 Impedance Heads: Types 8000 and 8001 by Brüel and Kjær

Manufacturer Product Data BP0244, printed pp.1–2: piezoelectric force/acceleration sensors sharing a housing and mounting point, separate channels, Figure2 construction, and mass-compensation guidance. Printed p.2 footnote distinguishes raw accelerance/dynamic mass from mobility/impedance and requires acceleration integration or post-processing for the latter.