Most Useful Electrical Testing Equipments - Cable and Pipe Locator

Cable and Pipe Locator :-

This instrument traces underground conductive networks such as water and gas mains, telephone, cable TV, and electric power cables. It determines buried lines depth and locates underground metallic masses such as valve caps and manhole covers.
 

To locate and trace an underground metallic line, the line is energized with a radio-frequency signal generated by the transmitter and then detected by the receiver. Inductive or conductive modes of operation are available.

 

The inductive operational mode does not require direct mechanical line connection. The transmitter can energize a buried line without the need to uncover it. Just place the transmitter on the ground or pavement above the line which, once induced with the transmitted signal, retransmits the signal through the ground and air in a pattern that corresponds to its path. The line carries the signal several hundred yards depending on its depth, the mineralization and conductivity of the soil, and the transmitter power setting.

 

The conductive mode of operation requires the line to be exposed so that a direct connection can be made. Conductive energizing is preferred over inductive energizing because it results in more highly defined signal coupling. The signal generated does not spread to other conductive lines in the vicinity of the traced line. Using a ground rod with the direct connection increases the energizing efficiency and, therefore, the length of line that can be traced.

 

Two methods of receiving the transmitted signal are peak detection and null detection. The method used depends on the placement of the receiver. When held at a right angle to the surface of the ground and moved back and forth across the line to be traced, the receiver detects peaks (maximum signals) when directly above the line. When the receiver is held so its face is parallel to the surface of the ground and moved back and forth across the line, the detection of minimum signal or null (absence of signal) indicates that the line is directly below.

 

Most Useful Electrical Testing Equipments - Clamp Earth Tester

Clamp Earth Tester :-

 

Stake-less testing is one of many methods of measuring earth electrode resistance. However what sets this method apart from all other earth electrode test methods is that it is the only method that does not require the use of auxiliary test electrodes or test leads. Since many earth electrodes are in locations surrounded by concrete or tarmac this is of real benefit. The lazy-spike method works well, but can easily be influenced by steel reinforcement or buried metal pipes. Using this clamp earth tester, it is very easy to measure the resistance of earth / ground electrode without disconnecting the electrode. 

Working Principle :-

Inside the clamp head of the earth tester, there are actually two cores. One core induces a test current and the other measures how much was induced. The input or primary voltage of the test current inducing core is kept constant, so the current actually induced into the test circuit is directly proportional to the loop resistance. This earth tester effectively makes loop resistance measurements. Stake-less measurements are loop measurements. There must be a series-parallel resistance path, and the lower the better. The more electrodes or earth paths in the system the nearer the measurement gets to the actual electrode under test true earth resistance. If there isn’t a loop to measure you could create one with a temporary jumper lead.