Magnetoresistive Sensing of Print Actuators
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Using two magnetic resistors (M-Rs) as sensors, in a temperature- and magnetic-disturbance compensated bridge, provides a robust feedback sensor for improving print actuator dynamics. Printer quality and speed are enhanced by feedback control on the hammer. In order to achieve this feedback, a method of sensing hammer location and velocity is required to determine the force at impact. The figure shows a small permanent magnet 1 attached to hammer 2. The M-R sensor 3 is held in a position that allows the magnet 1 to move over the M-R sensor 3 in a bridge 4 (R1-R2) which can adjust the DC level to zero. Two M-R sensors are used; M-R sensor 5 is mounted next to M-R 3. This makes the sensor track for temperature and also subtracts any external magnetic disturbances.