BARTINGTON INSTRUMENTS
Page 40 of 82 OM0408/49
12.2. Setting Up
Choose an operating site well away from sources of electrical and radio interference. The site
should also be free from magnetic materials and large non-magnetic sheets of electrically
conductive material, e.g. aluminium bench tops.
Note:
A reasonably stable room temperature is desirable.
12.3. Sample Height Adjustment
If possible a full 1cc sample container should be used. However, satisfactory measurements are
possible with a sample volume of less than 1cc provided the sample material is positioned at the
correct height and the appropriate correction factor, given in
Calibration
, is applied.
Note:
For best accuracy, each sample vial should be uniformly filled.
Place the vial in front of the sensor block and gauge the appropriate sample height for which
the sample material is symmetrically within the two horizontal lines. Adjust the sample height
setting screw, located below the cavity, to achieve the same sample position for when the sample
is within the cavity. Tighten the locking nut. The adjustment mechanism may be removed by
undoing the brass retaining nut.
12.4. Calibration
The measuring zone is 5mm in height and senses only over a small portion of the sample. For
this reason the sample appears infinite and volume susceptibility units apply.
The density of the sample material should be controlled, wherever possible, by compressing the
sample material in the bottom of the vial. The sample may be weighed to establish the density.
The tare weight of the vial is 0.69 g.
The vial has a constant internal area of 0.33 cm
2
, so the fill height and volume are linearly
related. The vial has a diamagnetic value of -0.55 x 10
-6
CGS which is constant at all practical
measurement positions. This value (or its SI equivalent) should be subtracted from the measured
value to give the correct value.
12.4.1. Fill Height/Volume Correction Factors
Table 3. Fill height/volume correction factors.
FILL HEIGHT (mm)
VOLUME (cc)
CORRECTION FACTOR
5.0
0.165
1.46
5.5
0.1815
1.40
6.0
0.198
1.35
