# Pcl and Gpr

Topics: Magnetic field, Radar, Electric current Pages: 4 (1076 words) Published: May 20, 2013
Pipe Cable Locator (PCL)

Theory of Electromagnetic detection
Mechanism behind PCL is Biot-Savart Law, which is an equation that describes the magnetic field generated by an electric current.

The law is used to compute the resultant magnetic field B at position r generated by a steady current I (for example due to a wire). It means a continual flow of charges which is constant in time and the charge neither accumulates nor depletes at any point. It is a physical example of a line integral: evaluated over the path C the electric currents flow. The equation in SI units is

where dl is a vector whose magnitude is the length of the differential element of the wire, in the direction of conventional current, and μ0 is the magnetic constant.

Since the field surrounds the conductor and obeys the RHSR as shown in the following figure, it is a vector quantity, in which each point has magnitude and direction.

Figure2: Magnetic field B at position r generated by a steady current I How can underground pipes and cables be located by PCL locator A Pipe Cable Locator detects a magnetic field around the line created by an alternation current flowing along the line.

Figure 3: PCL detect magnetic fields

Alternate electromagnetic current creates a moving and reversing magnetic field. When the receiver detects the presence of a conductor, signal appears. Afterwards, the strength of the signal is shown on the screen. The operator reads the response of the locator and interprets the result.

Figure 4: Alternate electromagnetic current
Difference between Passive and Active mode detection
For passive detection, the signals are naturally present in conductors. The only equipment is a receiver. The application is to sweep and search for the existence of conductors buried underground. It emits 50 Hz and radio frequency. Its detection by radio is less definite. It should not be relied upon for depth measurement. For active detection, it requires the...