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6. Repeat steps (1) to (5), whilst gently re-tightening the clamping screws, until the difference
between two readings and each pair of readings is circa 1nT. Light finger tightness only
should be used.
7. Replace probe protective cover and four retaining screws.
7.6. Offset Trimming
See Figure 10 for reference. The electronics in the magnetometer unit must be exposed to
perform this alteration as a potentiometer inside the casing must be adjusted.
1. Set up the theodolite as if to perform Inclination measurements.
2. Select the x10 range and set theodolite to position SU to achieve a null in I. Record this
angular value.
3. Rotate vertical circle to a ND position to achieve null and record the second value.
Note: In the presence of an offset error these values will not be 180
4. Adjust the vertical circle to a value which is the mean of SU and ND: (ND + SU - 180)/2.
5. Adjust the x10 offset potentiometer (item 35 in Figure 10) to produce a displayed
magnetometer value of 00000.
6. Select x1 sensitivity.
7. Adjust x1 offset potentiometer (item 34 in Figure 10) to produce a value of 0000.
7.7. Cleaning the D/I System
Caution: To clean the D/I System, use an air duster to blow out dust and debris if required.
Use appropriate personal protective equipment (PPE), such as eye protection, when
carrying out this task.
Caution: Avoid using chemicals such as solvents when cleaning the D/I System. Use a
damp cloth to remove grime from external surfaces.
Caution: Take particular care when cleaning around electrical connections. Bent or
damaged pins may cause the system to malfunction. The pins ONLY may be gently cleaned
using a soft material dipped in Isopropanol (IPA). Avoid any contact with the rest of the
BARTINGTON INSTRUMENTS
Page 27 of 32
apart.
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OM2020/5
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