Sorry to be so long answering your question. I was in a hurry when I read it and meant to get back and answer. Then I forgot about it. For whatever reason it crossed my mind so I will answer before I forget it again.
I us Silvergen SG6. I had an earlier model I used for 7+ years before it quit. I was very happy with it so I ordered another one. The man said the newer one was better. All I see is the stir rod rotates faster. The dial has a low and high setting. I simply set it in the middle. I use the WAG (wild a$$ guess) system to assume it is 10 ppm's. Whatever the ppm's I do get very good results.