Tear Down: Scientific calculator boils design down to two ICs

February 01, 2008

rich.nass-February 01, 2008

While it's too big to fit in your pocket, the 35s follows in the tradition of a long series of handheld calculators.

Every once in a while, I come across a product where I say, I've got to take that apart. It's not the most scientific way of choosing products to feature in our popular Tear Down section, but it works for me. The subject if this month's Tear Down was actually sitting on another editor's desk, in his own Tear Down queue. Because of my "history" with this product, I quickly volunteered to write this story.

While not the sexiest consumer product out there, our engineering audience will likely see the appeal that HP's latest scientific calculator had for me. The 35s, which this new model is dubbed, is similar in many ways to the 15c I bought twenty-some-odd years ago when I entered engineering school (note that I paid about $125 for my 15c, while the 35s costs about $60). There's no doubt that the 15c was the premier calculator of its time. Just about everybody in engineering school seemed to have one. The 35s, shown in Figure 1, is the latest in a long line of scientific calculators from HP.

The 35s arrived in time for the 35th anniversary of HP's first scientific calculator. Hence, the "35" moniker.

I bet many of you are smiling to yourselves saying the same thing, "yeah, I bought one of those, too." But the kicker for me, and I'd bet for many of you, is that my 15c is still going strong. In fact, it still serves as my everyday calculator. And it doesn't get lost like many of the other objects on my desk, such as the tape dispenser, stapler, and scissors, thanks to its use of reverse Polish notation (RPN). My family members take the attitude that it's easier to find another calculator than to learn RPN. And that suits me just fine. The 35s can be used in either RPN or algebraic mode, although it defaults to RPN when you first turn it on.

Another reason I wanted to take the 35s apart was to see how the design had evolved over the years. While I wasn't willing to destroy my 15c for the sake of this article, I did get some good insight from Sam Kim, the director of product development for HP's calculator group. He claimed to be the force behind the 35s and went into the design thinking that he wasn't satisfied with the company's current line of calculators. Kim said, "I really wanted to design something for the old-time calculator user while also attracting new customers."

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