the fiberglass probe but it isn't clear cut. The steel probe also goes better through gravels I guess due to the smaller diameter. | The thaw probe is normally a fiberglass or steel T-handled probe 3 to 6 feet in length. I (Bob Busey) go back and forth in preference. There are pros and cons for each. The Fiberglass probe is lighter but sometimes feels dangerously bendy. The main knock on the steel probe is that sometimes the pointed tip falls off, which creates and error in the graduated marks and makes it harder to stick into the ground. Also, the handle can unscrew at inconvenient times. So, on the whole I prefer the fiberglass probe but it isn't clear cut. The steel probe also goes better through gravels I guess due to the smaller diameter. | ||
[[Image:Thawprobe3.jpg|right|400px]] | [[Image:Thawprobe3.jpg|right|400px]] | ||
Revision as of 14:58, 18 April 2011
Introduction
WERC uses thaw probes to measure active layer depth in summer / fall and sometimes snow depth in winter. The directions that follow are pretty much the current procedure. The thaw probe is normally a fiberglass or steel T-handled probe 3 to 6 feet in length. I (Bob Busey) go back and forth in preference. There are pros and cons for each. The Fiberglass probe is lighter but sometimes feels dangerously bendy. The main knock on the steel probe is that sometimes the pointed tip falls off, which creates and error in the graduated marks and makes it harder to stick into the ground. Also, the handle can unscrew at inconvenient times. So, on the whole I prefer the fiberglass probe but it isn't clear cut. The steel probe also goes better through gravels I guess due to the smaller diameter.
Parts
Search Ben Meadows.com for Tile probe, which is the general industry name of the probe. This link will show you all the probes.
http://www.benmeadows.com/search/tile+probe
Any of those are probably fine. I have purchased both the metal one
and the Nupla fiberglass one. So, that's the probe but there aren't any graduations on it until it is
paired with something like this tape found at McMaster-Carr:
"Adhesive-Backed Paper Tape Scale Left to Right, mm grads, 20M, Yellow.
Part number 1937A22
http://www.mcmaster.com/
Then you also need a package of epoxy that you can get from Home Depot / Lowes / Freddies / or almost any hardware store. The two compounds harden in 5 minutes type of epoxy works best. If you buy a couple of those then you're set. For example: http://www.amazon.com/Permatex-84101-PermaPoxy-General-Purpose/dp/B000ALJ4NS/ref=sr_1_2?ie=UTF8&s=automotive&qid=1276807051&sr=8-2
Manufacturing Procedure
Follow these instructions:
- Run the tape from the tip of the probe up to the handle carefully sticking it in place trying to minimize wrinkles and such. The more wrinkles the easier it will be for the tape to be scraped off when it's going into the ground.
- Tear off the tip tape back to behind the thaw probe point so that all of the tape is on cylindrical part of the probe.
- Mix the epoxy and use your hand (in a nitrile glove) to evenly spread it over the length of the probe. You should have the epoxy go around the whole probe but thickest over the tape to protect it from the mineral soil.
- Allow the epoxy to dry and apply at least a second coat, perhaps third for longevity.
If you do all that, even though it's a bit of work, you should have a probe that lasts at least a year. Redoing the tape every so often is kind of the nature of the beast but this system has worked well for
us.
