Since the voltage across the motor terminals is proportional to the motor velocity, voltage feedback can be used to close the voltage loop to allow rudimentary speed control without needing an external feedback device such as an encoder. Benefits Voltage mode can provide a cost-effective solution when precise velocity control is not required ADVANCED Motion Voltage

±10 VDC Position

Analog position feedback where the voltage is proportional to the distance traveled. Typically found on linear actuators with the signal coming from a potentiometer. -10V indicates full retraction and +10V is full extension. 0 to 10V is also common. Benefits Inexpensive low-end type of feedback Key benefit is the feedback is absolute – no homing ±10 VDC Position

Current (Torque)

Frequent and accurate current sampling is necessary to close the current loop, which is the foundation for a sound motion control system. Current feedback is also used for torque control since output torque is proportional to motor current. Benefits DigiFlex® Performance™ servo drives make it easy to tune a high performing current loop AxCent™ servo drives come with Current (Torque)

Hall Sensors

Integrated with the motor, Hall Sensors are used for commutation feedback and sometimes rough velocity feedback. Benefits Hall Sensors are a low cost yet reliable type of commutation feedback Used for commutation because they provide absolute but rudimentary position within 1 electrical cycle Allows systems to move the motor immediately on start-up rather than wait Hall Sensors


Resolver Banner

A Resolver is a type of electrical device used to measure the relative angular position of a rotating shaft. They are commonly employed in various industrial and engineering applications where accurate angular position information is required. In servo systems, resolvers are attached to the motor shaft and used by the servo drive for velocity and Resolver


The motor velocity and rotor position is estimated by the drive using the motor back-EMF. This method is not intended for low speed applications or to hold position. Benefits Reduced cost and cabling due to the elimination of a motor feedback device ADVANCED Motion Controls’ Capabilities Sensorless feedback can be supplied on custom drive designs This Sensorless


Velocity feedback that outputs a voltage proportional to velocity. Similar to a small generator mounted to the motor shaft. Benefits These excellent velocity feedback devices were very popular in the past Encoders have supplanted tachometers because they can provide both velocity and position feedback in the same device ADVANCED Motion Controls’ Capabilities Some AxCent™ drives take Tachometer