I-buttons/Thermotrons!

Great news on the green roof research front! I have been diligently working to figure out how ibuttons, small computer chips that record temperature readings, work in order to begin collecting temperature data on our green roof. We want to record the temperatures inside the different trays of different soils in order to make conclusions about whether green roofs with native plants and/or added arbuscular mycorrhizal fungi improve heat insulation. In order to know this, we need to track the soil temperature at different times in the different soils. We will also compare it to the temperature on the green roof surface as a control. Luckily, we have little ibuttons, or thermotrons as Sarah and I have named them, to help us out. 

I have been performing small experiments on all of our ibuttons in order to verify that they take the exact same temperature reading while in the same environment. In order to set the experiment up, the ibuttons must be set on a mission (Sarah and I didn't make up that term, I know shocking). However, you cannot set a start time for all the ibuttons (we really wish we could). We want to start all the ibuttons at the exact same time so time is not a variable when analyzing the results. In order to do this, you have to set a mission time delay...This means that if you have 26 ibuttons it will take 26 minutes to set them up. The first ibutton mission time delay should be set at 26 minutes, the second at 25, the third at 24, etc. so all the ibuttons will start their mission at the same time. 

The next step in the small experiment I did was to place all the ibuttons in different environments, such as at room temperature, in the fridge, in the freezer, and on top of the green roof. Then, I analyzed the data. If all of the ibuttons took temperature readings at exactly the same time, then they should all have the exact same temperature readings in the different environments. 

The results were great. I calculated the averages and standard deviations for each of the ibutton's temperature readings at the different times. The standard deviations were for the most part below 1, with only a few above 1. 

This gave us enough confidence that our trusty ibuttons were able to do their job correctly. So, this morning Sarah and I set all the ibuttons to start their mission at 5:00 PM today. This gave us enough time to bury all the ibuttons about halfway down in the soil in the middle of the selected trays (the trays were selected randomly).

Here are the trusty ibuttons ready to start their mission! 

26 ibuttons in plastic bags

An ibutton ready to be buried alive!

The ibuttons were placed in a plastic bag because unfortunately they are not water proof. While the plastic bag may affect the temperature reading slightly, all of the ibuttons are in a plastic bag, so all the temperature readings will be affected in the exact same way. The small piece of paper labeled each ibutton's location and ID. The ibuttons are able to store 2,048 temperature readings. We set the ibuttons to take a temperature reading every hour. That means we will be able to leave the ibuttons out on the roof until late September when we will have to take them back inside to retrieve data and restart their missions . 

Me planting the ibuttons

An ibutton being buried in a control tray

A control ibutton taped to the green roof