What is the difference between 計測 and 測定?


When I wanted to use word 'measure' in the past I used 計測 or 測る. But recently
I got a message from a Japanese co-worker:

> 申し訳ありません  
>  18時前にネット障害がおこり最後の **計測** できませんでした...  
>  まだ復旧してないので明日18時に **測定** します

I understand what it says, but I am a little confused as to the difference
between 計測 and 測定. Would it be correct if I used 計測 in the last sentence too?
When do people use one over the other?




It appears to me the reason for choosing 「測定」in the last sentence may very
well have been something to do with 「定」. See [goo
辞書](https://dictionary.goo.ne.jp/word/kanji/%E5%AE%9A/#jn-149026):

> 物事を決めて変えない。さだめる。さだまる。

This kanji has the meaning of "making certain", "determine", "to firmly
establish", "to get fixed".「測定」means to determine the value of something
accurately. So when they talk about when it is possible to get an outcome, to
establish the value, they picked 「測定」. 「計測」just means to measure with tools.




It appears to me the reason for choosing 「測定」in the last sentence may very
well have been something to do with 「定」. See [goo
辞書](https://dictionary.goo.ne.jp/word/kanji/%E5%AE%9A/#jn-149026):

> 物事を決めて変えない。さだめる。さだまる。

This kanji has the meaning of "making certain", "determine", "to firmly
establish", "to get fixed".「測定」means to determine the value of something
accurately. So when they talk about when it is possible to get an outcome, to
establish the value, they picked 「測定」. 「計測」just means to measure with tools.

