Horizontal Loop Experiment

Geophysics Collection · Physics

Accession Number: 2019.ph.833


An experimental apparatus consisting of a large grey console unit (2019.ph.833.1) and a separate transmitter/ receiver coil (2019.ph.833.2).

The console, labelled “AF Phase Component Meter” has two large dial indicators on the slanted part of the front face. The right is labelled “In-Phase Component”, the left “Quadrature Component.” On the bottom edge of the lower, vertical face of the console are a series of jacks.

2019.ph.833.2: A smaller box, the same grey colour as the console has a brown coloured power cord attached to one face. It has a fuse and an outlet for a power cord on the same face. Two metal plugs emerge from one side.

Alternative Name: AF Component Meter

Primary Materials: Metal, Plastic.


2019.ph.833.2: The metal plugs are marked as “12v +” and “-” in black marker.
The marking near the power cord outlet is not clear, but may read “12v Trh Charger”

Writing on one side is faded and unclear, but may read “12v Transmitter”

Dimensions (cm):

2019.ph.833.1: Height = 24, Width = 20.5, Length = 43.2; 2019.ph.833.2: Height = 6.5, Width = 7.5, Length = 18.5.


This is a table top demonstration of the horizontal loop electromagnetic (HLEM) surveying method. HLEM surveying was used to map conductive minerals in the ground.

The AF Component meter was used in other table-top experiments, including the “Turam Large Loop Survey”, and “Model Magnetics.” The additional equipment required for particular experiments has not survived.


Very Good: The console has wear and discolouration around the knobs and general light wear.

The included textbook photograph shows a “transmitter/ receiver coil unit.” This has not been located.


University of Toronto Department of Physics Machine Shop/ Applied Geophysics Research Group.

Date of Manufacture: c. 1970-1990


This artifact was gathered from room 0007A in the McLennan building on March 21st, 2019.

This teaching instrument was designed by Professor Gordon West and used as part of the teaching lab run by the applied geophysics group at the University of Toronto Department of Physics. The lab was in operation based on table top experiments from roughly 1970 through 1990.

Historical Notes:

The horizontal loop method emerged in the 1970s and was used in the mid-1980s. Its technology was easier to use than the previous vertical loop method and provided a more detailed map of conductive features in the ground.

The applied geophysics group at the University of Toronto Department of Physics was a leading centre for developing and disseminating the technology of electronic surveying. Table top experiments such as these were a critical feature of teaching in this area.

Field instruments are often too sensitive, or otherwise impractical, to operate in an urban environment.

  • Donated to UTSIC