Lockin Mode:
This mode drives the cantilever with a fixed amplitude and pre-defined frequency. The PLLPro measures the cantilever oscillation amplitude and phase difference between the excitation signal and the detected signal. The lock-in amplifier then outputs an amplitude and phase signal defined by the digital loop filter, with available filter bandwidths ranging from 30 Hz to 4.5 kHz.

Self-Oscillation Mode:
In this mode, the PLLPro amplifies and phase shifts the detector signal, using the new signal to drive the AFM cantilever. Because the digital PLL is frequency selective, our configuration is much less susceptible to noise than other implementations.

During Self-Oscillation Mode the PLLPro can function in two separate ways: In constant excitation (CE), the PLLPro drives the cantilever at a constant amplitude. In constant signal (CS), the PID controller holds the detector signal amplitude constant.

PLL Mode:
In this mode, the reference oscillator of the digital PLL drives the AFM cantilever while the PLL measures its resonance frequency and oscillation amplitude. A PID controller maintains a constant phase shift between the probe drive and the detector signal.

During PLL Mode the PLLPro can function in two separate ways: In constant excitation (CE), the PLLPro drives the cantilever at a constant amplitude. In constant signal (CS), the PID controller holds the detector signal amplitude constant.

Contact Mode:
Because the PLLPro can measure the DC offset of the detector signal, the user can switch to Contact Mode measurement through the control software at any time. Also now possible are simultaneous imaging of the normal and (if provided by the preamp) lateral force average signals with measurements from any non-contact AFM mode.

To make use of this flexibility, user scripts can monitor the normal and lateral force averages and react to them, for instance by nulling them out after driving a process parameter, such as probe-sample bias with a DAC.

Programmable Modes:
You have the power to extend the modes and routines available on the PLLPro in innumerable directions. With scripting access to the PLLPro’s powerful control hardware and front-end software, almost all functions and components can be tailored to fit your experimental needs. The scripting language is easy to learn and is well documented. The language’s structures and functions correspond to the hardware operation in a natural and intuitive fashion. And all the tools to compile new code, including an assembler, have already been built
into the system.

The following page presents some example ideas for writing custom modes or other helpful routines that make use of the PLLPro’s enormous flexibility and accessibility. In the future be sure to visit rhk-tech.com for many other useful and instructive routines that come scripted and explained for you.