SOURCES OF MEASUREMENT ERRORS
When making flux density measurements, there are several conditions that can introduce error:
1) Operating the meter while the battery symbol shows low (battery symbol has a small amount of red at the bottom).
Instrument specifications are not guaranteed when a low battery condition exists!
2) Failure to zero the error signals from the meter, probe, and nearby sources of magnetic interference.
3) Subjecting the probe to physical abuse.
4) One of the most common sources of error is the angular position of the probe with respect to the field being measured. As mentioned in
Section1, a Hall generator is not only sensitive to the number of flux lines passing through it but also to the angle which the pass through it.
The Hall generator produces the greatest signal when the flux lines are perpendicular to the sensor as shown in Figure 3-21.
The probe is calibrated and specified with flux lines passing perpendicularly through the Hall generator.
5) As shown in Figure 3-22, the greater the distance between the magnetic source and the Hall probe, the fewer flux lines will pass through the
probe. This would cause the probe's output to decrease.
Handle the Hall probe with care. Do not bend the stem or apply pressure to the probe tip as
damage may result. Use the protective cover when the probe is not in use.
Figure 3-21
Probe Output versus Flux Angle
Figure 3-22
Probe Output versus Distance
3-30
