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Me too.I strongly suspect that Royer oscillator will be completely impractical.
Mr. Brian I agree with you.but I have no information about acoustic method.how it works? how to design it?I strongly suspect that Royer oscillator will be completely impractical. The values may be calculated correctly (I didn't check them) but the physical size and availability of them would make it impossible to build. Even a 100uF non-polarized tuning capacitor would be tough to buy but add to that the two 100H chokes and you are talking of something the size and weight of a small car. Theoretically you could make the tuning capacitor from two back-to-back 200uF polarized ones but I doubt you would find it stable enough for tuning purposes anyway. The problem is the transmitter (Pig) and receiver have to be on exactly the same frequency because the receiver bandwidth would be very narrow and a Royer oscillator would be very prone to drift with temperature and age if electrolytic caps were used. Even a few Hz difference would stop it working.
Are you constrained to using this method? I still feel an acoustic solution would be better.
Comparisons with ISS and interplanetary links are not really valid. The signal attenuation through 4m of soil is probably more than that from Mars to Earth!
And yes, I heard Sputnik in my earlier years - and that infernal Chinese satellite that sent a looped tape recording of their national anthem all day and night until it's batteries gave out. These days it's easy to hear the ISS downlink on a hand portable receiver.
Brian.
Me too.
Besides feasibility of inductor and capacitor values used in the design, it's unlikely that a free-running oscillator achieves the efficiency of a class-D amplifier driven by a precise analog or preferably digital oscillator.
At least the receiver bandwidth has a lower limit by the required detection speed for the moving pig. As mentioned in literature, the transmitter coil circuit will be partly detuned by the embedding steel tube. A high Q circuit might need electronic tuning means. Or you decide for a switch-mode coil circuit without resonance capacitor.
The comparisons with long-distance radio transmissions are only true in very general regard. Actual properties of the inductive near field are quite different from electromagnetic wave transmission.
There's effectively no attenuation of a VLF magnetic field by soil, steel tube is the dominant problem.
The acoustic method is similar to sonar. It uses Time Domain Reflectometry to find the distance from a known place or places.
Basically, from a fixed location (maybe where the Pig is dropped into the pipe) you send a short but powerful burst of tone then start a timer and start listening for a reply. The Pig also contains a microphone and a loudspeaker (possibly combined as one transducer), it listens for the tone and as soon as it hears it, it sends a tone back again. When the fixed point hears the reply, it stops the timer. From the velocity factor of the fluid in the pipe and how long it took before hearing the reply, the Pig's distance along the pipe can be calculated. If the reply from the Pig is at a different frequency, the receiver can eliminate echoes of it's own signal by filtering them out. It doesn't give you the Pigs coordinates but it tells you how far down the pipe it has travelled. Presumably you know where the pipe is so it should be easy to work out where it is located.
Brian.
Since there is a device inside the pipe (the PIG), I assume it is mostly empty.
Could you not excite a cylindrical waveguide mode (at microwave frequencies) and use the pipe to guide it? You could extract positioning information from the phase of the signal, or even two-way communication with readily available radio modules may be possible.
The acoustic method is similar to sonar. It uses Time Domain Reflectometry to find the distance from a known place or places.
Basically, from a fixed location (maybe where the Pig is dropped into the pipe) you send a short but powerful burst of tone then start a timer and start listening for a reply. The Pig also contains a microphone and a loudspeaker (possibly combined as one transducer), it listens for the tone and as soon as it hears it, it sends a tone back again. When the fixed point hears the reply, it stops the timer. From the velocity factor of the fluid in the pipe and how long it took before hearing the reply, the Pig's distance along the pipe can be calculated. If the reply from the Pig is at a different frequency, the receiver can eliminate echoes of it's own signal by filtering them out. It doesn't give you the Pigs coordinates but it tells you how far down the pipe it has travelled. Presumably you know where the pipe is so it should be easy to work out where it is located.
Brian.
Besides feasibility of inductor and capacitor values used in the design, it's unlikely that a free-running oscillator achieves the efficiency of a class-D amplifier driven by a precise analog or preferably digital oscillator.
[...] A high Q circuit might need electronic tuning means. Or you decide for a switch-mode coil circuit without resonance capacitor.
Please remember that I do this as a volunteer and I have to do other work to make a living. I have just come back from a two hour meeting that took 11 hours to travel to, thats why I haven't been able to answer. I got home late this evening and need some sleep before my brain will work properly again (if it ever did!)Mr. Brian plz answer my latest question.I'm waiting for 2 days!!!
You have both, clamp on sensors, particularly used in plants with many pipelines and hand held sensors. According to manufacturer catalogs and applications literature, some meters detection distance are feasible with thick walled large pipelines for the VLF type. Links have been given earlier in this thread.If I understand commercially available Pigs, they actually have a very short range and rely on the sensor being clamped around the pipe.
Many years ago, I made a sensitive inductive 50 Hz detector to locate underground power cables. I believe it had a resonant receiver coil circuit, but I'm not sure. Of course it used a low noise band-pass amplifier. In any case it worked quite well and served it's purpose.
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