Calibration and Use of B Dot Probes for Electromagnetic Measuring
ARMY MISSILE COMMAND REDSTONE ARSENAL AL TEST AND EVALUATION DIRECTORATE
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Modern electromagnetic radiation testing techniques require accurately calibrated field probes that can operate over a wide range of frequencies, without adjustments. This requirement is an outgrowth of the use of wideband radio frequency amplifiers and computer-controlled swept frequency generators. The computer can control the field strength accurately only if accurate sensor information is continuously available. One type of sensor that fulfills this requirement is the b dot probe. The b dot probe is a matched 50- ohm multigap loop which measures dbdt according to faradays law. To assure the accuracy of the probes, a calibration against the National Bureau of Standards standard dipoles is required. From this calibration data a polynomial is developed which when multiplied times the output of the probe in milliwatts will give the actual field strengths. The output of a digital power meter is fed into the computer which applies the calibration polynomial and allows a real- time electromagnetic field leveling to be accomplished. This technique is applicable any time broadband electromagnetic leveled field is required. This study also outlines the design and construction of a single-ended 50-ohm b dot probe, as well as the calibration and development of the required calibration polynomial for computer use.
- Test Facilities, Equipment and Methods
- Electricity and Magnetism