Once a month the RHK customer support department addresses commonly unknown support issues that concern RHK products and their capability.
Questions and comments are always welcome - info@rhk-tech.com |
 |
 |
More Tip Control : May, 2008 |
|
| SPM 1000 Universal Control System & XPMProTM Software |
| Have you ever needed to pull the tip away from the surface, but not wanted to use coarse motion?
Did you know the SPM100 provides this capability independent of the software?
It may be useful to pull the tip away from the surface a small amount without the need to keep the software running. The method described here works best when there are two piezos for z control, one used for z offset and one used for z scan. To utilize this, turn the z offset coarse and fine knob so the front panel analog feedback meter is as far to the left as possible. This means the z feedback piezo controlling the tip height is extended to its maximum length. This will occur when either both knobs are turned to zero or when both are turned to 10 depending on the polarity of the scan head. Once this is finished, use the front panel Reset switch to override the feedback loop and set its output to zero volts by locking it in the up position. When the voltage applied to the piezo changes to zero, the element will contract to its equilibrium length which guarantees the tip will move away from the surface. The actual separation between the tip and sample is unknown but can be estimated to be at least half the total z range of the scan head if the feedback meter was fully to the left before flipping the switch up. Often this is enough separation to safely make changes without losing the actual location of the tip over the sample. |
|
| |
|
Setpoint Modulation : April, 2008 |
|
|
| SPM 1000 Universal Control System & XPMProTM Software |
Have you ever wanted to acquire data under various tip height conditions or various cantilever force conditions?
Are you concerned with leaving the feedback loop open due to thermal drift and therefore don't trust adjusting the tip height by applying a fixed voltage to the z piezo and scanning under open loop conditions?
Did you know that you can adjust the tip height by leaving the loop active and changing the tip-sample separation by altering the feedback setpoint via computer control?
On the rear panel of newer SPM100 control units there is a Setpoint modulation input. If one of the output DACs is connected to this input, any voltage output by the DAC is equivalent to turning the Setpoint knob. Simply calculate the preamplifier gain (in the case of STM) to determine the shift in setpoint given an applied voltage. To determine the change in z height due to the changed feedback conditions, you can compare the average DC offset of the Topography channel under both conditions. |
|
 |
|
| |
|
Meet dataSAFETM: March, 2008 |
|
|
| SPM 1000 Universal Control System & XPMProTM Software Ver. 1.2 and above |
| Have you ever missed an important piece of data because you forgot to click the Save button before the end of the image? Have you ever realized an interesting event occurred during an image scan, but it was a few images later before the full ramifications of the data were realized and you really wish you have saved it?
Did you know that the dataSAFE feature in XPMPro can rescue you from these potentially tragic events? To activate the automatic saving of images to a temporary ring buffer, choose ACQ/Settings/Scan/SaveDisplay and make sure the Enable checkbox in the Image dataSAFE section is marked. You should also choose an appropriate temporary location for these files and decide how many to save. Don't worry about filling up your hard drive with files. When the number of files reaches the specified limit, the FIFO (first in First out) algorithm kicks in and starts removing the oldest file and replaces it with the most recent scan. Even after the program exits, these files remain on the drive until data is acquired at a later time. So days, weeks, or even months later you can resurrect that key piece of data that was not appreciated when it was first acquired as long as it was not overwritten in the meantime. |
|
 |
|
| |
|
Special Edition, XPMPro Features: February, 2008 |
|
|
We uphold our commitment to the advancement of SPM control software. We would like to introduce a few of the brand new features including:
- Higher sensitivity: Oversampling yields better signal to noise especially in slow scans
- Consistent results: Spectroscopy drift corretion keeps your data true.
- Optimize on the fly with visual feedback: Process and display spectroscopic data in real- time
|
 |
| |
|
Eliminate Z Drift: January, 2008 |
|
|
SPM 1000 Universal Control System & XPMProTM Software
Do you operate a microscope that has substantial thermal drift in the z direction or perhaps you are changing temperature on a microscope and want to keep the z data within a narrow range for high resolution imaging? If you are frequently adjusting the Z Offset knob in order to keep the topography channel in the middle of its range, let the SPM100 do the work for you!
Did you know there is a second, digital feedback loop available inside the SPM100 that can monitor the Topography signal and adjust an output voltage in order to keep the signal close to zero? Connect the Z Signal Monitor Output to DSP ADC#1 and then connect the DSP DAC to either the Z Position Modulation Input #1 or Z Offset External Control. If a separate Z Offset piezo element is available, the second choice is recommended.
To configure the loop parameters choose NAV/Aux Feedback/Settings. Set the mode to Z Offset Control and choose the loop polarity via the AUX Feedback Z Offset Invert. For the RHK line of UHV SPMs, this box needs to be checked. Set the Time Consant of the loop in the NAV window. A value of 2-5 seconds provides good results. Be careful to not set it too short or there is a risk that it will try to counteract the analog loop as it tries to follow the real surface variations. If you are concerned the loop may effect the topography data during imaging you can disable it while scanning with the Disable AUX Feedback During Scanning checkbox. The scan can then be paused between frames with the ACQ/Settings/Scan/Scan/Scan Delay parameter and the secondary loop activated for a fixed time to shift the topography channel back to zero. To activate the loop, check the Enable AUX Feedback box at the bottom of the NAV window.
 Z Offset Control (Screenshot) |
| |
|
Approach Motor, Tip Control: November, 2007 |
|
|
SPM 1000 Universal Control System & XPMProTM Software
Is your coarse approach conservative and therefore relatively slow?
Are you worried if you leave the room during the approach something bad will happen after it finishes since the STM tip is hovering less than a nanometer above the surface? Well, did you know you can activate an option that once the approach completes the z piezo can be retracted so tip is away from the surface? This can put your mind at ease when the microscope with its delicate tip is left unattended.
Open NAV > Approach Motors > Tip Control and make sure the parameter named "Tip Back After Approach" is active. To release the tip after returning to the scan head click "Yes" when answering the prompt. If you want to dismiss the window but leave the tip retracted, the tip can be pushed forward at a later time by using the Withdraw Tip button in the NAV > Manual Control window.
Tip Control Interface (Screenshot) |
| |
|
Approach Threshold: October, 2007 |
|
|
SPM 1000 Universal Control System & XPMProTM Software
If your scan head takes small "coarse approach steps" compared to the full z range of your piezo, you probably find yourself using the "+" button to take a few more steps forward once the automatic approach is done so the z piezo is close to the center of its range.
Did you know you can have the computer take care of this automatically?
If the Approach Threshold parameter is set to 0%, the approach will not halt until the z piezo is closer to the center of its range compared to the default value. Be careful if trying to use this when the coarse steps are quite large (50% or more of the z range) as one extra step may push the tip into the sample. For the RHK line of UHV microscopes where the step size is usually less than 1/10 of the z piezo size, 0% can be used safely.
Approach Threshold Interface (Screenshot) |
|
|
|
|
E-mail: support@rhk-tech.com
Telephone: (248) 577-5426
Fax: (248) 577-5433 |
| |
