What are five ways to check and test your EM locating signal?

Here are five types of ways to test and check your locating signal is accurate and can be assumed to be correct for onsite marking and SUI data collection.

1. Peak VS Null

Your peak signal and null signal should match, if the signal is round, and can be assumed to be correct. If they don’t match, there could be interference with the signal by a more conductive material, signal or cable.

TIP: When the Peak and Null don’t match, you can use the Two-Thirds plus One Rule. The true position of the locate will be half the distance of the peak and null marks, to the side of the peak position. This method must be within AS5488 locator tolerances for QLB to be marked as such.

2. Digital Depth

Lifting the EM locator a certain measured distance from the ground

-Lift the EM locator by 30cm, and the digital depth reading should match the increase by 30cm.

Tip: If inducting onto a cable or pipe, the transmitter must be at least 20 meters away for any depth measurements.

Depth measurements should be accurate to about +3-5%, if conditions are suitable.

3. Triangulation

Holding the receiver on a 45 degree angle and pulled to either sides (of the peak), till the receiver reading is balanced, either side should be equal, if the field shape is round.

4. Peak

Match readings on each side, Pull the receiver an equal distance on either side of center of the Peak signal and the equal and opposite distance should have matching readings.

5. Null

Raising the receiver straight up in null mode, The reading should still indicate a Null if the signal is round. If


Remember all markings are considered assumed to be correct as QLB (Quality Level B) under AS5488. When QLA (Quality Level A) Potholing (preferably NDD non destructive digging) is completed to verify for any construction projects involving any underground utilities.


Following the Five Ps of Safe Site Practice guidelines can ensure the right steps are taken, and duty of care is of the highest standard when dealing with utilities.

Plan, Prepare, Pothole, Protect, Proceed.

For more information: https://www.1100.com.au/what-are-the-5ps-of-safe-site-practice/

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