Still Chugging Along

August 18th, 2010

Its been a few weeks since the last post! I've had a little time off: went on a long weekend backpacking trip with my girlfriend, and then last week was out sick for a couple days. With time to make that up, I'll be still around here for another 2 and a half weeks! Which is a relief, because there's still plenty to keep me busy. I've spent the last couple weeks in the following ways:

-- Working on my coil and circuitry. The frequency at which the current in my coil oscillates is controlled by an IC chip that's basically a glorified RC circuit. It actually has a resistor and capacitor on the front end. I wanted to be able to step through several different frequencies, and I'm doing that by changing the R value. (For those who know/care about electronics, I'm doing this with my own 'digital potentiometer': a 555 timer sends pulses to a counter, the value of the counter goes to a demultiplexer that adds resistors to the line as the count goes up.)

-- First full field testing of my equipment!! Went out to the field, set my coil on the ground above one of the sensors, and flipped it on. This was a 'practice run' so to speak. We wanted to determine the working frequency range, play with different variables such as the orientation, distance away, to include mag-foil shielding or not, etc.

-- With data I created on the records, I got to start playing with Fourier Transforms. I wrote up matlab script to show a whole block of data, and then "pick" the time ranges of interest, fourier transform it, plot it, save it, and move on. I put pick in quotes, because I got the idea and code from Alistair Harding's (Scripps prof.) codes to pick seismic arrival times.

Now, I have some things to tune up, ideas where I can make things more convenient. I hope to get out to all three of the Bay Area sites next week and throw my coil at each of the three component sensors. Finally, I'll have the data that I can bring together. I just have to hope it works out and was worth the effort!