OptiMelt Automated Melting Point System - Stanford Research ...

Chapter 2 Melt Screen 29Select Camera if automated determination of melting points with the built-in camera isdesired.Select Visual-only if no automated determination of melting points is possible ornecessary.Visual-only determination of melting points is recommended for samples that melt withsevere decomposition or that undergo serious and unpredictable physical changes duringthe heating ramp. Examples of samples not amenable to automated determination aresamples that explode, boil away or bubble up the capillary tube. Use the sample buttonsto flag important sample changes during the melt in visual-only determinations.Onset Threshold (Onset%)Range: 0 to 100%, default: 70%Select the threshold value used by the Digital Image Processor for the automateddetermination of the onset point of a melt. Typical threshold values are between 60% and90%.Proper setting of the Onset% threshold involves carefully matching the visualidentification of the onset of the melt to the automated results for the substance beinganalyzed. This is often an iterative process. Visual onset determination is affected bysubjectivity associated with the identification of subtle changes at the start of a melt, andis also somewhat substance dependent. Onset thresholds are usually independent of ramprate for a given compound.Consult the Camera Thresholds Adjustments section in Chapter 4 for additional details.Clear Threshold (Clear%)Range: 0 to 100%, default: 10%Select the threshold value used by the Digital Image Processor for the automateddetermination of the clear point of a melt. Typical threshold values are between 25% and5%.Proper setting of the Clear% threshold involves carefully matching the visual results forthe end of the melt to the automated results for the substance being analyzed. This isgenerally an iterative process.Consult the Camera Thresholds Adjustments section in Chapter 4 for additional details.Single Threshold (Single%)Range: 0 to 100%, default: 50%Select the threshold value used by the Digital Image Processor for the automateddetermination of the single melting point of the substance being analyzed. Typicalthreshold values are between 60% and 5%.OptiMelt Automated Melting Point System