Working with Contact Surface Profilometers

Introduction

I wrote an MPhil thesis which dealt with the use of contact (stylus) surface profilometers for use in MEMS material property measurement. As a consequence, I have written quite a bit of MATLAB code for working with the data files generated by various models of surface profilometers. I also have some experience with the serial port data interface to older profilometers.

  • MATLAB code for loading profilometer data files
    Most profilometers have the ability to save the measurement data to a text file so that it can be exported to other programs. I have written MATLAB functions to load and plot the data for several profilometer models.
  • Serial Port Interfacing to Older Profilometers
    Older profilometers (Dektak IIA, AlphaStep 200) can only communicate with other equipment through a serial port. In order to download data files from these machines, you will need to know a little bit about serial port interfaces.

MATLAB code

These scripts are designed to process a text file generated by a surface profilometer. Supported profilometers:

  • Dektak IIA
  • Dektak 3ST
  • Dektak 8
  • AlphaStep 200
  • AlphaStep 500
  • Tencor P-10

There are separate scripts for each profilometer. All scripts are included in the .zip file.

Download scripts from MATLAB File Exchange

Read the help file of the scripts for usage information.

Serial Port Interfacing to Profilometers

Overview

This section describes the details of establishing serial port connections with Dektak IIA and AlphaStep 200 profilometers. For background discussion of serial port interfaces, I recommend this page: Interfacing a Mac Serial Port to RS-232 Lab equipment. It is based on 1990's Macintosh hardware, but the serial port information is applicable to all types of computers, and, in fact, this page includes a case study of interfacing to the Dektak IIA contact surface profilometer.

There are three steps for achieving successful serial port connections. First, the computer must be ready to receive and save data from the serial port, usually through a terminal emulation program. Second, the serial port communications settings must be set correctly (i.e., they must be the same for the computer and the profilometer), and the correct serial cable must be used. These settings are given for Dektak IIA and AlphaStep 200 profilometers, along with instructions for the final step, transmitting the data.

Terminal Emulation

In general, the profilometer will simply transmit a string of numbers through the serial port. The computer must be ready to receive and to save this data when it is transmitted. The easiest way for a computer to interface with the serial port to use a "terminal emulation program". This program will display and save whatever data is received at the serial port, and it will also allow you to change the settings of the computer serial port to match the settings of the profilometer serial port. A large number of terminal emulation programs are available; below are some suitable examples:

Before the data is sent from the profilometer, the terminal emulation program must be ready to save the data to a file, rather than just display it on the screen. For example, in TeraTerm (Windows), before the data is sent, go the the File menu and choose "Log File"; you will be prompted to choose a file name. All of the data that is received will be saved in this file.

Dektak IIA

Settings and Cables: The serial port interface for the Dektak IIA is wired as DTE, so a "standard" serial cable will not work; use a "crossover" cable (TXD/RXD wires reversed) instead. The Dektak can transmit at 300, 1200, or 9600 baud. This setting is controlled by jumpers on the circuit board inside the machine. the other settings are fixed: 8 data bits, no stop bits, two parity bits. I recommend trying 9600 baud first.

Transmitting Data: Set up your terminal program and make sure it is ready to receive data. After a scan has been taken, simply press the SEND key to transmit the data. Note that if you have zoomed (changed the left/right/upper/lower boundaries of the screen view) the data on the Dektak screen before sending it, the data file will have two parts, the 'zoomed' data and the 'complete' data. Also note that if you zero or level the data before transmitting, the transmitted data will be the levelled/zeroed data, not the 'original' scan data.

AlphaStep 200

Settings and Cables: The serial port interface for the AlphaStep 200 is wired as DCE, so a "standard" serial cable will work fine. The AlphaStep can transmit at a variety of speeds and settings, which can be adjusted from the home screen (see the AlphaStep 200 manual for details). NOTE: Many AlphaSteps have had the serial transmit function disabled in order to eliminate a screen message that appears when the machine is started. If you do not see a message on the screen that says: "Press Enter to enable Datalink" (or something similar), and the serial port does not appear to transmit data, you should investigate this possibility. The solution is a jumper setting on the CPU board; contact your qualified AlphaStep service center for details.

Transmitting Data: Set up your terminal program and make sure it is ready to receive data. After a scan has been taken, change the print setting from "Printer" to "Send" (see the AlphaStep 200 manual), and then push the PRINT key to transmit the data.


Important Disclaimer
The information on this page is provided without any kind of guarantee or warranty whatsoever. The information and situations described herein may not apply to you and your equipment. Consult your manufacturer-supplied manual and authorized service center for official information regarding your equipment.

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Page Created By MH Page Updated: 7 April, 2005