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What is Passive Locating?


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Understanding passive locating is essential knowledge for all good utility locators.

Passive mode is a simple way of locating underground utilities with a EMF Receiver Wand.

Utilities radiate specific electromagnetic fields, from this signals can be detected with a receiver, other signals can be measured with a receiver due to specific emitting frequencies 50-60Khz.

What do you need to Locate Passively?

You only need a EM Locator Receiver device, this Receiver Wand will need to have at least one Passive Mode. Most utility locating machines have this as standard.

What types of services can passive locating detect?

The five most common passive modes are: Power Passive (50/60 Hz), Radio Passive, Telephone Passive, CPS Passive, CATV Passive.

Most utility detectors have at least one passive mode, and usually encompasses power and radio passive modes.

What types of Passive Modes are mostly used in locating utility services? The three most used types of passive detection are Power Mode, Radio Mode and Auto Mode.

Power mode

It is simple that when an electromagnetic field is produced, its location can be detected via a receiver. So, when an AC current runs through any cable, it will inevitably generate electromagnetic field. Its location can be traced by using the cable locator. However, this is possible only in case of live current, while the current is passing through the cable. Thus, when there is no current flow, i.e. for instance the street lights are off, it can only be detected when a passive signal is strong enough from another source such as radio towers or power lines nearby.

Radio mode

Here, there is a use of radio signals which are of low frequency and long wavelength. When such a radio signal is passed through the ground, it can also get into any type of metallic utilities. That signal will be re-emitted by them and thus, its location can be traced by keeping the locator in radio mode.

Auto mode

The auto mode is combination of power and radio mode techniques. Both the methods are arrayed simultaneously. The best part is that this mode can confirm the presence of underground cables in the first site inspection itself.

Passive locating is a method used by contractors to check the area for unknown lines. This method detects any frequencies created by energized conductors and radio signals being radiated by utilities. However, this method does not allow the operator to distinguish between the types of lines. Passive locating only works on energized cables, that admit 50Hz or 60Hz, Passive modes can be effected if the power is turned off.

Look for clear signals on the peak indicator. Mark out, When you have consecutive marks you can usually draw a conclusion of where a locating of a utility might be and what direct in maybe heading. Passive modes are for an easy confirmation of utilities, but rarely works to detect all unknown utilities.

If there is only one power cable and you need to find it over a large space, passive mode can help you pin point the area in which better methods and techniques are used for accuracy of markings.

Limitations: Utility must be metallic with an EM field is needed for passive modes to work .

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