Lake Shore Model 480 Fluxmeter User’s Manual
Advanced Operation
5-7
5.5 COIL CALIBRATION
If coil parameters are not known and the user has access to reference magnet or other known field, the
Model 480 can be used to calculate the required coil parameter for magnetic measurement units. Once
a coil is calibrated the coil setup feature can be used to read the calibrated coil parameter. Calibrated
coil parameters can also be stored in instrument memory or a Model FCBL-6 accessory.
Coil calibration is disabled for Lake Shore probes because they are calibrated at the factory. Coil
calibration is disabled for if the instrument is operating in integrator units because no calibration of the
coil is necessary. As described below the feature will only calculate one parameter for each type of
magnetic measurement. More than one calibration can be done on the same coil but each calibration is
done separately. Coil resistance should be entered before a coil is calibrated if its resistance is
meaningful.
Measurement
Units
Parameter
Flux
V·s
Wb
Mx
Turns (N)
Turns (N)
Turns (N)
Flux Density
B
T
Area Turns (AN)
Area Turns (AN)
Moment
Wb·cm
Helmholtz Constant
Potential
A
Potential Constant
5.5.1 Before using Coil Calibration
Turn the instrument on and allow it to warm up. Measure the DC coil resistance and enter it with Coil
Setup if necessary. Choose the desired measurement units. If the existing value of the coil parameter
being calibrated is interfering with the measurement resolution set it to 1 using Coil Setup. Make
several measurements of the test magnet to assure repeatability. An improper range setting or
excess drift can cause difficulty in repeating measurements.
5.5.2 Calibrating a Coil
Begin the coil calibration sequence by resetting the reading with the
Reading Reset
key or the peak
hold value with the
Peak Reset
key. Make a measurement of the sample magnet or place the coil in
a known magnetic environment. Press the
Coil Cal
key. The
COIL CAL
screen will appear on the
display. Enter the actual value of the field in the chosen units. Press the
Enter
key to accept the
change or the
Escape
key to cancel the entry and return the previous value. The instrument will
begin reading with the new coil parameter. The sequence is successful if the display reading matches
the value entered.
5.6 COIL SELECT AND PARAMETER STORAGE
The Model 480 has non-volatile internal memory available to store up to ten sets of coil parameters for
user coils. All coil parameters (including input resistance and percent scale factor) can be stored in
each of the ten memory locations. Unused parameters can be left at their default value. Once the
parameters are stored they can be called up quickly whenever coils are changed.
This feature can be used to store parameter values in a Model FCBL-6 accessory and percent scale
factor into Lake Shore probes. Parameters stored in probe memory are called up when the instrument
is turned on.