Mohammad_Pirzadi
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Hi,
What system?
* Electromagnetical? --> (far from being RF or microwave). What antenna (length) do you use for those low frequencies? Lambda/4 = 750 km!! Btw. low frequencies are suitable for big distance.
* Optical? --> I don´t think so
* Acoustical? --> maybe possible.
***
In either case I really doubt that this low frequency makes sense.
Do you want to transmit data with this low carrier frequency? AM? FM?
What power supply do you use?
Klaus
It can certainly be done but losses are huge.
Please answer Klaus's question in post #2 first. Does this transmission have to carry any information (data) or is it's presence all that you need?
Brian.
It's not quite the same as pet locators because they use directional receivers which is fine through air but underground signals are dispersed widely and appear as 'hot spots' on the surface.
Non-metalic pipes may allow direct radiation but metal ones will screen EM waves. There is also the problem that the transmitting antenna (or coil) will be surrounded and possibly immersed in a substance with high dielectric contant which causes problems both with absorbing trhe signal and detuning the radiating element. If the PIG can make electrical contact with the pipe it may allow it to be used in a way similar to a feed point of a dipole, using the pipe itself as a radiating element, otherwise I see the best solution being to induce a current into the pipe by treating it as the secondary of a very low impedance transformer.
I did gound radiation tests many years ago (early 1970s) and found ground EM attenuation rises rapidly at frequencies above about 2Hz but electrical current conduction has a much wider bandwidth, in fact my experiments with injecting 1KHz tones between ground probes showed it could be detected about 1Km away.
I stress I have never done any work of this kind on pipelines so I'm making what I hope are intelligent guesses at solutions!
Brian.
Hi and thanks.The idea resembles a pet locator system. It does not require GPS.
The pet's transmitter is idle most of the time. It monitors your radio frequency continually. When it receives your radio command it transmits a beacon in response. You carry a directional antenna, allowing you to home in on the pet.
Advertised range is 400 feet. It's anyone's guess whether the signal can penetrate pipe and soil.
**broken link removed**
For ease of design and construction, it may be sufficient just to have your transmitter send out a 5-second rf burst once every minute. That may allow your directional antenna to keep track.
I agree, I was thinking in terms of several Amps of LF to a 'primary' coil with the pipe being a closed loop secondary. The induced current would radiate several metres at least and a sensitive and selective pick-up should find it easily.The idea of a 4AA powered transmitters sounds rather unrealistic to me. But we have to consider also pig speed and available detection time.
Hi
What about mechanical knocking at the wall of the pipe? Maybe once every couple of seconds.
And two (three) microphones.
Klaus
I agree, I was thinking in terms of several Amps of LF to a 'primary' coil with the pipe being a closed loop secondary. The induced current would radiate several metres at least and a sensitive and selective pick-up should find it easily.
I believe ground penetrating radar works at frequencies in the 400MHz region and might be able to locate the pipe itself but not a PIG inside it. Possibly GPR with a sensitive AM/FM detector could sense vibrations in the pipe from the PIG motion or a deliberate vibration sent from it.
Warpspeed's idea of using sonar TDR might work, it's simple to implement and as seen in recent aircraft crashes at sea, it can work over long distances in a hostile medium but I wonder if the shape of the pipe might cause so many false reflections that the real one would be impractical to identify. The principle would be that the PIG stays in 'standby' mode, listening for a particular tone pulse through a microphone. When it hears it, a loudspeaker sends another tone pulse back and the round trip time "time of flight" in conjunction with the velocity factor of the medium allows the distance to be calculated from a fixed location.
If the PIG has some kind of distance sensor on it (a rotating wheel in contact with the pipe wall for example) it might be able to report the distance it has travelled back to the fixed transceiver.
When these PIGs are used, is the pipe normally empty and what moves the PIG along the pipe?
Brian.
The question about "wireless power transmission" (should be better designated inductive coupling) has been already answered. You need to calculate actual field parameters. Probably 95 to 99.9 percent of the magnetic field generated inside the tube will shorted by the steel wall. So it's very little of "power transmission".
Instead of "thinking" you should better start to calculate.since the frequency is very low, I think the waves will pass the steel body of the pipe.
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