What's The Main Difference Between Class-1 and Class-0 Servos?

A Class-1 servo has an error integrator in the servo loop that is used to quickly resolve the final microradians of galvo position accuracy. A class-0 servo does not have this error integrator.

A Class-0 servo is the fastest way for the galvo to settle to within 99% of the intended position. The class-0 servo will then require several more step response times (time constants) to resolve the final 1% and settle to within 10s of microradians of the intended position. For the majority of applications, this level of repeatability is far superior to what the application requires.

For special applications that require settling to the single-digit level of microradians, the Class-1 servo is the best choice. After the step response initial time constant, the class-1 servo will then settle to within 99% of the remaining position in one more time constant, and 99% of that remainder in another time constant. Therefore a Class-1 servo will settle to the galvo single-digit repeatability specification in just a few time constants.

There are many other considerations when selecting the appropriate servo class. Please contact Cambridge Technology for technical assistance.