Do you want to block unnecessary impressions made by a user,which results in un-fair payment?

Frequency Capping Mod will helps you to overcome this problem.

This mod allows you to set time limit and number of times a user can able to make impression on same banner.

If impressions made by a user surpasses the specified number within specified time period,then openx will not log further impressions.

Openx will continues to log impressions only after the specified time limit is met.

Login as admin->Configuration->Go to Frequency Capping

Suppose, you don't want user to make impression on same banner for more than 5 times in 15 minutes then give 5 in first text box and 750 (15 X 60) as reset time.

So, if user make impression on same banner more than five time in any 15 period time then mod will not log other impressions into database and you can assure your advertiser that all statistics has true impression.