MSB MkI Calibration and use of formula
Each balance is supplied with a calibration standard (a sealed tube containing a solution of MnCl2.6H2O)
and a test sheet showing the value of the instrument's balance constant, CBal, (factory set to 1.000 ± 0.020).
Calibration procedure - using a known substance.
Refer to the formula on the label on the top panel of the instrument.
This is used to calculate the mass susceptibility of a sample from measured values.
Where:
l = the sample length (cm)
m = the sample mass (gm)
R = the reading for tube plus sample
R0 = the empty tube reading
CBal = the balance calibration constant
Using a substance of known Xg and measurements of the other variables in the formula the value of CBal can be checked.
The new value should be noted and used in subsequent calculations until the next calibration check.
Calibration procedure - using MkI standard.
If no such substance is available and there are doubts about the value of CBal, the standard tube can be used, as follows.
Put a clean, empty tube in the balance and use the zero knob to set the display to zero on the x1 range.
Remove the tube and insert the standard. Gently and slowly rotate the tube while it is in the balance
and note the extremes of the readings. Note the average of these extremes; this will be R to be used later.
R should be the same as Cstd. If it is larger than Cstd then the balance constant has decreased by
the factor of Cstd/R. A worked example should make this clear.
CBal (from test sheet) = 1.005
Cstd = 1019 (from the label on the tube)
R = 1025
New CBal = 1.005 x 1019/1025 = 0.999
Note this new value of CBal and use it in all subsequent calculations of susceptibility until the next calibration check.
