Measurement Device Repeatability

Most printing facilities have measurement devices of some sort- whether in prepress, press-side, or in the ink room. You're diligent about sending these off to be calibrated regularly (...right?), storing them properly, and keeping that pesky calibration tile in perfect condition. Even in the best environments, there is a certain amount of variability built in to all of these devices. The table below shows some common measurement devices and their repeatability- the variation in measurements taken by a single instrument on the same item and under the same conditions.

Repeatability	Reflection Density (< 2.0)	Transmission Density	DeltaE 2000	Dot %	Inter-instrument Agreement
X-Rite Products
eXact	± 0.010	n/a	0.05 CIE ΔEab	n/a	0.25 CIE ΔEab
i1 Basic Pro 2	n/a	n/a	0.10 ΔE94	n/a	0.40 ΔE94
938	± 0.005	n/a	0.05 CIE ΔEab	n/a	0.20 CIE ΔEab
504	± 0.005	n/a	n/a	n/a	0.01D or 1%
508	± 0.005	n/a	n/a	n/a	0.01D or 1%
SP64	n/a	n/a	0.05 CIE ΔEab	n/a	0.25 CIE ΔEab
341C	n/a	± 0.010	n/a	n/a	n/a
361T	n/a	± 0.010	n/a	n/a	n/a
Techkon Products
SpectroDens	± 0.01	n/a	0.3 CIE ΔEab	n/a	±0.01D/0.3 CIE ΔEab
SpectroEdge	± 0.015	n/a	0.3 Δ1976	n/a	n/a
RT120	± 0.010	± 0.010	n/a	± 1%	n/a
Beta Products
Presto	± 0.003	n/a	n/a	± 1%	n/a
S2 Xpress	± 0.003	n/a	n/a	± 1%	n/a
S4 Xpress	± 0.003	n/a	n/a	± 1%	n/a
Betaflex Pro	n/a	n/a	n/a	± 0.5%	n/a
Betaflex Control	n/a	n/a	n/a	± 0.5%	n/a
Betaflex Control 3D	n/a	n/a	n/a	± 0.5%	n/a
QEA Products
Flexo IAS-II	n/a	n/a	n/a	± 0.5%	± 1%

It's best to know the repeatability of your measurement devices when establishing the tolerances for a particular process, so that the known amount of variance is taken into account beforehand. Also, knowing what amount of variance in repeatability is normal for a given instrument will help alert you if a problem with the instrument arises. If your instrument is not listed in the table above, contact APR or your device manufacturer for more information. Happy measuring!