Analog 5-wire Resistive
In analog 4-wire resistive technology, one sheet has equipotential distribution in X direction, and the other sheet has equipotential distribution in Y direction. The two sheets measure each others' voltages. In analog 5-wire resistive technology on the other hand, one sheet (bottom sheet) has equipotential distribution in both X and Y directions. Voltage of the bottom sheet is measured by the top sheet.
Is there structural difference between 4-wire and 5-wire technologies?
Just same as analog 4-wire resistive technology, an analog 5-wire resistive sensor consists of top and bottom sheets which are facing each other with a gap in between. Unlike analog 4-wire resistive technology, electrodes are placed on four corners of the bottom sheet in analog 5-wire technology. The sensing process is as below.
The sensing process
- 5V is imposed on the electrodes A and C. The other side (electrode B and D) will be 0V (Ground). In this way, there will be formed an equipotential distribution parallel to AC and BD.
- Voltage of a touched point will be measured by the top sheet. If the central point between AC and BD electrodes is touched, 2.5V would be measured by the top sheet. If a point 1/5 away from AC (4/5 away from BD) is touched, 1V would be measured by the top sheet. Touched coordinate point in X direction will be measured in this way.
- After detecting the coordinate point in X direction, 5V is imposed on the electrodes A/B. Then, C/D will be 0V (Ground). The point between AB and CD (Y direction) would be measured by the top sheet, in the same manner as X direction.
- As the set of step 1 ? 3 is repeated, the touched points in X and Y direction keeps being detected.
OK, the electrodes for both X and Y directions are placed on the bottom sheet. The top sheet does not have electrode and just measures the voltage of the bottom sheet. Is there any functional difference between analog 4-wire and 5-wire resistive technologies?
An analog 5-wire resistive sensor was regarded as more durable than analog 4-wire resistive sensor. Although film/film structure is growing in number due to the large market of mobile devices recent years, film/glass structure was mainstream before the 2000s. Glass material is better than film material in resistance uniformity and environmental durability. As explained above, both X and Y coordinates are formed on the bottom glass, and the top film works only to measure voltage on the bottom glass in an analog 5-wire resistive sensor. Thus, even though the top sheet of film material was not good in the resistance uniformity and environmental durability, it had less affect on detecting function than analog 4-wire resistive .
I see, there is no equipotential distribution formed on the top sheet in analog 5-wire resistive. So, the top sheet did not need to be good at resistance uniformity and environmental durability in this sensing method.
Exactly, but the mechanical and environmental durability of ITO films has improved spectacularly. In actual use, mechanical and environmental durability is hardly different between 4-wire and 5-wire resistive technologies today.
