Choosing the Best TFT for a Glucose Meter
Many new glucose meter designs incorporate a multi-color TFT display . So what do you look for when selecting a TFT LCD?
First, a glucose meter measures and displays the amount of sugar (glucose) in a person’s blood. Most meters are portable and therefore battery powered making low power a major design concern.
WHY A TFT?
In the past, most meter used a monochrome display because they draw less power (Monochrome can be read without a backlight to save power) and they tend to be easier to read in direct sunlight. But some new designs are switching to TFTs.
TFTs (Thin Film Transistor) displays are multicolored modules that can produce between 64K and 64M unique colors. Many are able to display video depending on the chosen interface. TFTs are found in older cell phones, larger tablets, TVs, and most products that use larger sized multi-color displays.
One advantage of a TFT is the ability to select the screens background color.
The background could be green if sugar levels are good, yell is they are moving into a danger zone and red background to notify of immediate concern.
THINGS TO CONSIDER WHEN CHOOSING YOUR TFT:
1. Low Power
Glucose meters are portable which makes power consumption a major design issue since battery life is limited. Most TFTs require the backlight to be on for the display to be readable, but there are a few ways to reduce power draw.
2. Smaller Screen Size
The smaller the screen size, the less power needed to run the display. TFTs range between .8” to 12.1” This measurement is the diagonal distance from the corners of the glass.
2.4” is a common size in portable devices. It’s large enough to be readable and contain a touch panel, but also small enough to fit into a pocket.
Here is a low cost 2.4” TFT that can be a good fit for a portable medical application.
3. Dimming the Display
The product could dim or shut off the backlight after twenty seconds of non-use, allowing the user enough time to read the display and to conserve battery life if they forget to shut the screen off manually.
For suggestions on how to dim a TFT, check out this link.
4. Transflective Polarizer
Most TFTs contain a transmissive polarizer, which requires the backlight to be on for the display to be readable. This results in a high-power consumption any time the display needs to be on.
Transflective polarizers allow the display to be read without the backlight on which can save power. Here is a standard, off-the-shelf transflective TFT that allows the display to be readable in direct sunlight with the backlight dimmed: https://stg-focuslcds-staging.kinsta.cloud/product/e24rb-fw360-n
For more information on different LCD polarizers, please see the following article:
5. Sunlight Readable
To be truly sunlight readable, the display’s brightness should be 700 Nits or higher. The higher the nits, the more power drain. Of course, the higher the nit count, the more power required.
Note: A nit is the amount of light generated by one candle.
6. Touch Panel, Buttons, or Both
Touch panels (TP), also called touch screens, have become common place on many medical products. A TP can be incorporated into your glucose meter’s display to eliminate buttons or dials, although there are a few products that contain both buttons and a touch panel.
For more information on using touch panels in medical applications, see the following article:
7. Product Life
One of the biggest concerns and perhaps most overlooked concerns with medical applications is choosing a product that will be available for the life of the application. Most medical applications will need to go through FDA approval, which can be a long process and may take 3 or more years to get from prototypes to production. Don’t risk going through prototyping, testing and FDA approval just to find out that your display has been discontinued when you are finally ready for production.
Consider this when choosing the product for your application, and more importantly, when choosing your vendor. Product life should be a question for any vendor when developing a medical application. Focus LCDs is familiar with the long design and certification processes of medical applications.