ZERO FUNCTION
“Zeroing” the probe and meter is one of the most important steps to obtaining accurate dc flux density measurements. The ideal Hall
generator produces zero output in the absence of a magnetic field, but actual devices are subject to variations in materials,
construction and temperature. Therefore most Hall generators produce some output even in a zero field. This will be interpreted by
the meter as a flux density signal.
Also, the circuits within the meter can produce a signal even when there is no signal present at the input. This will be interpreted as a
flux density signal. Lastly magnetic sources close to the actual field being measured, such as those from electric motors, permanent
magnets and the earth (roughly 0.5 gauss or 50mT), can induce errors in the final reading.
It is vital to remove these sources of error prior to making actual measurements. The process of “zeroing” removes all of these errors
in one operation. The meter cancels the combined DC error signal by introducing another signal of equal magnitude with opposite
polarity. After zeroing, the only dc signal that remains is that produced by the probe when exposed to magnetic flux.
NOTE:
Zeroing the meter and probe affects only the static (DC) component of the flux density signal.
NOTE:
The process of zeroing also affects the analog signal.
There may be situations when the user prefers to shield the probe from all external magnetic fields prior to zeroing. Provided with the
meter is a ZERO FLUX CHAMBER which is capable of shielding against fields as high as 30 mT (300 G or 23.88 kA/m). The probe
is simply inserted into the chamber before the zeroing process begins.
In other situations the user may want the probe to be exposed to a specific magnetic field during the zeroing process so that all
future readings do not include that reading (such as the earth’s field). This is possible with the following restrictions:
1) The external field must not exceed 30 mT (300 G or 23.88 kA/m).
2) The field must be stable during the zeroing process. It should not contain alternating (AC) components.
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.
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