Strange effect!

[Davetech]

Perhaps I should keep my mouth shut since I had never even heard of the floatation effect. It certainly is counter-intuitive.

But it occured to me that maybe flotation could be ruled out if you run the weight measurement test without any electrolyte? If you still get a weight increase, it won't be due to floatation (unless it is floating on air... lol)

[HTwoGo]

Hi,
I have strapped one of my temperature sensors to an existing load cable with the following results, at 50 watts I am seeing a temperature gain of 2+ deg C over 10 minuets, (on the outside of the cable), this is far more than I was expecting, so I guess my existing leads are lighter than I expected, I have swapped the cables with 4.0 mm2 and the mechanics are better this now shows less than 1 deg C rise for the same load. But still I am seeing a 0.2g increase in weight! If the effect is purely electro thermal mechanical I would expect both positive and negative influences, but to date I have only ever seen this small positive increase then the expected decrease, perhaps there is purging of the air volume above the electrolyte with the H2 and O2 mix that may extend into the volume of air above the cell that may initially contribute a buoyancy effect on the cell that is masked as the mission progresses, the H2 may initially also be preferentially breaking the surface of the electrolyte due to its density, this effect is then lost as the system stabilizes? Comments?

Best, HTwoGo

[HTwoGo]

Perhaps I should keep my mouth shut since I had never even heard of the floatation effect. It certainly is counter-intuitive.

But it occured to me that maybe flotation could be ruled out if you run the weight measurement test without any electrolyte? If you still get a weight increase, it won't be due to floatation (unless it is floating on air... lol)

...next you will be telling me that water can burn using only electrisity!!
and that would be floating in air.

[tinu]

Hi,
I have strapped one of my temperature sensors to an existing load cable with the following results, at 50 watts I am seeing a temperature gain of 2+ deg C over 10 minuets, (on the outside of the cable), this is far more than I was expecting, so I guess my existing leads are lighter than I expected, I have swapped the cables with 4.0 mm2 and the mechanics are better this now shows less than 1 deg C rise for the same load. But still I am seeing a 0.2g increase in weight! If the effect is purely electro thermal mechanical I would expect both positive and negative influences, but to date I have only ever seen this small positive increase then the expected decrease, perhaps there is purging of the air volume above the electrolyte with the H2 and O2 mix that may extend into the volume of air above the cell that may initially contribute a buoyancy effect on the cell that is masked as the mission progresses, the H2 may initially also be preferentially breaking the surface of the electrolyte due to its density, this effect is then lost as the system stabilizes? Comments?

Best, HTwoGo

0.2g increase in weight is already much smaller than 1.1g!
So, it?s mainly thermal. You were right from the very beginning.

The pictures are excellent!
What I would do would be letting the power cables between the cell and the clamps a little longer. As they are now in the photos they are curved up (going from the cell to the clamp) and they seem to push down on the cell. (Of course, the cell is not shown on the balance and I can not be sure.) Is it possible that the increase of temperature is increasing the force of the wires pushing down on the cell? It may well be the case. But you are right; you have to see both influences: positive and negative and I would still pursue in that direction. So, I would play again with the wires, curving/bending them down (the opposite way of that leading to a weight increase) and then maybe letting them be longer also.

Also, the time interval between placing the cell on the balance and between the start of experiment may also count a lot. (I mean by that the time passed since the last mechanical action on the wires themselves)
Here it is: the cables are flexible. Bend them in your hand and then let them relax. Relaxation time may be very, very long; maybe many hours. (That?s due to the insulation). By changing the temperature, the relaxation speed varies; hence the force varies also?

Anyway, 1.1g/35W -> 0.2g/50W is already a huge progress! Just dig on it.
And please keep us informed.

Tx,
Tinu

[HTwoGo]

?going back to the old cables for convenience, I have run a number of missions to satisfy myself that there is no odd electronic interference, but the picture is little better.
I have set a 12V 50W lamp on the cell top and taken the cell out of the circuit, the balance is zeroed and a 10000 watt mission run taking 200 sec, then the system is stood for 200 sec to stabilize, the balance is zeroed and the protocol repeated.
The first mission was from cold so may be misleading, but 4 missions were run with one polarity and 2 with the polarity reversed, I can see little difference between them. There are air currents set up by the lamp and this I believe accounts for the changes in the readings, I must say that I didn?t expect this part of the project to be so problematic! I did initially think that cell weight loss would be a better way of measuring gas production but perhaps not.
Any comments.

Any one know anything about electrostatics? Could I have a charge building and leaking away?

I think I am going to set this aside for the moment and focus on the target hardware, this I think will not have many of these problems built in. I will update to this thread as long as think it is interesting readers.

Best, HTwoGo