How is the D3S ID calibrated?

It's self-calibrating!

The D3S ID self-calibrates using naturally occurring K-40. As a result, the D3S ID does not have to be calibrated annually. The device can be used continuously in the field over many years and still retain its calibration.

If you require a regular factory calibration check, service plans with annual calibrations options are available.

Full calibration of the device takes at the Kromek UK facility.