The LWDAQ (Long-Wire Data Acquisition) Specification calls for CAT-5 eight-way straight-through cables. We chose two varieties of CAT-5 cable and two matching modular plugs for use with the LWDAQ. Both cables are halogen-free, as required by European safety regulations. Both cables pass, for example, the CERN (Center European Research Nuclear) safety standards for subterranean installation. In our first long-term tests of the LWDAQ, we found that the reliability of the system was limited by the reliability of its cables. Since then, we have found that proper preparation of the cables, followed by proper application of matching connectors, strain reliefs, and protective boots, improves the reliability LWDAQ cables to the point where cable and connector failures are no more common than electronic and mechanical failures elsewhere in the system.
In this manual, we provide detailed instructions for making LWDAQ cables out of our recommended cables and connectors. We describe the making of white cables out of our white stranded-conductor cable, and blue cables out of our blue solid-conductor cable. The white cables can be up to 13 m long, and the blue cables can be up to 130 m long. The white cables are intended to act as LWDAQ branch cables (from multiplexers to devices), and the blue cables are intended to act as LWDAQ root cables (from multiplexers to drivers). That is not to say that you cannot have blue branch cables and white root cables. You certainly can have blue branch cables, and they can be up to 130 m long, just like blue root cables. And you can have white root cables as well, but they can be no more than 13 m long, just like white branch cables.
Both the blue and white cables have a foil shield, but the blue cable uses solid conductors, while the white cable uses stranded conductors. The solid conductors of the blue cable are electrically faster and present lower resistance, so that blue cables can be ten times longer than white cables. Because of its stranded conductors, however, the white cable is easier to prepare for connector application, and easier to install. Furthermore, the white cable is a standard CAT-5 cable with four twisted pairs, but the blue cable is a custom CAT-5 cable with only two twisted pairs. The remaining four conductors in the blue cable are untwisted, and used for LWDAQ power.
If your LWDAQ cables are short, perhaps because you are using the LWDAQ in your laboratory, consider buying ready-made straight-through Ethernet cables instead of making your own LWDAQ cables. Ethernet cables can be used as LWDAQ cables in most circumstances, as we explain below.
All LWDAQ cables are CAT-5 (Catagory Five) network cables, as specified in the LWDAQ Cables section of the LWDAQ Specification. Table 1 gives the color code and pin names for the connections at both ends of all LWDAQ cables.
| Pin | Signal | Wire Color | Description |
| 1 | T+ | Brown | LVD Transmit Positive from Driver |
| 2 | T- | Brown and White | LVD Transmit Negative from Driver |
| 3 | R+ | Orange | LVD Receive Positive from Device |
| 4 | R- | Orange and White | LVD Receive Negative from Device |
| 5 | +5V | Green | 5-Volt Power |
| 6 | 0V | Green and White | 0-Vold Return |
| 7 | +15V | Blue | +15-Volt Power |
| 8 | -15V | Blue and White | -15-Volt Power |
The cable can be CAT-5, or it can be a special case of CAT-5 in which only the brown and orange pairs are twisted together, but the remaining four wires are untwisted. Our blue cable is like that. It turns out that leaving four wires untwisted decreases the overall cable diameter, allowing the manufacturer of our blue cable to meet the CAT-5 dispersion and resistance specifications with a solid-conductor shielded cable, and keep the diameter within the CAT-5 specification as well.
The CAT-5 dispersion and resistance specification for cable with solid-wire conductors is far more stringent than that for cable with stranded-wire conductors. High-frequency signals travel along the surface of wires, as a consequence of the skin effect. We discuss the skin effect and how it distorts signals in transmission lines elsewhere. A 1 GHz wave travels in the top 2 μm of a wire. A solid copper conductor with a smooth surface and circular cross-section provides far better transmission at high frequencies than a stranded conductor of the same diameter, whose copper surfaces are less smooth and whose outer diameter is less circular. Stranded-wire cable, on the other hand, is far more flexible than solid-wire cable.
Stranded CAT-5 is intended for short cables, often called patch cables, and solid-wire cable is intended for long cables, such as those used to distribute a local area network throughout a building. We would like to give you a link to the CAT-5 specification, but we cannot find a site at which the specification is available for free.
Below is a graph showing how the returned analog signal becomes attenuated by the above cables as we increase the length of the cables. The graph shows the saturated image contrast we obtain from a BCAM instrument as we increase the cable length, and introduce repeaters. The total cable length is the sum of the lengths of all the cables that lie between the driver and the device.
Figure: Image Contrast for Cable Length. At the end of the root cable we have a ten-slot multiplexer fully-loaded with BCAMs. We obtain an image by taking a picture of the two lasers on one BCAM with the camera on another.
For lengths less than 100 m, we see the image contrast decreases as we expect from the voltage divider formed by the cable resistance (approximately 10 Ω per 100 m) and the terminating resistor in the driver (100 Ω). After that, the contrast begins to vary sharply with cable length. This sharp variation is an interaction between the driver's cable-length compensation system and the smoothing of signal transitions along the cables. The driver measures the time taken for an electrical signal to propagate to and from the device, a time we call the loop time, and uses the loop time to synchronize its digitization of returned analog signals with outgoing digital clocks. A 10-ns change in the loop time, which is the same as changing the total cable length by 1 m, can cause a significant change in the image contast. In addition to these rapid cyclic changes, we continue to see an underlying decrease in image contrast. At around 140 m without a repeater, the lasers stop flashing. The outgoing LVD signal has been attenuated beyond recognition by dispersion in the cable. When we add a repeater at 80 m or 130 m, we find that we can increase the total cable length to 200 m and 220 m respectively. Once again, failure is sudden, and takes place because the lasers on the BCAM stop flashing.
Our white cable is a halogen-free stranded CAT-5 cable, part number 2809 (data sheet pages one and two) from Quabbin Wire and Cable. Halogen-free cable is unusual in the United States. You will not find it on the Quabbin web site.
Manufacturer Part Number: 2809 Manufacturer: Quabbin Wire and Cable, USA Conductor: stranded tinned copper Insulation: foam polypropylene Shield: aluminized polyester foil Drain Wire: 26 AWG solid tinned Jacket Diameter: 5.6 mm max Jacket: low-smoke zero halogen Operating Temperature: 60 C max Flame Rating: IEC 332 part 1 Corrosive Gas: IEC 754 Smoke Emission: IEC 1034 Jacket Tensile: 2000psi min Jacket Elongation: 160 % min Tear Resistance (per ASTM D1004): 35 lb/in min. Approximate Price: $0.25 /ft
The white cable provides a foil shield and drain wire. We use the drain wire and a metal strain relief to connect the cable shield to the shield of a modular plug. The modular plug we recommend for all white LWDAQ cables is the 5-569552-3 from Amp (Part number A9111-ND from Digi-Key). This plug comes with a load bar, which is the little black part in Figure 2. The load bar makes it easy to push the flexible stranded wires of the white cable all the way into the connector, where they can be crimped by the connector's gold contacts.
Manufacturer Part Number: 5-569552-3 Digi-Key Part Number: A9111-ND Manufacturer: AMP/Tyco Electronics, USA Description: modular plug, shielded, 8-way, with load bar. For Cable Type: round cable For Conductor Type: stranded wire Approximate Price: $1 each
Along with the shielded plug, we use a strain relief, part number 558527-1 from Amp (Part number A9130-ND from Digi-Key). The strain relief holds the cable jacket firmly, and presses against the cable's drain wire, so that we have reliable connection between the cable shield and the connector shield.
Our blue cable is a halogen-free solid-wire modified CAT-5 cable, part number 08508 designed by Quabbin Wire and Cable specifically for the LWDAQA. The blue cable is faster on its two twisted pairs than the white cable, and offers less resistance. But it offers only two twisted pairs instead of the CAT-5 specification's four twisted pairs. The LWDAQ needs only two twisted pairs. The remaining four wires it uses for power.
Manufacturer Part Number: 08508 Manufacturer: Quabbin Wire and Cable, USA Conductor: solid copper Insulation: foam polypropylene Shield: aluminized polyester foil Drain Wire: 24 AWG solid tinned Jacket Diameter: 5.6 mm max Jacket: low-smoke zero halogen Operating Temperature: 60 C max Flame Rating: IEC 332 part 1 Corrosive Gas: IEC 754 Smoke Emission: IEC 1034 Jacket Tensile: 2000psi min Jacket Elongation: 160 % min Tear Resistance (per ASTM D1004): 35 lb/in min. Approximate Price: $0.25 /ft
The blue cable provides a foil shield and drain wire. The modular plug we recommend for all blue LWDAQ cables is the 5-569530-3 from Amp (A9115-ND from Digi-Key). Unlike the connector we recommend for the branch cables, this one does not have a load bar. The solid wires of the blue cable are stiff enough that you can push them all the way into the plug without them bending. There is another connector available AMP, part number 5-569550-3, Digi-Key part number A9112-ND, which does provide a load bar, but we find the load bar to be unecessary, and we prefer to avoid the trouble of dealing with one extra part in the assembly procedure.
Manufacturer Part Number: 5-569550-3 Digi-Key Part Number: A9115 Manufacturer: AMP/Tyco Electronics, USA Description: modular plug, shielded, 8-way, with load bar. For Cable Type: round cable For Conductor Type: solid wire Approximate Price: $1 each
Along with the shilelded, solid-wire plug we use the same strain relief with this plug as we use with the stranded-wire plug (558527-1, part number A9130-ND from Digi-Key).
The stranded-wire and solid-wire connectors are almost identical, but if you look at the crimping contacts with a magnifying glass, you will see one essential difference between them. The crimps of the stranded-wire connector have two teeth that bite straight down and through the insulation and conductors of each wire. But the solid-wire crimps have two teeth angles away from one another slightly, so that they bit down on either side of the solid conductor inside the wire.
Note that the white cable is fully CAT-5, and you can use it to make Ethernet cables according to the industry-standard Ethernet color codes and pinouts. But the blue cable is a modified CAT-5 cable. You can make an Ethernet cable with our blue cable, but you need to use a modified color code, as we explain below.
The above figure shows the various colors of connector boots we use LWDAQ cables. All our boots provide a protective cover for the connector locking tab. The cover allows you to drag the cable across the floor, and through apertures, without worrying about snapping the tab off. The cover also makes it more difficult to press the locking tab down to release the connector. We tried boots without the protective cover, and they are easier to use when you are plugging in and unplugging the connector frequently. But it is easy enough to cut the protective cover off the boot with a razor blade for those cables that you are frequently unplugging. So we settled in the end upon boots with the protective cover.
The boots provide a small flat space on one side in which you can write a number to distinguish between cables with the same boot color.
Our Cable-Making Kit contains the following.
To make cables according to our instructions, you will also need a scalpel or razor blade, a pair of wire cutters, a magnifying glass, and a bright lamp.
The figure below shows the end of a cable with a few inches of jacket and shield removed. The individual conductors are separated and arranged in the order in which they must be inserted into the connector. Also in the picture are the strain relief, and the black plastic loadbar, which comes with the connector. The boot is already on the cable, and the drain wire, which provides electrical connection to the shield at a laterstage in the connector application, is off to the left. Not shown is the connector itself. Your first step in making a cable is to push the plastic boot onto the cable.
Remove 50 mm of jacket from the end of the cable. Cut around the cable with a scalpel, bend the jacket at the cut a couple of times, and pull the jacket off over the end of the cable. You do not have to worry too much about cutting the conductors, because the shield protects them. But don't cut so hard that you pass through the shield and cut the wire insulation. With the jacket removed from the end of the cable, you will probably encounter the drain wire. Don't cut the drain wire, we will use it later with the strain relief to make the cable shield connection. The drain wire is connected to the shield inside the cable. Fold it back and keep it out of the way until we come to crimping the strain relief.
Tear off the foil shield. You have probably scratched it already with the scalpel, so it will tear easily. If not, cut it off with your wire cutters. Remove the transparent binder around the wires as well, which you might also have to cut with your wire cutters. Study the wire insulation where you made your scalpel cut, looking for nicks. If you see any, cut the cable back and start again.
Separate the wires of each twisted pair by inserting your nail, or a screw driver, in between the wires near the jacket, and pulling out to the end of the pair. Straighten the wires as best you can, and arrange them between your thumb and fore-finger in the correct order from left to right, as shown in above. Start by holding the brown wire between the thumb and fore-finger of your left hand. Without relaxing your grip on the brown wire, slide the brown-and-white wire between your thumb and forefinger until it presses up against the brown wire. Keep going until you slide the blue-and-white wore up next to the blue wire. The trick to gathering the wires up between your thumb and fore-finger is to resist the temptation to relax the pressure with which you secure the wires each time you slide a new wire in to join the others. If you relax the pressure, the wires come loose and get mixed up.
With the wires held in the correct order, and pressed up against one another, straighten them out some more. No matter how hard you try to straighten out the ends of the 50-mm wires, they are always too curly to fit into the load bar. You prepare them for the load bar by cutting them until they protrude by only 15 mm from your fingers. The eight wires should stick straight out from your fingers, touching one another, and be square-cut at the end.
Pick up a load bar. Hold it with the open side up and slide the wires in and through the loading slot. What you have now should look like the photograph above. The load bar has its open face towards us in the picture.
Alternative Method: Ed Diehl of Michigan University tells us that he prefers to insert the cables into the load bar one at a time, thus saving himself the trouble of gathering them together between his thumb and forefinger.
Hold the cable next to the connector as in the photograph above, so you can judge how close to the end of the jacket to place the load bar. The jacket should extend 5 mm past the base of the connector, and the top end of the load bar should be just past the bottom end of the gold-plated contacts. Cut the wires straight across 2-mm beyond the end of load bar, as shown in below.
Hold the connector with the locking tab down, and hold the cable with the open face of the load bar on the top. The brown wire is on the left, and the blue-and-white wire is on the right. The drain wire should be folded down and out of the way. Push the load bar into the aperture at the base of the connector. As the jacket begins to enter the connector, you feel some resistance. Ease the jacket into the connector. Once it's in there, force it even farther inside. When it stops, push harder and move the cable back and forth, to work the wires down to the end of the connector.
Let go of the connector. If you keep holding it, you risk pulling the wires out. Hold the cable only. The cable and connector should now look like the photograph below.
With your bright light and magnifying glass, examine the end of the connector. You should see eight wires, with their stranded conductors sparkling in the light, pressed up against the transparent end wall of the connector housing. If the wires are there, you will see each of them clearly, and you can be sure that you are ready to crimp the connector. But if you cannot see all eight wires clearly through the end wall of the connector, you must pull out the wires and the load bar and try again.
Assuming all the wires are visible, you are ready to crimp. Push the connector into the modular crimping tool as show below and squeeze the tool's crimping arms together. If you are in any doubt about how to use the crimp tool, follow the printed instructions that come with the tool in its packaging. You should hear a snapping noise at the end of the crimp. That noise is the jacket restraint snapping into place. Take the connector out of the tool. You may need to press down the locking tab on the connector in order to get the connector out of the crimping die. Look at the jacket through the narrow side of the connector and you will see the jacket restraint has been forced down and into the jacket, holding it in place.
Check that all eight crimp terminals are pressed down into the connector. None of the crimp terminals should stick out above the plastic ridges that separate them. Check also that the connector has a firm grip upon the cable jacket. A good grip on the jacket indicates a successful crimp.
Although the jacket restraint does hold the jacket in place, a good tug on the cable will loosen the jacket restraint's grip. Furthermore, we have not yet made a reliable contact between the shield of the connector and the shield of the cable. The strain relief (see photograph, item 2) solves both these problems for us. It holds the cable very firmly, and grabs onto the cable's drain wire to make the connection between the cable and connector shield.
The strain relief has two pins that fit into two notches at the base of the connector. The notches are at the base of the connector, where the cable enters, on the opposite side from the locking tab. The notches are almost invisible, but you can feel them with your fingers. The strain relief crimp tool comes with some clear drawings which will help you apply the strain relief correctly, and we you can also look at the manufacturer's drawing of the strain relief itself for some guidance.
Push the strain relief pins as far as you can into the notches, so that the strain relief sticks to the connector. Use the flat surfaces on the tips of the strain relief crimp tool to push the strain relief all the way into the connector, as show below. The strain relief should now be fixed firmly in place.
Wrap the drain wire a couple of times around the cable-gripping arms of the strain relief.
Hold the strain relief with the strain relief crimp tool as shown above and squeeze the tool's crimping arms together. The crimp tool will wrap the strain relief arms around the cable jacket, forcing the drain wire against the arms, and holding the jacket securely.
Trim the drain wire and push the connector boot up over the base of the connector. The finished product looks like the photograph below.
To complete your cable, put a connector on the other end as well. Remember to put the boot on first. Measure the length of the cable and add 40 mm to the required length before cutting the cable. Now remove the final two inches (fifty millimeters) of jacket, and you will end up, after following the procedure given above, with a cable of the correct length, give or take a few millimeters.
The figure below shows the wires of a blue cable exposed after the jacket and shield have been cut back. You will notice that the brown and the orange twisted pairs are wrapped in their own transparent plastic binder. You must unwrap this binder before you can separate the wires as shown in above.
The blue wire's conductors are solid copper, so they are stiffer. This means that they are more difficult to straighten out, but on the other hand they are easier to push into the connector. We recommend that you use the solid-wire connector without load bar. You follow the same procedure as you would for white cables, with the following changes.
When you make root cables, be sure that you are using the solid-wire connectors, not the stranded-wire connectors. If you use the stranded-wire connectors, the teeth of the connector contacts will attempt to cut through the center of the solid wires, and when they fail to do so, they will pass to one side, and the contact between them and the wire will be unreliable. In a few years, oxide will build up on the copper and contact will be intermittent.
You may find that you don't have space adjacent to your LWDAQ device for a strain relief and a connector boot. In that case, you can sacrifice shielding and toughness for a smaller connector. The figure below shows our cut-off, unshielded modular plug that is part of a low-profile cable. You make one of cutt-off plugs by cutting off the jacket-crimping part of an unshielded modular connector like the 940-SP-3088R from Steward Connector. The jacket-crimping part is the rear 11 mm. We made our cut-off plugs on a band saw, where we were able to cut three per minute without hurrying. At first, we cut off the connector's release tab along with the connector body, but after complaints from our users we started leaving the tab intact.
To make the low-profile cable, you strip the jacket and shield from the cable, add a cut-off plug to one end, and an ordinary unshielded plug to the other. Removing the jacket and shield allows you to get the wires through tight spaces. We forsee no problems with cables like these up to 100 cm long. If you are going to make them longer than that, we suggest you try the cables in their final environment, so you can see if they contaminate other instruments with broadcast noise, or if the LWDAQ signals are themselves contaminated.
To keep the unshielded cables short, you can use an RJ-45 union 50 cm to 100 cm from the cut-off plug. If you use a shielded metal union, you can connect the union housing to your local ground, so that the shield leading to the union will operate properly.
Out of ten low-profile cables we made, three did not work. We had to replace the cut-off connector because we had not crimped it properly. Crimping the cut-off connector takes some care, because crimpers like the one we recommend above use the rear end of the plug to stop you from pushing the plug too far into the crimper. The cut-off plug has no rear, and so you must be careful not to push it in too far. Once we discovered this problem, we were able to crimp the cut-off connectors reliably.
Our chief concern with these low-profile cables is not noise, signal integrity, and cross-talk, but rather the mechanical integrity of the connectors. The wires are held in place each by their own contact crimp. There is no other strain relief. We recommend adding a cable tie around the twisted pair bundles, about 10 cm from each connector. This helps spread cable strain across the eight wire crimps.
Another way to make the low-profile cable more rugged is to leave the jacket on for most of the length of the cable, as shown above. This hybrid low-profile cable is 100 cm long, with the final 20 cm bare of jacket and shield.
We do not provide a special test circuit for cables. We thought about designing one, but testing the high-frequency properties of the cable is difficult. Ethernet cable test devices can cost up to a thousand dollars. So in the end we decided to use what you have already on hand: the LWDAQ and a voltmeter. Testing a cable with the LWDAQ is a four-step process. You will need a LWDAQ with an analog image sensor of some variety, like the Inplane Image Sensor (A2036), the Camera (A2056), or a BCAM Head (A2048).
Step One: Hold both connectors in front of you with the locking tabs down. Make sure that the left-most pin on each connector is connected to the brown wire. If you are color-blind, you will have trouble with this step, so ask someone who is not color-blind to perform it. This step makes sure you have not reversed the order of the wires, an error that damages multiplexers and devices.
Step Two: Hold both connectors in front of you, and measure the resistance between their shields. This resistance should be < 10 Ω. This is the only check of the shield we perform: we assume that it will work correctly to block out noise and prevent radiation so long as it is connected at either end.
Step Three: Hold one connector in front of you. Measure the resistance between the shield and each of pins 3 and 4. Don't press hard on the two connector pins, because you will bend the plastic trench around the gold contact. This resistance should be > 1 MΩ. When either of these two pins is connected to the shield, it is possible for the cable to provide image capture with good contrast when it connects a device to a driver, but fail to provide good contrast when we combine the cable with a repeater or a multiplexer. It is far more likely that you will discover a connection between the shield and pins 3 or 4 when you are making a blue cable than a white cable. The two wires to which pins 3 and 4 are connected are bundled together in the blue cable, and are made of solid copper. When you crimp the connector, a plastic tab pushes down into the bundle of wires, and we have observed it to push aside the insluation around the wires, thus exposing them to the connector shield.
Step Four: Capture live images from an analog image sensor.
We know of no cable errors that can pass through all four of the above tests, but all tests are necessary.
The white cable is flexible: we can bend it back upon itself many times without seeing any effect upon the jacket, shield, or conductors. But the blue cable is much more stiff, on account of its solid-wire conductors. The halogen-free jacket is not as resiliant as a halogenated jacket. The result is a cable that can become disfigured after repeated right-angle bending, as Alex Asen describes below.
"I bent the new blue cable back and forth at a right angle twenty times. After the test, the jacket is slightly discolored, turning white from blue. The photograph accurately reflects the amount of discoloration. The bending test caused several breaks in the aluminum foil shielding. The foil, however, has a thin plastic backing that prevent it from tearing completely through. The plastic backing remained completely intact even in place where the foil broke. No single tear in the foil runs the entire width of the foil, so the electrical continuity of the shielding was not broken. Although it appears that a great number of bends would eventually break the continuity of the foil, after twenty bends there is no single gap larger than half the width of the foil. There is no visible damage to any of the wires inside the shielding and all passed testing with the cable tester."
We have the following report from Aatoli Kozhin, which appears to agree with Alex's findings.
"it was the simplest test, I have bended (90 degrees, about 0.5-1cm of radius) the cable few times in one place, check its integrity by the cable-tester, then opened the jacket and looked at the shielding aluminium foil. The foil was locally destroyed, The jacket was not destroyed, only slightly changed colour (became white) in place of bending."
Table 2 gives the pinout for a straight-through Ethernet cable. LWDAQ and Ethernet cables look the same. They use CAT-5 cable and have eight-way modular connectors on either end. You can use one type of cable in the place of another. In particular, you can buy commercial ethernet cables up to 10 m long and use them in your laboratory LWDAQ.
| Pin | Signal | Wire Color | Description |
| 1 | T+ | Orange and White | LVD Transmit Positive |
| 2 | T- | Orange | LVS Transmit Negative |
| 3 | R+ | Green and White | LVD Receive Positive |
| 4 | NC | Blue | Unused |
| 5 | NC | Blue and White | Unused |
| 6 | R- | Green | LVD Receive Negative |
| 7 | NC | Brown and White | Unused |
| 8 | NC | Brown | Unused |
The first thing to note about the straight-through Ethernet cable is that it connects precisely the same pins on its connectors as would a LWDAQ cable. One difference is that pins 3 and 4 pass share a twisted pair of wires in the LWDAQ cable, but not so in the Ethernet cable. Conversely, pins 3 and 6 share a twisted pair of wires in the Ethernet cable, but not so in the LWDAQ cable. This difference between the two cables has no effect upon their behavior at lengths of a few meters. The color coding is different of the two cables is different, too, but this does not affect short cables either.
Claim: LWDAQ and Straight-Through Ethernet cables are interchangeable for lengths up to a few meters.Let us consider what happens if we use a long straight-through Ethernet cable as a LWDAQ cable. The LWDAQ's T+ and T- LVDS (low voltage differential signal) propagates along the twisted pair of wires with colors orange-and-white and orange respectively. The R+ and R- lines do not propagate down a twisted pair. The high-frequency components of the signal recovered by the driver at the end of a long cable will be attenuated. If the signal returned from the LWDAQ device is 2-MHz analog data, such as that returned from a BCAM Head (A2051), or low-frequency measurements such as those from the RTD Head (A2053), this high-frequency attenuition will be of no consequence. But if the device is transmitting logic signals with 50-ns pulses, as some of our future devices will do, the returned signal might be unusable.
Claim: Any Straight-Through Ethernet cable up to 10 m long can be used as an LWDAQ Cable.If we use a LWDAQ cable as an Ethernet cable, the Ethernet R+ and R- signals don't get passed along a twisted pair of wires. Our experience is that a ten-meter blue LWDAQ cable will work for 10-Base-T but not 100-Base-T. A five-meter white LWDAQ cable will also work for 10-Base-T but not 100-Bast-T. You might hope that your computer will auto-negotiate 10-Base-T instead of 100-Base-T when it is communicating across such a cable, but that is not what happens. Instead, the computer selects 100-Base-T any time the device at the other end supports 100-Base-T, and then the communication is slow because of packet loss.
One final thing we might worry about is, "What happens if we connect a LWDAQ socket to an Ethernet socket?" If you look at the two cable pin-outs, you will see that the LWDAQ connects no power to any of the Ethernet signal pins, so no damage will occur to either device.
Claim: No harm will come to either device if we connect any LWDAQ socket to any un-powered Etherenet socket.We say un-powered because sometimes networks, especially ethernet-based phone networks, use the four free wires on the Ethernet cable to carry power for Ethernet devices. If power is carried on these pins, it might blow the LWDAQ R+ input. The power supplies themselves will conflict with one another, and both are, presumable, protected against short circuits.
Claim: No harm will come to a powered Ethernet socket if you plug it into any LWDAQ socket.If you use our blue cable to make a straight-through Ethernet cable, then you should change the color code of the Ethernet cable. Use the brown-white and brown wires for R+ and R-. If you use the usual Ethernet colors, Ethernet R+ and R- will not be twisted together, and the cable will attenuate a 100-Base-T signal.
Now let us consider Ethernet cross-over cables. The 10-Base-T and 100-Base-T cross-over cables exchange pins 1 and 2 with pins 3 and 6, but are otherwise the same as straight-through cables. A LWDAQ device will not work with such a cross-over cable, but neither will it suffer any damage. The same is not true for 1000-Base-T (gigabit) cross-over cables. These switch all the remaining pins around as well, and connect power in reverse to the LWDAQ device. The cable destroys the device. In the case of several A2051 devices connected with a gigabit cross-over cable, all seven logic chips on the board were destroyed.
If you follow the instructions we give here, and use the cable, connectors, and tools we recommend, you will make reliable, robust cables. White cables are more flexible, and easier to make. They are easier to make because the twisted pairs are not wrapped in individual binders. The blue cable contains two twisted pairs, and each is wrapped in its own binder, which you must unbind before you apply the modular connector. But the blue cables can be over 130 m long, compared to only 13 m for the white cables.
If you do not want to make your own LWDAQ Cables, and you are working in a laboratory where halogen-free cables are not a requirement, you can try using commercially-available eight-way straight-through Ethernet cables with the LWDAQ. You don't have to worry about damaging either the LWDAQ or Ethernet sockets through any confusion about which cable plugs into which socket. No such damage will occur, except possibly in the rare case of a powered ethernet socket, which might damage a LWDAQ device if you conect them together.
