Lake Shore 420, User Manual

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Lake Shore Model 420 Gaussmeter User’s Manual
Operation
3-3
3.4 SELECT RANGE AND AUTO RANGE
The Model 420 reads each Lake Shore probe type: High Stability, High Sensitivity, or Ultra-High Sensitivity.
These probes sense fields as low as 0.2 mG and as high as 300 kG. The tables below list full scale ranges for
each probe sensitivity, along with fixed display resolution.
Range Res. Range
Gauss tesla Gauss tesla Gauss tesla
High Sensitivity Probe High Stability Probe Ultra-High Sensitivity Probe
Range Range
±300 kG
±30 kG
±3 kG
±300 G
±30 kG
±3 kG
±300 G
±30 G
±3 G
±300 mG
Res. Res.
±0.1 kG
±0.01 kG
±0.001 kG
±0.1 G
±0.001 G
±0.1 mG
Res.
±0.01 G
±0.01 kG
±0.001 kG
±0.1 G
Range
Res.
±30 T
±3 T
±300 mT
±30 mT
±0.01 T
±0.001 T
±0.1 mT
±0.01 mT
Range Res.
±3 mT
±3 T
±300 mT
±30 mT
±0.001 T
±0.1 mT
±0.01 mT
±0.001 mT
±300 µT
±30 µT
±0.1 µT
±0.01 µT
For manual ranging, press Range and select one
of the full scale ranges displayed. The display to
the right appears.
Press Range to cycle through allowable full scale
ranges for the installed probe. To accept the new
range either wait about 6 seconds until the display disappears automatically, or press any key other than
Range .
In Auto Range mode, the Model 420 selects the
range with the best resolution for the measured
field. It can take up to 2 seconds for Auto Range
to work, so manual ranging may be better
sometimes. Press
Range until the screen to the
right displays. To accept the new range either wait about 6 seconds until the display disappears automatically,
or press any key other than
Range .
Do not use Auto Ranging with Max Hold operation or during small field measurement in a large background
field, such as measuring a small DC field in presence of a large AC field, or vice versa.
3.5 AC/DC
The AC/DC key toggles between AC and DC measurements. The annunciator immediately changes from
“DC” to “RMS” as applicable. One update cycle is required for a new display value.
In DC operation, the display shows the DC field at the probe with sign (orientation) followed by the
appropriate field units, and the letters "DC". The DC value is available over the Serial Interface and both
Analog Outputs.
In AC operation, the RMS readings meet specified accuracy from 10 to 400 Hz. The AC RMS reading is
defined as the square root of the average of the square of the field function taken through one period.
The AC value is available over the Serial Interface. The Corrected Analog Output yields a DC voltage
representation of the Peak or RMS reading, while the Monitor Analog Output yields a true analog waveform.
(In fact, the Monitor Analog Output is not affected by the selection of AC or DC.)
When changing to AC or DC, the unit maintains previously established Relative and Alarm setpoints, but Max
Hold operation changes (see Paragraph 3.2).
P r e s s R a n g e K e y
+ / - 3 .0 0 0 k G
+ 1 .4 2 0 k G D C
A u t o R a n g e