All locators have some form of antenna internally; this internal antenna picks up the electromagnetic field that radiates from conductive pipes or cables.

The very basic locator has one horizontally or vertically mounted antenna. These units are unable to give depth electronically but are still able to give depth by a passive means, for example a null unit can give you a general depth via a method called triangulation. The common split boxes were very popular in early days for many good reasons: they taught the locator operator to locate; they usually had a high frequency, which helped locate the basic services easily; and, they were very simple to use. Talk to a professional locator operator and they will usually have an old split box in the back of their van for back-up on those unique jobs where this type of unit worked well. Unfortunately most of these units are showing their age in technology and can struggle in congested areas. There is still a market for these types of units for councils, water authorities and excavation companies who only need to locate the basic services and some manufacturers are releasing more updated versions of this technology which will offer lower costs and ease of use.

Today’s more advanced locators offer faster processing power, can do more things at once and offer multiple antennae. All this technology, if done right, can offer the operator a simple machine to use while still giving good performance in more demanding locates. But be warned – all this advanced technology does have its drawbacks.

Processing power

Units these days offer high-powered processing speeds, while some even offer multiple cores. One of the advantages of this new processing power is the ability of these machines to do two things at once; for example locators may be able to show depth while still in locate mode, which eliminates the need to press the depth button as the depth is displayed when nearing the maximum centre of the magnetic field. Some experienced users dislike this feature as they feel it takes control away from the operator. It may also give the more inexperienced operator a false belief that the depth will be correct without doing the correct checks.

Multiple frequencies

How many frequencies do you need on your locator? 95 per cent of the time a maximum of four frequencies is more than enough as long as they provide a large spread – for example a low frequency between 512 Hz and 1 kHz, a medium frequency between 4 kHz to 8 kHz, a medium to high frequency from 28 kHz to 65 kHz and a higher frequency above 65 kHz to 200 kHz.

Remember owning the latest equipment can have its disadvantages as it has not been tested for reliability infield and like so many new products these days you usually become the guinea pig and have to put up with glitches in software and hardware; this is the price you pay for being the first to purchase. Over time the manufacturers do normally get things right but at the expense of the frustrated locator contractor.

It is wise to talk to a professional locator contractor and see what they use. Most of the time you will see professionals use some older units due to it being tried and tested. A lot of operators use locators that are over ten years old in design, but these operators swear by these units.

I personally own an old RD400. I use this unit to do A B comparisons with newer units on the market. This was a popular unit in the 1990s. It normally only had two locate frequencies (8 & 33 kHz), you had to push a button to get depth, and you required training to get the most from the instrument. Why is it still so popular? Well, it did most of what a contractor needed without any unnecessary bells and whistles, performed well and was highly reliable, with many units still going strong and usually easily repairable.

Remember when purchasing a new locator that you should look at exactly what you want to do.