ETS-Lindgren HI-3627 ELF Magnetic Field Meter - Manual (Page 26)

Page -- 18 HI-3627 Manual
Pipe Inspections
It was noted that the buried pipes leading to fire hydrants
tended to concentrate the currents flowing in the ground from
power distribution leakages. The field from this current could be
detected and measured. It was also noted that the field would
vary uniformly as the operator walked along the pipe. The field
would, however, exhibit significant variations at points on the
pipe where there was a break or a large amount of corrosion. In
this way a single operator with very little equipment could
inspect a large section of pipe for possible failures in a very
short period of time. This, of course, is a singular example that
only worked because of very unusual circumstances, but it does
show the versatility of this easy to use field meter.
Site Surveys
Site surveys are another useful application. This example was
in an office with several CRT terminals. It was found that
several times a day the images on the screens would start to
move in a waving fashion. It was discovered by surveying the
room that a power distribution cable for an industrial user was
routed near the room. The cable was moved and the problem
went away.