Thursday, December 22, 2005

An unexpected connection

I have a friend at work, an electrical engineer. I'll call him Bob. Actually, I always call him Bob, because that's his name. Anyway, Bob is a really nice guy who will answer my ignorant questions about electronics with a smile, a diagram, and a patient explanation of what I should do.

I had need to measure a temperature, and had a nice sensor picked out to do it. However, I needed to amplify the signal. No big deal, I thought. I know a little electronics, and routinely build things to measure stuff. But I hit a thorny (to me) problem: if I amplified the signal so that the variation in temperature would produce a useful voltage change, the value of the voltage would be close to the highest voltage my analog to digital converter could read. Hmm, I thought. Time to talk to Bob.

The solution he showed me was to use an op amp and input a small voltage that would be subtracted from the output value. The variation in output caused by temperature change would be easily resolved by the A to D, and I had plenty of room for the temperature to swing up or down.

The solution is probably very obvious to an EE. I, however, am not an EE, but a chemist with enough electronic knowledge to do some things. Bob showed me how to solve my problem using the graphical shorthand common to electrical engineers, drawing the parts, and reasoning, aloud, in a logical but only vaguely mathematical way about what voltage would appear here or there, and he led me through the way the solution worked. I understand the shorthand well enough that his trick is now in my arsenal of cool electronic things I can do. I am sure he would have been happy to just draw me a circuit to solve my problem, but instead, he taught me how to solve an entire class of problems for myself.

Skipping to another conversation I was having with a technician in the lab: We needed to change a part of a molecule so that it would be more soluble in a particular solvent. To anyone who cares, we were going to perform a transesterification. I drew the molecule on a white board, using the graphical shorthand common to chemists, and led my friend through how the parts of the reactants formed and broke bonds, and how we got the product we wanted, in a logical yet only vaguely mathematical way. The principle thus illustrated, the technician has a new reaction in her arsenal of cool tricks to make new molecules. I could have just told her what to mix together, but now she knows a new synthetic technique in chemistry.

In both cases, Bob and I could break down the problem using a simplified diagram of the problem, one that hides all but the most essential features. In no way do they reflect the underlying reasons why the systems act the way they do. Yet it is possible to follow the rules for manipulating the diagrams, tempered by a few chemical or electrical engineering principles (very simple principles, in both cases) and come to useful solutions to problems.

The graphics and rules for their manipulation hide all the details. There is no indication of the physics or chemistry underneath. But the explanations are good enough so that someone skilled in their interpretation can do something useful based on them.

It hadn't occurred to me that the same general approach works for chemistry and electronics, though I work with both quite a bit.


At Thursday, August 10, 2006, Blogger John said...

Hmmm, unexpected perhaps in some fields, but not unknown in physics. You might be aware that all (well not ALL) of quantum electrodynamics (QED) is describable in terms of (Richard) Feynman's Diagrams. Certain symbols represent electrons, photons, vertices as interactions and others. You can construct, with some knowledge of the symbols meaning, the integrals and equations for those interactions.


At Thursday, August 10, 2006, Blogger John said...

Oops, forgot an earlier example in physics, the Dirac bra-ket notation for quantum mechanics itself. Replaced all of those nasty Schroedinger PDEs and Heisenberg's continuous uncountably infinite element matrices. Again, useful information and intuitive conclusions based on compact symbology.


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