BARTINGTON INSTRUMENTS
Page 12 of 82 OM0408/49
4.5. SI and CGS units
The instrument may be pre-set to display the susceptibility value directly in either SI or CGS
units. The table below shows the basic mass or volume specific unit thus produced.
Mass and volume in SI and CGS units
Mass (
c
mass
)
Volume (
c
vol
)
SI
10
-8
(m
3
/kg)
10
-5
CGS
10
-6
(cm
3
/g)
10
-6
Numerical conversion from SI to CGS units is accomplished by dividing the SI value by 4
π
, i.e.
c
CGS
=
c
SI
/4
π
. The MS2 meter performs this function internally but by using the constant 0.4
π
to keep
the numbers in a similar range of magnitude.
4.6. Range Selection
The instrument may be pre-set to display the susceptibility value in either the 1.0 or 0.1 range.
The table below shows the the exponent value of the least significant digit (i.e. the last digit on
the LCD) for each range. The units in the table below for volume susceptibility.
Exponent values for least significant digit in 1.0 and 0.1 ranges
SI
CGS
1.0
10
-5
10
-6
0.1
10
-6
10
-7
On the 0.1 range a decimal point will be displayed, effectively moving all the digits on the LCD to
the left when compared with the 1.0 range. It should also be noted that one measurement in the
0.1 range will be an average of multiple readings taken over a period of 10 seconds.
4.7. Calibration
All sensors are calibrated either directly or indirectly to the diamagnetism of water (H
2
O), where
density
r
(rho) = 1.
c
mass
(mass susceptibility of H
2
O) is -0.72 x 10
-6
CGS
Therefore, for H
2
O,
c
vol
=
r
x
c
mass
= 1 x -0.72 x 10
-6
CGS.
Precise mass specific measurements are only possible using the MS2B sensor where the
sample volume is accurately defined.
