In an experiment i was measuring resistance of glass and found out that for a constant voltage applied across the glass plate, current was higher in high humid situation. I have taken a 2cm*2cm float glass sample of 3mm and on its both surface conducting tape of 1.2cm * 1.2cm was sticked in the centre. Conducting tape were then just used to apply voltage across glass.
Hi Purnendu Kumar. More information is nedeed about your experiment details for a correct answer. (chemical composition of glass, temperature, sample geometry)
However, if you are measuring the resistivity of a silicate glass, like a window glass for example, variations in room humidity will not affect its volume properties at low temperatures. In this (special) case, in order to introduce water to the glass volume you will have to bubble water in the melted glass (about 1500C) when you prepare your samples.
Perhaps you can make an electrode arrange in order to minimize surface currents.
The glass surface is covered by a molecular layer of water. The thickness of this layer changes as a function of relative humidity. I don't know if this information is helpfull to understand your problem.
As you are mesuring with upper and lower surface electrodes, the humidity influence of the bulk glass shoulg be neglectable. If electrodes are on the same side, then you will be measuring mainly the surface layer, that has more defects and the water layer cannot be neglected. Besides the layer, whoose thickness is function of the humidity, if sample is not polished, you will have pores partialy filed with water.
You can try to paint the side sufaces with something or simply cover them with insulating adhesive. If the humidity influence changes, than the sides surface water layers are conducting.
Another posibility is that the adhesive conductor is influenced. You can try using conductive paste or otherconductive adhesive.
Probably the easiest test will be if you have larger plate. If same electrodes show nearly the same change of the conductivity, when humidity is changed, then probably something is hapening with the setup. (Be prepared to get different resistance/conductivity
Just saw that few sentences are cut away because of lenght limitation.
Edit: I wanted to point, that changing the surface to height ratio, will change the influence of the extra volume. I am attaching the 2d results for the electrical current of an application that I am working on.(gimp unsharpened is for better visibility).
Tried calculating the influence and my guess is that increasing the electrodes to cover the whole sample will lead to 2.3 times decrease of the resistance instead of 2.8. Decreasing the electrodes to 6 mm will increase the resistance 3.5 times or less instead of 4.
So in my opinion. Find the influence and stay with the conditions that you have most results.
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