BSL PRO Software Guide - Biopac

237Find RateThe Find Rate function allows you to compute rate calculations (including BPM) for data that has already beencollected. Although this function uses the same algorithm as the online Rate calculation, it can be advantageousto perform rate calculations after the data has been acquired. One benefit is that off-line rate computations do notrequire that a separate channel (i.e., a calculation channel) be acquired. Since the number of acquired channels isreduced, other data can be collected and/or data can be sampled at a higher rate. The Find rate functionproduces the following Rate Detector dialog, which has the following options:See also: Rate Usage Guidelines in the Rate Calculation section on page 7103.Application Note 142 for further information.FunctionPeak detectRemovebaselineAutothresholddetectThe Function menu lists a variety of calculations. The most commonly used function is the Rate(BPM) option, which calculates a rate in terms of beats per minute or BPM. Other Rate Functionsare discussed in detail in the Rate calculation section on page 7102.By default, the peak detector searches for positive peaks (upward pointing, such as the R-wave of anECG signal) to calculate the rate of a waveform. In some instances, however, you may have to basethe rate calculation on negative peaks (downward pointing). To do this, select “negative” in thePeak detect section of the dialog box.The Remove baseline option applies the optimal high pass filter based on the other settings. Thisoption is useful for signals with a slowly fluctuating baseline.To control for this, check the Auto threshold detect box in the find rate dialog box. When thisoption is selected, Biopac Student Lab will automatically compute the threshold value using analgorithm that accentuates peaks and uses information about the previous peak to estimate when andwhere the next peak is likely to occur. This threshold detector is typically more accurate than asimple absolute value rate calculation function, and is able to compute a rate from data with adrifting baseline and when noise is present in the signal. For a detailed description of how thecalculation is performed, contact BIOPAC Systems, Inc. for the complete Application Note.