how to take singleshot photo below earth 1000m and down

No, at least not with an ordinary webcam -- most use a USB interface, which is only designed to work over ~15' -- 1000m is way too far to try to repeat/extend USB.

Ethernet is designed for 100m, so with 10 hubs you could do with using only of the less common (but still readi1ly available and inexpensive) "network" cameras.

I'm sure there are cameras/cabling systems specifically designed for such long-distance applications, but it's unlikely they'll be cheap. :-)

---Joel

Analog video will travel over a longer cable than USB digital cameras can use.

At the sending end:

You want to take the single ended video signal and make it into a balanced signal. Coax cables don't seem to do as well in tough environments as as twisted pairs.

Before you send the balanced signal over the cable, you want to boost the high frequencies. It is better to correct for some of the loss early in the chain.

There are video transport modules like the Optelecom-NKF 4000 and 4040 that will do up to 46 km:

There are also some modules that transport bidirectional serial data and contact closure signals together with video:

Regards, Arie de Muynck

Ummm.... USB is limited to about 5m in cable length. You can go much farther with ethernet, composite video, or fiber optic cable.

So, how will your video camera survive the approximately 175C degree heat found 1000 meter down?

As others have stated, USB doesn't travel very far. There are better technologies.

The primary problem with getting the signal back through some sort of cable is how you are going to thread that cable through the drill pipe from the head back to the surface. The problem is significant enough that horizontal boring systems don't use hard wired telemetry to send data back to the surface if they are staying within a few meters of depth. They use a low frequency r.f. link.

Due to the limited bandwidth, using a camera to monitor drill head sensor data is out of the question. The sensors are read directly (head temperature, orientation, compass heading) by an onboard controller and sent back as low data rate signals. Some drill head data (such as location) is read by the above ground receiver by using directional loop antennas.

If you are drilling to a significant depth, r.f. communications may be out of the question due to attenuation. But sticking to a lower data rate may make the wired link design simpler.

I worked for the directional drilling companies. For the downhole cameras, video is either transmitted by the special coaxial or by the fiber optics line. The USB is absolutely unsuitable for this kind of application; USB is the interface for the tabletop conditions. I wouldn't count on the video over Ethernet either.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

USB is flimsy interface intended for the tabletop applications. It fails even in the conditions of a car.

Having the wire all the way through the drill column is possible, although it could be inconvenient and expensive. The autonomous drillhead telemetry is severely limited in the range and in the bandwidth. There are the wireline downhole systems, and the systems communicating via the pressure waves in the drilling fluid as well.

There are some applications where there is a need to look out of the drill head.

Yes, this is how it works. However this technology can't go deeper or farther then about 15-20m, and the bandwith is ~100 bit/s only.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

I love down-hole electronics... my favorite customer was Schlumberger, for whom I made down-hole hybrid modules in the early '70's.

Run my module down-hole, haul it back up and throw it away, then buy a new module for the next data run ;-)

I had them send me modules that were "thrown away"... only spec deviation after exposure to 200°C... discolored gold plating ;-)

...Jim Thompson

What tends to kill it? It has the whole bad crc/re-send stuff at a pretty low level of the protocol, and with proper EMI and power supply filtering I would think most anything else would just case a packet here or there to become corrupted and be re-sent automatically?

I've worked on sonar arrays that operate at depth, interesting stuff indeed. After having to survive the large drop into the water from a plane or helicopter (smacking into water can be like hitting concrete), they drop down to depth and then operate for 6 hours or so before automatically sinking themselves to the ocean bottom Can't have the Ruskies picking them up now can we... Taxpayer forks out for a bunch of new ones for the next run.

Dave.

I used a few Tektronix 7912(?) Transient Digitizers (512=20 samples/5nS) a few decades ago. The Tek rep said their main=20 customer was an unnamed government agency that used them for "down=20 hole" experiments of a rather different variety. They bought a new=20 set after each "experiment" too, though didn't haul anything back=20 up. ;-) =20

These were exposed to a bit higher temperatures, though they only=20 had to withstand it for 16msec. They weren't exactly "discolored"=20 after. ;-)

--=20 Keith

Common mode and other interference shuts the USB at once. Weak connectors can't stand vibration and moisture. Galvanically coupled transceivers. USB is very sensitive to all sorts of problems with the signal integrity, especially in the presense of EMI. The cabling for USB has to be good and expensive to be operable at all.

Ethernet is much better interface.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant