The difference between trimmed and untrimmed resistors - Max operating voltage

[Kiriakos GR]

The difference between trimmed and untrimmed: To meet initial resistance tolerances of <5% we have to trim the resistor value by LASER.
This reduced the max. working voltage because the cut is placed inside the resistance layer.
This is an established standard  technology for Thick Film resistors.
For 5% and higher we meet the required resistance value tolerance field without trimming.
So we can avoid the LASER cut and achieve higher working voltage handling.

Above explanation were kindly offered by Frank Weise
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Senior Field Design Engineer
VPG Foil Resistors, Central & East Europe

Reason of ITTSB Blog this asking this clarification this is GST4020 resistor series -  Thick Film.
Trimmed resistor this has Max. working voltage of 4000V
Untrimmed resistor this has Max. working voltage of 6000V

GST4020 resistor series qualify for HV resistor box, ideal for insulation meters ( calibration test ).