SERIES
9900
9000
SERIES
GAUSSMETERS
SECTION I V continued
Menu Operation/Gaussmeter
Programming
use previously generated relative values (USE PREVIOUS) or generate new
values (GENERATE NEW). If the latter is selected, the following occurs:
A message will appear that states that the gaussmeter is ready to begin.
Pressing the ENTER pushbutton initiates the relative operation. (If the
channel's interface module and probe are not present, an error message will
appear instead. In this case, pressing the ENTER pushbutton will abort the
relative operation.)
In the ac mode, the relative operation begins in the lowest valid range. If the
existing field level exceeds this range, the next range is selected. This
continues until a range is found that can accommodate the field level.
No
relative values will be generated for those ranges that were exceeded. At this
point the relative field level reading is placed in the channel's information
block preceded by a reverse-video "R," (see Figure 111-0) for future reference,
and relative values are generated for this and all higher ranges.
In the dc mode, the relative operation begins in the lowest valid range. If the
existing field level exceeds this range, the next range is selected. This
continues until a range is found that can accommodate the field level. At this
point, the present field level reading is placed in the channel's information
block for future reference and a relative value is generated for this range. The
gaussmeter then downranges two range settings and continues the relative
operation, generating a relative value for this and all higher ranges.
In either mode, if the probe is moved or disconnected during the relative
operation, or if the reference field is extremely unstable, an error will be
reported and all relative values generated to that point will be reset. In this
case, pressing the ENTER pushbutton will restore normal menu operation.
Internally, ac and dc relative operations differ electronically. This difference is
transparent to the user, but
does
affect one aspect of machine operation.
The initial field for the ac mode will affect the maximum reading that can be
reached in a given range. For instance, if the initial relative ac field is 100.00 G
and the probe is operated on a 300 G range setting, an overrage condition
will occur when the field reading reaches 200.00 G (300 G-100.00 G
=200.00 G). This limitation does not exist for the dc mode of operation.
When operating in the MEASURE mode, the value of the relative field (the
field that existed before the relative operation was initiated) will appear in the
channel's information block preceded by a reverse-video "R." (See Figure 111-
D.) In the dc mode, the user can downrange
up to two ranges
to obtain better
resolution of the variances around the original field. For instance, observing a
20 kG
fieldwithout
the RELATIVE function enabled, allows only a resolution
of ±1 G on the 30 kG range. However, if the RELATIVE function is used, the
user can downrange to observe variances as low as ±0.01 G on the 300 G
range. This is valid only for the dc mode. Attempts to downrange more than
two ranges will result in an overrange condition.
NOTE: The probe should be zeroed (see PROBE ZERO, Section IV-1) before
performing the relative function or the relative values will also include probe
and circuit offset errors. When a probe is zeroed,
all previously generated
relative values will be reset and the relative function will be turned off for that
channel.
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