| 摘要 |
An electromagnetic sensing apparatus comprising an electromagnetic transmitter, at least one receiver device, at least one calibration device, a switch and a processing means. The electromagnetic transmitter generates a transmitter signal. The receiver device is spaced from the transmitter, senses a receiver loc al electromagnetic field proximate thereto and generating a receiver signal. Th e calibration device senses a calibration local electromagnetic field proximat e thereto, generates a calibration signal. The calibration device is positioned such th at the distance between the transmitter and the receiver device is greater than the distance between the transmitter and the calibration device. The switch is connected between the receiver device and the calibration device. The processing means include s a first input for receiving a signal from one of the receiver signal and the calibration signal and a second input for receiving a signal from the switch. The processing means compares the first input and the second input and monitors distortions in th e transmitter signal. The sensing apparatus may include a plurality of receive r devices in a variety of different configurations.
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