About a year ago, my sons and I performed an experiment regarding the conductivity of salt water vs. fresh water. It was a fun and interesting experiment for my boys, so I came up with an idea to try, playing off of that experiment.
I was curious if we could get data to pass through water, using Cat5e Ethernet and replacing a length of the conductors with salt water. In order to do this, we would need a few supplies, which include:
– Clear, non-conductive tube (at least 4 pieces)
– Clamps, to hold them in place
– Most conductive salt water mixture
– Category 5e, Ethernet cable
– Computers for each side
– Ohm meter
The first step we needed to do was actually a smaller experiment, which was to determine the best salt-to-water ratio. Our control was 1 cup of tap water. We started by measuring the resistance with zero salt added, this yielded a result of 210 k ohms. The next figures are the results of the same cup of water, adding 1 Tsp of table salt each time:
WATER Tsp Salt Resistance
1 1 35 m Ohms
1 2 90 m Ohms
1 3 84 m Ohms
1 4 84 m Ohms
Judging the above results, it appears that their is a point of diminishing returns as far as the ratio of salt and water and the amount of resistance in which it decreases.
To be sure, we ran the experiment again, this time increasing the salt amount by 1/2 Tsp. The results were as follows:
WATER Tsp Salt Resistance
1 0 210 k Ohms
1 .5 38 m Ohms
1 1 38 m Ohms
1 1.5 83 m Ohms
Given the above results, we determined that 1Tsp to 1 cup of water was a good ratio, as the resistance appeared to increase after 1Tsp of salt.
It was now time to set up the experiment. At this point, I should explain a few things about Ethernet and how it works. There are eight conductors total, in an Ethernet cable. Only four of them are used to transmit data. in both IEEE standards, 568A & 568B, these are the Orange/White, Orange, Green/White, Green wires. The other four are reserved for PoE (Power Over Ethernet) applications.
That said, we bound the tubes together, side-by-side, in order to reduce the coiling and make them straight (for ease of filling them with water). We then bound them on each end, at the same height, so they would fill to the tip of each end. The total length of each tube was 5 feet and the inner diameter was 5mm.
After this was done, we filled each tube with our mixture of salt water (determined by the previous experiment). We cut an Ethernet patch cable in half and separated the Green and Orange pairs. They were then untwisted and each conductor’s insulation was stripped off of the end, approximately 2 inches. These ends were then stuck down into the separate, water-filled tubes.
Before connecting these to computers on each end, I decided to perform a continuity test on the link, using an Ethernet tester. Once connected, the tester did not indicate a link and raised the suspicion that the water mixture would not provide enough continuity to establish a link. I tested this further by inserting the leads of our Ohm meter on each side of one of the tubes. Tough we received a reading (indicating continuity), the resistance was 74 k Ohms (74,000 Ohms), which would cause so much attenuation in the signal, that a PC’s NIC (Network Interface card) would not even establish a link.
I felt at this point, it would be futile to connect the two PCs to so much resistance, as it may damage the NIC card, furthermore, the tester uses much more voltage and could not determine continuity over the conductors, so a lower power NIC would not be any better.
At this point we ended the experiment with Negative results (which in the Scientific community, are still results).
I do feel that we can achieve our goal of passing data through water, however I hypothesize that the water’s mixture should contain more elements, such as magnesium, iron, copper, etc.. and the conductors should be closer together, allowing the data to pass through less water. I feel that we will build upon this experiment, using the variables I just mentioned, and hopefully achieve a positive result.
It still proved to be fun and my boy got a kick out it. So we did achieve SOME level of success!