Why Calibrate Your Spectrophotometer?
For the most part, today’s color measurement instruments are 100% digital. In fact, there are very few analog components inside, except for the light bulbs. Although they’re more stable than their analog predecessors, their tolerances are much narrower, and they need regular spectrophotometer calibration to stay within these tight specs.
Bulb Stability
As you use your instrument and the bulb turns on and off, it starts to change its character. Spectrophotometer calibration compensates for these changes in the bulb’s ability to create light. Careful calibration will keep the instrument stable for many months – even years – until the bulb reaches the end of its life.
Tile and Lens Cleanliness
Inside the instrument are the settings for two known points in color space – a defined white, and a defined black. Back at the factory, a full reflectance curve was built to define the white calibration tile, and a full reflectance curve was built to define the black point inside the black trap. Those exact locations for white and black are programmed right into the device for calibration.
If the white tile gets a little dirty, the white point will drop down the horizontal axis toward black. Not only does the white point drop, every point along that line drops along with it in differing degrees.
If the black point goes up because there’s dust in the trap, the black point moves upward toward white. As the slope of the line is changed, every point along that line is degraded. False passes can cause you to send products to your customers that won’t pass inspection. False rejections will cause rework that isn’t necessary. This is why you need to keep the trap free of dust, and the tile meticulously clean.
Treat the calibration tile as if it’s a precious optical device because it is. Generally, manufacturers suggest cleaning the calibration tile with warm water and a clean, lint-free, non-scuffing towel, but follow the user manual instructions for your specific device.
If you’re in an environment such as a printing area where there’s ink, or where paint films can be a problem or where compressors are blowing unknown gasses and oils into the air, water alone may not do the trick. You can use wipes that are specifically designed for eyeglasses or camera lenses that are moistened with isopropyl alcohol. Gently buff the white calibration tile until it is absolutely clean, and it will dry quickly without residue.
How Often Should You Calibrate Your Spectrophotometer?
Most instruments have a built-in timer that you can set to monitor the interval between calibration. You can set it for a certain number of hours, such as 8, 12, or 24, or you can set it for no interval at all and calibrate manually when you think it’s necessary. Set a schedule that’s based on your color workflow and environment. If you come on shift to an instrument that someone else has been using, you should recalibrate.
Some instruments allow you to verify calibration from within the device, without any software. For example, on the Ci60 series you’ll find a green tile with associated numbers built right into the device. Make sure the tile is clean, set the instrument to the appropriate values, and measure it. If your instrument reads within 10 – 15 hundredths of the L*a*b* values for both specular included and specular excluded, then you don’t need to calibrate. But if you find that your target does not measure within at least 2/10ths of the printed values, then it’s time for re calibration.
Spectrophotometer Calibration & ISO Compliance
A regular spectrophotometer calibration schedule will keep your device functioning as it should for a period of time, but eventually you must send it for service to maintain its performance and ensure accuracy. Factory certification will give you – and your customers – confidence that your instrument is reading and performing the way it should. As an ISO 9001 company, X-Rite recommends factory certification once a year, and many customers require proof of certification when choosing a supplier.
Check out our Caring for your Spectrophotometer post to learn what’s involved, and how X-Rite can help.
NetProfiler
Errors in measurements can be the result of many different factors, and most can be corrected by calibrating. NetProfiler is a cloud-based blend of software and color standards that makes it easy to adjust and validate instrument performance to ensure all spectrophotometers in your fleet are calibrated and performing as they should from the convenience of your own facility. It also automatically optimizes device performance to correct issues caused by age, wear or environmental conditions and identifies instruments in need of service before they result in off-color products.
X-Rite’s Service & Maintenance Offerings
X-Rite manufactures and supports color measurement solutions for global markets where color and appearance matter. We build and service each product in an environment that adheres to the highest standards and strictest tolerances. Our lean manufacturing process, Six Sigma mentality, and ISO 9001 and 17025 certifications provide confidence that every device you receive from X-Rite will work exactly as designed.
X-Rite is accredited by ISO/IEC 17025:2005 to certify our spectrophotometers. When you send your device to us, an X-Rite certified technician will verify and document your device’s incoming performance, inspect and clean it, test measurement accuracy, and confirm its repeatability and consistency. Your device will come back to you with a dated sticker or paper certification of NIST traceability to standard white.
Our Service Centers and Global Certified Partner Sites feature our most advanced testing tools, including temperature and humidity-controlled service areas. Our streamlined operations ensure that you will get your device back as quickly as possible.
