HP 6S Solar - mini review


Just for grins, I ordered a new-in-blister-pack HP 6S Solar. I figured it would be fun to experiment with HP's cheapest calculator. From the Museum description, I expected a minimal-feature machine. I was surprised to find a calculator fully worth the USD $8 I paid (shipping included.)

Although algebraic, not RPN, this is a full-featured calculator that is more powerful than my favorite HP-45.

It offers the following advantages over the HP-45:

  • LCD display and solar power - always on, never needs recharging.
  • 42 keys instead of 35
  • slim size really does fit in a shirt pocket
  • animal-friendly non-leather protective case. (Well, it's a cheap brown plastic envelope made out of environmentally non-friendly oil, but let's be polite and say something nice about it.)
  • instruction manual in English and French.
  • 6 levels of "stack" using parentheses
  • Base 2, 8, 10, and 16 arithmetic with bit-logic operations
  • more trig functions
  • Fraction mode, allowing entry of numbers like "four and one-third" (4 1/3) Fraction calculations stay in fractions until mixed with decimal numbers, then get converted. E.g. 1/3 + 1/3 = 2/3, but 1/3 + 0.25 = 0.5833333333.
  • Fixed or Floating display
  • single-digit correction "backspace" key for editing entry

There are a few drawbacks:

  • No RPN. Whoops.
  • Inexpensive manufacture; probably will last 5 years, not 50.
  • Statistics are 1-dimensional, not 2-d
  • Only one memory location "M", plus a stack-constant
  • Manual is poor quality without the traditional intelligence and useful examples
  • Keyboard layout is non-intuitive. Example: the four (shifted) functions for display modes (Fix, Flo, Sci, Eng) are not on adjacent keys. And the "shift" key is labeled "INV".

I have not had a chance to check accuracy. The manual claims internal 11-digit arithmetic, displayed as 10 digits. Mantissas go up to E+99. There are no thousands-group display symbols. The decimal point is easy to read. Mantissas are in a smaller font, so are clearly distinguished from the Radix. Like some non-HP calculators, fractions are shown with a very strange notation (because the display digits are 7-segment.) Keyboard feel is acceptable, at least for its price. Keys are rubbery, but make a positive click as they engage; I have not found any missed or doubled keystrokes.

Performance is lackluster. 2^5 = 32 takes about 2 seconds. There is no "OFF" key, common on solar calculators. I prefer solars that do have an off key; that allows the internal capacitor to charge up a bit, rather than running low. The calculator works OK in a darkened room with a single 60 watt lamp, but display contrast isn't great. In a sunlit room, display contrast is just fine.

All in all, a cute, semi-useful calculator with an HP brand name on it.


I've pointed out before that the 6S Solar is a superb field calculator.

The 6S Solar is small, thin, and light, and fits easily in a folding clipboard. It's already on whenever you open the clipboard. The display is legible in any kind of light, from flashlight to direct sun. And it apparently never, ever, ever runs out of power.

People in this forum rave about the shirt-pocket size and long battery life of Voyagers. Yet a 6S Solar is clearly far superior in both of these respects.

Does the 6S Solar have drawbacks? Most certainly. There is no RPN or programmability. The keys rock -- but not in a good way. It is clumsy with sexagesimal math, and so it is not handy for timed tests or surveyed angles. And sadly, it is no longer readily available or cheap.

For comparison, I recently got a Casio FX-260 for field use. The Casio offers some advantages. It has a better keyboard (still not great, but better). It offers real sexagesimal math. And it is still cheap and readily available.

But the Casio still does not match the 6S Solar in other respects. Most importantly, it has no battery backup. This means that it is awkward or impossible to use in dim light. It also means that the contents of the display and memory are lost whenever you close the clipboard.

Furthermore, the Casio is a tasteful brown color, which makes it easier to lose if you set it down on the ground. It is much less conspicuous than the 6S Solar, which has a flashy metallic faceplate. I suspect that the 6S Solar can generate enough bling-bling to serve as an signalling mirror on a bright day, but I have not actually tried it.

Bottom line: the Casio FX-260 is OK, but the 6S Solar is still my #1 choice as the best scientific calc for outdoor use on foot. You can easily carry it anywhere, and you'll never have to worry about bringing extra batteries.

Edited: 22 Aug 2005, 6:22 p.m.


The 6S is rugged and reliable, it's my main machine at work.

However, I have a complaint that might seem silly : the [AC] key reverts to degree mode ! Aaaargh !!!! Every time I press that one key I curse HP for this misfeature.

Another minor point : press 0 . 1 2 3 4 5 6 7 8 9
Now press 1 - it is ignored. The machine always displays the leading zero, which is useful to no one (I agree however that no one needs 10 digits of precision in real life).


GE's post, modified by me to omit the leading "0":

press . 1 2 3 4 5 6 7 8 9 Now press 1 - it is ignored. The machine always displays the leading zero, which is useful to no one...

The HP-41 does not automatically display the leading zero as a sub-unity number is entered without it, but will display it when the number is fully "committed" by ENTER or an operation. Thus, it will allow entry of a tenth digit (1 in your example), but not any more, as it has a 10-digit display.

The Voyagers are the only "high-quality" HP calc's with a 10-digit display (10C/11C/12C/15C/16C) that came along afterward. They will automatically display the leading zero as the number is entered without it, then refuse to accept a tenth digit.

I disagree with you -- leading zeroes are useful in that they clearly indicate that there is a radix to the far left of the number, which might otherwise be overlooked. Since the US uses a period for the radix, this is important for prevention of errors.

That's why the numbers are properly written "$0.26", not "$.26".

-- KS

Edited: 24 Aug 2005, 12:47 a.m.


You're right, there should be no leading zero in my example.
Actually, the 41 may accept a tenth digit, but the point was that the 6S does not.

I like this little beast, as a "lost-able" or "stolen-able" machine.

By the way, I found another 'bug' in the forum software : when using the buttons below the text area to compose a message, it inserts the marker at the end of the current text, no matter where the insertion point is at the time.

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