Contact mode is the simplest measurement regime. The feedback loop uses signal from the probe and adjusts the z-piezo of the microscope to make this signal as close to some user defined setpoint value as possible.

To use contact mode with Gwyscope GUI, use “Optical, contact mode” regime. Word “optical” means here that a optical lever technique is typically used, however this mode is also applicable to any other case where we have a single DC-like signal from the probe and want to operate feedback with it.

The way how to set up the setpoint depends on your actual hardware. To select the direction of the signal (if higher signal means higher force or opposite) you need to know your hardware and adjust the direction in the hwserver.ini file at the hwserver level. You can also temporarily change the directions via Override mode settings dialogue in the Settings menu.

The proportional, integral and derivative parameter of the feedback loop can be adjusted, while the integral term has far most impact on the result (and opposite, the derivative one has no impact at present).

The Z-manual control allows to move with z-piezo actuator when feedback is off. Feedback on button starts the feedback loop, Feedback off button stops it and drives z-piezo to zero. The “Approach”, “Move up” and “Move down” buttons can be connected to motors to control the approach, depending on the hardware settings or are left unconnected.