Thanks Tony the links were very helpful. I agree fixing the hot end clearance issue on the first layer is a better solution. My problem is that when I am doing a print that takes up a large part of the surface area on the bed 90% of the bed will be at the right clearance but the 10% is not due to the bed not being perfectly flat. So, correcting the problem sounds easier than it might be. Which means if I want to use the sensor I have to stay and monitor the entire first layer to restart the print if it pauses at these spots. After the first layer is down the problem no longer exists and the sensor will only pause the print when it should.
Based on your comments on calibration should I be able to set R minimum to a negative value? It seems not, because when I do that the M591 command ignores the R value and substitutes 0-160 for the R values. Is that what it should do?
These are the typical numbers I am getting. Once I get past any first layer issues this is a typical D591 result. It seems really good to me, would that be correct?
Duet3D laser filament monitor v2 on pin e0stop, enabled, allow 0% to 250%, check every 5.0mm, version 2, quality 222, brightness 255, shutter 77, measured min 155% avg 165% max 176% over 80.9mm
Thanks again for any help here.