A bit of clarification on iButton failures. I've experienced two types. The first is when you attempt to download data from the iButton and can't connect to the chip do so. The second is when the iButton starts recording bad data that can still be downloaded. This can be difficult to detect unless you look at the data from multiply iButtons at the same in adjacent columns in Excel with the data and time rows aligned. IButtons that should be recording the same temperatures as the rest don't. Typically they either drift and become less accurate, they narrow their response range, or they clip the high or low temperatures. Unless you do this Excel test you won't know if you have failures or not and may be reporting bad data. I've used a couple hundred iButtons over about 6 years now and this is what I've experienced.
John ________________________________ From: "[email protected]" <[email protected]> To: Emily Atkinson <[email protected]> Cc: "[email protected]" <[email protected]> Sent: Fri, June 8, 2012 12:54:42 PM Subject: Re: [ECOLOG-L] iButton temperature/humidity logger Even in dry soil relative humidity of the air is near saturation so you won't see any biologically meaningful differences. I've used temperature iButtons for a number of years in vernal pools to measure water depth and up until 2.5 years ago they were pretty waterproof and robust. That has changed and I seal them in liquid rubber which is easy to peel off once a year for downloading data. They are no longer robust even when dry and my failure rate has gone up from less than 5% to more than 15%. John Sent from my iPhone On Jun 7, 2012, at 12:08 PM, Emily Atkinson <[email protected]> wrote: > Hi, > > Has anyone used an iButton temperature/humidity logger specifically for > soils? I'm looking into installing some at my field sites. Any > recommendations/advice would be greatly appreciated! Thanks! > > -- > Emily E. Atkinson > Department of Geography > University of Wisconsin-Madison > Email: [email protected] > Lab group: marinspiotta.com
