6 responses to “Sensitivity”

  1. Chris Gammell

    The best example I can come up with for EE stuff is for Error Budgets. If you reduce all elements in a circuit to sensitivities, you know which are the most critical (and subsequently which to spend the most money on buying a quality part).

    For example, the feedback resistor in an op amp might need to have a much higher quality resistor, simply because small variations in the value of the resistor (due to temperature, time drift or otherwise) will cause large shifts at the output. Contrast that with a pull up resistor on a data line (which prevents a data line from drifting when it’s not driven) can have a large variation in values. The only thing that varies is the amount of current it consumes. As long as it pulls the line up to 5V when not used, it’s working and has no effect on the circuit otherwise. Digital in general does not have to worry about these effects, but analog does every single day.

    1. Carmen

      Way to steal my example, I was going to say the same thing :-).

      Adding to your point though, IC designers have to worry about all sorts of sensitivities. Process gradients, temperature, supply voltage, and transistor size are all important things to consider when designing an IC. I know during one of my classes where I was designing an opamp I spent most of the time on the front end differential stage making sure the two input transistors were optimized. I also had to learn certain layout techniques like common centroid and the use of multi-finger transistors to minimize process gradient sensitivities. It was a frustrating balancing act but for the most part I enjoyed it and learned a lot.

  2. Moiety

    The main parametes of my studies are energy use (electricity, stream, natural gas) and cost (operating and capital). The base case is the existing processes. The new case is the new process. Typically the main parameters that affect performance are temperature and vacuum pressure. Models are developed from experiments that describe their effect on the process. Ultimately a lower vacuum and higher temperature will decrease capital cost but will increase operating cost. Easily MINO. There are alos other considerations from for a chemical engineer, a sensitivity analysis (whether it is on a single equipment or the whole process) is a comparison. It is an optimisation study.

  3. Jonathan McGehee

    In our work in forensic engineering and particularly in vehicular accident reconstruction, you have to assess the sensitivity of many of the parameters that have a measure of inherent uncertainty such as coefficient of friction, vehicular weights, angles of approach and departure, etc. And the sensitivity is different every time. It is a very interesting phenomenon.

    Thanks for the helpful article.

  4. Weekend Journal: When The Deadline Is "Right Now" | Engineer Blogs

    […] making the decision to go ahead with the change. Do you slow everything down so you have time to do sensitivity analysis on your design change? Do you test or retest changes to a product or process to ensure the problem […]

  5. Weekend Journal — CSI: Component Stupidity Investigator | Engineer Blogs

    […] done when the product was first made. Instead, a bad design may have been design without regard to the sensitivities of certain critical parameters. Then when a part shifts ever so slightly from a vendor (though it could still be well within […]