1. Field of the Invention
The present invention relates generally to a solenoidal Hall Effects current sensor and more particularly to such a current sensor capable of calibrating X-ray generators and other devices that operate at high voltage ranges, and even more particularly to such a current sensor that enables the measurement of anode tube current and X-ray tube voltage as well as filament current.
2. Description of the Prior Art
The Dynalyzer systems, originally designed by Shapiro, Pellegrino, et al. at Machlett Laboratories, in Stamford, Conn., a division of the Raytheon Company, have been the standard devices for calibrating X-ray systems since their introduction in 1976. There have been relatively few improvements or changes made other than those necessitated by the termination of many semiconductor components. Optical sensing would be subject to possible negative effects of the oil from leakage into the optical cavities, so the Dynalyzer was insulated using SF6 (sulphur hexafluoride gas).
Another instrument, the Inspec 100 and 200, which were distributed by Greenwich Instrument use various optical sensing means. The Inspec 100 uses a large number of LEDs which were matched together to temperature stabilize them and produce a linear light output versus current for each of three ranges. The Inspec 200 used LEDs in the transmitter, and a feedback scheme where the current required to produce the light was the feedback element. A similar design was used in the GiCi 4000R, which was similar in operation to the Inspec 200.
Radcal Corporation, in Monrovia, Calif., introduced a torroidal Hall Effect current sensor using commercially available components, such as those manufactured by Ohio Semitronics. The filment circuit of the Dynalyzer has similarly used a Hall Effect current sensor since the 1970s, using a single turn of heavy wire and significant additional plastic insulation. The Dynalyzer IIIUV manufactured by Radcal, uses a torroidal Hall Effect sensor with multiple turns of wire to sense the anode current, and is insulated with SF6 gas at 30 psig. Several patents have issued which use torroidal Hall Effect sensor for measurement of X-ray current, including U.S. Pat. No. 6,545,457, which issued to Goto, et al. on Apr. 8, 2003 for “Current detector utilizing hall effect”; U.S. Pat. No. 6,545,456, which issued to Radosovich, et al. on Apr. 8, 2003 for “Hall effect current sensor package for sensing electrical current in an electrical conductor”; U.S. Pat. No. 6,252,389, which issued to Baba, et al. on Jun. 26, 2001 for “Current detector having magnetic core for concentrating a magnetic flux near a hall-effect sensor, and power switch apparatus incorporating same”; U.S. Pat. No. 4,823,075, which issued to Alley on Apr. 18, 1989 for “Current sensor using hall-effect device with feedback.”
Other devices for measuring or adjusting current in, imaging or otherwise monitoring X-ray devices are disclosed in U.S. Pat. No. 5,835,554, which issued to Suzuki, et al. on Nov. 10, 1998 for “X-ray imaging apparatus and x-ray generation detector for activating the same”; U.S. Pat. No. 4,768,215, which issued to Kiwaki, et al. on Aug. 30, 1988 for “X-ray generator with current measuring device”; U.S. Pat. No. 4,673,884, which issued to Geus on Jun. 16, 1987 for “Circuit for measuring the anode current in an X-ray tube”; U.S. Pat. No. 4,573,184, which issued to Tanaka, et al. on Feb. 25, 1986 for “Heating circuit for a filament of an X-ray tube”; U.S. Pat. No. 4,223,228, which issued to Kaplan on Sep. 16, 1980 for “Dental x-ray aligning system”; U.S. Pat. No. 4,177,406, which issued to Hermeyer, et al. on Dec. 4, 1979 for “Circuit for adjusting tube anode current in an X-ray generator”; and U.S. Pat. No. 3,878,455, which issued to Ochmann on May 15, 1975 for “Circuit arrangement for measuring the filament emission current of a cathode-ray or X-ray tube.”
As will be appreciated, none of these prior patents even address the problem faced by applicant let alone offer the solution proposed herein.