F.W. Bell 7030, Instruction Manual

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F.W. BELL Model 7030 Gauss/Tesla Meter Instruction Manual
Section 6 – Flux Density Measurement 6-9
ZEROING
(Continued)
dc Zeroing
For most situations it is preferable to shield the probe from all external magnetic
fields prior to zeroing. Provided with the instrument 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.
Handle the Hall probe with care. Do not bend the stem or apply pressure to
the probe tip as damage may result.
In other situations the user may want the probe to be exposed to a specific magnetic
field during the zeroing process. As an example, consider zeroing the probe when it
is exposed to the earth’s magnetic field. This will cancel the effect of the earth’s
magnetic field for all future readings. If a range is exceeded by the level of field
while zeroing, the lower range cannot be entered by the instrument.
Zero Prompt
The instrument will inform the user to zero a channel by flashing the appropriate
ZERO key on the front panel. The following are the conditions that will cause the
instrument to prompt the user to zero a channel:
•
The instrument was just turned on.
•
A probe was just inserted into the instrument.
•
Fifteen (15) minutes has elapsed since the instrument was turned on.
•
Fifteen (15) minutes has elapsed since a probe has been inserted.
•
The instrument’s internal temperature has drifted by at least 5
°
C.
Initiating Zeroing
To initiate zeroing on one channel
1) Prepare the probe for zeroing.
2) Press the ZERO key for the appropriate channel.
To initiate zeroing on all channels
1) Prepare all probes for zeroing.
2) Press and hold the ENTER key, then press the Channel 1 ZERO key .
The channel(s) will display the message “
Zeroing
” and a countdown indicates the
approximate duration of the zeroing process. Once zeroing begins it must be
allowed to complete. During this time, all controls are disabled except for the power
switch. When only one channel is zeroed, the remaining channels will suspend
operation during the zeroing process but will not lose their present zero point
information. The zeroing process is approximately 60 seconds when basic ac mode
zeroing is enabled and is approximately 2 minutes for advanced ac mode zeroing.