Page 14 - TEnnessee
P. 14
From the Locator’s
Troubleshooting a Problem Locate
Not too long ago, I was assisting a locator with some tech support on a locating issue. When troubleshooting a problem locate, I approach the problem by focusing on three core components of a locatable circuit: the signal transmitter, the underground utility, and the grounding conditions. If any of these three components are not ideal, we have no signal or weak signals which make locating very difficult if not impossible.
In this case, my fellow locator who had been in my training class earlier
in the year was facing an issue where the transmitter was producing very
low current flow and had text me for some advice. Most locating technicians understand that when current flows on a metallic pipe, cable or wire it creates a detectable signal wave, without current we have no signal wave. The greater the current level (amps) the stronger the force of the signal wave. Strong signal waves can be located at greater depths and greater distances. Low current output levels result in weak jumpy signal waves that are unreliable.
The locator directly connected the signal transmitter to the tracer wire which was accessible from a water valve and buried with the water main and connected the transmitter’s black lead to a ground stake at the corner. (Figure 1)
We started first by examining the signal transmitter. The transmitter is responsible for sending the current down the line which creates the detectable signal field, so ensuring
it’s functioning correctly was our first step. We looked at the output readings of the transmitter which showed the transmitter was applying almost 30
CONTINUED ON PAGE 17
12 • Tennessee 811
By Bob Nighswonger
Figure 1 Direct Connection method used to directly apply signal current to tracer wire. (only 2 mA achieved)
Figure 3 Locator confirms metal to metal connection is made between connection clip and copper tracer wire.
2024, Issue 4
Figure 2 Signal transmitter shows 29.9 volts of electrical pressure with only 2 mA of current flow achieved.
