Tuesday, February 5, 2013

Don't turn that dial!

Okay, so this is a little late, but I want to talk about my physics lab from last Wednesday. I haven't had a lab course since I took Chemistry my junior year of high school, and that was eleven years ago. Working with a lab partner, writing down results, adjusting the apparatus -- these are things I (until recently) thought I was probably done with. Since I'm trying to become a scientist, however, I may have to get used to this routine.

Anyway, the lab was split into two parts. The first part had me and a partner measuring the spring constant of a spring by pulling a force gauge attached to said spring. After recording the force from the gauge and the distance we'd stretched the spring, we could find the slope of a Force vs. Distance graph, and that slope was the spring constant in newtons/meter -- the higher the value, the stronger the spring.

The exercise was decidedly unrelated to electricity and magnetism (unless you want to talk about the fact that chemical bonds are electric in nature). I think the point was just to acquaint us with doing a lab, which I suppose is necessary given that some of the students haven't taken a lab course in eleven years.

After that, however, the professor had each of us individually play with an analog oscilloscope. We weren't attempting to measure anything with the oscilloscope -- just push buttons and turn dials so that we could familiarize ourselves with its function.

For those unfamiliar with an oscilloscope (I had heard of but never seen one before last Wednesday), it's a device that measures an incoming electrical signal and displays a corresponding Volts vs. Seconds graph.

Here's a picture of the model we were using:

Manipulating and calibrating the o-scope (as the prof called it) is a somewhat tricky enterprise. The display is divided into a grid, and you can adjust the number of volts and seconds per length of grid. As you can see, however, there are a wide variety of other knobs and controls that are required to produce a clean image of the incoming signal. And throughout this whole process, I was wondering, is this really necessary?

I mean, perhaps I'm putting the cart before the horse, but this is 2013; shouldn't there be an iPhone app that can do this for me? (Yes.) In fact, isn't that exactly what any piece of audio equipment does when it translates electric signals into sound -- measure the frequency and amplitude of the wave?

Yeah, I'm in an introductory E&M course. Yeah, we're going over the basics. But is learning to fine-tune an o-scope like a WW2 radio operator really going to be useful in our later physics careers?

I can imagine two ways in which it might be. The first possibility is that while of course there will be software that can identify the sinusoidal wave (or whatever) of an electric signal when we're working scientists, someone has to write that software. In that case, having an intuitive feel for what we're attempting to measure might be useful.

The other possibility I can imagine is that a working scientist will have to play with significantly more complex pieces of machinery, and training on a somewhat antiquated oscilloscope is a necessary first step toward that goal. I mean, you can't start with the LHC, right?

I thought of both these counter-arguments to my original complaint, but I don't know how much stock I put in either of them. Unless I'm actually going to use an oscilloscope as a scientist, isn't there something that more closely resembles a piece of modern scientific equipment that we could be using?

According to wiki:
Oscilloscopes are used in the sciences, medicine, engineering, and telecommunications industry. General-purpose instruments are used for maintenance of electronic equipment and laboratory work. Special-purpose oscilloscopes may be used for such purposes as analyzing an automotive ignition system, or to display the waveform of the heartbeat as an electrocardiogram.
Ah, I did not know that EKGs were essentially specialized o-scopes. That's neat! But I'm a little hazy on what "maintenance of electronic equipment and laboratory work" means for general-purpose o-scopes. A little more reading tells me that they can be used to test the changing voltage of a device to make sure it's working within expected parameters. That's obviously useful, but again I feel as if this is something that could be done by a piece of software. Do we really need a human to turn a dial until the display stops spazzing, or can we just use a do...while loop?

Anywho, I think that's enough griping for now. Perhaps I should be a theorist.

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