COKEVA 11940C Інструкція з експлуатації - Сторінка 8
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Друкувати сторінкуCokeva 11940C Operation Note
3‐1. OPERATION
3‐2.
Theory of Operation
3‐3. The Cokeva 11940C is a balanced magnetic field sensor that provides an output voltage proportional to the
strength of the magnetic field at its tip. Radiated magnetic fields couple directly to the Cokeva 11940C and produce an
output signal; radiated electric fields also couple to the Cokeva 11940C but do not produce an output voltage due to
the construction of the probe. The Cokeva 11940C uses a dual‐loop sensor and a balun to reject electrically coupled
signals. See Figure 2. The probe preserves frequency information and is ideally suited for use with a spectrum
analyzer. The Cokeva 11940C circuitry is passive and therefore only contributes thermal noise to any measurement
system. Inspect the probe tip for damage before using.
Figure 2. Magnetic Field Orientation for Maximum Coupling
3‐4. Antenna Factors
3‐5. The Cokeva 11940C is supplied with a calibration table mounted on its side. The table provides antenna
factors at five calibration points: 30 MHz, 100 MHz, 500 MHz, 850 MHz, and 1000 MHz. The antenna‐factor units
used in this table, dB(μA/m/μV), are accurate to ±2 dB in a 377 ohm field impedance. Add the antenna‐factor units
to the measured voltage in dBμV indicated on the spectrum analyzer to give magnetic‐field strength in dB(μA/m).
Refer to the following equation:
3