The depth of locate will depend on the model used, strength of the signal being detected, ground conditions and the condition of the line as a general rule, the following depths can be achieved:
• General locating up to 5m/15ft
• Sondes – up to 3m/9ft (using 512Hz/640Hz Sonde in cast iron pipe)
• Sonde - up to 5m/15ft (using 33kHz Sonde in non metallic pipe)
Q: Is there a way to calculate depth to a target line?
Yes, if using a locator with a single horizontal antenna this can be done using something that is commonly referred to as the "70% method".
Pinpoint the target line and set the locator sensitivity to give a reading of 100% or full scale deflection (fsd). Keeping the locator close to the ground move it to the left and right until the meter reading reduces to 70% of fsd and mark these points. The distance between these two points will be twice the depth to the centre of the target line.
Q: Can I measure the depth to a target line?
Yes, both most models (with the exception of the 480 series) can measure depth to a target line.
The locator utilizes two horizontal antennas to measure depth in much the same way as our two eyes can judge distance. The strength of the signals on these two horizontal antennas is compared and the system software uses this to calculate the depth electronically and indicate the reading on the display.
Q: How accurate is the depth reading?
As a general rule, the depth measurement accuracy is 5% of actual depth.
Q: Where is the best place to measure depth?
The best place to measure the depth on the target line is on a straight section avoiding tees, bends, or significant changes in depth; if you must measure depth in the vicinity of these features, try to do so at least ten paces away from the feature to minimize any effects from signal distortion. Also, never measure depth to a target line within thirty paces of a transmitter operating in the induction mode.
Q: How far will the transmitter signal travel?
This is one of the most frequently asked questions and one which manufacturers try to avoid answering. A detailed explanation is required to appreciate why this is.
The rate of signal loss on any given line is a function of its electrical characteristics, i.e. conductivity, capacitance and inductance relative to ground and other adjacent metallic lines.
Factors that affect locate distance include:
• Frequency selected
• Condition of the target line
• Soil conditions
• Effects of signal coupling
• Sensitivity of the receiver
• Signal current on the line
It is not possible to alter the characteristics of the line itself, so the key is to minimize the factors that affect locate distance.
The transmitter signal can be tailored to ensure it has the best chance of travelling the furthest amount of distance and for this reason, choice of signal frequency is important. As a general rule, always use the lowest frequency possible for the given method of signal application as low frequencies tend to travel further than higher frequencies. For signal application always use direct connection first, followed by signal clamp then induction. However, there is likely to be an optimum frequency for any given line and situation. The only true means to determine this is through experimentation.
Q: Can I locate non-metallic lines?
Generally, it is not possible to locate non-conducting, or non-metallic lines with ordinary pipe & cable locators on their own. However, many utility companies install tracer wire above or alongside their non-metallic services and these can be located in the normal manner. For non-metallic drains, ducts and pipes, these can be located with the aid of a Sonde, or in case of the CCTV inspection cameras, a Sonde is frequently built into them just behind the camera head.
Q: What is a Passive Signal?
Power and Radio are considered passive signals; these signals are often present “naturally” on buried metallic utilities and they provide a convenient means of searching for these utilities without the need to connect a transmitter. Loaded power cables radiate 50/60 Hz energy that can be detected by the receiver in Power mode. However, power signals may also be present on other cables and metallic pipes as a result of coupling. Long wave radio transmissions penetrate the ground and cause radio frequency currents to travel along metallic utilities and these can be detected with the Radio mode. Passive signals should never be used for identifying the line being located.
Q: What is an Active Signal?
An active signal is one which is generated by a signal transmitter at a specific frequency and imposed onto the target line through either direct connection, use of a signal clamp or induction. An active signal allows the user to target a specific cable or pipe, pin-point its position, measure depth and/ or current and trace the route.
Q: How should I clean my equipment?
DO NOT use solvents for cleaning. If it is necessary to remove mud or grime, use a sponge dampened with warm water. A mild soap may be used to loosen ingrained dirt. Periodically wipe the display window with an anti-static fluid. DO NOT immerse the receiver or transmitter in any liquid during cleaning.
Q: What type of batteries should I use?
This will depend on the model – all alkaline batteries used (non rechargeable) are standard batteries like AA, C cells, D cell, PP9 batteries (smoke detector batteries), the smaller sondes use button style batteries similar to those used in watches and small calculators.
All rechargeable packs are sealed and should never be opened. Replacement packs should be bought from Metrotech or a regional repair center.
• Rechargeable battery types will be different for different models and from receiver to transmitter.
• The correct battery charger must be used to avoid damage to the unit, or possible harm to the operator, or fire.
• Battery chargers frequently contain electronics which govern the rate of charge even if the voltage, polarity and current rating are the same – other chargers could cause damage , harm or fire.
• Never dispose of batteries in a fire.
• Always dispose of batteries responsibly and follow your company’s policy for battery disposal.
• Beware that there are shipping regulations regarding the shipping of battery’s & battery packs – particularly Lithium Ion – check with your carrier before shipment, or call Metrotech for guidance.
• DO NOT turn any battery charger on/off repeatedly when charging. Each time the unit is turned off/on the charging cycle starts again – it could result in overcharging and shortening of the life of the rechargeable batteries – in extreme cases it could result in overheating or fire.
• Always use the locator before charging again.
Q: Can you use the transmitter while it is recharging?
No, the chargers are NOT designed to supply power for locating. On some models a separate power lead is available (as an option) so that the transmitter can be powered from a vehicle. DO NOT try to make one using the charging plug – the wiring configuration is different to that of the charger.
Q: What is the difference between direct connection and induction?
As the name suggest, direct connection is simply that; the output from the transmitter is connected directly to the target line. Induction on the other hand is based on the principal of electromagnetic induction. The transmitter has an internal coil of wire that when energized produces an electromagnetic field (at a given frequency) which will induce, or couple to any metallic line the transmitter is placed over. Direct connection is the first choice for signal application as this method utilizes lower frequencies this reduces the risk of signal coupling to adjacent metallic lines and the signal will travel further along the target line. However, in cases where direct connection is not possible, induction is a suitable method of applying the transmitter signal.
Q: What is signal distortion and why does it affect locating?
To understand signal distortion and how it affects the locate it is important to first understand that when locating cables and pipes the locator is not actually detecting a cable or pipe, but rather the electromagnetic field, active or passive, that radiates from them. Therefore, anything that affects this electromagnetic field, and there can be many reasons, can in turn affect the locate position and/ or depth measurement.
Q: How do I locate a CCTV inspection camera head (sewer camera)?
Many camera systems incorporate a Sonde, if not in many cases one can be attach a Sonde to the rod behind the camera head. Sondes have specific frequencies – if operating in a cast iron pipe use 512Hz/640Hz Sondes – if locating inside a plastic pipe a 33 kHz will work. Sondes will not work in ductile iron or steel pipes.
Q: Can I use a Sonde in a metal pipe?
Low frequency Sondes operating at 512/640 Hz can be used in cast iron pipes and detected at depth ranges of up to 3m. Sondes cannot be used in ductile iron or steel pipes.
Q: What is a Sonde?
A Sonde is a small battery powered signal transmitter that can be inserted into drains, duct and pipes, normally on the end of a flexible rod. Locators that have the correct frequencies can locate Sondes. To read depth to a Sonde the receiver must have a “Sonde” mode this includes a separate algorithm for Sonde depth measurement.
Many CCTV inspection cameras (include a system powered Sonde – most locators with the correct frequency can be used to locate them. A special Sonde mode is again required for depth measurement.
Q: How do I minimize coupling (bleed-over)?
Unwanted coupling of signal is one of the most common locating problems, increasing errors in the locate position or depth of the target line due to distortion and often leading to the marking of the wrong line. To minimize these unwanted effects ensure:
• Avoid applying the signal using induction; use direct connection or a signal clamp where possible
• Use the lowest frequency possible for the given method of signal application
• Use the minimum power output that can be detected
• Avoid applying the signal in congested areas
• Extend the ground stake as far from the connection point as possible
• Avoid using structures for grounding, as other services may be bonded to them
• Use double-ended connections to by-pass the ground return
Q: What is rebar? How can rebar affect the locate signal?
Rebar is the common name for the metal bars used to reinforce concrete structure.
When locating over an area containing rebar, the locate signal may lose clarity or spread across a wide area. If this happens, then the rebar is to blame. To check, raise the locator up by about 0.5m, (18inches) or knee level, and reduce the sensitivity; this should clear or minimize any effect from the rebar.
Q: How do I measure current?
This feature works much the same way as depth calculation.
The vLocPro has a current measurement feature that can assist the user in correctly identifying a target cable. This feature is also useful to determine how much signal there is at a given point, which can assist in fault location and also to understand how much signal is left on the target line.
Q: How accurate is the current reading?
As a general rule, the current measurement accuracy is 5% of actual current.
Q: Where is the best place to attach the conductive lead?
Directly to the target cable or pipe you wish to locate. Use the safest connection point offering a good metal connection i.e. valves, bolts, armoring etc. Remember that the ground stake is the safest of grounding options – NEVER ground to any there metallic structure that has an above ground or below ground structure – as it will radiate the locating signal as well as, and sometimes better than the line being located.
Q: How do I know my instrument is working?
Check the batteries, all associated cables and clamps, and ensure everything operates as described in the user manual. In addition, having a known test site is helpful in determining if the instrument is working properly.
Q: Can I get accurate results when inducing a signal onto a water main?
Yes, however, this is not the recommended method; direct connection is. Paying close attention to the receiver's signal strength will ensure an accurate locate can be achieved.
Q: What must I consider when using a signal clamp on a cable?
The cable must be grounded at both ends for a successful locate when using a signal clamp.
Q: My Metroclamp has a gap at the back, is this a problem?
No, it depends on the type of cores used in the clamps – in the case of most Metroclamps they are designed to have a gap, it is roughly the thickness of a business card, and may be cleaned by using a business card as a gauge. The vLoc clamps use a different material and there should be no gap on those.
Q: What can I do in poor soil conditions to get a stronger locate signal?
There are a number of actions you can take to improve grounding of the transmitter signal in poor soil conditions.
• Pour water around the ground stake.
• Try moving it to an area where more moisture is present.
• Running an “extension” cable from the transmitter earth (black) lead to a nearby road sign, or other similar metal object, may increase your signal.
Q: Can I use my locator to find buried treasure?
No, Vivax locators are designed specifically for the detection, location and tracing of buried utilities.
Q: Where is Metrotech located?
Please visit the “Contact Us” page on this web site. It has addresses, contact numbers and Google maps.
Q: Do I need a RMA # to send my equipment in for repair?
No. We do not require RMA #`s but we do request that you include your PO# or preferred payment method, name, contact phone #, symptoms if known, `ship to` street address and `bill to` address. Please indicate if an Estimate, Pre-Approved limit and/or Priority Service is required.
Note: that there is no charge for priority repair service, other than corresponding shipping costs, such as overnight instead of ground.
Q: My unit is not working, is there any repair I can do to fix it?
We only recommend changing the batteries and checking the conductive attachment leads. Any other repairs should be performed by a qualified Metrotech Repair Center.
Q: Where do I send my unit for repair? What address?
If the dealer you purchased the Metrotech locator from has a service center, contact them.
For additional information, or the address of your nearest authorized dealer, please contact:
3251 Olcott Street, Santa Clara CA 95054
Tel : +1-408-962-9990
Fax : +1-408-734-1799