BARTINGTON INSTRUMENTS
Page 23 of 82 OM0408/49
Sample insertion and removal is facilitated by a hand operated platen. It is normally fitted with a
moving platen with a 27.5mm stem. For measurements of anisotropy of magnetic susceptibility
(see
Appendix 3. Anisotropy of Magnetic Susceptibility Measurements
) the alternative 18.5mm
stem supplied must be fitted.
6.2. Dual Frequency Measurements
Fine grained materials exhibit frequency dependent susceptibility. This is especially significant
where grains of the single domain order are present (around 0.03
m
m diameter), where very
rapid changes in frequency dependency occur with relatively small changes in diameter. In
naturally occurring materials, these grains are widely distributed in size and give rise to a fairly
uniform frequency dependency of susceptibility in the low kHz range in which the MS2 operates.
The coefficient of frequency dependency (
c
FD
) can be expressed as the change in susceptibility
per decade frequency divided by the low frequency susceptibility (
c
LF
), where the low frequency
susceptibility will always have the higher value.
c
FD
% = 100 x ((
c
LF
-
c
HF
) /
c
LF
)
where the frequencies used for LF and HF are in the ratio 1:10.
The frequencies used by the MS2B sensor are given in the product brochure. The LF frequency
is carefully chosen to avoid interference from the ninth harmonic of 50Hz, and from the eighth
harmonic of 60Hz electrical mains supplies. For further information regarding frequency
dependance and the use of dual frequency measurements, please refer to
OM0409 John Dearing
Handbook
, available from Bartington Instruments.
6.3. Single Frequency Measurements
When dual frequency measurements are not required, the LF (low frequency) range should
always be selected as this will give results to the best precision.
6.4. Setting up the Sensor
Before any measurements can be taken, the MS2B must be plugged into the connector on the
front of the MS2 meter via a TNC-TNC cable and the MS2 should be turned on. Ensure that the
sensor is not situated on or near any materials with high magnetic susceptibility or those that
are electrically conductive.
6.4.1. Centring
Perfect centring of the sample within the sample cavity is accomplished by adjusting the rest
position of the moving platen. To reveal the nylon adjustment screw, remove the cap at the top of
the sample insertion mechanism handle.
