Touchscreen sensitivity parameters

9 Oct 2008 - 8:40am
5 years ago
4 replies
3634 reads
Mabel Ney
2008

We are looking to define usability guidelines for touchscreens.

Can anyone point me to some documentation, research or guidelines
regarding the ideal parameters for touch activation force / sensitivity
/ pressure?

Mabel Ney

Principal Interaction Designer

IDEXX Architecture Team

One IDEXX Drive

Westbrook, Maine 04092

207-556-6891

Comments

9 Oct 2008 - 11:57am
Dan Saffer
2003

On Oct 9, 2008, at 6:40 AM, Ney, Mabel wrote:

> Can anyone point me to some documentation, research or guidelines
> regarding the ideal parameters for touch activation force /
> sensitivity
> / pressure?

So there are two types of "sensitivity" per se. One is involves
latency and the other involves duration.

Latency is the delay (usually measured in milliseconds) between the
moment an action is initiated and the moment the effect of that action
becomes detectable. Latency should usually be as low as possible; high
latency means a noticeable pause or stammer in the activity,
especially with any animation or movement. In the world of interactive
gestures, latency usually refers to the gap between manipulating an
object and seeing it respond, especially in systems that use
projectors. There will always be some latency between the source image
(on the computer) and the displayed image (on a projector/screen), but
a latency under 20ms is ideal, as the system will seem very responsive
to user input.

The other kind of sensitivity involves duration: How much time is
required with a finger touch before the system registers a touch event
and executes an action? This can vary by audience and by the type of
touchscreen it is (capacitive, acoustic surface, infrared, and
resistive). For a public kiosk, you may want very deliberate, long
taps (50ms+), but in general a 20ms+ touch is going to be fine. For
personal devices you may want to allow users to adjust the sensitivity
themselves.

You might want to throw out anything under 20ms to account for
accidental touches or brushes with a finger (or in some cases, a
sleeve).

It's also good practice to have the trigger for actions be onRelease
instead of onPress. Gives the user time when their finger is on a
button to move it off (and thus not trigger the onRelease) for self-
correction of errors.

Dan

Dan Saffer
Principal, Kicker Studio
http://www.kickerstudio.com
http://www.odannyboy.com

9 Oct 2008 - 12:28pm
Mabel Ney
2008

Thanks Dan. This is great. Another consideration is pressure to
indicate a touch. That will also get into durability of the screen
mechanics. An ELO document for their Accutouch mentions: the
activating force is typically less than 4 ounces (113 grams). Have
you see anyting in this regard?

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Posted from the new ixda.org
http://www.ixda.org/discuss?post=34093

9 Oct 2008 - 1:19pm
Dan Saffer
2003

On Oct 9, 2008, at 10:28 AM, Mabel Ney wrote:

> Thanks Dan. This is great. Another consideration is pressure to
> indicate a touch. That will also get into durability of the screen
> mechanics. An ELO document for their Accutouch mentions: the
> activating force is typically less than 4 ounces (113 grams). Have
> you see anyting in this regard?

I'm assuming this is just for resistive touchscreens. I don't think
any other kind requires "pressure" per se. (Some capacitive systems
don't even require actual touching, nor do some projector based
infrared.) This force may vary by manufacturer/model.

Not sure what the average weight of the human adult finger is, but ELO
has been making touchscreens since the 1970s, so they probably know
what they are talking about.

Dan

Dan Saffer
Principal, Kicker Studio
http://www.kickerstudio.com
http://www.odannyboy.com

9 Oct 2008 - 2:07pm
Terry Fitzgerald
2008

some more stuff about touchscreen sensitivity
http://code.google.com/p/iphone-haptics/

Terry F

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