Servo Recorders

Abstract

Probably the most widely used laboratory recorders are those built around a motor-driven servo loop. A motor drives the pen across the chart until a position sensor observes that its location agrees with the requirement of the input signal. There are many possible implementations of this basic principle. The motor, for instance, may be limited to less than one full turn, with direct connection to a pointer carrying the pen or stylus (this is usually thought of as a meter movement rather than a motor), or it may be a more conventional motor, either ac or dc. Those recorders that include two independent servo systems driving the pen parallel to the X and Y axes (X-Y recorders) are discussed in Chapter 4.