Underground information collecting apparatus having a noise cancel function

摘要

In an underground information collecting apparatus which comprises a steel rod with an end to be inserted into the ground and which is for collecting on the ground underground information detected by a sensor mounted in the end, a noise receiving coil is provided to the rod in the vicinity of a main receiving coil which receives a magnetic signal transmitted from a transmitting coil through the rod and which produces a receiving signal. An amplitude and phase adjusting circuit adjusts a noise amplitude and a noise phase included in an induced noise signal obtained in the noise receiving coil to produce an adjusted noise signal having an adjusted noise amplitude and an adjusted noise phase. The adjusted noise amplitude and the adjusted noise phase are adjusted to be coincident with a noise amplitude and a noise phase contained in the receiving signal obtained in the main receiving coil, respectively. A differential circuit subtracts the adjusted noise signal from the receiving signal to cancel a noise component from the receiving signal.