ICSPI nGauge AFM User manual

User Manual
Version 1.1
Atomic Force Microscope

nGauge AFM User Manual 2
Table of Contents
Introduction ..................................................................................................................................................3
1.0 Safety and Precautions ........................................................................................................................... 3
2.0 Overview .................................................................................................................................................5
2.1 AFM Basics .......................................................................................................................................... 5
2.2 sc-AFM Basics...................................................................................................................................... 5
2.3 nGauge AFM Components.................................................................................................................. 6
2.4 nGauge AFM Capabilities and Limitations .......................................................................................... 6
3.0 Setup .......................................................................................................................................................6
3.1 Where to set it up ...............................................................................................................................6
3.2 How to set it up...................................................................................................................................7
3.3 Installing the Software ........................................................................................................................ 9
4.0 Basic Operation.....................................................................................................................................10
4.1 Software Overview............................................................................................................................10
4.2 Preparation and Approach................................................................................................................11
4.3 Imaging..............................................................................................................................................12
4.4 Analyzing Data ..................................................................................................................................14
5.0 Post-Processing..................................................................................................................................... 14
5.1 Gwyddion.......................................................................................................................................... 14
6.0 Troubleshooting....................................................................................................................................15
7.0 Advanced Controls................................................................................................................................17
7.1 Frequency Sweep - Advanced Controls ............................................................................................ 17
7.2 Approach - Advanced Controls .........................................................................................................18
7.3 Scan - Advanced Controls ................................................................................................................. 18
7.4 Menu Button - Advanced Controls ...................................................................................................19

nGauge AFM User Manual 3
Introduction
Congratulations on purchasing the world’s first single-chip Atomic Force Microscope (sc-AFM)
system! nGauge achieves magnification that far surpasses that of an optical microscope, so that you may
explore the world with nanometer-scale resolution.
The most up-to-date instruction manual can always be downloaded from
www.icspicorp.com/resources.
Please read this instruction manual before operating your new instrument to learn how it works,
how to set up and operate the hardware and software, how to prepare samples, and how to visualize
your data. The nGauge team has made every effort to improve the ease-of-use of AFMs, and we
welcome any feedback that may improve your experience.
1.0 Safety and Precautions
The following warnings and precautions should be observed to ensure the safety of the user and
the instrument:
Use only the power supply provided. The driving electronics are designed to accept 7.5Vdc, and
an internal fuse prevents the input current from exceeding 1A.
The stage contains moving parts that could pinch. To avoid minor injury, be aware of the moving
parts.
Avoid disassembling the system. If not done properly, this could result in damage to the
electronics or the mechanical components.
Be extremely careful when handling an AFM chip. They are very fragile and will break if the tip is
touched. AFM chips should be stored in their box with the tip facing DOWN, and removed using
the tweezers provided. If necessary, the AFM chip can be placed on a flat surface with the tip
facing up. The AFM chip can be picked up by hand by the board as long as you are careful to
avoid touching the tip.
The tip, located at the edge of the
board, is extremely fragile.

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AFM chips should be stored with the tip
facing DOWN in the storage box. Use
tweezers to pick them up.
The AFM chip can be placed on a flat
surface with the tip facing up.
The AFM chip can be picked up by hand
as long as you don't touch the tip.
This is a zoomed-in photo of the AFM
chip. The chip is extremely fragile.

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2.0 Overview
2.1 AFM Basics
Unlike optical microscopes that use light and lenses to magnify, or electron microscopes which
use electron beams to generate an image, Atomic Force Microscopes (AFMs) use a very sharp tip to
measure tip-sample interaction forces and generate a 3D reconstruction of a sample surface. The tip is
raster scanned over a 2D area while a controller maintains a constant tip-sample force by adjusting the
tip's Z height. The control effort then represents the height of the features on the sample.
Conventional AFMs typically use a probe comprising a sharp tip on a silicon cantilever. A laser
beam is reflected off the backside of the cantilever onto a 4-quadrant photodetector that measures any
small displacements of the cantilever. A piezoelectric Z-scanner controls the height of the probe while a
piezoelectric XY stage raster scans the sample in X and Y.
2.2 sc-AFM Basics
A single-chip AFM (sc-AFM) operates in almost exactly the same manner as a conventional AFM
except that all of the essential components are integrated onto a chip. The chip is a
MicroElectroMechanical Systems (MEMS) device that uses the most advanced manufacturing process in
the world to produce tiny, ultra-precise scanners and sensors on a ~1x1mm silicon chip.
An sc-AFM has a cantilever and a sharp tip, but instead of a laser it has an integrated
piezoresistive strain sensor to measure tip displacements. The tip and sensor are attached to a MEMS
scanner that can position them in X, Y, and Z with sub-nanometer resolution.

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2.3 nGauge AFM Components
The nGauge AFM system includes all of the following components. A computer (not included)
with a USB port is required.
1. Stage
2. Sample Platform
3. Thumb Nut
4. AFM Chips
5. Power Supply
6. USB Cable
7. Tweezers
2.4 nGauge AFM Capabilities and Limitations
The nGauge AFM operates in tapping mode, in which the cantilever oscillates at its resonant
frequency and makes intermittent contact, or “taps” the sample surface. It can scan areas of up to
20x20x10um in X, Y, and Z respectively with <1nm RMS Z noise.
Any solid sample can be imaged, including both conductive and non-conductive, but the AFM
cannot operate in liquid and cannot image liquid samples. Some samples, particularly polymers, may be
difficult to image due to surface charging.
3.0 Setup
3.1 Where to set it up
The nGauge AFM is small, simple, and portable, and can be set up just about anywhere.
However, for best results, it is recommended that you adhere to the following guidelines:
Flat surface: The system should be set up on a flat, level surface, like a desk or tabletop, with
enough space to ensure that the stage does not get bumped or moved while imaging.
Vibrations: The unique design of the nGauge AFM minimizes the effects of common sources of
vibrations, such as those caused by people walking by, doors opening and closing, and building
vibrations. However, it is best to set the system up on a solid, stable surface away from as many
sources of vibration as possible.
Air Drafts: The system is not immune to air drafts and should be set up away from air vents,
drafty windows, etc. If air drafts are unavoidable and present a significant problem, a box or
enclosure around the system may be required.

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Electrical Noise: The system meets the FCC guidelines for electrical interference, but it is best to
avoid setting it up near sources of electrical noise, such as server rooms or rooms operating
high-power equipment.
3.2 How to set it up
Setup of the nGauge AFM is very simple.
1. Remove the
components from the
carrying case. Set the
stage upright on a flat
surface.
2. Plug the power supply
into a wall outlet and
into the power
connector in the
stage.

nGauge AFM User Manual 8
3. Connect the USB
cable to a computer
and to the USB
connector in the
stage.
4. Completely unscrew
and remove the
thumb nut from the
stage

nGauge AFM User Manual 9
5. Open up the AFM chip
box and pick up an
AFM chip using the
tweezers
6. Carefully place the
AFM chip onto the
alignment pins on the
stage with the tip
facing down. During
this step, the sample
platform should be
retracted sufficiently
to avoid any contact
between the tip and
platform.
7. Replace the thumb
nut and firmly tighten
it.
3.3 Installing the Software
The software required to operate the AFM can be found on the USB stick provided, or
downloaded from www.icspicorp.com/resources. To install the software for windows, run the
executable installer “nGauge_setup_x.x.x.x_windows.exe”. To install the software on Mac OS, simply
mount the disk image “nGauge_setup_x.x.x.x_mac.dmg” and drag the nGauge application into the
applications folder.

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If network connection is available, the software will automatically check for updates from the
ICSPI server. This information is displayed on both the home screen and in the updates section of the
menu. To manually query the ICSPI update server for new updates, click Check Updates under the
updates section of the menu.
The open source AFM post-processing software called Gwyddion is a very useful tool and should
also be installed. You can download it from the Gwyddion website: http://gwyddion.net/download.php.
See section 5.1 Gwyddion for more details.
4.0 Basic Operation
4.1 Software Overview
Launch the software by double-clicking on the nGauge program on your desktop or searching for
nGauge in the start menu. If the AFM is powered up and connected to the computer with the USB cable,
the splash screen should display the message "AFM Ready". If not, refer to section 6.0 Troubleshooting.
The setup and imaging workflow is divided into three ordered tabs: Sweep, Approach, and Scan.
To navigate between the three tabs, click on the desired tab in the progress bar at the top of the page.
The menu button at top-right of the page brings out a detailed settings menu for all aspects of AFM
configuration. The settings in this menu are not required for normal operation and most users will never
need to use these controls. Please review section
7.4 Menu Button - Advanced Controls for details.

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4.2 Preparation and Approach
Once the AFM has been set up and the software installed, you are ready to start imaging.
Launch the software, wait for the message "AFM ready", and click the Enter button. Place your sample
on the sample platform, making sure you don't touch the tip. If the sample will not fit under the tip,
lower the sample platform by clicking on the Approach tab, then clicking and holding down the Retract
button until the platform is low enough. Position the sample so that the area to be scanned is directly
under the tip. Ensure the sample is stable on the sample platform, and that it won’t tilt, roll, flutter,
drift, or otherwise move while imaging.
Navigate to the Sweep tab and click the Sweep button to perform a frequency sweep of the
cantilever. This may take a few seconds. The Amplitude graph should display a smooth curve like the
one below, with a maximum value greater than 1. If not, click on Show Advanced Controls and adjust
the Cantilever Drive Amplitude. Continue Sweeping and adjusting the amplitude until the peak is around
3V. Click the Approach tab to proceed.

nGauge AFM User Manual 12
In the Approach tab, click the Approach button to initiate the auto-approach. The sample
platform will rise quickly and then slow down for a final approach once the sample gets very close. The
data being streamed on the graph represents the cantilever oscillation amplitude, and it will begin to
decrease as the sample gets close and tip-sample interaction is observed. When the auto-approach is
complete, the tip will be engaged with the sample and you can proceed to imaging. If the cantilever
oscillation amplitude does not track the setpoint or the amplitude oscillates, please refer to section 6.0
Troubleshooting.
4.3 Imaging
In the Scan tab, choose the image resolution you would like by selecting the number of pixels
per line and the number of lines per image. The higher the resolution, the longer it will take to complete
a scan. The Time spent at each point field indicates the amount of time that the tip dwells above each
point of the scan and ultimately determines the scan speed. A smaller number in this field increases the
scan speed, but if the scan is too fast the resulting image may be blurry or distorted.
Click Scan to begin imaging. The image will begin to build up line by line. The color in the image
represents the height of the features, and some minor corrections (line leveling, plane leveling) can be
applied to the raw data to display a clearer image by checking the Level Image checkbox on the left side
of the screen. There you will also find the options to display the topography, phase, or error images in
both the forward and reverse directions. A profile view can be found below the image that displays the
cross-section (height) of the current line being scanned. When the scan is completed, the line under
your cursor would be displayed on the line profile plot. You can widen or narrow the line profile by using
the scroll wheel.
The Z actuator is split into Coarse Z and Fine Z controls. The Fine Z has a smaller range, and it’s
the control that is used to track sample topology while scanning. If a sample has tall features that extend

nGauge AFM User Manual 13
beyond the range of the Fine Z control, the image will get clipped. To increase or decrease the Fine Z
scan range, click on the Menu, then under PGAs increase or decrease the Z Fine. For maximum imaging
resolution, the smallest Fine Z range should be used. It is also possible that the sample topology is not
centered around the middle of the Fine Z range, which could result in image clipping. The Approach tab
displays a graph with the Fine Z position. If it appears that most of the image data is at the lower or
higher end of the Fine Z range, you can click Show Advanced Controls and increase or decrease the
Coarse Z to center the data. In some cases, you may even need to Disengage and then re-Approach.
There are several parameters that you can control to improve the imaging performance. The
Time spent at each point is the number of microseconds that the tip will dwell above each data point.
As you decrease this value, the scan speed will increase and the controller will have less time to track
the sample topology, leading to poor image results. The Set Point is the tip oscillation amplitude that
the controller will try to maintain as the tip scans over the sample surface. It can be thought of as the
amount of force that the tip exerts as it taps the surface, where a lower setpoint exerts more force. A
lower setpoint can often give better results, but is also more likely to damage the tip or sample, and
when the setpoint gets too low the imaging performance may suffer. A PI controller is used to maintain
a constant tip oscillation amplitude throughout the scan by adjusting the Fine Z height. The Proportional
and Integral control in the advanced controls section are used to adjust the response of the controller,
and can be tuned to give the best sample tracking performance. See section 6.0 Troubleshooting for
more details for PI tuning.
At any time you can click Pause and Resume to temporarily halt and then resume the current
scan, or you can Pause and then Reset to re-start the current scan at the beginning. When the scan is
complete, you will be able to click Save to save the image as a .gwy file which is native to Gwyddion (a
post-processing software), and as a .png image. You can also save the data as a .tsv file where the data
points are arranged in a 2-d tab and line separated table. The image will be saved in the folder specified
by Path, which you can click on to change. All 6 images (topo, phase, error forward/reverse) will be
saved, and a Unix timestamp will be appended to the file name.
To zoom into a region of interest, you can drag across the displayed image to select an area to
zoom in. Click Scan again after the selection has been made to scan the region of interest. To reset to
the original scan area, click Reset Zoom. If Reset Zoom button is disabled, the AFM will scan the default
area.

nGauge AFM User Manual 14
When you are finished with the AFM, go to the Approach tab and click Disengage to safely
disengage the tip from the sample. After the disengage routine is completed (a few seconds), hold the
Retract button to rapidly move the sample downwards to the point where there is sufficient separation
between the sample and the tip to safely remove the sample. It is advisable to always disengage and
retract when finished with the AFM lest any external disturbances (such as accidentally bumping into
the stage) cause the tip to crash into the sample. Caution: the tip is extremely fragile so please avoid
crashing the tip into the sample while removing the sample.
4.4 Analyzing Data
Once a scan is complete, users often want to extract some quantitative data about the sample,
like the height or width of a specific feature, or the RMS roughness of the surface. These measurements
are best acquired using Gwyddion, a powerful AFM post-processing program that is explained in section
5.0 Post-Processing.
5.0 Post-Processing
5.1 Gwyddion
Gwyddion is free and open-source software for AFM image post-processing. It can be
downloaded here: http://gwyddion.net/download.php . The nGauge user interface can save images in a
Gwyddion-supported format (.gsf) which can then be dragged and dropped into Gwyddion to open
them. The Gwyddion user manual gives detailed descriptions of the program's capabilities, but below
are some useful functions that are commonly used:
Data Process --> Level -->
Polynomial Background
If there is any tilt or curvature in the image, this function will help
remove it. You can specify the polynomial degree in the horizontal and
vertical directions.

nGauge AFM User Manual 15
Data Process --> Correct Data
--> Align Rows
If each horizontal line in the image does not quite line up with the ones
above and below it, this function will subtract the height differences
line-by-line. "Median of differences" works well.
Data Process --> Basic
Operations --> Limit Range
A random high or low pixel can throw off the contrast in an image. This
function allows you to set a high and low value to remove outliers or
extra large features.
Tools --> Crop Data
Crop out unwanted parts of an image.
Tools --> Extract Profile
Drag a line over your image to view the profile.
Tools --> Statistical
Quantities
Display values like RMS roughness and Ra. A box can be dragged over
your image to select a specific area to measure.
View --> 3D View
Display a 3D view of the image. You can rotate or scale this 3D image,
change the colors, and save it.
Once you are satisfied with the post-processed image, you can save it as JPG, PNG, etc using the
Save As option. You will be prompted with export options in which you can customize the resolution,
scale bars, font sizes, colors, and other options.
6.0 Troubleshooting
Issue
Solution
Hardware not detected by
computer
Unplug and then plug in the USB and/or power. Restart the software if
necessary. In your computer's Device Manager, check to see if there is a
COM port called Bossa Program Port or AT91. If there is no COM port by
these names, but the hardware shows up as a USB device, right click on
the USB device, click Update Driver Software, then Browse My Computer
For Driver Software, and navigate to "C:\Program Files
(x86)\ICSPI\nGauge\firmware\ISP\sam-ba_3.1.1\driver\atm6124_cdc.cat".
After installing this driver, try unplugging and plugging in the USB cable,

nGauge AFM User Manual 16
and restarting the software again.
Stage will not move
Restart the software and make sure that the hardware connects properly
by watching for the “AFM Ready” notification on the splash screen.
The sample platform can only be lowered so far before a limit switch
prevents further travel. Once the limit switch is triggered, you will not be
able to retract any more, but you should be able to approach. However, if
there is no functional AFM chip affixed to the stage, the platform cannot
approach. Override controls exist in the Menu button on the top right of
the screen. After clicking the Menu button, the Motor Controls can be
used to approach without a functional AFM chip.
If the stage still will not move, contact [e-mail] for help.
Auto approach will not
run
An AFM chip must be affixed and running at resonance in order to start
the Auto Approach. If an AFM is already affixed, go to the Frequency
Sweep tab and click Sweep. A smooth curve with an obvious peak should
be shown. If the maximum value of the peak is less than 2V, click on
Advanced and increase the Amplitude, then sweep again. If the top of the
curve is cut off, decrease the amplitude and sweep again. If the frequency
sweep plot data is flat and noisy, tighten the thumb nut on the AFM chip.
If the problem persists, the AFM chip may be damaged.
Frequency sweep flat
A frequency sweep should return a smooth curve with an obvious peak. If
instead the data is flat and noisy, try tightening the thumb nut on the AFM
chip to make a better electrical connection, and sweep again. If the data is
still flat and noisy, the AFM chip may be damaged. Click on the Menu on
the top right of the screen and scroll down and click Read All. If any of the
values under Resistances is greater than 1000, the AFM chip is damaged
and must be replaced.
Peak value of frequency
sweep is lower than 1 or
getting cut off above 3.3
Click on show advanced options and adjust Cantilever Drive Amplitude
(%). Increase the value if peak value is lower than 1; decrease if greater
than 3.3. Generally, a drive amplitude of 20-35% is appropriate.
Drift in Z when imaging
If there are large line-to-line variations in height, the sample may not be
secure. For instance, if imaging a lightweight sample (e.g. piece of paper),
air drafts may cause significant drifts - fasten the sample down with a
heavy object.
If the approach completes early and the image does not contain
topography information, it is possible that the surface is charged. One way
to verify this is to perform another frequency sweep. If a complete curve is
obtained, with the peak at a new frequency, the sample may need to be
discharged before imaging.
Noisy image
If the image results are excessively noisy, this may be caused by vibrations
or air drafts. Try moving the stage to a different location, placing the stage
on some soft foam or bubble wrap, or place a box over the stage to
eliminate drafts.
Data "plateaus"
The Z actuator is split into Coarse Z and Fine Z controls. The Fine Z has a
smaller range, and it’s the control that is used to track sample topology
while scanning. If a sample has tall features that extend beyond the range
of the Fine Z control, the image will get clipped. To increase or decrease
the Fine Z scan range, click on the Menu, then under PGAs, adjust the Fine
Z. For maximum imaging resolution, the smallest Fine Z range should be

nGauge AFM User Manual 17
used. It is also possible that the sample topology is not centered around
the middle of the Fine Z range, which could result in image clipping. The
Approach tab displays a graph with the Fine Z position. If it appears that
most of the image data is at the lower or higher end of the Fine Z range,
you can click Show Advanced Controls and increase or decrease the
Coarse Z to center the data. In some cases, you may even need to
Disengage and then re-Approach.
PID Controller Tuning
The PI controller measures the tip oscillation amplitude and subtracts this
value from the setpoint to give an error term. The error term is multiplied
by the Proportional (P) coefficient and the Integral (I) coefficient to
generate a response in the Fine Z. If the P and I coefficients are too low,
the controller response will be slow and the tip will not track the sample
topology very well. If the P and I coefficients are too high, the controller
may oscillate and the image will look like noise. One method of tuning the
P and I values is to set them both to zero and increase the P until it begins
to oscillate, then decrease P by a bit. Then begin to increase the I until it
begin to oscillate and decrease I by a bit. For more detail, refer to
https://en.wikipedia.org/wiki/Ziegler%E2%80%93Nichols_method
7.0 Advanced Controls
The main controls that are visible in each screen should be sufficient for normal imaging
conditions. However, each tab in the navigation contains advanced controls that can extend the
functionality or control of the scan. In addition, there is a side menu available by clicking the button on
the top right of the screen that will enable access to all of the controls available.
7.1 Frequency Sweep - Advanced Controls
In the frequency sweep tab, click on Show Advanced Controls. These additional controls are for
running a manual frequency sweep and controlling the driving frequency and tip oscillation amplitude.
When the advanced controls are displayed, the drive frequency can also be set by clicking the sweep
graph at the desired frequency.
Start Frequency
The frequency at which you would like to start a manual frequency sweep
Stop Frequency
The frequency at which you would like to stop a manual frequency sweep
Step Size
The step size, in hertz, that the manual frequency sweep will increment. Step Size
determines the number of data points in the results.
Manual Sweep
Manual Sweep will perform a frequency sweep from Start Frequency to Stop
Frequency, incrementing the frequency by Step Size. The results will be displayed
in the main Frequency Sweep plot.
Clear
Clears all the results from the main Frequency Sweep plot.
Amplitude (%)
Controls the amplitude of the driving signal applied to the Z actuator. This can be
thought of as the tip oscillation amplitude. Increasing this value will increase the
tip oscillation amplitude.

nGauge AFM User Manual 18
7.2 Approach - Advanced Controls
In the approach tab, click on Show Advanced Controls. These additional controls are for the
controller, and the coarse Z positioning.
Proportional
The proportional gain coefficient of the PI controller. See section 4.3 Imaging
for details on tuning the controller.
Integral
The integral gain coefficient of the PI controller. See section 4.3 Imaging for
details on tuning the controller.
Setpoint
The tip oscillation amplitude that the controller will try to maintain. Increasing
this value can be thought of as applying less force between the tip and sample.
Decreasing this value can be thought of as applying more force between the tip
and sample.
Enable/Disable
Manually turns the controller on or off.
Z Coarse
Controls the coarse Z tip position. Increasing this value retracts the tip away
from the sample, decreasing this value approaches the tip towards the sample.
This controls the AFMc chip's integrated Z scanner and should not be confused
with the stage controls that raise or lower the sample platform.
7.3 Scan - Advanced Controls
In the scan tab, click on Show Advanced Controls.
Scan Mode
Switch between the normal "Area" mode which scans a square 2D area, and
"Line" mode which scans a long 1D line. The "Line" mode results will still be
displayed as a 2D image, even though only a single line is being scanned
repeatedly.
Leveling Direction
To correct for the 15 degree tilt of the AFM chip relative to the sample, a
hardware leveling feature is applied. Leveling Direction switches between
adding or subtracting the 15 degree tilt and is device-specific. Different types of
AFM chip may require different Leveling Directions.
Leveling
If the raw data of an image still contains significant tilt in the Y direction, This
value can be increased or decreased to compensate.
Z Coarse
The Z actuator is split into two controls: Coarse Z and Fine Z. Fine Z has a
smaller range and is the channel that the PI controller uses to follow the
sample topology during a scan. Coarse Z has a large range and is simply used to
coarsely position the Z actuator so that that the entire sample topography is in
the range of the Fine Z.
Proportional
The proportional coefficient of the PI controller. Increasing this value increases
the response time of the controller, but increasing it too much can cause
instability in the Z actuator.
Integral
The integral coefficient of the PI controller. Increasing this value increases the
response time of the controller, but increasing it too much can cause instability
in the Z actuator.
Setpoint
The tip oscillation amplitude that the controller will try to maintain. A lower
setpoint is analogous to applying a larger force between the tip and sample.
Enable/Disable
Turns on or off the PI controller that maintains a constant tip oscillation
amplitude equal to the setpoint by controlling the Z actuator (Fine Z).

nGauge AFM User Manual 19
7.4 Menu Button - Advanced Controls
In the top right corner of the screen, click on the button with three horizontal lines, the "menu"
button.
Motor Controls
Controls the sample platform. Motor Speed adjusts how quickly the platform
moves. Approach makes the platform move up, Retract makes the platform go
down, clicking either Approach or Retract takes a single step, while clicking and
holding Approach or Retract moves the platform continuously.
PID Controller
Proportional is the proportional gain coefficient of the PI controller. Integral is
the integral gain coefficient of the PI controller. Setpoint is the tip oscillation
amplitude that the controller will try to maintain. Enable/Disable turns the
controller on or off.
DACs
Digital to Analog Converters (DACs) output analog voltages. These voltages
drive the X, Y, and Z actuators. The DAC controls allow you to set the voltage
level that is being applied to any of the actuators, including the lateral
actuautors (X1, X2, Y1, Y2), the Coarse Z and Fine Z, and the Leveling control
(which is integrated into the Z actuator). There is a conductive path to the AFM
tip and the Tip control allows you to set the tip voltage. All DACs range from 0-
3.3V
PGAs
Programmable Gain Amplifiers (PGAs) are able to scale the voltages output by
the DACs. The PGAs are used to adjust the XY scan size, the range of the Coarse
and Fine Z, the amplitude of the AC driving signal on the Z actuator, and the
amount of leveling that is added to each scan. PGA values can range from 0-
140%.
ADCs
Analog to Digital Converters (ADCs) read analog voltages. Clicking Read All will
display the current voltage level of the current sensing circuits for X, Y, and Z,
as well as the voltage levels of the amplitude and phase measurement circuits.
The ADCs range from 0-3.3V.
Resistances
Measured resistances of the MEMS actuators. Click Resistance button to
refresh measurements.
DDS
DDS (direct digital synthesis) section controls the drive signal frequency. To set
a new frequency, change both start and end frequencies to the desired
frequency.
Safety Configurations
Encapsulates various safety features. Safety thresholds and features may be
modified or disabled in this section.
Approach Low Limit specifies the low signal threshold that constitutes a safe
situation for auto-approach. If the measured signal at the beginning of auto-
approach is lower than the specified value, the approach will be aborted. It is
recommended to leave the setting at its default value of 0.7 V.
Check Resistances refers to the safety routine that is executed prior to every
Sweep, Approach, and Scan command. If enabled, the software will measure
resistances and check for any anomalies.
Limit Switch refers to the end-stop mechanism to prevent motor from driving
the stage too low. In the unlikely circumstance that the switch is damaged and
you cannot retract properly, you can uncheck the limit switch feature to

nGauge AFM User Manual 20
override the mechanism.
Updates
If internet connection is available, this section shows if the software and
firmware used are up to date. If updates are available, please go to
www.icspicorp.com/resources to find the newest versions of software and
firmware. Click on the Check Updates button to query the server again for
availability of updates.
Advanced
Lock Button: locks/unlocks most of the advanced controls. The locked controls
can render the system inoperable if not used properly, so user beware.
Force Curve: opens a window where you can run a routine to generate a
noncontact force curve. A force curve ramps the Fine Z from 2V to 0V, then
back up to 2V and measures the cantilever oscillation amplitude and phase.
The resulting graph shows the tip-sample interaction force with respect to tip-
sample distance.
Reset AFM: resets the hardware. Please close and reopen the software to
connect to the hardware again.
Restore Defaults: reset all of the settings to the default values.
Release Port: release the USB connection.
Choose Firmware: currently Windows only. Opens a window that allows you
to locate the firmware update. Firmware update files are binary (.bin) files, and
can be downloaded from our support page.
Enter Bootloader: erase the firmware program to allow for firmware updates
or flashing custom firmware. To reprogram firmware, please click the “Update
Firmware” button after choosing the firmware update file and entering into the
bootloader. Caution: do not click this button unless you need to reprogram
firmware and that you are confident with the process as this will erase current
firmware. Contact [e-mail] for any questions regarding firmware
updates.
Update Firmware: currently Windows only. Reprograms the nGauge unit with
the version of the firmware binary selected (see “Choose Firmware” button).
Caution: ensure the connection to the unit is stable, and do not spam-click
this button. Improper usage may result in a unit locked in a non-operable
state.
Notice: it may require more than one run of the “Update Firmware” routine
to successfully reprogram. Messages will pop up in the bottom left corner
while the unit is reprogramming, attempt after the message report the end of
the routine.