Getting an Invalid Measurement Error when taking a measurement or calibrating a 500 series instrument.
This can be caused by a few issues. Here are some basic troubleshooting steps to help.
Checking the lamps. This can be done by holding the unit 2 to 3 inches above a flat surface, then closing the shoe, causing the unit to measure. You should see light being emmited from 3 three lamps. if you only see one or two, the unit will need service.
Check the battery voltage. This can be done from the Main Menu by highlighting Configuration. The bottom number on the right is your current battery voltage which should be between 5.9v to 6.1v if the battery voltage is less than 4.9v the battery could be too low for measurement and will need charging or replacement. The part number for the battery is SE15-126 and can be obtained from www.xrite.com
If both the lamps and battery are good, the last step is restoring factory defaults (Warning when resetting all stored data will be lost). A factory reset can be done by pressing the "Up", "Down" and "X" keys simultaneously. The screen with go blank, then a message will be displayed asking if you wish to Load Defaults. Highlight "Yes" and press enter. The main menu should appear and a full calibration will need to be done. Here is a link to a PDF of the manual and steps walking you through a full calibration: www.xrite.com/documents/manuals/en/528-500_500_Series_Operators_Manual_en.pdf