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A high precision method for measuring very small capacitance changes Ashkan Ashrafi and Hossein Golnabi
 

Summary: A high precision method for measuring very small capacitance changes
Ashkan Ashrafi and Hossein Golnabi
Institute of Water and Energy, Sharif University of Technology, 8639 Tehran, Iran
Received 26 January 1999; accepted for publication 5 May 1999
A novel method for measuring very small capacitance changes based on capacitance-to-phase angle
conversion is introduced in this article. This new method is the improved or linearized version of the
nonlinear capacitance-to-phase angle conversion method. The main features of this scheme are the
very good linearity, extremely high stray immunity and a very high resolution. The experimental
results of the prototype version of this scheme have also been reported. By using this prototype and
a simple capacitive transducer, a minimum detectable distance of about 16 nm can be achieved. This
means that a capacitance change of about 0.7 fF (0.7 10 15
F) in a capacitance of 22 pF can be
resolved, so the minimum resolvable relative capacitance is about 32 ppm. By the theory it can be
seen that the minimum resolvable relative capacitance of 2 ppm could be achieved by this method.
1999 American Institute of Physics. S0034-6748 99 03808-3
I. INTRODUCTION
During the past years capacitive transducers have found
many applications. For measuring a very small capacitance
change there is a demand for a reliable high precision read-
out circuit. In principle, measuring small capacitance change

  

Source: Ashrafi, Ashkan - Department of Electrical and Computer Engineering, San Diego State University

 

Collections: Engineering; Computer Technologies and Information Sciences