OptiMelt Automated Melting Point System - Stanford Research ...

74 Maintenance and Calibration Chapter 4listed in the final Report against your visual records. If the automated values differ fromyour manual entries beyond the specified accuracy specifications of your OptiMelt, adjustthe Digital Image Processor (DIP) thresholds (Onset% and Clear%) to better match bothsets of numbers. Use the Melt Graph (computer screen, or printout) to do a graphicaldetermination of the Y-axis values (%) corresponding to the temperatures identifiedvisually as the onset and clear points. Program the new percentage values into yourOptiMelt using the Onset% and Clear% buttons in the Setup Submenu of the Melt Menu.Repeat the melting point determination and readjust the camera thresholds until the visualand automated melting point measurements agree within the accuracy of your instrument.The Single% threshold is used to detect and calculate the Single MP temperature. SingleMPs are sometimes associated with the meniscus point, but more often to the clear pointof the melt. If necessary, generate and adjust Single% thresholds using the sameprocedure used to assign percentages to the onset and clear points through graph analysis.Camera Optical AlignmentThe digital camera built into OptiMelt faces the capillaries and relies on a simple opticalsystem to magnify the images of the samples. The digital images collected duringtemperature ramping are analyzed in real time by the Digital Image Processor (DIP). TheDIP relies on camera alignment information, previously stored in the OptiMelt’smemory, to zoom in on the area of the images where the samples are physically located.Stable optical alignment between the heating block and the camera is essential foraccurate and reproducible automated results. If the mechanical alignment between theheating block and the camera changes for any reason, the position of the samples withinthe digital images will shift and the effectiveness of the DIP algorithms can becompromised.It is important to update the camera alignment information stored in theOptiMelt’s memory on a regular basis. This becomes particularly importantafter the heating block is moved, fastened, cleaned or repositioned.OptiMelt includes a menu-driven procedure that can be invoked at any time toautomatically update the camera alignment information stored in your OptiMelt system.To update the camera alignment information, the following steps must be followed:1. Insert three sample tubes, with at least three millimeters of white powder into thesample slots.2. Press the System Tab to access the System display.3. Press the Calibrate button on the System screen and enter the calibration password(‘cal’) to enter the Calibration menu (Figure 36). All units have the same password.See Figure 36.4. Press the Align Cam button to start the Camera Optical Alignment procedure.OptiMelt Automated Melting Point System