11-04-2011 11:47 AM
T1 and T2 or Thot and Tcold is read by Lakshore 336 temperature controller. and dV from K182 voltmeter. as you know I also control T1 and t2 temperatures from lakeshore, I mean temperature graient. What do you think about it?
11-04-2011 02:05 PM
Hi
If you connect the dV wires to the entry of the lakeshore, you need to be sure that the two connectors at at the same temperature. I suppose the connection is made with copper to the nanovoltmeter.
You measure dV through the + wires. Suppose that initially you have T1=100 °C and T2=100 °C.
Increase a bit T1,
you get T1=101 and T2=100, dT=1K and you measure dV1
then T1=102 T2=100, dT=2K and measure dV2
and so on (I am applying a sinus gradiaent, and get something like 50 to 100 points, with a max dT of 3 or 4)
then plot dV versus dT, get the slope value m
the intercept should be zero but it will be not (offsets, that s why you need to measure the slope)
You get the slope : to this value you add (wire correction) for the contribution of the + wire
Look in the graphs I sent you before, at 100 °C the contribution of the + wire is 28 microvolt
m+28 microV is the value of the Seebeck coefficient of your sample.
Try with a sample (Pt wire, or Ni...) and post back if you need !
regards