Page 15 of 82 OM0408/49
Set the meter to the 1.0 range for the initial measurement of any sample, to establish the
approximate result, before switching to the more sensitive 0.1 range. If the value of a sample is
greater than 1000 then the most significant digit will not be seen if measured on the 0.1 range,
leading to an apparent gross error in the result.
Irrespective of the type of sensor being used, measurements are accomplished using the
following procedure.
1. Take an ‘air’ reading by pressing the ‘Z’ push button with the sample to be measured away
from the influence of the sensor. The display will appear blank and a colon will appear to
show the instrument is ‘busy’. The completion of a Z cycle will be announced by a bleep and
the display will show all zeros.
2. Place the sample within the influence of the sensor and press the ‘M’ button. The ‘busy’ colon
will appear and the display will show the previous reading until updated at the completion of
the current measurement period. This is announced with a beep. At this time serial data will
be transmitted.
3. If either push button is enabled at the completion of a cycle then a repeat measurement will
be taken.
4. To measure weakly magnetic material, select the more sensitive x0.1 range and compensate
for any thermally induced drift by making a series of measurements:
a) Zero to air by pressing ‘Z’ button = R
0
( = 0)
b) Measure samples = R
1
, R
2
....
c) Measure ‘air’ = R
Final
The mean of an ‘air’ measurement before and after the sample is subtracted from the n
th
sample measurement R
n
:
Corrected value R
k
= R
n
- n x (R
Final
- R
0
)/N
where N is the total number of measurements after the initial zero (including R
Final
)
In the case that only one sample measurement is taken: R
k
= R
1
- (R
Final
- 0)/2
When taking manual measurements, attempt to keep the time between measurements as
consistent as possible. If recording values by hand then the previous value can be read whilst
the current measurement is taking place, thus saving time and improving precision.
The drift correction can be done automatically using Multisus or Bartsoft where the time of
each measurement is recorded, and the is drift applied linearly as a function of time.
To Next Page
Loading...
