Barcode Verifier Calibration: Why is it Important?

 In Barcode Verifier, Verifier Validation

Let’s first clear up a common confusion. There are seemingly two kinds of calibration for barcode verifiers:

  • user calibration
  • factory calibration (sometimes called recalibration)

User Calibration

Axicon calibration cardA new Axicon verifier comes with a NIST-traceable calibration card.  Users are encouraged to calibrate the verifier regularly. There is a reminder for this in the software.

The Axicon calibration card contains precise, photographically imaged barcodes with calibrated dimensional and reflective values. Scanning the appropriate barcode adjusts the verifier to known dimensional and reflectance values. These establish the basis of comparison to the other barcodes the verifier will test and grade.

Over time, the LEDs will fade. User calibration boosts the signal amplitude based on the values from the calibration card. When the verifier knows the correct foundational reflectance values, it can accurately evaluate the actual reflectance values of a printed barcode.

Axicon also recommends annual factory recalibration. What is that and why is it necessary, if users are already calibrating their verifier?

Factory Calibration

Axicon factory recalibration is called VCAS: Verifier Conformance Alignment Service. VCAS includes recalibrating with the user calibration card, but it also involves additional maintenance services.

Aging is one cause of LED fade. Another cause is dust and vapor in the user environment. which coats the optical path and lowers reflectance values. Over time, signal amplification from user calibration will cause other problems to emerge. Verifier sensitivity to electrical noise increases.

Factory calibration involves cleaning the internal optical path. This includes replacing the scan window and carefully cleaning the mirrors, lens, filters, and sensor. Delicate disassembly is required in a clean, static-free workplace. The recalibrated verifier is returned with signed and dated certificate of ISO conformance and a new NIST-traceable calibration card.

Hidden Benefits of Factory Recalibration

Annual factory calibration establishes a trajectory with regular check-in points. Like any precision instrument, a barcode verifier has a performance log, maintenance history, and eventual replacement. With a well-maintained verifier, it is reasonable to expect a service life of ten or more years with proper maintenance. Over time, annual factory recalibrations track incremental performance changes. This allows the user to monitor and plan a replacement and avoid the inconvenience of a sudden failure. Things only fail when they are used and needed.

 No Calibration Required—Buyer Beware!

Some verifiers do not require calibration. How does that work?

These “verifiers” are barcode scanners using verifier-emulating software. They are not purpose-built to comply with the ISO standard* for a barcode verification device. The aging process and environmental factors make them less and less accurate over time. The results may be optimistic, grading bad barcodes well, or pessimistic grading good barcodes poorly. Either way, the risk of barcode liability is unmanaged. Beware of clever marketing language:

  • “ISO-formatted reporting” which means that the data is arranged in the ISO template. It does not mean that the data is accurate.
  • “Never needs calibration means it cannot be calibrated. It is a serious disadvantage repurposed into a feature. Ahh the poetry of marketing.

Let the buyer beware! Insist on a signed and dated Certificate of ISO Conformance and a protocol for factory recalibration. This applies to new and used verifiers. Insist on an ISO compliance certificate and, for a used verifier, a copy of the calibration log showing the serial number of the device. What looks like a good deal is actually a trap if it doesn’t protect you against the considerable liability of a bad barcode.

*ISO 15426-1 for linear verifiers and ISO 15426-2 for 2D verifiers

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