DM15L RPN Scientific Calculator – HP-15C Inspired Upgrade with Programmable Functions, Complex Math, Matrix Support, and Stainless Steel Design

If you are a fan of HP RPN calculators, and cannot justify $500 for a 20-30 year old used calculator, SwissMicros has the calculator for you.If you don't know what RPN is, this is probably not for you.I have used HP calculators since the late 80's. My first was a 32S, but I was always envious of some of the higher models. I have toyed with 28's, 42's and 48's. I have always preferred RPN, but due to limitations of my job, RPN was not a viable option. Recently I changed companies, and we had 12C Platinum's readily available. Not really the perfect calculator for scientific purposes of a power plant, but it was the only RPN calculator that the company could purchase at the store. Wanting a bit more, but not willing to risk my 32S in a power plant, I wanted a bit more calculator, but was unwilling to spend several hundred for one.This was the perfect calculator for what I wanted. Much cheaper than a HP, much more powerful than a 12C Platinum that my company provides me.The keys are not the same as an original HP, and lack the beveled front edge that I have grown to love, but they click very similarly and I feel that I will get used to them quickly. Though I think I would still like to have that bevel. The screen font is made of pixels and not seven segment display, so while not the same as the original, this could be considered as an improvement.Pros-Same physical size, fits flawlessly in a premium HP Voyager leather case, all of your 15C programs run (faster), comes with leather(?) sleeve, much cheaper than a museum piece from HP. Reasonably fast shipping, 5 business days from Switzerland to my home in the US. Adds Real Time Clock features to the 15C. Runs 15C ROM in emulation.Rugged construction. Not the same as HP's Voyager series. The back is a metal tray much more rugged than an original Voyager. The front metal bezel around the screen is much thicker metal than an original Voyager. When you pick this up, you know it is not a flimsy plastic calculator.Cons-Flaw on LCD screen. I attached a picture. This did not affect the function of the calculator, but it did make it harder to read, making a 0 look like a Q. I went to SwissMicros web site and found an email address and emailed Michael directly. Within a day, I had a response that a screen would be shipped to me. A little over a week later, I had a replacement LCD and a simple 15 minute repair later the flaw was gone.Lack of manual. Not really the problem of SwissMicros, but a limitation of this unique situation. Swissmicros may be able to construct this recreation of the original, but they cannot provide HP's copyrighted material. A little digging on the web and I had a PDF of the original 15C manual.In box there was no manual on how to make adjustments to the emulator that runs the calculator ROM. The instructions you need are readily available on the manufacturers web site.Minor issues with broken links on the SwissMicros website. Links to updated ROMs don't work right, but viewing all files allowed me to get to the updated files I needed.

These days there is not much need for a calculator these days more powerful than this. For more sophisticated work I could fire up Mathematica or write in Fortran, or R. However, a scientific calculator from time to time is handy, and this one is a recreation of one of the very best, emulating the HP-15c using the original ROM code. There is no need to liberally use parentheses to get around wrong operator precedence (looking at you, Excel); because in RPN there are no parentheses.The firmware of the DM15L has a little more memory available for data and code than the HP-15c. Externally it is like the original except for a micro-USB port which could be used to update the firmware. It does not take power from that port. Battery access is different; and beware that a violent drop might knock the battery loose.Its keystrokes are little stiffer and a little shorter than on my HP48G, but distinctly positive, and much better than typical rubber dome keys of other brands. The keys are painted. Alas, the days of double-shot injection molded keys are long gone. It is too early for me to tell about battery life, although you can set the CPU speed at either 12 or 48 MHz which I imagine would not have the same battery lives. At 12 MHz it is still faster than the original. The backside, like original, has the “micro-manual”. The contrast of the printing could be improved.The nice thing about the clone is the HP-15c manuals apply, and are freely available. The Advanced Functions Handbook is an education in itself. Because it uses the original HP ROM code, the numerical methods used by the machine remain outstanding. There are no bugs that I can find; typing in examples from the manuals produces matching results in all cases I have tried.The handiest (for me) feature this calculator has is linear regression; so easy to use, so easy to undo mistakes, just right for making calibration curves for [in my case] chemical lab equipment. Need to solve a system of linear equations? No problem (if more than 3x3 typing is tedious enough to want to use something else). Numerical integration? Robust. Root solver? Robust. Complex numbers? Yes.In short, it does anything you’d need out of scientific calculator [not out of a computer] and does it well. It’s handy. If HP wanted to issue the HP-15c for the third time, they could do worse than to go to Swiss Micros to make a production run. 5 stars.

It replaced my old HP 15C calculator and it is a very capable scientific calculator as the original HP 15C is.However, perhaps I have received a used product, since the coloring of the key function letters are faint and hard to see in the low light. The old HP 15C had better colour contrast for the key function letters. Otherwise, if you are looking for a portable and useful scientific calculator with a long battery life, you may not find any better calculator (I wish the original HP 15C was continued to be produced, I really missed it).