Hi Marina, Curve fitting is used to do this conversation, employing a 4th order polynomial. The polynomial coefficients used depends on the range resistor selected on the gsr daughter card.
So with the polynomial being: Resistance (in Ohms) = p1*x^4 + p2*x^3 + p3*x^2 + p4*x + p5 x corresponds to the raw adc value and the coefficients are as follows: Internal Resistor: Polynomial coefficients 40kΩ: P1 = 6.5995e-09, P2 = -6.8950e-05, P3 = 0.2699, P4 = -476.9835, P5 = 340351.3341 270kΩ: P1 = 1.3569627e-08, P2 = -0.0001650399, P3 = 0.7541990, P4 = -1572.6287856, P5 = 1367507.9270 1MΩ: P1 = 2.550036498e-08, P2 = -0.00033136, P3 = 1.6509426597, P4 = -3833.348044, P5 = 3806317.6947 3.3MΩ: P1 = 3.7153627e-07, P2 = -0.004239437, P3 = 17.905709, P4 = -33723.8657, P5 = 25368044.6279 And obviously the conductance (in Siemens) is the reciprocal of the resistance. Take a look at GspP.nc for an implementation of this, specifically the Gsr.calcResistance() function: http://code.google.com/p/tinyos-main/source/browse/trunk/tos/platforms/shimmer/chips/gsr/GsrP.nc Mike On Thu, Jun 30, 2011 at 7:06 PM, <[email protected]>wrote: > Dear all, > > I would appreciate a lot if someone could give me the conversion between > the output units of the GSR sensor module (Shimmer2r) and the standardized > microsiemens units for conductance. > > Thanks in advance for your helpkind, > > marina > > ______________________________**_________________ > Shimmer-users mailing list > [email protected] > https://lists.eecs.harvard.**edu/mailman/listinfo/shimmer-**users<https://lists.eecs.harvard.edu/mailman/listinfo/shimmer-users> >
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