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

Ok so some of you probably know a weirdo like me who collects calculators. I know I'm not normal, I long y calculators. I don't even really use them for work but I never got over how useful they were.Anyway growing up I used my Dad's HP 11C which my brother ultimately lost. So about a decade ago I went and bought my own used HP 15 C and one for Dad as it was superior to the 11C. I loved it. But the calculator was showing it's age.I used my Dad's 11 C in calculus in highschool and ultimately upgraded to a Ti 89, and an HP 48 G series.One thing I loved about the HPs was RPN. Anyway I deployed to Iraq and while overseas I missed the opportunity to buy the HP 15 C limited edition. These days you can buy them but because of how few are out there you need to purchase a second hand item at prices upward of $1000.When I discovered the Swiss Micro DM 15L I couldn't pass it up. It arrived in a timely manner, especially considering it shipped from Europe. But more importantly this machine rocks.I don't have a 15C limited to test it against, but it certainly is faster than my older model. This calculator uses the exact same voyager layout as the 15C, the feet are sturdier, has a USB port, uses RPN, and is without a doubt my new favorite calculator.If you know someone who collects calculators this is definitely one to give them. I absolutely love everything about it. The keys, the machine work that went into the casing. This calculator is great.

Excellent re-make of the HP workhorse!I have been searching for years for an HP-15c calculator. All I could ever find for decent prices were used HP-11s units, which, while nice, are financial in nature and not really useful for my own engineering work. I love the landscape layout and RPN entry system. Once you learn and become used to this layout and entry method, "regular" calculators seem painfully clunky.SwissMicros makes these "clones", using the original HP microcode. This means they give the same results, and have generally the same 'quirks' that the original HP models exhibited. But with larger memory storage, 4x the speed, sturdy metal cases and wonderful clicky keys.They're firmware upgradable, include a real-time clock, user selectable operating speed (12Mhz or 48Mhz), three display fonts for your viewing pleasure and long battery life off a single CR2032 coin cell. Perhaps not the decades we got from the LR44/357's in the original HP models, but certainly many months or years depending on your usage patterns. Easy to replace when needed with four screws.Nice heft to the unit, feels very nice in your hands. The keys are clicky, giving very good tactile feedback on button presses, with a solid feel to the whole thing overall.Am I pleased with my purchase? YES, very pleased.Would I purchase again? OH YES! I actually have this unit on my desk, and a smaller version (the DM-15 credit-card sized) in my purse. Don't leave home without one!

I like everything about this calculator except for the feel of the keys. I've been using the original HP15C since 1985 and also bought the limited edition version. I wanted another one to keep at work so I bought this one. The keys on the HP version have a great feel and doesn't need much press force. This calculator needs more force to push the keys which gives it a clunky feel and it takes some time getting use to. Also I found that if you press the keys too fast, the numbers won't register which leads to mistakes in my calculations. I have to slow down and recheck everything I do. I'm at least glad that somebody reproduced this model.

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.