Multimeter with wireless probes? - Page 1
Forum section: electronics / testgear

author: Tcucore
author_rank: Newbie
timestamp: March 29, 2016, 10:51:51 pm
content: I recently started work at a local transit authority maintaining the CAD/AVL hardware on the buses. I'm finding myself checking continuity over lengths of 30+ feet regularly. Is there such a thing as wireless probes, and where can I buy them.

author: trevwhite
author_rank: Frequent Contributor
timestamp: March 29, 2016, 10:57:30 pm
content: You could possibly hack something together from the cheap RJ45 checkers. They have a remote termination and a tester. That might be a cheap option if you dont mind it being a bit DIY.

author: Brumby
author_rank: Unknown
timestamp: March 29, 2016, 11:02:10 pm
content: As in the RJ45 tester case, remote continuity testing is often done by having 2 or more conductors available, where the remote end has a complementary device attached.The simple case is for a 2 wire setup with a shorting plug at the remote end. You simply test for continuity between the two ends in front of you. This tests both wires at once, but if there is a break, you won't know which wire it is in.

author: EEVblog
author_rank: Unknown
timestamp: March 29, 2016, 11:04:55 pm
content: Quote from: Tcucore on March 29, 2016, 10:51:51 pmSure

author: RobertoLG
author_rank: Frequent Contributor
timestamp: March 29, 2016, 11:19:40 pm
content: something like this maybehttp://www.jaycar.com.au/Test-&-Measurement/Network-Testers/Computer-Network/2-in-1-Network-Cable-Tester-and-Digital-Multimeter/p/XC5078with some hacking

author: Brumby
author_rank: Unknown
timestamp: March 29, 2016, 11:26:50 pm
content: Quote from: Tcucore on March 29, 2016, 11:10:56 pmGive me a couple of days and I'll see if I can throw some ideas together for you - hopefully by the end of the week.

author: Brumby
author_rank: Unknown
timestamp: April 01, 2016, 03:30:58 am
content: Well, the challenge was far more difficult than I had envisaged and the prospect of designing a general purpose solution for wireless leads became impossible in the limited time I had available, so I concentrated on putting together a more task specific solution. This was not without difficulties also, and the end result is a project that was aimed at providing the very specific task of continuity testing - which was the original challenge.My first thoughts were along the lines of applying the principles of a time domain reflectometer to check for discontinuities. While there was some merit in that - it was really only a single ended testing process and there were several issues that would need to be addressed. Besides, the brief was for remotes probes. The end result of my efforts to date, while effective for the purpose, is not particularly well constructed, so please forgive me for the crudity of this model - I didn't have time to build things to a more functional scale or paint it.The principle of operation is essentially straightforward and while I will give you some basic concepts here, there are some elements which I am keeping close to my chest for patent reasons. The stage 1 prototype presented here is for a single wireless probe, but there are some discoveries made along the way that are indicating two probes is doable - and possibly more. The ability to measure voltages has some fundamental issues with the physics I'm using, but there are a couple of curious phenomena I've observed along the way which have intriguing implications. This stuff is staying very much out of the public view.Simply put, the continuity testing process requires passing a current through the conductor under test - and the challenge is to supply that current wirelessly. BUT that current has to run through a local circuit. It also has to be isolated from the environment, otherwise multiple measurements in the same location will interfere with each other. Tesla's wireless power concepts don't play well with these constraints.The solution I've developed has the technician at one end of the conductor under test, making direct contact with that end of the conductor with one probe, while the second probe is attached to the emitter head of the wireless probe unit. A receiver is situated at the remote end of the cable under test and it connected to that free end.From here on, things get interesting.The wireless probe system uses an ionised stream of air to provide a current path from the transmitter to the receiver, but creating and sustaining that ionised stream is where the true challenges lay. Without going too deeply into the specifics (which is where the IP is) I can say that the ionised stream is created by a combination of local electric discharge and a laser bean - where that laser beam is aimed at the receiver. The specific wavelength of the laser is a closely guarded secret, as is the specific modulation of the electric discharge. What is important is that the laser beam intensity must achieve a value of 1.21GW/m2. For the electric discharge head to be effective, it will need very precise modulation and timing and this is being controlled by an Arduino clone. It will also require several KV, but the actual voltage is not nearly as critical as the laser.Once the ionisation has occurred at the emitter, it propagates through open air along the laser beam, which supplies energy to maintain the ionisation state. This is why that 1.21GW figure is most important. As you would expect, there are losses in this beam, so the range of the wireless probe is limited - however a simple corner reflector system at the receiver can reflect the laser back onto itself, making use of the remaining energy to help stabilise the ionised stream.In constructing the ionisation igniter head, I found some ordinary sewing equipment had the necessary shapes to support the required discharge criteria, which was most fortuitous. Interestingly, I discovered that needles, with their sharper points, were ideal as the cathodes, while the slightly more blunt tip of a pin worked best for each of the anodes. You can see the logic in that, so I won't go into explanations. The one thing, though, is that I found alignment of these electrodes somewhat of a hit and miss affair, until I got down and dirty with some mathematics which gave me insight into a rather fascinating parameter.As it turns out, the whole emitter assembly is affected by a combination of the Earth's magnetic field and the Coriolis effect. This influence needs to be compensated by the angling of the igniter electrodes according to a function of the latitude where the equipment is being used. In the southern hemisphere, this translates into an anticlockwise orientation (as viewed from the laser) which increases as the latitude increases. According to the math, as you approach the equator, the ideal orientation is perpendicular and as you move further north, they are orientated more and more in a clockwise direction. Circular polarisation of the laser is also beneficial, but it, too depends on latitude. Some brief excursions into fractal designs for the igniter head show promise in alleviating, if not eliminating, this limitation.The simplest things are the best - and the receiver could not be simpler! It is entirely passive and consists of nothing more than a mettalised corner reflector and a test lead. Here is the prototype, simply clipped on a (weighted) ice-cream container for a stable target.As you can imagine, setting up the igniter head of a cobbled together prototype has its challenges, but there was one simple technique that I discovered quite by accident - but has proven to be a godsend. By placing a finger at the focus point of the electrodes and applying about 10% of the operating voltage (unmodulated), you can sense all 6 - so when you can feel pins and needles, you know you're close!Here's the igniter controller:While there are undoubtedly a lot of questions you may have, there are a lot that I just cannot answer publicly - but there are some 'FAQ' style questions I can answer.1. This system requires an ionisable gaseous environment. It cannot work in a vacuum and the range decreases with altitude.2. Is the current in the beam dangerous? Not significantly, no. It's just a few mA, once the stream is established. The ionisation energy comes from the laser.3. Is the laser dangerous? In a word: Yes, but time is a factor. It would be a simple matter to add a safety mechanism which can kill the laser before it has had time to do any mechanical damage ... except for your eyes - It's a frickin' laser!4. What is the range? Not telling - but the OP would find it useful.Maybe it's time to look at Indiegogo

author: jeremy
author_rank: Super Contributor
timestamp: April 01, 2016, 05:29:20 am
content: I'm not going to give you an April Fools answer sorry.The problem with measuring continuity over wireless is that there is no loop for electrons. What might be more helpful is to measure using a similar means to an LCR meter; ie, inject a known sine wave at one end, and test for it on the other end. You can very easily make a ~100Hz sine wave oscillator (maybe with a little amplifier also), and the AC voltage mode on your multimeter should be able to register whether it is present or not as long as you can use the chasis as a ground. You might want to switch the sine wave on and off every two seconds or so, so that you know you are truly picking up the original sine wave. Also, making a buzzer sound while the wave is being generated will keep you from constantly checking if there actually is a sine wave being generated.I've used this approach before, but I can't say I've used it on something as large as a bus...Edit: FWIW, you can measure voltage using lasers under some circumstances:http://www.sciencedirect.com/science/article/pii/0030399277900068(sorry, paywall)

author: Mr.B
author_rank: Unknown
timestamp: April 01, 2016, 06:07:19 am
content: @BrumbyI think you may have outdone Meredith Perry there...

author: Brumby
author_rank: Unknown
timestamp: April 01, 2016, 06:21:24 am
content: Quote from: jeremy on April 01, 2016, 05:29:20 amSeems you missed the fundamental operating principle.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: April 01, 2016, 06:41:40 am
content: .

author: ivaylo
author_rank: Frequent Contributor
timestamp: April 01, 2016, 06:50:17 am
content: What's wrong with everybody? The Fluke remote display stuff has a better than 30' spec -http://en-us.fluke.com/products/digital-multimeters/fluke-233-digital-multimeter.html#features

author: jeremy
author_rank: Super Contributor
timestamp: April 01, 2016, 08:09:43 am
content: Quote from: Brumby on April 01, 2016, 06:21:24 am?Quote from: ivaylo on April 01, 2016, 06:50:17 amI think the problem is more that one of the probes needs to be 30' away from the other one, not that the display needs to be 30' away from the probes.

author: Mr.B
author_rank: Unknown
timestamp: April 01, 2016, 08:59:01 am
content: Quote from: jeremy on April 01, 2016, 08:09:43 amThe only slightly sane advice I can come up with is...30 feet of 16AWG flex.Not "remote" as such and definitely not wireless, but it will work.

author: Berni
author_rank: Super Contributor
timestamp: April 01, 2016, 10:58:48 am
content: One way to do it is to inject a RF carrier in one end and have a probe that is tuned to it to poke around. Problem with that is that RF follows all sorts of weird laws so it could couple in to other wires or resonate in things.If you are working on vehicles then you probably want to use the metal shell as a return conductor. That way you could put a specific blinking pattern on the wire in one end with a crocodile clip that clips on a near by metal screw and then have a probe that recognizes that pattern on the other side.

author: haveissues
author_rank: Contributor
timestamp: April 01, 2016, 01:10:30 pm
content: Ground one end of the wire and test for continuity against ground on the other?

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 01, 2016, 01:21:47 pm
content: Let's hope that @Tcucore realizes this has become an April Fools joke.There is no practical solution to "wireless probe" for things like current and voltage.

author: SL4P
author_rank: Super Contributor
timestamp: April 01, 2016, 01:52:15 pm
content: Outside the scope of the joke...Why not put a modulated low energy RF signal on the conductors wrt ground (like a telco cable tracer)And probe for that signal at a viable level at the far end.Keep the freq low enough that it will drop off rapidly in the event of a break into the conductor.

author: mmagin
author_rank: Frequent Contributor
timestamp: April 01, 2016, 05:32:06 pm
content: Quote from: jeremy on April 01, 2016, 05:29:20 amMaybe if OP is willing to do this in a vacuum:https://en.wikipedia.org/wiki/Electrodynamic_tether

author: robert_
author_rank: Regular Contributor
timestamp: April 01, 2016, 07:22:56 pm
content: Wireless Probes?Just buy a "830" Meter, get its enclosed probes, pull on the wires a little and you got a set of wireless probes. Also makes that 830 much safer.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: April 01, 2016, 07:42:43 pm
content: Quote from: jeremy on April 01, 2016, 08:09:43 amJust use two of them if you're not using groundAlso similar laser induced plasma channel systems already exists for passing large amounts of power......typically high energy weapons. Seehttps://en.wikipedia.org/wiki/Electrolaser

author: mos6502
author_rank: Frequent Contributor
timestamp: April 02, 2016, 06:01:01 am
content: Where is the actual problem with making the test leads 30' long?This one has a 24' coiled cord:http://www.amazon.com/OTC-3642-Truck-Circuit-Tester/dp/B005J3KR92/

author: MarvinTheMartian
author_rank: Frequent Contributor
timestamp: April 02, 2016, 06:45:25 am
content: Quote from: Brumby on April 01, 2016, 03:30:58 amI started to think to myself when reading your post that I really don't know anything at all!Though as I read further into it, I thought I can't be so ignorant as to not know what the hell you are talking about - then I saw the pictures and that clinched it!Well done, must have taken you a while to get this one up.

author: Brumby
author_rank: Unknown
timestamp: April 02, 2016, 06:49:01 am
content: I just put together a couple if ideas in a logical manner.I did not realise that the fundamental idea was not new:Quote from: ChunkyPastaSauce on April 01, 2016, 07:42:43 pm... but mine had current limiting.

author: ChunkyPastaSauce
author_rank: Unknown
timestamp: April 02, 2016, 07:05:19 am
content: Quote from: Brumby on April 02, 2016, 06:49:01 amI had an earlier post, but deleted because I didn't want to give away april....But like 90%+ or more of what you said was in the realm of possibility in some way or another.... I didn't know what to believe until I looked at it for a while. You kinda had me for a few lol

author: Tcucore
author_rank: Newbie
timestamp: April 03, 2016, 10:46:37 pm
content: I've purposed a network cable testing tool for continuity testing. I had a good laugh at all of this. Your guy sure have a good sense of humor. Thanks for making my day a little better than it was just a few minutes ago.