Features

• Single Channel (MDT694A) & 3 Channel (MDT693A) Versions
• 3 User Selectable Output Ranges up to 150 V
• High Current Drive Capability (60 mA)
• Precision, Low Noise Outputs
• Internal/External Voltage Control
• RS232 Interface and Graphical User Interface Software
• 3 Channel Scan Balancing
• Master Scan Controls
• Compatible With our Full Line of Piezo-electric Actuators

The Thorlabs MDT693A and MDT694A Piezo-Electric Controllers have been designed to take advantage of the very high resolution achievable with low voltage piezo stacks (100 V compared to 1000 V). Both models combine precision control of the output voltage for maximum piezo resolution, along with a high output current capability to allow external modulation of the piezo. Computer control is available on both models via an RS-232 interface. For the added protection of your sensitive, low voltage piezo devices, a selectable output voltage range switch has been added with three selectable ranges: 0 to 75 V, 0 to 100 V and 0 to 150 V. Additionally, the three channel MDT693A offers Master Scan controls that allow internal or external control of all three channels simultaneously.

Piezo control can be achieved manually using the a front panel adjustment knob, electrically using a 0 - 10 V signal input into a front panel BNC connection, or remotely using the RS-232 interface and Graphical User Interface (GUI) software provided with the unit. Please refer to the Software Tab for more information on the GUI.

A firmware update is available for the MDT693A. Please visit our download page for details.

The output is provided on a convenient BNC connector located on the rear panel. A BNC (male) to SMC (male) adapter is included for each output to provide compatibility between our various stages and piezo actuators.

Please note: when powering off the unit, the piezo output may expeience a voltage fluctuatuation. While this will not damage the piezo actuator, it will change the position of the connected optomechanical device. To avoid this, Thorlabs recommends disconnecting the the output from the controller (i.e., unplug the BNC from the back panel) prior to powering off. To eliminate the risk of electric shock, we recommend adjusting the voltage control to 0 V prior to disconnecting the piezo.

For complete specifications and conditions, please download the Operating Manual available on the Drawings and Documents tab. Also please note that there may be a voltage spike when the controller is initialized, resulting in a slight movemenf of the attached piezo; if your application would be adversely affected by such an initial movement, we recomment our BPC203 3-Channel Benchtop Controller, which does not exhibit this effect.

Software

Version 1.6.1

Includes GUI for control of the controller.

Also Available:

• Firmware Version 3.01 for the MDT693A
• Library Files for LabVIEW

The MDT693A and MDT694A include a standalone software package capable of operating the unit remotely. The main window imitates the front panel with control knobs to adjust each channel independently, and a display to view the current settings. The output voltage of the piezo driver is directly controlled through software, eliminating the need for external control voltages such as lab power supplies, frequency generators, or analog output cards.  

Also included are modules to operate the MDT693A in the master scan mode. In this mode all channels can be controlled with the same adjustment. Separate gain scaling and offset is available to calibrate the piezos to one another.

In addition, a software signal generator module allows the user to input basic modulation control. Simple functions such as sine waves, ramps and pulses can be configured to control the piezo output.

All user functions for the MDT693A and MDT694A are available within the provided software. Third-party software (e.g., LabVIEW) control is also possible through a provided serial command line interface.

A firmware update is also available for the MDT693A via the link to the left.

Piezo Driver Bandwidth Tutorial

Knowing the rate at which a piezo is capable of changing lengths is essential in many high-speed applications. The bandwidth of a piezo controller and stack can be estimated if the following is known:

1. The maximum amount of current the controllers can produce. This is 0.5 A for our BPC Series Piezo Controllers, which is the driver used in examples below.
2. The load capacitance of the piezo. The higher the capacitance, the slower the system.
3. The desired signal amplitude (V), which determines the length that the piezo extends.
4. The absolute maximum bandwidth of the driver, which is independent of the load being driven.

To drive the output capacitor, current is needed to charge it and to discharge it. The change in charge, dV/dt, is called the slew rate. The larger the capacitance, the more current that is needed.

So for example, for a 100 µm stack, having a capacitance of 20 µF, being driven by a BPC Series piezo controller with a maximum current of 0.5 A, the slew rate is given by

Hence, for an instantaneous voltage change from 0 V to 75 V, it would take 3 ms for the output voltage to reach 75 V.

Note: For these calculations, it is assumed that the absolute maximum bandwidth of the driver is much higher than the bandwidths calculated, and thus, driver bandwidth is not a limiting factor. Also please note that these calculations only apply for open-loop systems. In closed-loop mode, the slow response of the feedback loop puts another limit on the bandwidth.

Sinusoidal Signal

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The bandwidth of the system usually refers to the system's response to a sinusoidal signal of a given amplitude. For a piezo element driven by a sinusoidal signal of peak amplitude A, peak-to-peak voltage V_pp, and frequency f, we have:

A diagram of voltage as a function of time is shown to the right. The maximum slew rate, or voltage change, is reached at t = 2nπ, (n=0, 1, 2,...) at point a in the diagram to the right:

From the first equation, above:

Thus,

For the example above, the maximum full-range (75 V) bandwidth would be:

For a smaller piezo stack with 10 times lower capacitance, the results would be 10 times better, or about 1060 Hz. Or, if the peak-to-peak signal is reduced to 7.5 V (10% max amplitude) with the 100 µm stack, again, the result would be 10 times better at about 1060 Hz.

Click to Enlarge

Triangle Wave Signal

For a piezo actuator driven by a triangle wave of max voltage V_peak and minimum voltage of 0, the slew rate is equal to the slope, or:

or, since f = 1/T:

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Square Wave Signal

For a piezo actuator driven by a square wave of max voltage V_peak and minimum voltage of 0, the slew rate limits the minimum rise and fall time. In this case, the slew rate is equal to the slope while the signal is rising or falling. If t_r is the minimum rise time, then:

or