The aim of the PLL and the AGC is to lock the drive signal in phase while keeping the oscillation amplitude at its peak resonance value. This separates conservative and dissipative processes, and ensures quantitative measurements. The PLL/PID option – available on the MFLI, UHFLI and HF2LI Lock-in Amplifiers – makes it possible to optimize one or multiple feedback loops thanks to simulation tools that determine P, I, and D values for a given target loop bandwidth. Indeed, the PID Advisor within the LabOne control software relies on quantitative DUT transfer function models.
While scanning, all signals available internally such as phase, amplitude, frequency, and excitation voltage can be output to analog BNC or recorded digitally with the LabOne data acquisition (DAQ) module or one of the LabOne APIs. The data can be aligned to form an image, provided some end of line trigger (EOL) or fast scan axis is fed as a trigger signal to the instrument. Multiple images can then be acquired at once, even over multiple eigenmodes or harmonics.