Collins Dictionary of the English Language:
Main entry: equal, adj.
1. (often foll. by to or with) identical in size, quantity, degree, intensity, etc.; the same (as).
2. having identical privileges, rights, status, etc.: all men are equal before the law
3. having uniform effect or application: equal opportunities
4. evenly balanced or proportioned: the game was equal between the teams
5. (usually foll. by to
) having the necessary or adequate strength, ability, means, etc. (for): to be equal to one's work.
6. another word for equivalent
I searched for the phrase "see that the quality is equal" on Google and found a number of hits for dubious German-English glossaries, but nothing else. For the sake of thoroughness, I also searched for "see to it that the quality is equal" and "make sure that the quality is equal" - nothing. There is one relevant hit for "see that the quality is right" (http://www.oldbaileyonline.org/html_sessions/...
), which would be an acceptable (though not the best) way to express the idea.