Posts

When evaluating a touch screen for a hardened handheld product (the system must survive a 3-5 foot drop onto cement, and cleaning with alcohol and water), how does resistive multi-touch compare with projected capacitive, particularly for gloved hand (1-2 layers of latex or nitrile), multi-touch and gesturing GUI’s?

Scott, you get one question and one bonus question all rolled into one Touch Guy answer.

With more than 50,000 iPhone touch screens being replaced per month with cracks, broken touch screens have become a big business so we kinda like the breakage. But I guess a broken screen keeping you from your Facebook page is a lot different than not being able to reprogram a defibrillator! Before Touch Guy cuts to the answer, he TouchGuy_Basicwants to emphasize that good product design means the whole assembly – touch screen, LCD, and enclosure – need to be skillfully integrated to meet the breakage requirement. And that is a good segue into reminding you that Touch International provides bonding of the touch panel to the LCD with a shock absorbing optical gel that substantially reduces breakage in mission critical devices.

The simple answer to what technology is most breakage resistant is…..it’s a tie. This is because both products can be made using all plastic components. New top level hardcoats resist scratches  and claim to have a hardness of 6H (traditional plastic touch panels have a hardness of 3H or 4H), and they have always been resistant to most harsh chemicals…alcohol is wimpy
compared to the super-hot acids and lye that these things see in processing.

All things being equal, you would pick the all plastic projected capacitive over multi-touch resistive (MARS) for optical clarity and longevity; however, while projected capacitive will perform nicely with two layers of nitrile gloves, if a doctor, soldier, or pilot wants to occasionally want to use a scalpel, thick work gloves or a pencil, you better go with MARS because it will work with absolutely anything.

As a parting shot, Touch Guy wants to say that this is a very general answer, and knowing the application and its requirements might result in a solution that uses a specialty glass like safety or bullet proof glass that might be better than an all plastic solution.

Until next time, Touch Guy

My engineers claim gestures on multi-touch resistive do not work nearly as well as they do on projected capacitive (PCT) used in a variety of consumer devices, like the iPhone – why is this? Have there been any recent breakthroughs with resistive multi-touch? I would appreciate any new input on this subject.

Hi Alex:

When you are comparing iPhone/iPad projected capacitive (also called PCT or P-Cap) to any other (even identical) projected capacitive sensors, you may not find the performance to be as good as Apple ’s product.  How can this be?  It is because Apple has had a really big head-start (as in years).  You and yours are playing catch-up, and it will take a while for you to integrate the prior art (yes, Apple did not invent multi-touch) with the new, to achieve the same thing.

Here is a good example:  Using a multi-touch demo, you can use the pinch gesture to make the picture really small….so small, that you will not be able to “catch” the corners and expand it…it will stay really small untilTouchGuy_Basic you reset the program.  Apple has anticipated the picture getting too small, so their software will accept nearby fingers and “guess” that the user wants to expand that photo, and it will.  There is a lot of anticipation in the iXX software that makes it better than your stuff.  Touch Guy is a hardware person, so you can guess that he will point the blame finger at the software folks.

Now to your original question…  MARS is different only in the pressure required to enable the gestures.  Otherwise, the gestures should be the same and the performance the same as projected capacitive and better, of course, with input from pens and pencils.  Keyboard entry is noticeably better with sure-footed MARS than with projected capacitive, which seems to often “guess” wrong at which key you wanted (auto correct to the rescue).

For more info on multi-touch, check out Touch International’s Putting the ‘Touch’ in Multi-Touch White Paper.

Touch Guy

What’s the difference between resistive multi-touch and projected capacitive multi-touch and why would someone choose one over the other? – Mike Zimmerman, South Carolina

Dear Mike:

I am the long-time cheerleader for projected capacitive touch technology, so my answer may be biased, but here it is:

If you are a mechanic using a touch screen to fill out an overpriced car repair estimate, you should use resistive multi-touch touch screens (MARS); everyone else should use projected capacitive multi-touch technology (MulTI-Touch).

Touch Guy’s projected capacitive mantra is 1) it will never wear out, so it’s a better investment, 2) it has great optics and 3) it is multi-touch capable. The only downfall to projected capacitive technology is that it will not respond to every input device (i.e. pens, pencils, credit cards); only those that are conductive.

For all the mechanics out there, here is why you want to use Resistive multi-touch:

Let us assume that our mechanic, Mike, will use a torque wrench to reach over and activate the diagnostic machine’s touch screen – this requires a pressure sensing touch screen (aka resistive). Or when he fills out the repair estimate on an electronic recorder, he can use the nearby pen or pencil to input information. Mechanics will also like the palm rejection that MARS has. Palm rejection is achieved by ignoring touches in part of the screen and accepting them where the writing will occur (this is used in signature capture devices). Plus, when every nano-watt counts, resistive technology consumes less power than capacitive.

But using resistive multi-touch technology comes at a cost when comparing it to projected capacitive technology. MARS is really just a 4-wire resistive touch screen cut up into severalf small 4-wire touch screens, so it will wear out with use. And the optics are not as good as projected capacitive because it has the same reflections of a standard 4 or 5-wire resistive touch screen. MARS-groupies point out that resistive touch has worked plenty-good for the last 25 years and the benefits of multi-touch, low power and no-drift coordinates make it a long term winner. Touch Guy is not convinced but thinks multi-touch resistive is a niche product.

Until next time,
Touch Guy