As a kind of high-accuracy mass metrology, electronic balances are widely used in school, laboratory, and factory due to its excellent accuracy, fast response speed, high reliability, and easy operation. Sensor, electronic and microcomputer technology played an important role in electronic balance, and electronic balance magnet is one of the representative applications of cast Alnico magnets.
The weighing principle of electronic balance is bases on the balance between electromagnetic force and gravity. The major components of electronic balance include power, electromagnetic force equilibrium transducer, photoelectric sensor, keyboard, display, and control circuit. The electromagnetic force equilibrium transducer in equilibrium under no-load condition. The position of moving coil will change after placed object to electronic balance, then influence light intensity which received by the photosensitive element, then output current will be also changed. This variation will control the moving coil current after processed by the microprocessor, therefore, equilibrium transducer will be back to the equilibrium state. Meanwhile, current change of the moving coil will translate into the digital signal by the microprocessor, and display reading rapidly.
Error sources of electronic balance come from many aspects, include acceleration and temperature variation. To avoid error sources caused by temperature, electronic balance magnets should be utilized low temperature coefficient magnet. Sintered Samarium cobalt magnets can exhibit excellent thermal stability and measurement range, but its cost price is extremely high. Cast Alnico magnets are acknowledged as the most suitable electronic balance magnet under this circumstance.