haas@wasatch.utah.edu (Walt Haas) (06/13/89)
I'm shopping for a good way to test coax and twisted pair cables used in Ethernet, Arcnet and broadband. One way would be to spend a lot of money for a large, heavy TDR that would give me lots of information. But there are now on the market units that send a pulse down the cable and tell you on a little display whether a reflection came back and whether it represents a short or open. This gives you some information, less than a TDR would give you but maybe enough to solve most problems. In particular I'm looking at a thing called a Cable Scanner built by a company called M-Test. Does anybody in netland have one of these? Who are their competitors? What percentage of problems can be solved this way, vs. what percentage need the full TDR treatment? Thanks in advance for any beta -- Walt Haas haas@cs.utah.edu utah-cs!haas
jgd@rsiatl.UUCP (John G. De Armond) (06/13/89)
In article <2021@wasatch.utah.edu> haas@wasatch.utah.edu (Walt Haas) writes: >I'm shopping for a good way to test coax and twisted pair cables used in >Ethernet, Arcnet and broadband. One way would be to spend a lot of money for >a large, heavy TDR that would give me lots of information. > >In particular I'm looking at a thing >called a Cable Scanner built by a company called M-Test. Does anybody in >netland have one of these? I've observerd the Cable Scanner in use and have used it a bit. My general impression is that it is useful for determining the length of a known good cable and for finding catastrophic failures (cuts, shorts, etc) but for the problems we've had, it has been of little use. The catastrophic failures can usually be observed visually (someone ran a chair over the cable, etc). When the failures are marginal or intermittent, these little pocket instruments leave a lot to be desired. A crushed cable or an intermittent connector or an improperly crimped connector will not show up on these boxes unless the condition is bad. What you have to do is determine whether the threshold of detection is in the same ballpark as when the tranceivers quit working. I've found little to beat the 'O-scope based units, especially the ones like the Tektronics scope with the strip-chart option. You can literally detect non-intrusive bending of a cable with this unit. Connectors - even correctly crimped ones - show up clearly. And since you can make hardcopy, you can build a history file of each cable. This history is the absolute best way to quickly diagnose changes. You can also quickly detect unauthorized new taps with little trouble. If your budget can handle it, get both instruments. If you can only afford one, get the scope. It is more than worth the effort in handling. John
benderly@cs.columbia.edu (Dan Benderly) (06/13/89)
In article <2021@wasatch.utah.edu> haas@wasatch.utah.edu (Walt Haas) writes: >I'm shopping for a good way to test coax and twisted pair cables used in >Ethernet, Arcnet and broadband. One way would be to spend a lot of money for >a large, heavy TDR that would give me lots of information. But there are now >on the market units that send a pulse down the cable and tell you on a little >display whether a reflection came back and whether it represents a short or >open. This gives you some information, less than a TDR would give you but >maybe enough to solve most problems. In particular I'm looking at a thing >called a Cable Scanner built by a company called M-Test. Does anybody in >netland have one of these? Who are their competitors? What percentage of >problems can be solved this way, vs. what percentage need the full TDR >treatment? > >Thanks in advance for any beta -- Walt Haas haas@cs.utah.edu utah-cs!haas I have used both a full-blown TDR and, more recently, a product called the Hand Scanner (I don't remember off-hand who the manufacturer is. If there is interest I will lokk it up & post it). I was very happy with the hand scanner. It costs ~$1200, and did everything I needed it to do. It will detectan open or a close, and tell you how far away the condition is. It is *very* easy to use. If you have an old oscilloscope (or a new one, I suppose), the product will let you attach it & function as a full-blown TDR (I haven't tried this function, but that's what the manual says). You can hook up a printer or PC to it, obtaining a record similar to that produced by the Tektronix strip- printer output. All in all, I am a very happy customer. Disclaimer: I have only used the product on coax. While they claim that it can help with TP, I haven't tried it. I have no vested interest in this companyother than their survival so that they can provide support :-) Dan benderly@cs.columbia.edu
rsmith@vms.macc.wisc.edu (Rusty Smith, MACC) (06/13/89)
In article <2021@wasatch.utah.edu>, haas@wasatch.utah.edu (Walt Haas) writes... >I'm shopping for a good way to test coax and twisted pair cables used in >Ethernet, Arcnet and broadband.................. > In particular I'm looking at a thing >called a Cable Scanner built by a company called M-Test. Does anybody in >netland have one of these? Who are their competitors? What percentage of >problems can be solved this way, vs. what percentage need the full TDR >treatment? > If this is the Cable Scanner built by MicroTest, I saw their sales brochures and it looked nice. Just before this we recieved a 3 Com Lan Scanner. It is similar in size to the Cable Scanner. Unfortunately it arrived brain damaged and kept going back to the main menu in the middle of testing cable. We are waiting for the replacement. We wanted something more portable than a regular TDR that would test broadband cables, thick and thin ethernet as well as twisted pair ethernet. For a $1000 this looked like the solution, but we won't know for a while yet. Rusty Smith Internet: rsmith@vms.macc.wisc.edu MACC Data Communications Bitnet: rsmith@wiscmacc (608) 263-6307 Univ. of Wisconsin @ Madison
ron@ron.rutgers.edu (Ron Natalie) (06/13/89)
Cabletron makes a relatively inexpensive TDR that is good for both Ethernet (and I believe 75 Ohm cables as well). We've got one, but I'm not sure that we've made real good use of it. Generally, it reassures us that there is nothing wrong with the cable. It is useful for figuring out when someone has broken your thinnet or unhooked the terminator. These handheld units can probably do that as well. -Ron
jsa00564@uxa.cso.uiuc.edu (06/14/89)
I recently purchased one of Micro-Test's Cable Scanners. So far, it has been very usful in finding breaks in our twisted pair cable environment. It appears to be very flexible for many types of cable, and can be calibrated for any other types. (It has Thick/Thin Ethernet, ArcNet, Twisted Pair parameters in memory). The instrument will also do some other non-TDR features, such as measure IEEE 802.3 traffic on a cable, and determine some RS-232 conditions (baud, handshaking, etc..). All in all a good unit. (Don't bother getting the "large case" though, it's just a 35mm camera bag...) ------------------ Jeff Autor jsa00564@uxa.cso.uiuc.edu at the University of Illinois also affiliated with Valmont Electric, Danville, IL Opinions expressed are my own.
hjp@bambam.bedrock.com (Howard J. Postley) (06/14/89)
In article <2021@wasatch.utah.edu>, haas@wasatch.utah.edu (Walt Haas) writes: > I'm shopping for a good way to test coax and twisted pair cables used in > Ethernet, Arcnet and broadband. > ... > In particular I'm looking at a thing > called a Cable Scanner built by a company called M-Test. Does anybody in > netland have one of these? Who are their competitors? What percentage of > problems can be solved this way, vs. what percentage need the full TDR > treatment? > > Thanks in advance for any beta -- Walt Haas haas@cs.utah.edu utah-cs!haas I have a couple Cable Scanners. I think that they're a great deal. I also have a full TDR which I hardly ever need anymore. The Cable Scanner and Sniffer pretty much solve all of my problems. I don't know who M-Test's real competition is but I have seen the box being OEMed by a bunch of people. I'll be selling my TDR, in fact I think that we already did - it isn't necessary anymore. //hjp -- Howard Postley internet: hjp@bambam.bedrock.com Ideal Point, Inc. uucpnet: uunet!bambam!hjp phonenet: +1 215 578 6901 uspsnet: 13428 Maxella Av M/S 236; Marina del Rey, CA 90292
hjp@bambam.bedrock.com (Howard J. Postley) (06/14/89)
In article <99@rsiatl.UUCP>, jgd@rsiatl.UUCP (John G. De Armond) writes: > In article <2021@wasatch.utah.edu> haas@wasatch.utah.edu (Walt Haas) writes: > >I'm shopping for a good way to test coax and twisted pair cables used in > >Ethernet, Arcnet and broadband. > >... > I've observerd the Cable Scanner in use and have used it a bit. My general > impression is that it is useful for determining the length of a known good > cable and for finding catastrophic failures (cuts, shorts, etc) but for > the problems we've had, it has been of little use. The catastrophic > failures can usually be observed visually (someone ran a chair over the > cable, etc). When the failures are marginal or intermittent, these little > pocket instruments leave a lot to be desired. A crushed cable or an > intermittent connector or an improperly crimped connector will not show > up on these boxes unless the condition is bad. This is 100% contrary to what I have found. We use our for exactly what is described above, and it works great! The only problem is that it tells you that there is a problem, but not in which direction so you have to move it to another test point. Crushed cables, bad crimps, and bad connectors and Ts are very hard to find visually. The cable scanner may ignore them on a first pass but if you adjust the tollerance threshold, it will tell you if your cable doesn't meet the spec for it's type, even if it's a perfectly good cable. The cable scanner knows what the impedance is supposed to be, what the tollerances are supposed to be. It has a toggle for teflon and PVC cable to accomodate for the minor differences between them. > What you have to do is determine whether the threshold of detection is > in the same ballpark as when the tranceivers quit working. I've found > little to beat the 'O-scope based units, especially the ones like the > Tektronics scope with the strip-chart option. You can literally > detect non-intrusive bending of a cable with this unit. Connectors - even > correctly crimped ones - show up clearly. And since you can make hardcopy, > you can build a history file of each cable. This history is the > absolute best way to quickly diagnose changes. You can also quickly > detect unauthorized new taps with little trouble. The cable scanner has a way to plug it into a normal o-scope to get this kind of information. The price difference is significant, to say the least. It also has an interface to a PC (and the software to use it) which can add histrories and a good bit of other information. > If your budget can handle it, get both instruments. If you can only > afford one, get the scope. It is more than worth the effort in > handling. Our budget could afford it and we found that the duplicity was totally unnecessary. We felt that our money was much better spent on an ethernet analyzer than on more cable analysis equipment. Tek makes some great stuff but the price you pay is based on something else, especially in this case. You could easily duplicate that kind of unit by integrating several pieces for less than 20% of the cost. Maybe closer to 10%. The thing is, you could afford to buy several cable scanners and have a bunch of people checking the various subnets of a new installation at the same time; that will also save you money. //hjp -- Howard Postley internet: hjp@bambam.bedrock.com Ideal Point, Inc. uucpnet: uunet!bambam!hjp phonenet: +1 215 578 6901 uspsnet: 13428 Maxella Av M/S 236; Marina del Rey, CA 90292