PDA

View Full Version : I need some kind of electronic testing device, but I don't know what


Drum God
09-17-2017, 11:32 PM
My house has internal coax cabling. There is an outlet in each of several rooms. The input of ends of the cables come out of the wall at an exterior corner of the house. What I want to do is identify which cable goes to which room. Is there a device that I can plug into the outlet in a room and then detect that device at the exterior end of the cable?

Mr Downtown
09-17-2017, 11:50 PM
Easiest thing is to just attach a battery to one end, such that you have 1.5 volts across the center conductor and the outer shield. Then a flashlight bulb will illuminate when connected across the opposite end. You can also introduce an audio signal, if you are in any way handy with a soldering iron, from something like an old transistor radio, and listen for the audio at the far end with a little speaker or earplug.

Iggy
09-17-2017, 11:50 PM
Plug a DVD player into an extension cord and drag it outside near the exterior corner of the house. Hook up the coax to the DVD player. Hook up a tv to the other end. Swap around the output wires on the DVD player until you get a signal on the tv. Wash. Rinse. Repeat until all wires identified.

Crazyhorse
09-18-2017, 12:08 AM
Or, as you suspected there is a kind of electronic testing device made specifically for this purpose. Something like this (http://www.homedepot.com/p/Klein-Tools-VDV-Coaxial-Explorer-Plus-Tester-VDV512-058/202520424).

Gorsnak
09-18-2017, 12:37 AM
You can do it with a regular multimeter, too. Just short out one of the jacks and use the meter in continuity mode at the other end to find it. The multimeter has the advantage of being useful in a host of other situations.

ftg
09-18-2017, 08:14 AM
Plug a DVD player into an extension cord and drag it outside near the exterior corner of the house. Hook up the coax to the DVD player. Hook up a tv to the other end. Swap around the output wires on the DVD player until you get a signal on the tv. Wash. Rinse. Repeat until all wires identified.

The chances of the OP having a DVD player with RF coax out is tiny.

While a device like an old VCR will work, then you still have to have a TV with analog RF in and is portable.

Just do the short and test thing. A multimeter is really handy for this and a ton of other things. If you own a home you need one. You can get a cheap one for under $10. (Harbor Freight gives them away with a purchase quite often.)

But be sure that nothing is connected anywhere on any of the possible circuits you are testing.

shunpiker
09-18-2017, 08:57 AM
I just bought one of these for that purpose.

VDV512-058 klein tools coax explorer. (https://www.google.com/search?q=VDV512-058+klein&source=lnms&tbm=isch&sa=X&ved=0ahUKEwji8qXr467WAhVJQyYKHewnDgEQ_AUIDCgD&biw=1200&bih=599)

It has 4x, color-coded senders that ping to the yellow receiver when you push the button. The light illuminates to color-match the one you're attached, too. I didn't say that very well, but hopefully it gives you an idea of what it'll do.

Drum God
09-18-2017, 01:44 PM
You can do it with a regular multimeter, too. Just short out one of the jacks and use the meter in continuity mode at the other end to find it. The multimeter has the advantage of being useful in a host of other situations.

I wish to learn more about this. What would be an effective way to short one of the jacks? I could take an old piece of coax and thread it onto the jack, then, moving to the other end of the old cable, bend the center conductor to touch the threads on the outside of the connector. Then, go outside and use the multimeter to probe for continuity between the center conductor and the threads of the outside connection. When I hit continuity, I have identified that location. Does that sound about right?

Gorsnak
09-18-2017, 02:43 PM
Yup, that's pretty much it. You can short the jack out in any number of ways. The method you describe may work, but might not result in very reliable contact between the pin and the threads - though if you could jam something in the end to squeeze the pin against the threads it may work fine. If you have a coax patchcord you're willing to sacrifice, you could cut it, strip the insulation back, fold back the shield, strip the inner insulation, then wrap the shield around the centre conductor. Secure with a wirenut and you'll have a super reliable short. But you could also just take a paper clip, bend it into a U, stick one end in the centre hole in the jack and use some sort of clip to press it against the threads.

Then as you surmise you go to the other end and check continuity. To be absolutely certain you're reading the short you created as opposed to some cable fault, you might have a second person remove and replace the short while you read continuity so that you can see the meter respond.

Using a toner like shunpiker suggests is quicker and easier, but leaves you with a single-use tool.

gnoitall
09-18-2017, 03:09 PM
Yup, that's pretty much it. You can short the jack out in any number of ways. The method you describe may work, but might not result in very reliable contact between the pin and the threads - though if you could jam something in the end to squeeze the pin against the threads it may work fine. If you have a coax patchcord you're willing to sacrifice, you could cut it, strip the insulation back, fold back the shield, strip the inner insulation, then wrap the shield around the centre conductor. Secure with a wirenut and you'll have a super reliable short. But you could also just take a paper clip, bend it into a U, stick one end in the centre hole in the jack and use some sort of clip to press it against the threads.

Then as you surmise you go to the other end and check continuity. To be absolutely certain you're reading the short you created as opposed to some cable fault, you might have a second person remove and replace the short while you read continuity so that you can see the meter respond.

Using a toner like shunpiker suggests is quicker and easier, but leaves you with a single-use tool.I've used the same toner/chaser to trace coax and telephone wiring in the house, so that's two uses. (They're different uses because they're different attachments to the same tool).

Meh. I don't understand the phobia about "single-use" tools anyway. Specialization may be for insects, but insects have a valid role in the ecosystem, so that's a crap criticism.

md2000
09-18-2017, 03:28 PM
Simple short Take a short piece of regular cable you chopped off so that there is a connector on one end. the other end, strip and short the outer braid jacket to the center. attach this to the wall socket. Go to central feed and check each wire with multimeter - ohms setting. (disconnect all cables from devices) Should be open circuit infinite ohms on any disconnected cable, 0 ohms on shorted cable. Label cabel and repeat with next room.

If you have a cable with male end coming out of the wall instead of a socket - most stores (used to) sell an end-to-end connector, screw female connectors on each end; so you could take two regular cables and attach them. Your wall plate sockets (if you have them) probably incorporate one of these, and if you take the wall plate off there's a screw connection on the other side too.

Gorsnak
09-18-2017, 04:37 PM
I've used the same toner/chaser to trace coax and telephone wiring in the house, so that's two uses. (They're different uses because they're different attachments to the same tool).

Meh. I don't understand the phobia about "single-use" tools anyway. Specialization may be for insects, but insects have a valid role in the ecosystem, so that's a crap criticism.

I've got nothing against single-use tools at all. But, if faced with having to buy a toner or a multimeter, I'd buy the multimeter unless I knew for a fact I was going to want a toner in the future. The multimeter is just so much more useful.

Full disclosure: I have both a toner and a multimeter in my toolbox.

Crazyhorse
09-18-2017, 05:55 PM
The multimeter is more useful overall and as noted they are so inexpensive they can practically be considered to be free, but for the OP if it's just a question of wanting the simplest and most straightforward way to solve this problem the dedicated tool makes it a lot faster and easier.

I guess it comes down to how much value they put on their time. It takes time to short each outlet and walk outside and test one by one with a multimeter. If one or more of the cables actually is shorted on its own, that is going to throw a wildcard into the testing that requires even more time and effort to figure out. The dedicated tool can check 4 outlets at a time with just one trip outside and will also detect genuine shorts or faults in the cables at the same time.

Isilder
09-18-2017, 05:56 PM
Or for the ability to identify N cables, buy N resistors, eg 10 Ohms, 60, 100, 150, 200, 250 ... and install them at the one end, and then go out and detect the resistance at the other end.



Do not get confused with the eg "50 Ohms" (75 and 100 are available) of the coax cables rating.. thats the so called AC "resistance"... thats more the ratio of the inductance to the capacitance ... and the mismatch there creates AC noise and attenuations.

Blakeyrat
09-18-2017, 07:03 PM
My house has internal coax cabling. There is an outlet in each of several rooms. The input of ends of the cables come out of the wall at an exterior corner of the house. What I want to do is identify which cable goes to which room. Is there a device that I can plug into the outlet in a room and then detect that device at the exterior end of the cable?

The keyword you're looking for is "toner". Something like this: https://www.techtoolsupply.com/Pocket-Coaxial-Cable-Tester-Toner-p/pvpt2.htm

It comes in two parts. One plugs into the cable and produces a recognizable tone along its length. The other part will produce a sound when screwed into the other end.

You might be able to use the kind for Cat-5 network cables, which are a lot more common, if it has alligator clips on it. They're a bit nicer because the receiver uses radio so you can actually hear the tone from a foot or so away from the cable, meaning you might be able to follow it through the wall. I'm not 100% sure they work with co-ax though.