BSL PRO 4 Manual - Biopac

Part B — Acquisition Functions 127Math CalculationThe Math Calculation performs standard arithmetic calculations using two waveforms or one waveform and aconstant. It is also possible to use other Calculation channels (such as a Rate Calculation channel) as an inputchannel for a Math Calculation channel, as long as the Calculation channel used as a source channel has alower channel number than the Math Calculation channel.1. Choose MP > Set Up Channels.2. Click the Calculation tab.3. Check an Acquire box for the Calculation channel you want to contain the filtered data. You may alsocheck the Plot and Values boxes as appropriate for each channel.4. Click the Preset pull-down menu and select Math.5. Click the Setup button in the Input Channels dialog to generate the Math dialog.Use the pull-down Source menus to select the source channels (Source 1 and Source 2).The Sample rate line provides the sample rate for the channel selected as Source; the channel sample rate maybe different than the acquisition sample rate.Use the pull-down Operand menu to select a function. In the example below, analog channel 1 (Source: A1) isadded to analog channel 2 (Source: A2). To use this summed waveform as an input for another MathCalculation channel. One useful application would be to divide this waveform (C0) by K, where K=2, thusproducing an arithmetic average of source channels A1 and A2.The “Constant” entry is activated when “K” is selected as a Source.As an alternative to creating an additional Calculation channel for dividing the summed waveform, you canuse the scaling function to perform the same task. To do this, click Scaling… button and then set the Map(Scale) value for the summed waveform equal to +5 and –5 (to correspond to Input Volts values of +10 and –10 respectively). This will effectively plot the sum of channels A1 and A2 as the arithmetic mean of the twowaveforms.For additional libraries of online Calculation options, consult the sections on Function Calculationchannels and the online Equation Generator (Expression, page 131). These types of Calculationchannels can be used to perform more complex operations on waveforms. Although Calculationchannels can be “chained” together (so that the output from one serves as the input for another) toform more complex calculations, a separate channel must be used for each function. Since onlysixteen Calculation channels are available, not all calculations can be performed. Additionally,chaining more than three or four channels together can require considerable system resources.For complex calculations (such as squaring a waveform then adding it to the average of two otherwaveforms) the Equation Generator (Expression) is a more efficient solution. All of the featuresavailable online in the Math Calculation channels can also be computed after an acquisition using theWaveform Math option (see page 260), which will eliminate the problem of system overload.BSL PRO Manual