Attached to this post, is a document prepared in 2005 comparing the different types of flow testing equipment on the market. I personally use the M1104 Micrometer. Its an American flow meter, heavy duty, highly accurate and made by a good company. There are also two austrlian made units avaliable, one by AMBIT instruments in Melbourne and Gould Instruments in Queensland.
The video below was taken when I was much younger, using an AMBIT box, the system failed as we had no pressure and not much flow. Something was most likely turned off someone. Thats why we flow test 🙂