1) accelerometer: an instrument for measuring acceleration of the earth.
2) electrode: a device set up (typically a pair of metal rods with a voltmeter
connecting the two) for measuring the electrical potential difference in the earth
between the electrode pair. 3) Geiger-Muller counter: a device for measuring
radioactivity by detecting and counting ionizing particles. 4) geophone: a device
that measures velocity by converting ground movement into voltage. 5)gravimeter: an
instrument used to measure gravitational acceleration. 6) hydrophone: a microphone
designed to be used underwater for recording or listening to underwater sound. 7)
magnetometer: an instrument for measuring the strength and direction of magnetic
fields, 8) RF coil: a receiver of radiofrequency signals in equipment used in
magnetic resonance and electromagnetic induction methods. 9) radio wave antenna: an
antenna attached to a receiver used to detect radio waves (a type of electromagnetic
radiation with frequencies of 300 gigahertz (GHz) and below). 10) scintillation
detector: an instrument for detecting and measuring ionizing radiation by using the
excitation effect of incident radiation on a scintillating material, and detecting
the resultant light pulses. 11) seismometer: an instrument used to measure ground
motions by detecting relative movement between a "stationary" mass and a frame
coupled to the earth. Typically seismometers contain sensors to measure motions on
multiple axes. 12) sodium iodide detector: a device for measuring gammma radiation
at various frequencies that uses sodium iodide as the detector. 13) VLF receiver
antenna: an antenna designed to detect radio frequencies in the range of 3-30 kHz.