On Tue, Oct 29, 2019 at 11:50 PM, gusagar54 wrote:
The protector is just that, a protector, and even more: it decreases de
efficiency of the capacitive touch screen, so the idea is taking it out at
once.
Different types of protectors exist for plastic screens: One is just meant to protect the plastic screen surface from scratches (and fingerprints) while being handled during manufacturing and transport, the other is meant to protect the screen from scratches during use.
The first type of protector is usually peeled off by the user once he starts using the device, the second type is often applied immediately thereafter. This type of protector was common in the old days, when screen digitizers were resistive. The one in the NanoVNA is resistive, not capacitive. The resistive digitizer consists of two transparent and slightly conductive layers at close proximity but not touching. Pen pressure makes the two layers touch and the resulting resistance pattern across the layers along the X- and Y-axes is determined. The position of touch may be derived from the resistance pattern. Resistive panels need a flexible (plastic) top layer, which is scratch-sensitive. That's why many users of resistive film screens used to apply a replaceable scratch-protection film.
A capacitive touch screen needs just one solid outside surface. It can be made from glass(like) material. The proximity of the finger or a special pen has a capacitive influence and the location is determined by the panel's electronics. The transparent covers that people put on their phone's screens are mostly for shock protection.
All modern telephone and pad touch screens are capacitive.
It's easy to see and feel: A resistive screen (like the NanoVNA's) is visibly deformed (dimpled) when the pen is put onto the surface, whereas with a capacitive screen, no movement is visible.
Raymond
