SeekTech SR-60
underground lines (electrical conductors like metal cables and pipes) or Sondes (actively transmitting beacons). When the fields are simple and undistorted, then the information from sensed fields is representative of the buried object.
If those fields are distorted and there are multiple interacting fields, it will cause the SR-60 to locate inaccurately. Locating is not an exact science. It does require the operator to use judgment and look for all the information available beyond what the instrument readings may be. The SR-60 will give the user more information, but it is up to the operator to interpret that information correctly. No locator manufacturer will claim that an operator should follow the information from their instrument exclusively. A wise operator treats the information gained as a partial solution to the problem of locating and combines it with knowledge of the environment, utilities practices, visual observation, and familiarity with the instrument to arrive at an informed conclusion.
Locating accuracy should not be assumed under the following conditions:
1.When other cables or utilities are present. “Bleed over” may produce distorted fields and illuminate cables or pipes unintentionally. Use lower frequencies when possible and if possible eliminate connections between the two cables (such as common bonding to ground).
Figure 68: Bleed-over
2.When tees, turns, or splits are present in the line. When following a clear signal that suddenly becomes ambiguous, try seeking in a circle of about 20’ around the last known point to see whether the signal picks up again. This may reveal a branch, joint, or some other change in the line. Be alert to
“split opportunities” or sudden changes of direction in the utility being traced. Turns or tees can cause a sudden increase in the Distortion Indicator response.
3.When Signal Strength is low. A strong signal is necessary for accurate locating. A weak signal can be improved by changing the grounding of the circuit, frequency, or transmitter connection. Worn or damaged insulation, bare-concentric cables, and iron pipes exposed to ground will compromise Signal Strength through leakage to ground.
4.Far-end grounding will change Signal Strength significantly. Where far-end grounding cannot be established a higher frequency will provide a stronger signal. Improving ground conditions for the locating circuit is a primary remedy to a poor signal.
5.When soil conditions vary. Extremes in moisture, either very dry or water-saturated, may affect measurements. For example, ground that is saturated with salty water will shield the signal severely and be very difficult to locate in, especially at high frequencies. In contrast, adding water to very dry soil around a ground stake can make a major improvement in signal.
6.In the presence of large metal objects. Simply walking past a parked car during a trace, for example, can cause an unexpected increase or decrease in Signal Strength, which will revert to normal when past the distorting object. This effect is stronger at high frequencies, which “couple” more readily onto other objects.
The SR-60 cannot change the underlying conditions of a difficult locate, but changing frequency, grounding conditions, transmitter location, or isolating the target line from a common ground can change the results, by making a better ground connection, avoiding signal splits, or reducing distortion. Other locating receivers will give an indication that they may be over the line but they have less ability to determine the quality of the locate.
The SR-60 provides more information. If all of the indicators are aligned and in agreement, mark-outs can be made with more confidence. If the field is distorted it shows immediately. This allows the operator to do something to isolate the target line, change the grounding, connection point, move the transmitter, or change the frequency to get better reception with less distortion. For extra certainty, take steps to inspect the situation, such as by requesting potholing.
In the final analysis, there is one “most important” component in the locating task – the operator. The SR- 60 provides an unprecedented amount of information to
