Abstract
An a.c. bridge has been constructed for the measurement of the resistance of platinum-resistance thermometers. It is based on a multidial 2-stage ratio transformer, using a single reference resistor of 25Ω, and operates at a frequency of 320Hz. The measuring current of 1 or √2 mA is carried by the standard and unknown resistors in series, and the potential drops are compared by means of the ratio transformer, using a single gain-stabilised detector. The ratio transformer is separately excited to ensure that the current in the potential circuit of the bridge is not significant. The bridge has five switched decades for a range of 111 Ω, and the residual unbalance is indicated on a direct reading meter with a most sensitive range of 1 mΩ full scale. Feedback of the quadrature component of signal from the detector eleminates the need for manual reactance balance. The resolution is better than 10 μΩ and the overall linearity better than 20 μΩ. A recorder output (± 1V) is provided.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Proceedings of the Institution of Electrical Engineers
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
