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.