HP 48SX vs 28S


Hello, I own both a 48SX and a 28S, but am thinking of selling one. Which one should I keep. Both seem to have their advantages. I like the large key set of the 28S - saves having to enter alpha mode everytime I just want to save a number. Also, I noticed the 28S has a "trace" option in printing that appears to be missing on the 48SX. (anyone know how to "trace" print on the 48SX?) However, the clamshell is clumsy for single hand holding of the calculator. One big disadvantage of the 48SX for me is the manual. The manual for the 28S is much better for the novice. I mostly use the calculators for numerical calculations where I need quick access to variables to save numbers. I am a chemist and am not doing calculus on the calculator or other types of higher order math. Any advice??


Keith --

Overall, the HP-48SX is more capable. The three things I like about the HP-28C/S are:

  1. The dedicated ALPHA keys (as you mentioned)
  2. The UNITS library with SI definitions
  3. The CONVERT function, which is nice for converting compound units (especially British-SI)

The HP-48SX allows compound units to be attached to values, so the conversions might be possible, but they aren't as intuitive to me.

-- KS


Why sell either?
Both calcs go for some of the lowest prices (compared to other HP calcs) on "that auction site"

Keep both and then you have two toys to play with.



I would tend to agree to keep both. But then I generally have one sitting there unused. I also have a 15C, 32sII, and 97 in addition to the 28S and 48SX. I can only use so many calculators at one time! :) One maddening thing about all of these is that each one has mathematical functions in different places. That is one advantage of the 48SX over the 28S, there are more mathematical functions right on the keys. With the 28S they are all at least a shift key away, and many are on the soft keys under a menu. Convenient when you have the menu up, but inconvenient when you don't. I'm leaning toward keeping the 28S and either selling or "decommissioning" (taking out the batteries) the 48SX. My only hesitation is maybe I am missing some big advantage to the 48SX that I haven't thought of?

On another note, how hard to find is the TVM card for the 48SX?


My opinion is that you should not sell neither even you don't use them. How many HP calcs just sitting unused? I bet many. But if you decide to sell the 28S cheap, let me know.


I would like to mention the really nifty Chemistry ROM Card (by The Pocket Professional) for the HP 48SX.

It has loads of chemistry related equations that can be used in a "What if?" fashion. Not to mention the requisite periodic table, library of constants, etc.

I bought one for my HP 48SX and use it in my HP 48GX. However, I do not know if a 48 GX card will work in a 48 SX machine. IIRC The GX cards have one more contact than the SX cards.

Of course, this brings up the serial interface, which allows programs downloaded from the Internet to be loaded into a 48SX/GX.


Thanks for the input. I do have the chemistry card for the 48SX, but have not found it overly useful, only because it is faster for me to just do the calculations myself on the calculator rather than plug them into variables and have the program solve them. Maybe I should give it a second try though. I know I did not explore all the features.

I have read about the serial interface, but have not tried that. Is there a good source for the cable? Does the interface work on PC only or also Mac?




Reading your post, I now remember that the HP 48SX was a tad slow at solving those equations. The HP 48GX is a faster machine, with its Saturn processor over-clocked by design by HP. Using the equation writer "feels" much better on the GX for the same reason.

The serial interface kit for the HP 48SX/GX might be a special order item at HP. Googling for it, I found the follwing Web page (HP Graphing Calculators - Accessories):

<a href = "http://h10025.www1.hp.com/ewfrf/wc/document?dlc=en&lc=en&cc=us&docname=bpia5177"></a>

Serial interface kit

The serial interface kit links HP 48g and HP 49g series calculators
with Windows compatible PCs. The kit includes:

5-meter serial cable, 10-pin to 4-pin connector

CD-ROM with PC software (Windows 95, 98, and NT 4.0)

User's Guide (F1897A)

Serial interface cable

The serial interface cable links HP 48g and HP 49g series calculators with IBM compatible PCs.

{above text copied from the URL shown above}


HP Calc dot org's "HP 48 Chemistry Programs" page is here:

<a href = "http://www.hpcalc.org/hp48/science/chemistry/"></a>


I agree that you should keep both. However, if you feel you have to get rid of one of the machines, my preference would be for the less capable but more elegant machine, the 28S. I own a 28S since the first day it came out (which replaced my 28C only a year after I bought it), and find it to be a well-balanced machine. The 48, at least in my mind, has already crossed the line between a pocket calculator and a personal computing device, and as such is overkill in too many circumstances. Besides, the sheer size and number of keys (visible at once) gives it an intimidating aura. I never managed to become friends with the 48. And if you need something more objective: I find the keys and display of higher quality than the various 48 I have. One model, a late 48GX, even has a blueish LCD which looks really cheap. No, the 28S it is for me, gentlemen!



No, the 28S it is for me, gentlemen!

One hundred percent agreement in all points! The 28 has a real "HP"-keyboard, it has dedicated alpha-keys and a decent display. The 48 has the lowest contrast, hardest to read display of all HP calculators I have seen so far. And then, there is no fumbling around with zipped pouches, you just close it like a book and it is very well protected. I wonder, why they did not continue this series?

Greetings, Max


The 48 has the lowest contrast, hardest to read display of all HP calculators I have seen so far.

Then you have probably not seen an HP-42S display. The low contrast display was the only thing I disliked about my 42S.



I used my 28s for about 16 years. It took me through college and was of great use. Even later during my professional career as mechanical engineer it served me well. I agree about the great LCD contrast. And the tactile feel of the keys is fantastic. The downs were that to many important math functions are burried deep inside different menues and the form factor. It took to much space on the desk and I did not like to use it folded. Once I managed to loose a hole bunch of my own programs when swaping batteries. Only because the third battery got stucked in the case and won´t come out. The battery door became somewhat brittle over time.


The 28S is an interesting beast indeed, one of my favourites from a product design point of view.
I've always found it weird how the 28S is worth the least of almost any vintage HP calc on the used market. Anyone want to ponder a guess as to why that is?
At one stage they were almost worthless, you could barely give one away, but it seems to have picked up a bit in recent years.



Anyone want to ponder a guess as to why that is?

All of the clamshell models suffer from the worst designed battery door in HP history (right down there with the SPICE series). I once had a 19bii that would launch the door when the calculator was opened. It was funny once or twice, and was then sold. I think another reason for their lack of popularity is also the short time they were in production. Both the 28c, and later the 28s were the top of the line 4th gen. calculator for only 2 years each before being replaced by a faster, and more feature-rich HP48. I have one of all of them, but seldom use the HP28.


I want to clear up any confusion about the HP 48GX's Saturn processor running beyond design specs.

The HP 48G/GX's fourth-generation CPU chip

"... has four advantages over the third-generation chip used in the HP 48S/SX. First, it is produced using a different CMOS process, allowing better stability with onboard voltage regulation circuitry. Second, these improved voltage characteristics and several low-level optimizations allow the new CPU to operate at twice the speed of its predecessor. ..."

Quoted from "An Advanced Scientific Graphing Calculator" by Diana K. Byrne, Charles M. Patton, David Arnett, Ted W. Beers, and Paul J. McClellan in the August 1994 issue of the Hewlett-Packard Journal, pages 6 through 22.


As you wrote, both the 28S and 48SX have their advantages. If you really
decide to sell one of them, I'd suggest keeping whichever one you happen to

For me, the biggest disadvantage to the 28S is the inability to input anything
except by keying it in. With the availability of the 48 and 49 series, I
consider the 28S to be unsuitable for storing lengthy programs, or, for that
matter, a large number of short programs.

The 48 and 49 series don't include any built-in print trace mode, but by using
the vectored ENTER capabilities, you can implement (among other things) your
own highly customized print trace mode. See
for more information.


Edited: 11 Dec 2007, 4:05 p.m. after one or more responses were posted


I agree with most of what has been posted. The biggest disadvantages to actually using the 28 are twofold: clamshell design which can only practically be used as a desktop calculator. It's very clumsy to use in your hand, especially if you need menus or the alpha keyboard on the left side. Second, as was mentioned, nearly all functions are under the shift key or menus, thus adding at least one or two (or more) keystrokes to get to the mathematical function you want.

I agree the screen on the 28 has better contrast than the 48, BUT the viewing angle on the 28 is worse than the 48. The different contrasts on the 28 seem to have different optimal viewing angles. When rotating the 28 (not side to side) up and down, the display goes from very clear to almost non-existent. Not sure what is happening with the LCD to make this happen. Whereas on the 48, I have not noticed a viewing angle problem, just a weak contrast from the "greenish-blue" screen.

Also, I agree about the battery door design being the poorest of any. Also, what is up with the "type N" batteries HP choose to use?

For now I am still exploring both calcs, but have turned more attention to the 48SX. I'm sure the 48G/GX are faster, but I wonder if they are as easy or more difficult to use. I probably would sell the 28S, but I learned more about how BOTH the 28S and 48SX work from the 28S manual than the 48SX manual. Since RPL was new with the 28S, I suspect HP took more care in introducing all features to the user than they did with the 48SX. Seems like they are assuming a lot of familiarity on the part of the user in the 48SX manual. Same was true with the 48G+ that I once had and soon sold. Couldn't figure out how to really use the calculator features from the poorly written (and small - only one volume) manual. Gone are the days when HP wanted users to know everything about their products!


In re the 48G+, to be fair, if one got hold of the 48 Series AUR, it made the machine much more transparent and powerful... and fun to use.

I've still got mine and use it and my only complaint is the same I have for any graphing calc- too big. Otherwise, with the AUR, you can with some pleasure figure out the calculator.

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