Lake Shore Model 460 Gaussmeter User’s Manual
3-6
Operation
Max Hold and Max Reset (Continued)
The
Max Reset
key clears the Max Hold value. The Max Hold value is also reset upon power up or
when changing from AC or DC. Max Hold may also be used in conjunction with the Relative display
(refer to Paragraph 3.9). Max Hold functions differently when being used with AC or DC fields as
follows.
In DC operation, the Max Hold feature holds the field reading that is largest in magnitude. This is
intended to monitor slowly changing signals. A field change not visible on the display can not be
recorded in DC Max Hold. The display shows only the magnitude of the maximum reading.
In AC RMS operation, the maximum RMS value displayed is held, i.e., operates the same as DC Max.
In AC Peak operation, a hardware circuit traps peaks in the Hall voltage. In this mode, the unit displays
the magnitude of the highest peak of an impulse or event. For best accuracy, the event must be at full
amplitude for at least a few milliseconds.
In the case of the Vector Magnitude display, turning on Max Hold will cause the vector source display to
be replaced with MAX. Turning on Max Hold for Vector Magnitude means the maximum value
calculated will be displayed. It does not mean each of the individual component max hold readings are
used to form the Vector Magnitude display. When Max Hold for the Vector Magnitude is turned off, but
Max Hold for the X, Y, or Z channels is on, the individual maximums are for display only and are not
used for the calculation of the Vector Magnitude display.
3.3
ZERO PROBE
The zero probe function is used to null (cancel) out the zero offset of the probe or small magnetic fields.
It is normally used in conjunction with the zero gauss chamber, but may also be used with an
unshielded probe (registering the local earth magnetic field). If three separate probes are being used,
each probe may be independently zeroed. For the three-axis probes, each axis may be independently
zeroed. Users wishing to cancel large magnetic fields must use the Relative function. The zero probe
function is not available for the Vector Magnitude display.
NOTE:
For best results, the instrument and probe should warm up for at least 5 minutes before
zeroing the probe, and at least 30 minutes for rated accuracy. The probe and the zero
gauss chamber should be at the same temperature.
NOTE:
Some Lake Shore probes are equipped with a clear plastic sleeve intended to protect the
tip of the probe when not being used. The sleeve is designed to slide up and down the
probe cable. If you need to place the probe in the zero gauss chamber, you must slide the
protective sleeve back, exposing the tip of the probe, before placing the tip in the chamber.
To zero the probe in the zero gauss chamber, first allow the temperature of the probe and chamber to
equalize. (A large temperature discrepancy affects the quality of the calibration.) Carefully place the
probe tip into the chamber. Orientation of the probe is not critical. Once inserted, press the channel key
(in this case, Channel X), then press the
Zero Probe
key and observe the following display.
Pr e s s En t e r Wi t h
Pr o b e At Ze r o
Se t t i n g Ch a n n e l X
Press the
Enter
key. The
*CALIBRATING*
message is displayed, followed by a return to the normal
display. Do not move the probe while calibrating. The probe is now zeroed. For best results, periodic
zeroing of the probe is recommended.
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