mounting the porous sample for rotation about an axis such that different portions of the sample are spaced at different distances from the axis;

rotating the sample about said axis at a substantially constant speed of rotation;

measuring a first parameter indicative of fluid content in each of said different portions of said sample comprising detecting said fluid by one dimensional magnetic resonance imaging along the sample in the direction of spatial separation between the different portions thereof using a phase encoded magnetic field gradient to spatially resolve each portion along the sample, wherein said magnetic resonance imaging comprises one dimensional single-point ramped imaging, which includes the steps of:

(a) progressively increasing the gradient of a magnetic field directed in a first direction from zero to a predetermined maximum value;

(b) applying to the sample an RF pulse at each of a number of different values of magnetic field gradient between zero and said predetermined maximum value;

(c) detecting a nuclear magnetic resonance (nmr) signal from the sample resulting from each excitation pulse to provide a first set of data comprising respective values of magnetic field gradient and the respective values of the detected nmr signal from the sample;

(d) after said magnetic field gradient reaches said predetermined maximum in said first direction, reducing said field gradient to zero without applying an RF pulse to said sample;

(e) progressively increasing the gradient of a magnetic field directed in a second direction opposite to said first direction from zero to a predetermined maximum value;

(f) applying an RF excitation pulse to the sample at each of a number of different values of magnetic field gradient between zero and said predetermined maximum value;

(g) detecting a nuclear magnetic resonance signal from said sample resulting from each excitation pulse to provide a second set of data comprising respective values of magnetic field gradient and the respective values of the detected nuclear magnetic resonance signal from the sample;

(h) determining the values of said first parameter at said different positions along the sample from the first and second sets of data;

(i) determining the value of a second parameter related to the force to which each portion is subjected due to said rotating of said sample; and

(j) outputting at least one of;

(i) the values of the first and second parameters; and

(ii) data based on said values.