A. B. Kotb1, Ibrahim M. H. Saad2 , F. M. El-Lithy1, and M. Helmy A. Raouf2
1Faculty of Engineering, Al-Azhar University, Cairo, Egypt
2National Institute of Standards (NIS), Cairo, Egypt
All of the capacitance practical applications require precision measurements of capacitance.
To increase calibration accuracy of capacitance, consideration of the accuracy limitations is
composed by the connection errors and parasitic capacitances. Transformer – ratio arms
bridge is used extensively in the accurate and precise measurements of many types and sizes
of capacitances. Hence, they have many advantages over other measurement devices.
The basic circuit of transformer-ratio bridge is demonstrated and its main measurement errors
are investigated to be avoided or reduced. A new design of transformer-ratio capacitance
bridge is proposed to decrease the bridge errors to minimum values. This new bridge design is
based on a fixed number of secondary turns in the standard arm of the bridge. It is balanced
with the unknown capacitance by variable standard decades capacitances. This new design
improves accuracy and precision of capacitance measurements that carried out by this bridge.
Advantages and disadvantages of our new capacitance bridge design are studied and a future
work is recommended.