1 James N. Bellinger University of Wisconsin-Madison 25-February-2011 Z-sensor News James N. Bellinger 25-February-2011 Good news this time!

2 What is the problem with Zsensors? Z sensor distances did not add up – Simple calculation, compare with calibration, all looks OK – Review of CAD drawings, no smoking gun – LOW PRIORITY, little effort available Start with MAB positions and work outwards – Z positions of transfer plates don’t agree with PG measurements Start with PG positions of ME4 and work in toward MAB – disagreements with MAB predictions of O(cm) James N. Bellinger 25-Feb-2011

3 Obvious check Take a ruler, measure the distances and compare with sensor readings – Can’t do it with field on, other tasks have priority when field is off Xiaofeng measured these on Transfer Line 2 in January James N. Bellinger 25-Feb-2011

4 Z sensor Layout on Plate James N. Bellinger 25-Feb plunger Z-sensors are mounted symmetrically on a mounting box, which is pinned to the transfer plate. When disks are assembled, the Z-tubes push in on the plungers

5 What was measured James N. Bellinger 25-Feb-2011 Distance from face to box edge measured by Xiaofeng using a ruler. Error O(.5mm) ? CAD coordinates mm edge mm reference I can treat both measurements the same way since the assembly is symmetric Tube Face = Ref + Zsensor = Edge+Zruler ⇛ Reference position ≈ Zruler – Zsensor Expect

6 Explanation of Plots I map both Z2 and Z1 calculations onto the same place in the picture: Always using XiaofengMeasurement – Zsensor The standard Z-sensor measurement calculation (relative to the reference point) is – Z(mm) = 10 (V-offset)/scale Motivated by Xiaofeng vs Zsensor plots (not shown) I tried – Z(mm) = 10 (-V-offset)/scale These are Normalized slope and offset James N. Bellinger 25-Feb-2011

7 Predicted reference position using standard formula James N. Bellinger 25-Feb-2011 Z(mm)=10*(voltage-offset)/scale Wide spread of values in the wrong place

8 Predicted reference position using modified formula James N. Bellinger 25-Feb-2011 Z(mm)=10*(-voltage-offset)/scale Tight spread of values where they should be

9 Conclusion From the facts that – The reference prediction is now where it ought to be; at the back of the Z-sensor – The rms of the prediction is of the order of ruler measurement error rather than >2mm I think we can conclude that the sign on the voltage term in the Z calculation formula is wrong – Use Z=10*(-V-offset)/scale IR sensor was not tested here Thank you Xiaofeng! James N. Bellinger 25-Feb-2011