Simple signal transmission using long steel pipe

[[email protected]]

I am a mechanical/hydraulics engineer with an application which may be
more suited to you guys' expertise. What I want to do is transmit a
signal from a remote (up to 5km) device through a long piece of steel
pipe. The remote device incorporates a sensor which produces a simple
signal (on/off) which I would like to detect remotely. Is this feasible
to transmit a sigal (electrical or sound) without any signal boosters
etc.? If this is in no way feasible I have other solutions but this
would make a real neat, simple and cheap solution. Your advice/help is
much appreciatd.

 

[bruce varley]

I am a mechanical/hydraulics engineer with an application which may be
more suited to you guys' expertise. What I want to do is transmit a
signal from a remote (up to 5km) device through a long piece of steel
pipe. The remote device incorporates a sensor which produces a simple
signal (on/off) which I would like to detect remotely. Is this feasible
to transmit a sigal (electrical or sound) without any signal boosters
etc.? If this is in no way feasible I have other solutions but this
would make a real neat, simple and cheap solution. Your advice/help is
much appreciatd.

This is second hand, so I can't provide much info. There was a posting to
this or a related NG way back in response to a similar question. It
mentioned that there is a heating system in Europe that is distributed in
some way throughout a building. It transmits the heat as a hot liquid medium
in pipes, and commands are transmitted acoustically through the liquid.
Useful for old buildings with old systems, where the pipes exist but
installing signal paths separately would be difficult. From a physical point
of view, acoustics should be good at such a task, sound travels well and
rapidly in low-compressibility media such as vapour-free liquids. The
substantial acoustic impedance mismatch between the liquid and the pipe
would minimise loss. Discontinuities such as bends could be another
issue....

 

[[email protected]]

I am a mechanical/hydraulics engineer with an application which may be
more suited to you guys' expertise. What I want to do is transmit a
signal from a remote (up to 5km) device through a long piece of steel
pipe. The remote device incorporates a sensor which produces a simple
signal (on/off) which I would like to detect remotely. Is this feasible
to transmit a sigal (electrical or sound) without any signal boosters
etc.? If this is in no way feasible I have other solutions but this
would make a real neat, simple and cheap solution. Your advice/help is
much appreciatd.

Acoustic transmission seems like a possibility, and you can do a
preliminary test with a hammer, a contact probe stethoscope (or just an
ear to the pipe) and a couple of cell phones. Where is the pipe located
anyway?

 

[Ken Smith]

I am a mechanical/hydraulics engineer with an application which may be
more suited to you guys' expertise. What I want to do is transmit a
signal from a remote (up to 5km) device through a long piece of steel
pipe. The remote device incorporates a sensor which produces a simple
signal (on/off) which I would like to detect remotely. Is this feasible
to transmit a sigal (electrical or sound) without any signal boosters
etc.? If this is in no way feasible I have other solutions but this
would make a real neat, simple and cheap solution. Your advice/help is
much appreciatd.

Folks in the oil industry transmit information by modulating the pressure
of the drill mud. If your data rate is very low, you could do something
like that.

If you have a pipe in the soil, you can still send an electrical signal
down it. The soils resistance is enough higher than the pipes. You will
be dealing with a very small signal. The real problem is the other
contact of the transmitter and receiver. They need to be as far from the
pipe as practical. Your signalling frequency needs to be quite low. I'd
suggest the local mains frequency divided by 2 as a good first guess.

 

[Robert Latest]

On Tue, 11 Apr 2006 18:54:05 +0800,

It
mentioned that there is a heating system in Europe that is distributed in
some way throughout a building. It transmits the heat as a hot liquid medium
in pipes

What a baroque description of a mean central heating system. I like it.

robert

 

[John Larkin]

I am a mechanical/hydraulics engineer with an application which may be
more suited to you guys' expertise. What I want to do is transmit a
signal from a remote (up to 5km) device through a long piece of steel
pipe. The remote device incorporates a sensor which produces a simple
signal (on/off) which I would like to detect remotely. Is this feasible
to transmit a sigal (electrical or sound) without any signal boosters
etc.? If this is in no way feasible I have other solutions but this
would make a real neat, simple and cheap solution. Your advice/help is
much appreciatd.

If the pipe can be grounded at both ends, a current transformer could
induce a signal at one end, and another could pick it up at the other
end. Leakage to earth along the way would cause losses, but I suspect
it's workable at several km.

Not hard to try: a couple of regular metering-type CTs, a signal
generator and an audio amp at the drive end, another amp and
headphones to receive.

John

 

[Frithiof Andreas Jensen]

On Tue, 11 Apr 2006 18:54:05 +0800,


What a baroque description of a mean central heating system. I like

it.

Patent Speak!

 

[Paul Hovnanian P.E.]

If the pipe can be grounded at both ends, a current transformer could
induce a signal at one end, and another could pick it up at the other
end. Leakage to earth along the way would cause losses, but I suspect
it's workable at several km.

Not hard to try: a couple of regular metering-type CTs, a signal
generator and an audio amp at the drive end, another amp and
headphones to receive.

John

What's in the pipe? What's it made of? What diameter? How are sections
attached?

I'm thinking of a waveguide, but the losses could be too high for
something not optimized for RF use.

 

[[email protected]]

sorry for the delay in replying - this is my first chance to check the
group. The steel pipe is one continuous length of 2" diameter with a
bore of 1-1/2" and will usually contain sea-water. There are no
supports required as the pipe is suspended (almost) vertically in a
well-bore. Sending pressure pulses is a possiblity but oe Legris's idea
of transmitting a sound wave is interesting.

 

[Paul Hovnanian P.E.]

sorry for the delay in replying - this is my first chance to check the
group. The steel pipe is one continuous length of 2" diameter with a
bore of 1-1/2" and will usually contain sea-water. There are no
supports required as the pipe is suspended (almost) vertically in a
well-bore. Sending pressure pulses is a possiblity but oe Legris's idea
of transmitting a sound wave is interesting.

An RF waveguide is definitely out of the question. I'm not sure if
hydrostatics follows the same principles as electromagnetics do, but you
should figure out what maximum wavelength will propagate along a pipe of
these dimensions and with what losses. Then, some information theory
wizards can help you select an appropriate modulation scheme.

The problem is relatively simple with two values (on and off). A two
tone scheme might suffice, with one for 'on' and the other for 'off'. If
you have some ideas about the characteristics of the ambient noise (RMS
pressure vs frequency), the signal power can be calculated for a maximum
error rate.