Calibration Standard

4D Technology worked with PTB and HALLE Präzisions-Kalibriernormale GmbH to create a depth standard for vertical calibration and verification of the 4D InSpec Surface Gauge. The standard includes grooves from 1 um to 900 µm deep. 4D uses the 100, 200, 600 and 900 µm grooves for 4D InSpec calibration. The geometry of the standards is shown below. Each standard comes complete with a storage box as shown.

The standard is made from very pure copper (OFHC-Cu) which provides the best surface qualities (arithmetical mean deviation Ra = 1 nm, waviness Wt = 50 nm, flatness 50 nm over 20 mm measurement length). The copper disks are 90 mm in diameter and 10 mm thick. After machining the disc with rotationally symmetrical grooves, wire EDM is used to cut the disk into twelve segments of equal size which are then chemically nickel-plated to a thickness of 5 µm. The surface hardness of the standards is then about 500 HV and wear-resistant.

The grooves in the uncalibrated standard are estimated to have uncertainties in their depths of about 200 nm. These standards will be measured at the factory using a 4D InSpec which was itself calibrated using a certified standard. The nominal groove depths will be noted upon shipment.