BSL PRO 4 Manual - Biopac

128 BSL PRO ManualFunction CalculationThe Function calculation can be used to perform a variety ofmathematical functions using two waveforms or a waveform and aconstant. Function Calculation channels compute new waveformsin a manner similar to the math Calculation functions, but provideaccess to higher order functions. Like math Calculation channels,function Calculations can be chained together to produce complexfunctions (such as taking the absolute value of a waveform on onechannel and Calculating the square root of the transformedwaveform on another channel). These same functions are alsoavailable under the transform menu in BSL PRO for post-hocoperations. Many of these functions can also found in the onlineEquation Generator (see Expression on page 131 for details).To have BSL PRO perform a Function Calculation in real time:1. Choose MP > Set Up Channels.2. Click the Calculation tab.3. Check an Acquire box for the Calculation channel youwant to contain the filtered data. You may also check thePlot and Values boxes as appropriate for each channel.4. Click the Preset pull-down menu and select Filter.5. Click the Setup button in the Input Channels dialog togenerate the Function dialog.Other Functions are available in the online Expression calculationchannel (see Expression on page 131). Function Calculations canbe chained together to produce more complex Calculations,although it is more efficient to program complex functions usingthe Equation Generator (Expression).The Sample rate line provides the sample rate for the selectedchannel (may be different than the acquisition sample rate).FunctionAbs Returns the absolute value of each data pointAtan Computes the arc tangent of each data pointExp Takes the e x power of each data pointLimit Limits or “clips” data values that fall outside specified boundariesLn Computes the base e logarithm for each data pointLog Returns the base 10 logarithm of each valueNoise Creates a channel of random noise with a range of ± 1 VoltSin Calculates the sine (in radians) of each data pointSqrt Takes the square root of each data point.Threshold Converts above an upper threshold to +1 while converting data below a lower threshold to 0.Thresholding Algorithm Assume a domain variable t t start,t start 1, t start 2,with t start being an integer, a real-valued signal y(t) defined for all t, and two real valued levelsy low and y high satisfying the relation ylow yhigh.Define the Threshold function thresh(t) function such that:thresh(t start) 1 y(t 0 y(t) ystart) y lowlowthresh(t) 1 y(t) y0 y(t start) yhighlow thresh(t 1) y low y(t) y highFilter CalculationThe Filter Calculation channel allows you to perform real time digital filtering on analog, digital, orcalculation channels. To have BSL PRO apply a digital Filter Calculation in real time:Visit the online support center at www.biopac.com