from the tip of the top clean grain elevator paddle (TDC) to the deflector plate. If it's outside of spec, adjust the elevator head to bring it into spec. Once it's in spec, make any tension adjustments at the bottom of the elevator so that you don't change the clearance.
I must be an idiot. but I still cant see how to measure this damm thing...how can u get anything in there? It also looks like on my machine its about4-5" away. Yet the yield monitor seams to be working fine. I will try to take a couple of pics of it.
Bring a paddle on the elevator chain to the very top so it is vertical. Then measure from the tip of the paddle to the top of the elevator housing. if it is too much tighten the elveator chain with the bolts on the sides of the elevator head. Make sure to give yourself slack with the adjuster on the bottom.
Linux, I think that you may be trying to measure the wrong piece. The deflector plate is a stainless plate right above the clean grain elevator chain. The impact plate is on the yield monitor sensor which is about 4-5 inches away from the paddles. Just take the grain flow sensor out of the way and look in from the front of the elevator. You should be able to see in there and measure using bolts or rod or whatever. Hope this helps Jimmy