Device for measuring electric current by use of electro-optical crystal

• US 6,573,699 B1
• Filed: 09/12/2000
• Issued: 06/03/2003
• Est. Priority Date: 10/05/1999
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Fujii, Akira, Wakana, Shinichi, Sekiguchi, Hidenori, Hama, Soichi, Nagai, Toshiaki
• Primary Examiner(s): Cuneo, Kamand
• Assistant Examiner(s): NGUYEN, TRUNG Q
• Application Number:
  US09/660,321
• Time in Patent Office: 994 Days
• Field of Search: 324/500, 324/523, 324/750, 324/751, 324/753, 324/96, 324/73.1, 324/244.1, 324/305, 324/727, 324/76.49, 356/237, 350/396, 350/96.11, 350/390, 359/245, 359/257, 359/315
• US Class Current: 324/96
• CPC Class Codes: G01R 1/071 containing electro-optic elements
• CPC Class Codes: G01R 15/241 using electro-optical modulators, e.g. electro-absorption probes containing electro-optic elements G01R1/071

Abstract

A device for measuring an electric current of a target circuit includes a pair of contact pins, a resistor electrically connected between the contact pins, a voltage drop appearing across the resistor when the contact pins come into contact with the target circuit to direct the electric current to the resistor, and an electro-optical crystal electrically connected between the contact pins in parallel with the resistor, the electro-optical crystal having a voltage applied thereto responsive to the voltage drop appearing across the resistor, wherein the voltage applied to the electro-optical crystal changes polarization of a light beam passing therethrough, thereby allowing the electric current to be measured from the polarization.

Claims

1. A device for measuring an electric current of a target circuit, comprising:

a pair of contact pins;

a first resistor electrically connected between said contact pins, a voltage drop appearing between said contact pins when said contact pins direct the electric current to said first resistor; and

an electro-optical crystal electrically connected between said contact pins in parallel with said first resistor, said electro-optical crystal having a voltage responsive to said voltage drop,

wherein said voltage of said electro-optical crystal changes a polarization of a light beam passing through said electro-optical crystal, measuring the electric current between said contact pins on the basis of said change of the polarization.

2. The device as claimed in claim 1, further comprising a first delay element electrically connected between said electro-optical crystal and one of said contact pins, said first delay element compensating for a travel delay of the electric current passing through said first resistor.

3. The device as claimed in claim 2, further comprising:

a second resistor electrically connected in series with said first delay element between said contact pins, a junction between said second resistor and said first delay element being connected to said electro-optical crystal; and

a second delay element electrically connected in series with said first resistor between said contact pins, a junction between said second delay element and said first resistor being connected to said electro-optical crystal.

4. The device as claimed in claim 1, further comprising conductive films that substantially shield said electro-optical crystal, said conductive films having said voltage substantially applied thereto.

5. The device as claimed in claim 1, further comprising a compensation-purpose crystal that compensates for birefringence characteristics of said electro-optical crystal.

6. The device as claimed in claim 5, further comprising a heater that applies heat to the compensation-purpose crystal to compensate for temperature dependency of said electro-optical crystal and said compensation-purpose crystal.

7. A device for measuring an electric current between said contact pins, comprising:

a pair of contact pins;

a resistor electrically connected between said contact pins; and

an electro-optical crystal electrically connected between said contact pins in parallel with said resistor, said electro-optical crystal having a voltage responsive to a voltage drop appearing between said contact pins when an electric current passes through said resistor.