Strange effect!

Hi all,

in preparation for some research I have built a simple sell on an electronic balance able to resolve 0.01g, the power supply and balance are controlled and report to a Pc and I am able task the system to run a setup and log the results, the preliminary results have me scratching my head.

On energizing the system I see an apparent initial INCREASE in the weight, of about 0.75 grams, with the expected loss of weight as the task is run. The complete cell weighs some 850g. the running parameters are top volts max 5 volts, middle amps 5A max, bottom weight. The conductors are as flexible as I can get and are supported some 100mm from the cell, the balance does not move up and down when weighing and will correctly weigh a 1g mass with the wires connected. If it was electro magnetic I would expect the result to be instant, the cell is covered but not sealed.

Any ideas welcome ?!!!!! 

Htwogo

Excellent setup, Htwogo!!!

And awesome results!
I?ll be very, very interested in following your experiments.

For the moment I just want to let you know that I?ll be scratching my head besides you?
I?ll be thinking on the subject but right now I?m in a big hurry.

Here is one dirty idea; you?ll probably have to check it if not dismissed already:
- magnetic interaction between the cell&wires and something in the electronic balance (or something existing bellow/around it), due to the magnetic field at 5A.

If you replace the cell with a simple resistor and run the experiment again, you should know if this is the case. If it?s not, it?s needless to say that the discussion and the associated excitement will follow. The effect seems very strange indeed.

Another kind request for you in order to figure out what is happening would be to repeat the experiment and to vary the current/voltage in a linear manner from 0-5-0V and to plot the results. It may not tell much but it may reveal something extra.

I?d be also interested in telling us more about your setup (balance and software), if possible. Is it custom made?
(At that resolution and with automatic acquisition, a lot of extremely exciting hypotheses can be verified, in a lot of areas!)

I very warmly welcome you aboard,
Tinu

The strange weight increase seems to be due to some influence from the power leads, perhaps heating of the polymer jacket. I draw this from the recovery after the power is removed and the reported weight is seen to recover. Also I removed the leads, zeroed the balance, ran a 100 second task at 6V @ 5A powered down and removed the leads, here I only saw a steady weight reported with no change with time.

The ramp up did however show little current flow until 2.5V, I will look at this when I get my new cell configured, and running on DI water. This would suggest that the cell is not a dead resistance but has some threshold potential that must be over come before current can flow.

Best HTowGo

http://en.wikipedia.org/wiki/Ballooning

Quote

Gas balloons are filled with gases such as:
hydrogen - not widely used for aircraft since the Hindenburg disaster because of high flammability (except for some sport balloons as well as nearly all unmanned scientific and weather balloons).

Logic would assum that it vibration due to ION movement, effecting scale. If not the case then perhaps ION flow affects gravity This is really interesting, I would try pure DC also.

George King
georgeking@cosmicsalamander.com

He probably meant using battery power to eliminate possible influences from the variable power supply you are using; however, it sounds like you are using a well regulated, lab-type supply.

If you suspect conductor heating, I would use heavier guage wire, but that presents a problem with the conductors being "as flexible as possible". Trying to think of a way around that...

Actually, if you suspend the electrodes of the cell in the water by the power cables themselves (hanging from vertical), so that none of the cell?s parts is in physical contact with the walls of the glass or with its bottom (but electrodes still completely submerged), then those effects due to the cables should be at least significantly minimized. If the cable length from the ?hanging point? to the water level is short enough, I hope that the consequences of wire dilatation will fall under the available weighting resolution.
   
It may very well be due to thermal effects after all, judging by the second graph. Almost linear increase (a good approximation for dilatation) followed by an exponential decrease, due to the cooling (caloric exchange with the environment).
My initial hypothesis (magnetic interaction) is clearly not of prime importance. That?s obvious. If it was, that exponential fall after cutting power off wouldn?t be there. Thermal effects fit the picture much better. (And I apologize for questioning it, as you clearly dismissed magnetism at the end of the first post; at a first glance, without zooming in, the fall seemed pretty instantaneous to me, as seen on the first graph)

Hope it helps.
If not, please post more, eventually about the cell itself as well as others details of the setup, as you may consider relevant.

Tx,
Tinu

P.S. Using a full ?on the balance setup? is actually not a bad idea at all. Not because the source may not be good enough but because it would eliminate from start the main thermal dilatation effects. A small rechargeable 9V may provide for a short time enough voltage (although at low current) at a relatively small added weight. It would not be much of an issue that voltage and current will remain un-recorded. (Both can be measured in advance and their exact value is not of concern here). But the small pain in the ? (technically speaking) would be, imho, to switch the cell on-off remotely, without really disturbing the balance.
Assume that, indeed, a weight increase will be felt in the above case. Now, that would be meaning one hard& long head scratching! Almost can?t wait the final outcome.

Well, floatation is the second candidate to the strange effect after thermal. I?ll explain myself, mainly for all readers; I assume you are familiar with it, HTwoGo.

Contrarily to any common sense, floatation of electrodes might lead to an increase in the weight of the cell.
Here it is a simple experiment in supporting the above, experiment that can be checked with almost any balance. Take a glass with some water. It will weight one value. Put your finger in the water, without touching the glass. You?ll see then the glass weights more. Why? Because due to floatation (Archimedes), your finger is pushed up. But due to Pascal and Newton 2nd, this force is transmitted through the water to the bottom of the glass, being felt as a supplementary pressure, measured by the balance as a supplementary weight.

I come back: Assuming that part of the electrodes weight is supported by the power cables and, through them, further supported by /transferred to the external setup, this part of the weight is not initially recorded by the balance. When electrolysis begins, due to the bubbles attached to the electrodes, a fraction of that part of the weight is no longer supported by the wires (and by the external setup) but is supported by the bubbles and further transferred to the balance, as per above-paragraph explanation. Hence, bubbles start to form -> balance starts indicating a weight increase.

I still have to figure out how to overcome this without all on-the-balance setup. I also can?t be 100% sure of the above, never done that except the first experiment with a common balance, but at least that?s physics say it should happen.

Pls comment,

Tinu

P.S. Also, I apologize for my limited English. If I was confusing, please indicate in which part.

pics