You can use IR thermometer to measure the sheet temperature. No matters of substance. http://www.youtube.com/watch?v=fhkqtxq8pYw

Thanks. That would probably give some idea of the heating, but if I want an accurate estimate, like within a few degrees? Is there some kind of simple thermal responsive dye that changes color at a defined temperature available?

You can measure the resistance change. If you have a four-point geometry, you can get a precise voltage drop for a given current. The resistance change is in first approximation proportional to the temperature change. You could calibrate it by equilibrating the film to a given temperature and measuring the resistance with a low current that does not change the film temperature. See also http://en.wikipedia.org/wiki/Resistance_thermometer

I agree with Dieter, measuring the temperature change would be a very elegant solution.

Try thermochromic liquid crystals (TLCs), they can be tailor made to suit the temperature range you need and the colour change can be easily detected , although they can be quite expensive

There are digital temperature probes available in the market which can measure the temperature of the solid surfaces heated by any method. Worth keeping one if you need it frequently.

Dear andreas,

you refer this following

There is hot wire electrodes.

You can calibrate the temperature with open circuit potential of the ferri ferro cyanide redox couple and the Nernst equation

(if that is applicable)

My first instinct is to suggest a tiny thermocouple, but this depends on a lot of factors. What is the substrate? Are you in air, or in a bath? Will the film stand up to being touched by a probe? Noncontact methods depend on emissivity, which will require calibration.

You can use IR thermometer to measure the sheet temperature. No matters of substance. http://www.youtube.com/watch?v=fhkqtxq8pYw

i agree the adivice of Shridhar Mundinamani. IR thermameter maybe an effecitve method to ueasure the temerature

From my experience I think you can simply spot weld a K-type Ni/NiCr thermocouple to the edge of your film. Then it will be easy to measureand monitor the temperature of the film during the heating.

Thanks all of you for great tips, I hope to have time to try out these ideas soon!

I agree colleagues who suggest the thermocouple or IR thermometer devices.

I suggest to contact Rolf Shuster from KIT. His group is working on microcalorimetry in electrochemical conditions. http://www.ipc.uni-karlsruhe.de/kom/english/426.php

How about a camcorder iR, is a noninvasive method for creating maps of temperature and observe their evolution over time. It should work fine as long as there is not much mass of dissolution or thermostatting jackets between the electrode and the camera

I agree with Schmachtel to calibrate the temperature with open circuit potential of a mixture of ferri ferro cyanide redox couple and using Nernst equation. I did calibrate my system in this way for microwave enhanced electrochemical systems.

Measure the losses (i.e. heat generation) by the change in impedance of the wire and then calibrate it.

(This works only for AC, not DC!!!)

It's similar to hot-wire thermometry. If you're heating with AC source with input frequency of ω, the voltage drawn across the metal film should contain 3ω component as well as ω because electrical resistance of a metal is normally temperature dependent. If you can extract this 3ω signal with a lock-in amplifier, the temperature rise will be calculated as (2*V3ω)/(α*Vω) where α is the temperature coefficient of resistance of the metal. Try if you are using AC.