Test Barcode – Verifying the Verifier
A test barcode is an image with known errors and attributes built into it. A properly working verifier will detect these errors and attributes and report them accurately. This is the only way an end user can be assured that the verifier is working as it should and therefore this is the only way a verifier users can have confidence that their verifier is authoritatively controlling their bar code relate risk.
Bar codes that do not perform as they should carry significant financial and reputation risk to the brand owner, graphics designer, contract printing and packaging because they adversely impact the performance of the supply chain and retail operations. Several major retailers impose hefty fines and charge-backs for poorly performing bar codes.
Test barcode images are manufactured under controlled conditions to achieve engineered flaws, and they are themselves verified by a master or judge device. In fact the device that GS1 uses to certify test barcode cards is called “The Judge”. The Judge is what assures the NIST (National Institute of Standards and Technology) traceability of the test barcode cards.
Test barcode cards come in a wide assortment, based on the type of bar code symbology for which the verifier needs to be qualified, and in particular the proper combination of that bar code’s X dimension and the verifier having and using the correct aperture. As of this writing, GS1 offers a test barcode card for EAN/UPC, a test barcode card for Datamatrix, a test barcode card for Databar (RSS), a test barcode card for GS1-128, a test barcode card for ITF, attest barcode card set for linear symbologies only, and a test barcode card set for linear and Datamatrix symbologies.
These test barcode cards are called Calibrated Conformance Standard Test Cards or CCSTC’s. As the name implies, these test barcode cards provide a conformance standard against which the verifier is compared and evaluated. These test barcode cards contain calibrated or known errors and attributes.
CCSC’s are manufactured to provide a conformance challenge to the verifier: they challenge the verifier to assure that it is in agreement with the CCSTC, which has specific engineered flaws designed into each symbol. Those engineered flaws are accurately measured and documented on the CCSTC. The verifier results must match the documented flaw within a specified tolerance or margin of error, in order for the verifier to be “compliant”.
CCSTC’s are not the same thing as the reflectance calibration cards often provided by the manufacturers of ANSI/ISO compliant verifiers. Reflectance calibration cards are a benchmark that the verifier uses to configure its internal reflectance settings. Against these settings, the verifier then measures and evaluates the reflectance values of the bar codes it verifies. This can be confusing because of the use of the word “calibration” in both CCSTC’s and reflectance calibration cards, but the meaning is not the same in both cases. In the case of CCSTC’s, the test barcode cards themselves are calibrated; in the case of reflectance calibration cards, the verifier is being calibrated against the card.
Using a CCSTC is not a strategy for making a non-complying verifier ANSI/ISO compliant. This is because a verifier that is non-compliant was not manufactured to consistently pass the stringent, independent test protocol that ANSI/ISO compliance requires. A non-complying verifier might be found to be ANSI/ISO compliant at times and not at others. It is like a ruler made of rubber—it is accurate a times but not at others.