Connecting the Nanosurf Manual Controller to a Zurich Instruments HF2LI or HF2PLL
In March 2011, Nanosurf and Zurich Instruments announced a cooperation to establish the HF2PLL as official upgrade path for Nanosurf’s EasyPLL. This post shows how to connect Nanosurf’s Manual Controller to the Zurich Instruments HF2PLL.
The Manual Controller combined with the HF2LI allows for adding offset voltages to the df signal (frequency deviation) of the Phase Locked Loop. In this way, it allows for manually setting the frequency setpoint using the fine feeling of your fingertips. It can also be used to control other parameters of an AFM setup.
The list of controllable parameters includes:
- Frequency deviation (df)
- Drive amplitude
- Arbitrary voltage on any Aux Output
|Nanosurf Manual Controller box.|
The AFM system which was set up by the Molecular Self-Assembly Research Group of Professor Kühnle, University of Mainz, allows for manually controlling the frequency setpoint of the phase locked-loop in order to optimize the image quality of an NC-AFM scan.
To connect the Manual Controller to the Zurich Instruments lock-in amplifier, an adapter to the Lemo connector has to be built according to the information you find in “Building Instruction” below.
|Block diagram of the AFM system incorporating an HF2LI lock-in amplifier from Zurich Instruments and a Manual Controller box from Nanosurf.|
The ZCtrl port of the HF2LI has to provide the power supply (±12V) for the Manual Controller. Furthermore, the Aux Input of the HF2LI has to read the returned analog offset voltage from the Manual Controller. Therefore, a Y-cable is needed that connects the Lemo connector of the Manual Controller to the ZCtrl and the Aux Input of the HF2LI. Here you find the necessary technical information for the connectors.
- Lemo Connector PCA.0S.304.CLLC37 Datasheet
- BNC Connector (half BNC cable)
- RJ45 connector with cable (sacrifice a network cable). Be referred to our user manual for a pin description of the ZCtrl connector.
- Short piece of four-core cable
Shield: Offset- (GND)
|Pin 1: +12V
Pin 4: -12V
|Pin 1: +12V
Pin 2: Offset+
Pin 3: Offset- (can be grounded)
Pin 4: -12V
|Lemo connector||Lemo connector disassembled|
One of the four PID controllers of the HF2LI is used as a generic interconnectivity module providing only proportional gain. The output is written to the Aux Output offset (and thus added to the df value, which is output at the same Aux Output). The PID is configured as follows:
The HF2LI configuration file can be downloaded there:
By default the Aux Input performs an averaging of 256 samples in a moving average manner. This is a sensible setting for this purpose as it has to reduce noise while still providing sufficient bandwidth.
Connectivity to Scan Controller
The voltage encoding of the df – df offset is fed into the scan controller as the feedback signal which is set under “Aux outputs”. Depending on the scan controllers’ feedback, the sign of the encoding has to be chosen accordingly.
These images, which were recorded in non-contact mode using an HF2LI, were kindly provided by Philipp Rahe from the Molecular Self-Assembly Research Group Kühnle, University of Mainz, Germany.
P. Rahe, J. Schütte, A. Kühnle
NC-AFM contrast formation on the calcite (10-14) surface
J. Phys.: Condens. Matter 24 (2012) 084006