Dear Dennis...
analogZONE's Dennis Feucht answers your design queries in his new Circuit Design Clinic!
August 2006
Dear Dennis... analogZONE's Dennis Feucht answers your design queries in his new Circuit Design Clinic! August 2006 |
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analogZONE presents a new, interactive analog design service to readers! Send us your design questions (with relevant data; schematics in JPEG or GIF, please) for some free engineering advice from analogZONE's circuit consultant, Dennis Feucht, on how you might solve a design problem or improve circuit performance. Submissions may be edited for clarity or brevity, and submitters and their email addresses will remain anonymous (unless otherwise indicated). Please send your questions to Dennis here.
Isolated Dc Current Sensing
A reader in Florida writes:
I have a weird problem I am working on which is not SMPS. I plan to design a module to detect the dc current in a wire using a transformer as the sensor. The unknown dc current is between 1 A and 50 A. I am thinking of using a C I ferrite core transformer. The wire carrying the unknown current will pass through the window, which single-pass I believe is 1 turn.
My thinking is to have the test wire magnetize the core to 50% of saturation flux at a current of 50 A, so that the sensor is still approximately linear at 50 A with over-range to 100 A. There will be several windings put on which will be used to measure the resulting B-H loop. The idea I have is to estimate the unknown current based on the degree of non-symmetry of the B-H loop caused by said unknown current...