What is the Difference Between Electromagnetic and Moving-Coil Instruments?
1 Answers
Electromagnetic and moving-coil instruments differ in the following aspects: 1. Different structures: Electromagnetic instruments consist of fixed coils; moving-coil instruments are composed of permanent magnets, pole pieces, and a cylindrical iron core. 2. Different characteristics: Electromagnetic instruments feature simple structure, strong overload capacity, and the ability to operate on both AC and DC; moving-coil instruments offer high sensitivity, stable and reliable operation, low power consumption, and minimal influence from external magnetic fields. 3. Different principles: In electromagnetic instruments, the fixed coil carries the measured current, magnetizing both the fixed and movable iron pieces, which repel each other to generate a torque that drives the pointer, with the deflection angle proportional to the square of the current; in moving-coil instruments, the movable coil carries the measured current, experiences force in the air gap magnetic field of the permanent magnet, and generates a torque to drive the pointer, with the deflection angle proportional to the current.