Automated Inspection of Tell-Tales and Indicators

Anne Corning & Shaina Warner

Instrument clusters, symbols, and indicators on the dashboard of an automobile are crucial for the safety and performance of the vehicle. Typical indicators in modern cars include the speedometer and temperature gauges; symbols to indicate if a door is open, a passenger is not strapped in, or the parking break is engaged; a warning light when the gas tank or oil pressure gets low; or the “check engine” light indicating a malfunction.

The individual symbols—also called “tell-tales”—are standardized by ISO and other industry and regulatory bodies to ensure that drivers of any vehicle in any part of the world will be able to interpret critical information for vehicle operation. Whether you’re in Indiana or India, the low fuel indicator symbol looks the same, ensuring you don’t run out of gas.

While 82% of new automobile models released in the U.S. in 20191 incorporated display screens into the vehicle center stack for infotainment controls (e.g., navigation, radio), most auto makers still rely on a traditional backlit dashboard panel to show the essential instrument cluster and indicators used to monitor vehicle status.

Vehicle dashboards like this one with backlit control gauges, tell-tales, and digital displays help drivers travel safely, day and night.

Requirements for Automotive Controls, Tell-Tales, and Indicators

Automotive controls and indicators are standardized not only by the specific symbols used, but also in terms of their visual clarity and brightness when illuminated. Standards from the National Transportation Safety Board in the U.S. dictate the “location, identification, and illumination” of tell-tales and indicators. Other regions have parallel sets of regulations, such as those from the Canada Motor Vehicle Safety Standard 101, the European Union’s ECE Regulations, and the Chinese Standard GB 4094.2-2017.

Just a few of the more than 150 standardized tell-tale symbols specified for use in automobiles worldwide.

Vehicle manufacturers need reliable, accurate methods to measure and document the visual performance of dashboard panels to ensure compliance with these standards. Radiant offers an automated visual inspection solution for testing illuminated characters that is helping automakers to test their products for compliance. A ProMetric® Imaging Colorimeter used with our ProMetric®  or TrueTest™ software platforms creates an automated inspection system that can evaluate multiple symbols simultaneously at production speeds.

Inspecting Automotive Dashboards and Controls

Measuring light and color across instrument clusters can be a challenge due to the number of indicators, the varying location of symbols, and the range of colors on a panel. Accurate evaluation can prove complex for automated inspection systems and human inspectors alike. Radiant has addressed this challenge, however, with a powerful software tool called Auto-POI, or Automatic Points-of-Interest. 

Auto-POI allows users to automatically select points of interest based on location or color and luminance values (Lv and CIE x,y thresholds), and then run calculations on a single character or group of like characters to ensure uniformity within or between symbols regardless of location, shape, size, or color. The Auto-POI system yields comprehensive data, including average luminance across characters, points of minimum and maximum luminance, color value, and dominant wavelength, for compliance reporting.

To learn more, view our recent Webinar “Truly Automated Light and Color Measurement for Tell-Tales and Indicators.” In it we discuss and demonstrate the process of automating multi-point inspection for complex instrument clusters to measure all illuminated characters on a panel at once. With a ProMetric system and Auto-POI, you can toggle between programmed luminance and color thresholds to evaluate symbol sets for cross-symbol uniformity and harmonization, and automatically register POI for all symbols, even when components are rotated or moved.


This webinar is the first in 4-part series focused on light and color measurement solutions for automotive quality inspection. Upcoming webinars in the series are:

Effective Evaluation of Non-Rectangular Freeform and Curved Displays
Thursday, May 7 from 11:00 am – 12:00 noon, PDT

Measuring the Visual Quality of Head-Up Displays from Conventional to AR HUD
Tuesday, May 12, from 8:00 am – 9:00 am, PDT

Measurement Solutions for Vehicle Interior and Exterior Lighting
Thursday, May 21 from 11:00 am – 12:00 noon, PDT




  1.   Barry, K., “Choose an Infotainment System You’ll Love”, Consumer Reports, May 1, 2019.


radiant vision system wechat