In a recent journal published by Czech Technical University, Prague (CTU) - Geoinformatic FCE CTU (link) there is a paper on calibration of digital level. This paper reported about the cooperation of CTU and Jupem Malaysia i.e., Geodesy Section of Jupem on automatic calibration of digital levels for Jupem. The project started in 2009 and the calibration system was set-up at Jupem which took nine days for the installation to be completed.
Read the paper by Vyskocil & Lukes (2015) entitled "Horizontal comparator for the system calibration of digital levels - realization at the Faculty of Civil Engineering CTU Prague and in the laboratory of the Department of Survey & Mapping (JUPEM) in Kuala Lumpur" - here.