Piezo Stack Amplifier, 3 Channel, Open-loop Position Control

In open-loop, a piezoelectric actuator can reach its nominal displacement in approx. one third of the period of its first resonant frequency. The resonant frequencies for all our devices are provided for different loads, see specifications on the individual product pages. For loads in between, a linear relationship between the load and the resonant frequency can be assumed. Example: With 105 g load, the resonant frequency of the NanoPositioning linear stage NPXYZ100 in z-direction is 250 Hz. It can reach its nominal displacement within 1.3 ms. When the stage is excited with a sharp electrical pulse, the stages resonant frequency will be excited resulting in position overshoots with a damped oscillation. Hence, shorter electrical pulses may result in higher super-elevation, but not in shorter rise times.

Another boundary for fast open-loop operation is the current that can be provided by the piezoelectric amplifier. The diagram displays the max. sinusoidal frequency which can be supplied by the NPC3 and NPC3SG amplifiers as a function of the capacitance of the piezoelectric transducer and the voltage amplitude. For other models please see user manual for drive frequency curves.

All Newport NanoPositioning devices with strain gauge feedback feature a sensor identification chip (SIC) and a calibrated pre-amplifier that is housed inside the device, or in a small box that is part of the cable. This pre-amplifier ensures high sensor signal homogeneity that results in considerably higher position accuracy compared to alternative designs where the pre-amplification is done inside the amplifier only. But the calibrated pre-amplifier has even more advantages. In cases when an actuator has to be replaced, there is no need to re-adjust the electronics as long as it is the same actuator type. The SIC contains all relevant information including model type, travel range, etc., and ensures a seamless integration and operation.

In manual control, the output voltage/position can be set for each channel separately using the 30 step encoder knob on the front panel (where applicable). Pressing the knob toggles between open-loop and closed-loop. The last setting is saved in memory and is loaded after restart. 

Analog control: In analog control, the output voltage/position is controlled by an analog signal applied to the modulation input (0V-10V). In open-loop control, 0 V corresponds to -20V output voltage, and 10V corresponds to 130 V output voltage. In closed-loop control, 0 V corresponds to zero displacement and 10V corresponds to the maximum nominal closed-loop displacement. Analog control and manual control can be used simultaneously and are additive.