審判 and 判定: the official, the decision, and judging
Compare an official stopping play, a decision changed after video review, and judging whether a machine works normally without assuming the result.
審判 (しんぱん): the person making a decision
「審判が笛を吹いて試合を止めた。」 (“The referee blew the whistle and stopped the game.”) The official is the person who stops the match. That action does not establish who committed a foul or who eventually won.
「映像を確認した審判は判定を変更した。」 (“After reviewing the video, the official changed the decision.”) Read the decision changing after video review. Keep the person making the judgment separate from the content of the decision.
判定 (はんてい): a ruling or the act of judging
「審判の判定に従って試合が再開された。」 (“The game resumed according to the referee's ruling.”) The ruling is linked to play resuming. Resumption does not report the match's final outcome or a victory for either side.
「検査結果から機械が正常かどうかを判定する。」 (“We use the test results to determine whether the machine is operating normally.”) Here the task is to judge whether a machine is operating normally. Judging whether it is normal does not report a normal result already established.
Separate the person, target, and result
Asking who the 審判 is differs from asking what the 判定 is or what is being judged. The machine example also shows 判定 outside sport.
A changed ruling is a reported result, while checking whether a machine is normal describes a judgment task. Do not turn the state being investigated into the result of that investigation.
Does using 判定する to judge whether a machine is normal mean it has already been judged normal?
Show the answer and why
No. It states the act of judging whether it is normal. Distinguish that from an established result and from 審判 as the person making a decision.