S Yang, 4/4/2005LCFI: Test jig sensor device design P1 Objectives: The use of a mechanical probe against a non-contact optical probe is based on : - it is simple to make - it costs less - less set up time However, its accuracy depends highly on the sensitivity of the test piece to the contact force on which the probe exert when taking measurement. The current CMM machine at Oxford uses a mechanical probe which exerts a force of 7g vertically and 2g horizontally. The purpose of this exercise is to establish how the test piece will react when a vertical (out-of-plane) force is exerted on it. Our aim is to construct a load displacement curve of the dummy test piece due to mechanical force from the probe. The mechanical probe is acceptable ONLY IF the touching force is SMALL, we need to find out how small this needs to be. LCFI: thin ladder development

S Yang, 4/4/2005LCFI: Test jig sensor device design P2 Overall test jig and measurement devices conceptual design The combined linear and surface profile mapping sensing device

S Yang, 4/4/2005LCFI: Test jig sensor device design P3 The plots shows the out of plane displacement at the load point due to a touching force exerted at the centre of test piece by the probe With gravity on Spring elements

S Yang, 4/4/2005LCFI: Test jig sensor device design P4 The plots shows the out of plane displacement at the load point due to a touching force exerted at the edge of test piece by the probe

S Yang, 4/4/2005LCFI: Test jig sensor device design P5 Contact force calculation (Microsoft Excel) * Subject to confirmation Brian Haws said to me on 24 th March 2005 :- The force on one plate of 10mm diameter capacitor with a spacing of 250um, with 5 volts applied is ^-7 Newtons (minus seven!)

S Yang, 4/4/2005LCFI: Test jig sensor device design P6 The available capacitance sensor in Oxford which used to be used for ATLAS project can be re used in our design. The whole device can be built in-house in Oxford workshop.

S Yang, 4/4/2005LCFI: Test jig sensor device design P7 Vertical sensor device design detail engineering drawing 1: Gravity direction

S Yang, 4/4/2005LCFI: Test jig sensor device design P8 Vertical sensor device design detail engineering drawing 2:

S Yang, 4/4/2005LCFI: Test jig sensor device design P9 Capacitance plate gap size Gap size confirmed by Micro- stage reading Electronic read out of capacitance (proportional to gap size) Elevation view Plan view