Which antenna mode should you use, Peak, Null, Combined?
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- Опубліковано 2 січ 2021
- Back, before Covid, when we could actually travel interstate, I attended a meeting with a group of other locators. During it, there was a discussion about which antenna mode you should use when locating. I can’t quite remember how the topic itself came up. It certainly wasn’t on the agenda, but it was something like, “On the receiver do you use combined mode, or do you locate in peak and then confirm in Null?”
Surprising, despite there being a lot of locators in the room, many of whom were experienced and had been in the locating industry for several years, there was still quite a heated debate with a range of different opinions.
There were those in the room that are trainers and they stated that you should locate in Peak and then confirm in Null and never use combined mode.
There were others that said that was impractical in the real world and that they only use combined mode and reminded the others that the service they offer is only a guide and you have to dig down and prove the underground utility, so if it is a few millimetres out here and there it is no big deal.
There were others that said that despite the locator being in combined mode, they were smart enough to be able to look at the screen and see what the peak was doing and see what he null was doing and they could tell when they weren’t lined up correctly and that they did not need to individually select peak and then null.
There were actually a couple of other responses as well, but I can’t quite remember them right at the moment.
In the end, with no one willing to admit that the other method was better than what they do, we finally decided to just move on. Locators can be a bit of stubborn breed and sometimes it’s easier to just agree to disagree lol.
So hence my excitement when the very next week I went out to do this service proving job and found that I had an optic fibre trace wire that, for some reason, wasn’t giving me a round signal. At first, the locate seemed fine, it didn’t seem like I had any issues with it, but it was only when I went to confirm with null mode that I found there was an issue.
Now yes, there will be some that will watch this video and will say that the combined mode was a touch over a foot out, so that is fine and is perfectly acceptable. But that was today on this job. What about if tomorrow’s job it is two feet out, what about if it is 4 foot out.
I say for the peace of mind, for yourself, to know you have done the locate correctly, a quick little sanity check is worth the extra couple of minutes it might take over the entire locate.
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www.geelongcablelocations.com.au
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Geelong Cable Locations are the experts to call when you need to know where underground cables and pipes are buried.
We service Geelong, Melbourne and Country Victoria.
We offer:
- Electromagnetic Field Locating (also known as digital locating, or just cable locating)
- Ground Penetrating Radar
- Non-Destructive Digging (also known as hydro excavation, or vacuum excavation, or even just known as NDD)
- Concrete scanning
- Acoustic locating (perfect for locating poly water pipes)
- Drafting
- GPS plotting
- Project management
We’ve been in business since 1998, making us one of the oldest and most experienced service locating companies in Victoria.
Our manager Ben Minutoli was the first in Victoria to obtain his Dial Before You Dig certification and, to date, we’re still the only company in Victoria to have multiple technicians within the company who are DBYD certified (if you don't know, that’s the highest level of certification for a locator in Australia).
Actually, if you don't know about the Dial Before You Dig certification you can find out more about it here, at a blog post Ben wrote when it first came out: geelongcablelocations.com.au/...
And you can also read more about it on another blog post he wrote 12 months after it was started, as well as some tips on how to know which locator to pick to come out to your site: geelongcablelocations.com.au/...
If you have a question about either of those blog posts or, better still, if we can be of any assistance to you with any of your locating needs-or even if you’d just like to discuss a project you’re working on-then feel free to call us toll-free on 1800 449 543.
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Music for this video sourced from www.bensound.com
Great video. There are likely a few (like me) who take a locating course every 3 years and RE-LEARN all that stuff that has been forgotten. thanks for the refresher.
Thanks Brian, yeah I am exactly the same. Although to be honest has been a lot longer than 3 years since I did my last course. I should really go and enroll in another one now while I remember. And as you say, its not to learn how to locate, but more to remember the stuff we have forgotten hahahahah
Excellent stuff!
The theory of the offset of P and N is taught in locating course, however what you’ve captured is a real world example. 👍👍
Cheers mate
This is so helpful! I have not heard of half over before. Great stuff.
ahh really?
Yeah, to be honest, I have never really been a fan of it.
Have known it for years, but I hate having to mark something at a location that is different from where the instrument is telling you it should be.
If I have a locate like this, I will generally find a different earth or hook on somewhere else or try and change it around so that I can get a round signal.
But in situations, as I had here, where there is nothing else in the area, it's just very odd that I wasn't getting a nice round signal.
So that is when you have to pull the old textbook out and do it the scientific way.
But this one did make it even better, because I was able to dig down and prove that it does actually work.
It's not often we get to do that on jobs we go on.
Really great video!
This cannot be a rule for every time Null and Peak do not line up as I have had Null off by 1 meter and peak directly over the cable that I clamped onto. This particular locate was marked with paint and I was just locating the same utility. My locate was 32 in (1 m) away from where the first person had painted marks on the ground. The rep that I was working with decided to dig up my locate and expose the cable. I could reproduce the marked results with null which had a 32" (1m) difference from the directional peak locate, which was directly over the cable. We exposed the cable to verify that the peak locate was the most accurate.
In my opinion, if a locator does not pothole the locates, then painting on the peak locate position is the best practice.
You can also use the peak at different levels to see if the magnetic field is distorted and affecting your locate. Try this, find a peak close to the ground, mark and then raise the locate 1 foot (30 cm) and relocate the peak. You can use these two known points to help determine the buried position.
Visually ;)
Peak locate 1' (30 cm): *
Peak locate @ ground: _______*________
The direction of the target locate: *
Actual pipe: *
Thanks for the video, it was excellent. Let me know your thoughts. gamorris@mmm.com
Hi Gary, thanks for taking the time to watch the video and give a detailed comment and a great tip.
Yes I actually prefer the lifting up and checking depth method, it is a lot easier and quicker to do.
Interesting to hear about your experience with the peak and null. I'm sure there is a scientific reason behind what happened that day, but hey, I guess its why we always say, the marks are only a guide, you still need to dig down and always confirm.
Enjoyed the vid, a great real world demonstration.
Thanks Ben, appreciate you taking the time to leave a comment on it, thank you.
Great video thanks
Cheers Mark
Hi Ben - nice video, however I would prefer you to tell people how to fix the non-round field so that it becomes round and you can then locate accurately - there are 5 things that you can do that will fix your non-round field.
hahahah, nah mate, I don't want to start teaching people on video. Happy to give a few tips here and there and to show what not to do and what can go wrong, but when it comes to teaching guys, I would prefer they go to the experts like you guys where they can learn exactly how to do it right and learn the theory behind why you do it different ways, This way, regardless what situation they come across in the field they will be able to tackle it as they have learnt why it is doing what it is doing.
Hello, so ive looked at your videos, and I feel like you really know your stuff. Have you ever tried a vivix unit to compare to the radiodetection? Just like your comparison of the peak and null showing different locations, im wondering if radio detection versus vivax would be different, and which is closer to actual. Specifically im asking about vivax vloc3 pro. Thank you
Hi Dcbrunk,
Yeah I have actually swapped over to the Vivax and that is my main go to locator these days.
In terms of differences locators will always have there favourites, but I say it is like BMW vs Mercedes. They are both great units. Some years one model might be better than the other, but they both get you from A - B.
I haven't done a side by side test with them and exposing the service, but have done many side by side test with just standard locating and they both are the same.
I like the Vivax more because of the batteries and the sonde mode, plus I like some of the extra features it has.
However I hate the power mode in it, so I do still constantly pull out the RD.
I'd love to find out how you dug such a skinny hole under that cone. Can you please post a video of how you did that?
I always find I have to go wider as I go deeper.
The hole under the cone was likely done with a Vac, or Hydrovac truck.
Sorry Ray, have only just seen this message.
And yes, as Brian has perfectly pointed out, it was done with a hydro excavator.
When you know exactly where to dig it is awesome, as you can dig straight down on it and don't need to make a huge hole.
curious, which textbook?
What do you mean?
As in what is the name of the textbook?
It's more of a saying or a phrase than an actual book, but the system of pinpointing the true position of the cable when peak and null don't line up is generally written in the manual you get when you buy your locator.
It's normally also taught at locating courses.
@@GeelongCableLocations thank you
@@liuzhuo8362 Have a look at ABCXYZ of Locating by Radio Detection