Video: fx-115ES PLUS

Review: Eddie's Math and Calculator Blog

Casio is releasing the newer versions of the fx-115ES, the fx-115ES PLUS. Comparisons, product of f(x), distributions, and other new features are added.

Still waiting for a solar RPN calculator, HP.

Edited: 24 Apr 2012, 8:49 a.m.

Very complete review. Thanks.

A bit Off Topic:
I have the old model (115 es) and I like it, it has a lot of functions for its price. My rating is 4/5 stars. I cannot give it 5/5 due to the next drawbacks:

1) In MathIO entry mode, there is no keyboard buffering, so when entering a long formula, the calculator redraws after each key press, but as the formula becomes longer and slower redraw, it can miss keystrokes. So I always use it in LineIO mode.

2) There is no a piece of rubber on the back of the calculator to stop it from sliding all over the table.

And probably as consecuence of the second drawback, in my case, it does not rest on 4 points (just in 3 points) so while pushing buttons on the calculator makes the calculator go up and down making loud "clack-clack" noises which annoy me. I fixed this problem putting some rubber on the back.

Eddie, can you confirm if both problems happen in the new plus model?

I think the 115ES (original) is OK, but (seemingly) unlike a lot of people here, I prefer the Sharp 516 (and even the 506). I think the big difference to me is that the Sharps have more commands available on the keyboard, which makes it a faster general use calculator. If I have to go into menus, I might as well go all out and use the 50g.

One thing I'd like to see would be a solar powered programmable. It seems like it should be possible, even if it would have to throttle its processing speed while running.

The problem with solar powered devices is that it's harder to implement constant memory. This makes a programmable much less probable.

I see they finally added integer/fractional part. It would have been even better if they'd also added mod, but at least with I/F-P we can fake it.

I have to correct myself. They've added an integer portion function and a quotient/remainder division operator. The latter will display both the quotient and remainder, but if used in a chain calculation only the quotient is retained. I can't find a fractional portion function, other than calculating it as x-int(x).

At least unlike HPs its built-in integrator produces the correct result for frac(x) from 0 to 6.4 in about twenty seconds. With the upper limit at 6.3 it gives a close result in about two minutes. At 6.5 it times out.

I thought the fx-115ES PLUS had the fraction function too.

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The problem with solar powered devices is that it's harder to implement constant memory. This makes a programmable much less probable.

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Casio does have a solar programmable: fx-3650P. I ended up using the TAS because I don't believe Casio sells it in America.

The Program editing mode is kind of buired in the MODE menu.

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I think the 115ES (original) is OK, but (seemingly) unlike a lot of people here, I prefer the Sharp 516 (and even the 506). I think the big difference to me is that the Sharps have more commands available on the keyboard, which makes it a faster general use calculator. If I have to go into menus, I might as well go all out and use the 50g.

One thing I'd like to see would be a solar powered programmable. It seems like it should be possible, even if it would have to throttle its processing speed while running.

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What I like about the EL-516 (Sharp) is that you can store four formulas for future use. (F1, F2, F3, F4)

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Casio does have a solar programmable: fx-3650P.

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It's solar + battery, AFAIK. (I have one, too.) The battery protects memory content when the calculator is off, and kicks in when there's insufficient current from the solar panel for regular operation.

The self-test (now known as the DIAGNOSTIC) for the fx-115ES Plus (a.k.a. fx-991ES Plus C) is performed differently compared to the old non-Plus model. Below I've patterned a description of the new tests on that for the old model found in the article at a well-known calculator site:

    DIAGNOSTIC PERFORMANCE - Casio fx-115ES Plus and fx-991ES Plus C

The diagnostic for the fx-115ES Plus/fx-991ES Plus C is invoked by

holding the SHIFT and "7" keys, then pressing the ON key.  The

following is displayed for six seconds, after which the diagnostic

terminates without any other effects:

    DIAGNOSTIC

    Press AC

    (Do NOT press AC.  That would abort the diagnostic.)

WARNING:  Continuing below will result in the clearing of all data

          memory and mode settings.

Proceed with the diagnostic by pressing the "9" key before the 

6-second time-out is reached.  The diagnostic simultaneously

activates all LCD pixels and annunciatiors, and then waits.

Pressing the SHIFT key four times will cycle the display through

four additional test display patterns.  

A SHIFT key press continues the diagnostic with this firmware

version and checksum display:

    LY727X VerA  [then a 3-second delay before next line]

    SUM 11B4 OK  

    Pd- Read OK  [with a 3.5-second delay after "Pd-" before "Read OK"]

    Press AC

    (Values shown are for one particular unit.)

Press AC.  The contrast test screen is displayed:

    CONTRAST

    11h

    LIGHT       DARK

     [<]        [>]

Press cursor-left and cursor-right keys to change the contrast

setting value ("11h" in the above illustration) and the visible

contrast of the display.

Press AC to start the keyboard test.  "00" is displayed in the upper

left corner of the display to indicate start of the keyboard test.

The keyboard test requires individually pressing all keys, except

the ON key.  The order of the first 11 keys is a little unusual due

to the cursor keypad, after which the order follows left-to-right,

top-to-bottom order.  As each key is pressed in order, the number in

the display increments by one.  If a key is pressed out of order,

the number will not increment until the correct key in the sequence

is pressed.  After "=" (the last key of the keyboard test) is

pressed, the following exit menu is displayed:

    TEST OK

    Reset All

    Press AC

Press AC to complete and exit the diagnostic.

Pressing ON at any point during the diagnostic aborts the process

and returns normal calculator function.

This diagnostic appears to be more sophisticated than that of the older model. It appears that some type of checksum with other internal diagnostics are taking place.

I like the Plus version's expanded function set. However, mechanically the Plus is somewhat disappointing. There are a lot more curved and rounded surfaces along the edges and on every key. The hard cover creaks against the calculator body when the unit is picked up, indicating a flimsier or more ill-fitted design compared to the old model. The label for the constant and conversion factor table is applied canted slightly on the inside of the hard cover. More serious is the shape of the individual keys. The side and bottom edges are all curved...only the top edge is straight. This allows a key to cant slightly clockwise or counter-clockwise though the panel key hole and cause a ragged uneven presentation. The keys of the older model have straight top and bottom edges to promote the key settling in its panel hole perfectly upright and level with the other keys in that row. The frequently-used shifted functions at the top-left of most keys have been imprinted using an odd yellowish-orange paint that under some lighting conditions is very hard to see. Casio should not have allowed these "style" changes. They detract from one of the finest scientific calculators for its price available anywhere ($17.99 US at Target stores and other locations).

I wish that complete calculator state was preserved upon automatic or manual shutdown, but all levels of previous calculation history and results display are lost just like on the old model. Automatic shutdown now occurs after 625 seconds, rather than the old model's 350 seconds.

My speed tests use a continuous-sum function that closely reproduces function execution performed by a 2500-iteration Savage benchmark. This indicates that the fx-115ES Plus is about 12 percent faster than the old fx-115ES:

       Model          Execution Time (seconds)

    fx-115ES Plus          1101

    fx-115ES               1233

    HP-15C                 5840

    HP 42S                  605

    HP 50G                   65

    HP 15C-LE                48

    HP 30b                    6

The fx-115ES Plus manual seems a little better than that of the older model because it is actually a booklet and not a large fold-out sheet. The Plus manual is available on the Casio website here.

Edited: 1 May 2012, 4:54 p.m.