Resistive touch panels

Resistive touch panels (RTP) have traditionally been the most common touch panel technology in the industrial market.

There are two main types of resistive touch panel, 4-wire and 5-wire RTP. Each consists of a two layer construction for determining the X and Y coordinates.  Typical applications include handheld devices or any product that requires a low cost single touch solution.

4-WIRE – RESISTIVE TOUCH PANEL

The most cost effective touch panel is the 4-wire RTP. These have an Indium Tin Oxide (ITO) resistive coating on the inner side of each layer to create the X axis and the Y axes. Voltage is then applied to each layer individually. Once touched both layers make a contact, the co-ordinates for the X and Y axis are then calculated using a voltage divider.

One disadvantage to the 4-wire RTP is that the flexible coversheet (top layer) acts as one of the axes as well as a uniform voltage gradient. Certain factors can cause the linearity and accuracy on this axis to decrease, including for example environmental conditions and high frequency of operation.

Occasional re-calibration may be required to maintain a level of touch point accuracy. A typical life time durability for repeated touch on a single spot is 1 million times, based on a finger touch.

5-WIRE – RESISTIVE TOUCH PANEL

The 5-wire resistive touch panel offers a similar construction and design concept to the 4-wire RTP. The 5-wire RTP only uses the bottom layer to create both X and Y axis coordinates and the top layer acts as a voltage probe. This results in excellent stability, durability, sensitivity and reliability due to the top layer not being used for one of the axes.

The 5-wire RTP is an ideal touch panel solution for applications where touch durability and reliability are crucial or the touch input is potentially from an inanimate object.
A few benefits of the 5-wire RTP are:

• A constant level of accuracy, even if the top layer is damaged
• Touch response and accuracy is unaffected by harsh environmental conditions
• Calibration only required after initialisation of the system

We aim to provide everything you need to integrate your display and touch panel into your system. We can supply controller boards that allow you to easily interface to your systems and equipment. Interface examples include USB, RS232 and PS/2. Operating systems supported include Windows, CE and Linux.