The thin dielectric film capacitive displacement transducer to nanometer

The paper deals with the new capacitive transducer for small displacements (from a few micrometers to a few millimeters), denoted the Thin Dielectric Film Capacitive Displacement Transducer (TFCDT). This principle is based on the properties of a very thin dielectric film between the faced electrodes. The film may be applied by a dielectric, such as alumina. The transducers are designed in a differential form. Their electrodes have to be constructed by either photo-chemical- or laser etching. A few implementation prototypes (IPs) of the TFCDT have been designed and constructed. The first of the IPs (TO IF) has been constructed in two forms, for linear and rotary displacement by a dielectric spray varnish with thickness of about 2 μm. The second of the IPs (II°IP) has been designed and constructed only in the form for linear displacement, with different techniques for achieving lower thickness of the alumina dielectric film. The test results on both the I°IP and II°IP are critically analyzed. The sensitivity and linearity obtained, respectively, are about: 5 pF/mm, 0.6 pF/°, 25×10^-6, 2 nF/mm, and 7 nm/μV, nearly in the absence of nonlinearities. A feature for improving the sensitivity and linearity, respectively, to about 40 μV/nm and to a few×10^-8 is also illustrated. A variable absolute scale of capacitance and capacitive voltage divider based on the TFCDT is also proposed