Measure SQL Azure Transaction Rate
You can use this script written by Dimitri Furman from Microsoft. It will  measure transactions/sec per database.  You need to run this against the database where you want to measure transactions/sec. I tested this against V12 version and it works.

https://blogs.msdn.microsoft.com/dfurman/2015/04/02/collecting-performance-counter-values-from-a-sql-azure-database/