Comparing button pressure between various HP calculators & DM15L

[Antonius]

The required pressure it takes to operate a calculator is very personal. It is hard to quantify the feel between the various models, but I thought I would use a very rudimentary method (very unscientific though) to compare some models I have in my possession. it is a very repeatable method in which other users can also post their results.

METHOD: Take a simple dial scale (not digital, I tried but the numbers change too fast), place the calculator center on the base, and zero the weight. Then I placed a flat-tipped pen on the center key and very slowly pressed down till the button clicked or I heard a sound from the calculator. That weight is recorded.

HP Prime: 100g
HP50G: 175-190g
HP35s: 175-185g
HP12C (1988): 175-185g
*DM15L: 300-350g (Enter key 200g) (Brand new, 1 day old)
HP10B+II: 175-200g

I hope this helps new users to compare and get insight into the differences. Note, it is not scientific, and I don’t have a penetrometer so I can do more accurate measurements on each key.
I think the big takeaway is the pressure required to press the DM15L.

[Dave Britten]

I've taken a very similar approach using my wife's digital-scale measuring cup with a calculator laying over the top. That one has reasonably fast updates to the read-out, but not so fast that I couldn't read the numbers.

And I've observed results similar to yours: SM calcs tend to require quite a bit more force than HPs, and the force from key to key is much less consistent.

[EdS2]

I think I vaguely recall that Swiss Micros' keyboards will wear-in during initial use, in which case a brand-new item might need a higher force than a well-used one. Does that ring a bell with anyone?

[Dave Britten]

(10-19-2022 07:36 AM)EdS2 Wrote:  I think I vaguely recall that Swiss Micros' keyboards will wear-in during initial use, in which case a brand-new item might need a higher force than a well-used one. Does that ring a bell with anyone?

I suspect that it's a combination of wishful thinking and acclimation. I haven't noticed any significant changes in mine that I've owned (and used) for a few years. You can open up the calculator and slightly over-flex the keys a bit to loosen up the springs/legs, but I don't really recommend doing this, as I've had a number of the plastic legs in my DM42 break even without it. I've had to epoxy at least 3 or 4 broken legs in mine. Not too difficult if only one leg on a key is broken, but if both break, good luck getting the key glued in the proper position...