gas blending

Does anyone have experience or advice between purchasing a Dräger OxyTest 2000 compared to an Analox O2 Portable, for testing oxygen content of the mixed gas in breathing cylinders after filling at any point before diving.

I’m in the final stages of gathering the materials for a Nitrox Stick. I was going to go with a Static Blender chamber but the manufacturer is out of 2” components. So I’m using a 2” pvc pipe. What are your suggestions on either Practice Golf Balls or Bio-balls for the blending? …And why...