Displays for portable measuring devices

Industrial metrology has been growing rapidly in recent years. Producers, who want to provide their customers with the highest quality solutions, are introducing further verification steps into their production processes. Some include using advanced measuring devices, which also respond to modern industrial design trends. One can see this advance in the way the content is displayed – measurements used to be read from clocks, now are displayed on screens.

From the user perspective, a portable measuring device should be exact in the first place. The most important thing will be the accuracy of the measurement taken. Efficient reading of displayed data would be most helpful in facilitating his work. This strongly depends on selecting the most accurate display. There is a variety of solutions available on the market, which can be successfully implemented in this type of equipment. This article highlights a selection of display models from our offer, including solutions that will work under extreme conditions. 

OLED displays    

OLED displays are common in portable measurement devices. These are primarily monochrome modules under 5 inches, ideal for presenting basic data.    

OLED diodes, out of which the OLED display matrix is made, are simultaneously the source of light. This results in high contrast and full viewing angles for unrestricted access to the content on display, both in light and in darkness. Moreover, OLED displays are resistant to extremely low and high temperatures – they can work reliably in a temperature range of -40 to 80°C, allowing both indoor and outdoor applications.     

Unisystem offers more than 150 models of OLED displays in sizes from 0.49 to 5.5 inches. One of the interesting examples is Winstar model WLEP02566400DGAAASA00, available in 3.55 inches size and 256×64 px resolution. It is a Smart Display solution. The manufacturer provides software for designing graphic user interfaces (GUIs) with a library of ready-to-use elements.    

The table below lists examples of OLED Winstar displays offered by Unisystem. These are solutions applicable to various portable devices, including measuring equipment.

parameter   size / resolution    structure  active area  outline dimensions  interface  operating temperature  colors available   
WEO012864AC   0.96” / 128×64   COG   21.74 × 10.86 mm   26.70 × 19.26 × 1.26 mm   6800, 8080, SPI, I2C   -40~80°C   white   
WEO012864AJ   2.42” / 128×64   COG   55.01 × 27.49 mm   60.5 × 37.0 × 2.11 mm   6800, 8080, SPI, I2C    -40~80°C   white / yellow    
WEX025664D   5.5” / 256×64    COF   135.65 × 33.89 mm   146.0 × 45.0 × 2.05 mm   6800, 8080, SPI   -40~80°C   white / yellow / green   

LCD-TFTs  

LCD-TFT could be recommended if color graphs are presented on the screen of a portable measuring device. In intense light conditions the excellent content readability depends on the resolution but also on the brightness of the display. The full viewing angles will be an extra asset. One should pay attention to an adequate operating temperature range, since exceeding the limits indicated by the manufacturer can lead to the failure of the module. It is best to use solutions with the widest possible operating temperature range, even from -30 up to 80°C.  

   

Winstar’s WF40ESWAA6MNN0 meets these requirements – it is a 4-inch LCD-TFT with a 480×480 px resolution, 1000 cd/m2 brightness, and 80°/80°/80°/80° viewing angles. Its operating temperature range is specified between -30° and 80°C. This model implements MIPI DSI, an interface designed primarily for mobile devices. It features high performance at low power consumption, as well as resistance to electromagnetic interference.   

E-paper displays    

Usually e-paper displays are associated with consumer e-book readers. Still, these solutions are becoming popular in public spaces, such as digital signage systems. What’s more, e-paper displays will also work well in industry applications.    

For example, the 4.3-inch ED043WC3 designed by E Ink’s engineering team, can be implemented in portable measurement devices. The content presented on e-paper displays is perfectly readable thanks to properties, such as unlimited viewing angles. The only condition for it is an external light source, since e-paper displays do not use a standard backlight, like LCD-TFT solutions. Although it is possible to provide an e-paper display with an additional light source, such as LEDs. A drawback of e-paper technology may be the limited temperature ranges – for the ED043WC3 model it is defined from 0 to 50°C. If the temperatures get lower or higher, the e-paper will not work properly and may be damaged. To avoid it other temperature control methods should be installed, like heaters or fans.   

E-paper solutions, as well as other discussed content visualization technologies, are constantly evolving. Currently, there are e-paper displays adapted to work in low temperatures, however still not below -10°C. That is why e-paper displays are commonly used in retail, enabling further automation of price management processes by introducing e-paper price labels on shelves and in refrigerators.  

The above review of displays presents only a selection of solutions that are currently available on the market. One could also easily implement AMOLED displays in portable measuring devices, if budget allows. However, this technology is now more common in commercial equipment such as phones and tablets.  

What technology would work best for the device you are designing? Contact us - we will gladly help you in selecting the best solution.  

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