Technical Bulletin – VLT Devices/Meters

Articles > Technical Bulletin – VLT Devices/Meters

There are several electronic handheld Visible Light Transmission (VLT) devices available on the market from numerous manufacturers around the world. NONE of them measure 100% accurately. They all have a tolerance, usually +\- 2 to 3 percentage points, however we have seen some devices that have a tolerance of +/- 5 percentage points – to clarify… this reading is percentage points not percentage (%).

Example, if an individual was using a handheld electronic VLT device on vehicle glass that had a tolerance of +/- 5 percentage points and the expectation was a net VLT reading of film and auto glass of 35% VLT, that particular VLT device could read anywhere between 30-40% VLT provided it was calibrated correctly prior to each use.

The user of these VLT devices, must read and follow the testing/calibrating requirements as per the manufacturer operating instruction manual. Each VLT device purchased from a manufacturer includes the following points in their operating manual:

• Calibrating the VLT device prior to each use. Calibration pieces are supplied with most devices.
• Handling the VLT device with care – they are a sensitive device.
• Make sure that the battery is charged and replaced regularly.

For the best results and if possible, position the vehicle in a location that is in the direct sun.

If you are thinking of purchasing a handheld electronic VLT device, please research the device operating instruction and limitations prior to purchase.

If you do not have or misplaced manufacturer operating instructions from a current VLT meter being used, please research the VLT meter manufacturer for operating instructions for the model being used.