HF2LI-PID Quad PID Controller

The HF2LI-PID option builds on the HF2LI and seamlessly integrates no less than 4 high performance PID (proportional integral derivative) controllers for general purpose control. The controllers provide the means to efficiently implement closed loop control on several measured physical units.

HF2LI-PID Key Features

  • 4 fully programmable PID controllers
  • Full proportional, integral, derivative parameter control
  • Flexible set point configuration: toggle, external, manual, cascaded
  • Anti-windup
  • Arithmetic unit
  • PID Tuner and PID Advisor tool with 4 simulation models

HF2LI-PID Upgrade and Compatibility

  • Option upgradeable in the field
  • Cannot operate in parallel with HF2LI-RT Real-time option
  • Compatible with all other HF2LI options

HF2LI-PID User Benefits

  • Improve closed-loop bandwidth compared to LabVIEW implementation by orders of magnitude
  • No external PID hardware required, better performance, less system noise
  • Out-of-the-box closed-loop control solution: no programming required (e.g. LabVIEW,C)

HF2LI-PID Applications

  • Automatic gain control (AGC)
  • Kelvin probe force microscopy (KPFM)
  • Dual-frequency resonance tracking (DFRT)
  • SPM tip protection
  • Axis control, Z-control for scanning applications
  • Laser stabilization, Pound-Drever-Hall loops (narrow-band)
  • Dual-sideband analysis (SNR improvement)
  • Engineering of electronics

HF2LI-PID Functional Diagram


The HF2LI-PID ideally complements the HF2LI-PLL option for many resonance applications, but is also very attractive if just paired with the HF2LI lock-in amplifier. Zurich Instruments is the only lock-in amplifier vendor offering performant PID controllers in the same box, providing an evident integration advantage. The HF2LI-PID option is standard for the HF2PLL.

There is a variety of input units that can be selected, including demodulator outputs and auxiliary inputs. Also the output units selection is very flexible, offering control of units such as amplitudes, frequencies and auxiliary inputs.

Arithmetic Unit

A basic arithmetic unit allows to perform the following calculations and use the result as PID input:

  • |Z(n+1)| - |Z(n)|
  • X(n+1) - X(n)
  • |Z(n+1) - Z(n)|

Where Z(n) = X(n) + i Y(n) is the complex output of the n-th dual phase demodulator and R(n) = |Z(n)| the associated amplitude output. 

PID Advisor

The PID Advisor tool is embedded in the graphical user interface and supports the user in efficiently determining loop parameters. This is often a time consuming task, but is very simple with the Zurich Instruments software. Moreover the loop can be simulated with 4 built-in models, increasing the likelihood of immediately finding appropriate settings. The PID Tuner can further support the optimization of the previously estimated parameters.

HF2LI-PID Specifications

Configuration Quad-PID
Regulation bandwidth More than 5 kHz for each PID controller
Total update rate 100 kSa/s
Regulated units (PID inputs) X, Y, R, and Theta from demodulators 1 to 6, auxiliary input 1 and 2, frequency deviation from PLL 1 & 2
Controlled units (PID outputs) Amplitudes of oscillators 1 to 8, frequency of oscillators 1 to 6, auxiliary outputs 1 to 4, digital output DIO (16 bit)
Controllable loop parameters Set point, center point, TC mode (time constant, gain) and PID mode (Kp, Ki, Kd), range, enable

Note: availability of the regulated/controlled units depends on installed options 

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