Hello again!  As I’m sure my legions of internet fans will know, this past week was my second in Columbia University’s plasma lab, where I am designing a phase shifting circuit for use on the CTX (Collisionless Terrella Experiment).  My main challenge this week was to decipher a paper written by three Iranian scientists on how to construct a frequency dependent resistor for use on my circuit.  Unless I can get a signal that does not change in amplitude as my output for all frequencies that the experiment deals in, this circuit isn’t going to work.  This leaves me with two options, one of which is to find an analogue solution, one that deals only with basic circuit elements, which I have failed to adequately produce this week.  The other solution, which I am now leaning more in favor of, is to incorporate digitizing elements into my circuit and program a microchip to do exactly what I want to do in terms of getting the proper resistance.  This sounded like a sort of deus ex machina when my professor suggested it as a last resort, but since I have not programmed a microchip in a very long time, I want as much time as possible to fiddle with my digital components so that I don’t have to scramble at the end of the summer to get the device working.

I referenced Goldilocks in the title of this post because that is exactly what this week felt as I sat in the lab modifying my frequency dependent resistor circuit by testing it with different values of various components, looking for the configuration that was just right.  This process of trial and error was frustrating at times because the circuit proposed by this paper is complicated enough that to analyze it mathematically would be a significant waste of time, but the authors insist that by following a very precise procedure I should get the effect that I need.  I’m trying not to get discouraged (it is only my second week) but the fact that the paper I’m working with hasn’t gotten me the result I needed is not a very productive feeling.  I’m giving myself a couple more days of the Goldilocks routine, but if a significant amount of progress hasn’t been made by that time, I’m going to have to start considering the digital solution a little more seriously.

I should give the authors of this paper I’m working with a little more credit.  The circuit does exhibit a resistance that decays with frequency.  The problem is it introduces a phase shift that also varies with frequency, which is the worst possible thing for the circuit that I’m trying to design.  It also says in the paper that the circuit should not exhibit a phase shift, so I’ve been taking their word for it and just assuming that if I try enough configurations of the circuit with different components I will eventually obtain the desired effect.  By the end of this week, I hope to either be significantly closer to achieving the goal of decreasing resistance without a variable phase shift or to have prepared myself to start tackling the digital solution to this problem.

That’s all for tonight.  Goodnight adoring internet fans!

 

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