Place Motion Sensors for Torsional Vibration Modes

How do I place motion sensors to monitor the torsional modes present within the shake tower constructed from the PASCO structures components.
www.pasco.com/structures/#widget_1_slider_4
www.pasco.com/prodCatalog/PS/PS-2103_pasport-motion-sensor/index.cfm
www.pasco.com/prodCatalog/UI/UI-5401-DIG_pasco-capstone-single-user-license-digital-do/index.cfm

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