CHAPTER 1 GETTING STARTED
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Adventurer ™ Balances Service Manual
1.7 The Load Cell
Figure 1-4 illustrates a typical Magnetic Force Restoration (MFR) Load Cell.
The force of a weight placed on the Weighing Pan moves the Hanger which is guided by the
Upper and Lower Flexure Arms. The Load Flexure transfers the force vertically to the Ratio Beam.
The Ratio Beam Flexures form a pivot for the Ratio Beam. When the Ratio Beam is moved, the
Force Coils mounted on the Ratio Beam are moved. The Force Coils are located in the magnetic
field created by the Permanent Magnets. The magnetic forces are affected by temperature. A
Temperature Sensor is attached near the magnets to measure the temperature and allow the
electronics to compensate for the changes in temperature.
Operation
A mass placed on the Pan applies a downward force to the Load Flexure by means of the Hanger.
The Load Flexure moves one end of the Ratio Beam which pivots, moving the Force Coil up into
the air gap of the Magnet. The Force Coils are located in the field of the Permanent Magnets. The
movement of the Vane (which is connected to the Ratio Beam) is detected by the Position Sensor.
The Position Sensor contains a sender and receiver. When the Vane moves, the amount of light
sent to the receiver also changes. The change in the position of the Sensor Vane is measured and
used along with the Temperature Sensor signal to adjust the current in the Force Coils. The
current in the Force Coils produces a magnetic field which restores the Ratio Beam to its normal
position.
Figure 1-4. Load Cell Assembly.
Ratio Beam
Flexure
Vertical
Flexure
Top Bracket
Hanger
Bottom Flexure Arm
Flexure
Magnet
Printed Circuit
Board
Temperature
Sensor
Position
Sensor
Vane
Force
Coils
Ratio
Beam
Counter
Weight
Upper Flexure Arm
Pan
