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Seeking: SI derived units with higher base powers.

  1. Apr 25, 2013 #1
    Hey guys,

    I'm currently working on a chemistry setup and we're building some protocols. We decided that every communication on the protocol between two devices will be in SI units. However, for a data descriptor I plan to use 4 bits per standard SI unit. This means that units for variables can go from -8 to 7.

    Now, I'm wondering if there is any measurable SI derived unit which has a higher power than 7 or lower than -8?. I can only get to -3 or +4, but that's it. Anyone suggestions?

    For instance, if you have pressure in hPa, this is kg * s^-2 * m^-1, the lowest is -2, highest is 1. Farad is kg^-1 m^-1 A^2 S^4, highest 4.
    Last edited: Apr 25, 2013
  2. jcsd
  3. Apr 25, 2013 #2

    I like Serena

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    Welcome to PF, Knaapje! :smile:

    My recommendation: don't use just 4 bits!
    It's just not worth all the problems you'll get.
  4. Apr 25, 2013 #3
    In total I'll be using 7 * 4 = 28, or 32 bits because alignment. I'm just curious if there is anything which we can actually measure has more than 7 or less than -8 powers.. Went through Wikipedia as well and just get stuck on 4. Also, it has to be as little as possible to keep everything at reasonable speed. Sending a message that's twice as long just to be sure seems a bit silly.
  5. Apr 25, 2013 #4

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    As I said, it's likely not worth the trouble.
    Sending a message that is twice or 4 times as long will (almost) never be a problem.
    Handling problems because you have too little space to transfer what you want to transfer really is a problem.
  6. Apr 25, 2013 #5


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    Bits are cheap as chips, as they say. Neither processor power nor channel bandwidth are likely to be a serious problem for you unless you are communicating with a submarine of a deep space probe.
  7. Apr 25, 2013 #6


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    If you really want to save bandwidth, why not just use the ASCII text for the standard abbreviations of unit names?

    "F" for farad is only 8 bits, not 28 :smile:

    And when things go wrong, human-readable messages make debugging easierr.
  8. Apr 25, 2013 #7


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    Dude! This is the 21st century! Nobody quibbles over bits. That's what they did in like the stone age.
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