BSL PRO Software Guide - Biopac

76 Part CCalculation channel scalingInput valueScale value10 V constantInput value x (sample rate/samples to be mean averaged)It is important to note that this rescaling should be performedindependent of any rescaling performed on analog channelsthemselves. Even if an analog channel is being rescaled to someother units, the Input values in the calculation channel scalingshould be set to +10 Volts (next to Cal 1) and -10 Volts (next toCal 2).The "Scaling" option for Calculation Channels corresponds to the source Analog Channel input (and not the source channel'smapped value). Typically, the default scaling settings will be fine. However, if the calculation values will be on a different scalethan the original units, you need to change the scale of the calculation channel to reflect the new units (i.e., liters/sec to liters).Click the Scaling… button to generate the Change Scaling Parameters dialog, which includes options that allow you to modifythe units or linearly scale the output.Rescaling involves multiplying the “Input value” by a factor determined by the sampling rate and number of samples meanaveraged across. As an example, if data was acquired at 75 samples per second and you wanted to integrate across an interval of10 samples, you would set the Integrate > Scaling parameters so that an Input value of +10 Volts corresponded to a Scale valueof 75 and an Input value of -10 Volts corresponded to a Scale value of -75.Plot Standard Curve – Windows onlyThe Plot Standard Curve command is only available in X/Y mode. A Standard Curve is a graph used in colorimetry tohelp determine the concentration of a solution, wherein the light absorbance value of the solution is compared to standard values.BSL PRO can generate a Standard Curve on a plot of Concentration vs. Absorbance of known solutions, which can then be usedto determine the concentrations of unknown solutions.About Standard CurveColorimeters, or spectrophotometers, are useful for determining such things as the amount of glucose,cholesterol or protein in blood. Colorimeters use a monochromatic light source (composed of a singlewavelength). They output an Absorbance value, which is a measure of the percent transmission of lightthrough a liquid. Because the light is monochromatic, Beer's Law can be applied. Beer’s Law states that theabsorbance value is directly proportional to the concentration of the solution. One or more solutions ofknown concentrations, called Standards, are used to generate a “Standard Curve”plot. The concentrations ofunknown solutions can then be determined from the Standard Curve data.Before plotting a Standard Curve, you must first set up two Channels in a BSL PRO file to represent your X-axis (normally“Concentration”) and Y-Axis (normally “Absorbance”). Refer to “Setting up a file to plot a Standard Curve” on page 678. Consider starting with the sample file “StandardCurve.acq” for preset X-Axis and Y-axis units and scale.Review the sample file “StandardCurveData.acq” for sample data.Plot your curve by pressing the Plot Standard Curve button on the Toolbar.dialog.This will generate the Plot Standard CurvesVisit the online support center at www.biopac.com