High bandwidth Rogowski transducer with screened coil
A current measuring device is disclosed, comprising: an electrically conductive coil having a first end and a second end; a first screen surrounding the coil and arranged to provide a current path from the second end of the coil to a location proximal to the first end of the coil; and a second screen surrounding the first screen and the coil.
1. A current measuring device comprising:
an electrically conductive coil having a first end and a second end;
a first screen surrounding the coil and arranged to provide a current path from the second end of the coil to a location proximal to the first end of the coil, wherein a first end of the first screen is proximal to the first end of the coil, and a second end of the first screen is proximal to and electrically connected to the second end of the coil;
a second screen surrounding the first screen and the coil; and
an electrical integrator having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal is electrically connected to the first end of the coil, the second input terminal is electrically connected to the first end of the first screen, and wherein the output terminal provides an integrator output with respect to a ground to which the second screen is electrically connected.
2. The current measuring device as claimed in claim 1 , wherein the coil forms a loop, with the first end being located proximal to the second end.
3. The current measuring device as claimed in claim 2 , wherein the loop is opened or openable to form a gap between the first end and the second end.
4. The current measuring device as claimed in claim 1 , wherein the conductive coil comprises a Rogowski coil.
5. The current measuring device as claimed in claim 4 , wherein the Rogowski coil comprises any of: a clip-around coil, a closed-loop coil, a printed circuit Rogowski coil and a coil wound on a non-conductive former.
6. The current measuring device as claimed in claim 1 , wherein the second screen is electrically insulated from the first screen and the coil.
7. The current measuring device as claimed in claim 1 , wherein at least one of the first screen and the second screen is an electrostatic screen.
8. The current measuring device as claimed in claim 1 , wherein at least one of the first screen and the second screen is arranged to reduce capacitive coupling from external conductors to the coil.
9. The current measuring device as claimed in claim 1 , further comprising a former, around which the coil is situated.
10. The current measuring device as claimed in claim 1 , wherein the electrical integrator is arranged to provide an output voltage that is substantially proportional to an integral with respect to time of a voltage between the first end of the conductive coil and a first end of the first screen.
11. The current measuring device as claimed in claim 1 , wherein an electrical resistance exists between the second input of the electrical integrator and the ground to which the second screen is electrically connected.