Current measuring device

Abstract

A current measuring device for detecting current flowing in a current path includes a magnetic sensor for detecting a magnetic field and a magnetic sensor for detecting earth magnetism, the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor being disposed along the direction of magnetic flux induced by the current flowing in the current path, wherein an earth magnetism component detected by the magnetic field detecting magnetic sensor is canceled by using earth magnetism detected by the earth magnetism detecting magnetic sensor.

1 . A current measuring device for detecting current flowing in a current path comprising a magnetic sensor for detecting magnetic field and a magnetic sensor for detecting earth magnetism, the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor being disposed along the direction of magnetic flux induced by the current flowing in the current path, wherein an earth magnetism component detected by the magnetic-field detecting magnetic sensor is canceled by using earth magnetism detected by the earth magnetism detecting magnetic sensor.  
   
   
       2 . The current measuring device according to  claim 1 , wherein the current path has a right angle portion in section, the magnetic field detecting magnetic sensor is disposed at a vertical upper side to one side of the right angle portion of the current path, and the earth magnetism detecting magnetic sensor is disposed out of the vertical upper side to the one side of the right angle portion of the current path.  
   
   
       3 . The current measuring device according to  claim 1 , wherein the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor are disposed on one sensor chip, and a circuit chip for processing signals from the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor is disposed in parallel to a line connecting the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor.  
   
   
       4 . The current measuring device according to  claim 1 , wherein the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor are mounted on a circuit chip for processing signals from the magnetic field detecting magnetic sensor and the earth magnetism detecting magnetic sensor.  
   
   
       5 . The current measuring device according to  claim 1 , further comprising a magnetic core having a gap around the current path, wherein the magnetic field detecting magnetic sensor is disposed in the gap of the magnetic core, and the earth magnetism detecting magnetic sensor is disposed out of the gap of the magnetic core.  
   
   
       6 . A current measuring device for detecting current flowing in a current path comprising two magnetic sensors disposed along the direction of magnetic flux induced by the current flowing in a current path so that the detection directions thereof are opposite to each other, and an earth magnetism component is detected on the basis of the output difference of the two magnetic sensors to cancel the earth magnetism component thus detected.  
   
   
       7 . The current measuring device according to  claim 6 , wherein at least one of the two magnetic sensors is manufactured on a circuit chip for processing signals from the two magnetic sensors by an MOS manufacturing process.