The high voltage value has been adjusted initially in the quality control department at Hitachi in the
course of checks on the instrument, but not for some MC/PMT combinations. With the high voltage
adjustment (check) the field engineer should make sure that the combination of instrument
(photomultiplier tube, electronic components) and measuring cell work in the expected signal range.
If the signal is not in the required range, the photomultiplier tube (PMT) voltage has to be adjusted to
make the signal levels comparable between the different instruments. BlankCell reagent is used to
check the signal level (refer also to Chapter 6, Assay performance explanation, for more details)