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Lake Shore Model 480 Fluxmeter User’s Manual
Advanced Operation 5-9
5.7 RANGE SELECTION
Range selection is difficult to define for the Model 480 because of its different measurement units but
the operation is simple. The input range can be increased to measure large signals or decreased to
measure smaller signals with better resolution. All available ranges are accessible during range
selection. At that time the full scale range and reading resolution will be shown. Full-scale range and
resolution are listed for V·s units in the Specifications detailed on Page 1-2.
There are two decade range selections available for DC and DC peak measurements. Input resistance
(Paragraph 5.3.1) can be changed to allow a third decade of measurement range. Coil construction can
also be changed to alter the range boundaries in magnetic units. The DC range setting is stored
separately from the AC range setting.
There are four decade range selections available for AC measurements and three for AC Peak
measurements. More ranges are allowed for AC because they do not suffer from the drift associated
with DC measurements. Drift on the high gain ranges make them unusable for DC measurement. A
smaller integrating capacitor is used for AC measurements allowing even more gain. The difference in
capacitance is why the largest full scale AC range is smaller than the largest full scale DC range. AC
ranges are specified with 100 k

input resistance. Coil construction can be changed to alter the range
boundaries in magnetic units.
As an example of coil parameters altering range boundaries consider using the highest DC range of
300 mV·s. If a coil with an area turns of 100 cm
2 is used on the highest DC range for flux density
measurements the resulting range boundary in gauss would be 300 kG. If a coil with an area turns of
1000 cm
2 is used on the same range the resulting range boundary would be 30 kG.
If coil parameters are entered and units are selected before range is chosen the Model 480 will
calculate and display the appropriate full scale range and resolution in the selected units. Because of
the construction of the Model 480 some over range should be expected. Over range is typically 10% of
the full scale shown but it is not guaranteed.
To changing the range, press the Range key. The following is a typical display.
Select­With­°®
+/-­30.0000­mVs
Use the  or  keys to cycle thru the available ranges. Press the Enter key to accept or press the
Escape key to cancel and return to the normal display.
5.8 READING RESET
The analog integrator in the Model 480 must be reset to zero at the beginning of a DC measurement
sequence. Resetting the integrator removes any flux change or integrator drift that has accumulated
since the last reset. The DriftTrak™ algorithm (Paragraph 5.9.3) can greatly reduce the number of
resets needed for DC measurements. AC and AC Peak measurements do not require reading reset
because modifications to the integrator bring the reading to zero when no signal is present. DC Peak
measurements require peak reset (Paragraph 5.11.4) instead of reading reset.
The integrator in the Model 480 is designed to recover quickly from a reading reset. A new reading is
available 200 ms after the
Reading Reset key is released. Reading reset can also be achieved through
computer interface or using the external reset feature (Paragraph 5.16).
If the Model 480 appears to have more drift just after a reset than it does 10 to 30 seconds later it could
be a result of dielectric absorption (Paragraph 2.1.5). If the resulting error in reading is too large for the
measurement application the error can be reduced by resetting a second time a few seconds after the
first reset.
To reset the reading press the Reading Reset key and release.