Monday, December 7, 2009

Data Collection

When I first decided collecting data would help defend against scrutiny, I had no idea it would be so complicated.

The idea of what I now call thermal ballast isn't new but like so many good ideas, without science it's guess work. Common Americans are hesitant to spend money on guesses. I believe in sustainable and the need to revise our collective way of thinking/living, so bring in the science!

Brad Hankins aka dbBrad and Ben lay 3 more sensors in the top layer of sand. Two sets directly under these and one more set above in the slab. 12 total here in the heat sink.

I'd had enough of an electrical background to have an idea what a thermocouple was. So brilliant and simple, anyone could use it. Just get the right two materials, the right kind of wire, eliminate interference, static, signal drop and deterioration, do not have any solders in line and keep all your runs the same length was just some of the advice I found. Not so easy really.

Design Build means when you can't do it, you find someone who can. On a blind call from the phone book I was pleased to find Don Colvin of Mukilteo. He found some off the shelf sensors with stainless steel casings and was able to re-solder them maintaining direct burial specifications to better, tougher CAT V line, test and record an offset (a primitive accuracy improvement based on a constant temperature oil bath). This would have been a good time to calibrate the sensors too, but with a full crew and a big tractor on site, the sensors needed to go into the ground.

Interested in the notion of an Annualized solar storage system, Don Colvin even delivered the sensors.

The sensors have been buried for a while now and all that is left is to automate the process of collecting data and interpreting it. I'm surprised at how complicated it is everytime I go through the logistics. It seems overwhelming and when I put it down for a while, it seems so simple again.

As a result, to date, data has only been collected manually, a tedious process of hooking up a gizmo with a 10 microfarad resistor, a nine volt battery, 4 terminals and an ohm meter. Resistance may be futile (Borg) but its also equates to temperatures.

The trick is to automate the system to collect data on a specified frequency. Besides being more accurate (no human error) it also gives us the chance to take extra readings, throw away anomalies and average other readings and store this information. The computing power is minimal so I intend to use an old machine (windows NT). My energy conservation side doesn't want it to run all the time either.

Lab jacks are a component recommended by Don that will manage 8 senors each. More sensors means more lab jacks. We went with 24 sensors and will need three labJacs. We'll also use LabView to manage the labJacs.

Problem include: the old computer only has two usb ports, I'd like the machine to turn on and off but this requires another piece of software and a system more prone to failure, The new versions of LabView may not work with Windows NT, and we can take readings as often as we like. But as an example, 24 sensors, 24 hours a day, 365 days a year over say a reasonable 10 year study is 2,102,400 numbers to look at and cross reference.

At this point there is far more data than sense. We need a data/sense converter in the form of an algorithm, a way to process the data and hopefully represent it in a graphical manner relative to the sensors, insulation, weather, heated space, etc, to try and understand where the heat is moving and how much heat is making it into the dwelling during the heating season.

I suspect I may be looking at stacks of printouts looking for highs, lows and numbers that don't make sense. Maybe the great idea and data will spark interest from a clever graduate student with access to a big computer!

Photo compliments of Google Image Search

In the mean time, I can measure probes of curiosity when I want to with the gizmo. One thing this has let me see is that the sandy soil here changes temperature quickly, responding to the temperature of the sky and the rain that falls out of it. Cold rains can cool the soil instantly several feet down. It's not uncommon for a 44 degree F. value to be 5' underground. This summer, sand 4' down was at 65 degree's F.

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