Displays
Transforming the industrial user interface
In this article, Ian Crosby, sales and marketing director at Zytronic, highlights potential issues when designing touch interfaces for industrial applications
H
uman Machine Interfaces (HMI’s) used in hazardous or industrial applications have a difficult life, and their designers
face many challenges when integrating interactive technologies into these systems. A new generation of touch controllers will transform the design of industrial projected capacitive (p-cap) touchscreens, with technical innovations that deliver better performance and functionality than ever before. Specifically, a much higher drive voltage brings improved tolerance of unfavourable conditions. This article highlights potential issues when designing touch interfaces for industrial applications and explains how the latest touch controllers and their new features can help engineers overcome such problems.
Improved noIse ImmunIty The biggest constraint on p-cap touchscreen performance is noise immunity. When the touch controller receives a signal from the sensor, it must distinguish between genuine and false touches (created by electromagnetic interference, or EMI). A finger pressed firmly onto the screen will give a clear signal – but that signal will be weaker if the user is wearing gloves, is touching lightly, or if the screen is behind thick cover glass, and/or the surface is contaminated. The key to improving sensitivity is the drive signal applied to the sensors Transmit (Tx) array of electrodes by the touch controller. The level of this signal is a classic trade-off, a low voltage signal can be
56
overwhelmed by EMI from the environment, a high drive voltage can create interference in the sensor itself, which can potentially degrade performance. Most p-cap touchscreen manufacturers are
forced to use a Tx signal with a DC current of between 20-30V, due to limitations in available “off-the-shelf ” touch control components and ASICs. However, Zytronic’s new ZXY500 range of controllers have been purpose designed to operate at an industry leading Tx drive voltage of up to 40V, enabling full multi-touch detection in extremely challenging industrial applications. The results of this innovation are dramatic.
The higher drive voltages reduce the influence of noise on the data captured. A significant source of this noise is the proximity of the display itself. With all projected capacitive touchscreens, it is necessary to have a gap (air or resin filled) between the front of the display and the rear of the touch sensor, and the new ZXY500 controller now allows this gap to be substantially reduced, depending on the size and type of display selected for the system. This not only allows the whole interface to become slimmer and more compact, it also reduces optical parallax between the display and the overlaying sensor, improving the user experience and accuracy of touch. Each Zytronic projected capacitive touch
sensor is manufactured with a conductive matrix laminated within the rear surface of the screen. This matrix consists of an array of ultra- low resistance, microfine electrodes, which are
March 2019 Instrumentation Monthly
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80
