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Bye-bye Sharp EL-556D & Hello Casio FX-991ES

June 11, 2009

Finally decided to replace the Sharp EL-556D, my scientific calculator since 1991.

A friend — though we are no longer in contact — bought it for me. It’s a very basic one but very handy for me. It has 30 physical constants, which had saved me lots of time during my study in Physics. I also wrote down the definitions of some constants on a piece of paper to remind myself.

I changed the batteries once in my PhD study and twice after graduation. Due to the battery leakage, the calculator did not work well in the last few years, and I also didn’t use it as often when I was a student.

I still need the calculator for my work. That’s why I installed SpeedCrunch in my PC. Recently it stopped working again and I didn’t want to just replace the batteries because there’s some stain left by the battery leakage.

It’s time to get a new one. My need is very simple — it must have physical constants. Two models from Casio offer that: FX-570ES and FX-991ES. They are almost the same except the power part. FX-570ES uses one AAA battery and FX-991ES uses a LR44 & solar cell (therefore it’s slightly lighter). (Not that I don’t want a Sharp, but it’s because I couldn’t get it by ordering online.)

I chose FX-991 because it’s slightly cheaper. The box is pretty thick because of the user guides in 8 languages.

It offers 40 physical constants, 10 more than Sharp EL-556D’s. Especially it provides Planck constant (h) as well as reduced Planck constant, (ħ), which is often called “h-bar”. This will be quite handy for me, though I have memorized them by heart. 😉

If you think, “Wow, that Sharp EL-556D is an antique”, well, you haven’t seen the one my adviser use (and are still using it). My adviser has a calculator from HP 10C series introduced in 1980s:

I am not sure what the exact model he has, but I recall that I was quite amazed to see it’s still working! That’s about in the year of 2000.

Note: In FX-991ES’s user guide, it suggests to replace the battery at least once every three years even if the calculator is operating normally. This can avoid the damages due to the leakage from a dead battery. Hmm.. if I did this my Sharp EL-556D would be still working well.

4 Comments leave one →
  1. Rich H permalink
    January 30, 2012 11:25 am

    Hi – no idea if a reply on a thread this old will be flagged up to you, but if you do read this, I wonder if you still have a copy of the manual for the 556D? I found mine after all these years – and it still works – but can only use the basics as I cannot remember the more esoteric key inputs.


    • January 30, 2012 5:40 pm

      Hello, I am not sure that I still have it. I haven’t seen this calculator after got another one.

  2. Rich H permalink
    February 2, 2012 10:37 am

    OK – thanks anyway! I found this:- which is almost the same.

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