Measurement Definitions

SELECTED AREA Single point sample time value Area from point-to-point (including endpoints) area integral max (maximum) mean min (minimum) p-p (peak-to-peak) slope stddev (standard deviation) Endpoints BPM Delta (delta amplitude) Delta S (delta sample) Delta T (delta time) frequency Table of Measurement Definitions Measurement tool area BPM Definition The area measurement is similar to the integral measurement except that instead of using zero as a baseline for integration a straight line is drawn between the endpoints of the selected area as the baseline. The Beats Per Minute measurement uses the start and end points of the selected area as a measurement for one beat, calculates the difference in time between the first and last selected points, and divides this value into 60 seconds/minute to extrapolate BPM. This is the result you would obtain if you took ((1/AT)*60) for a selected area. If more than one beat is selected, it will ï not calculate the average (mean) BPM in the selected area. Note: In order to get an accurate BPM value, you must select an area with the I-Beam cursor that represents one complete beat-to-beat interval. One way to do this is to select an area that goes from the peak of one cycle's R wave to the peak of the next cycle's R wave (R-R interval). Delta The Delta (delta amplitude) measurement computes the difference in amplitude between the last point and the first point of the selected area. It is particularly useful for taking ECG measurements because the baseline does not have to be at zero to obtain accurate, quick measurements. Delta S The Delta S (delta samples) measurement is the difference in sample points between the end and beginning of the selected area. Delta T The Delta T (delta time) measurement is the difference in time between the end and beginning of the selected area. Freq The Frequency measurement converts the time segment between the endpoints of the selected area to frequency in cycles/sec. The Freq measurement computes the frequency in Hz between the endpoints of the selected range by computing the reciprocal of the AT in that range. It will not calculate the correct frequency if the selected area contains more than one cycle. You must carefully select the start and end of the cycle. Note: This measurement applies to all channels since it is calculated from the horizontal time scale. Table of Measurement Definitions Measurement tool Definition | (integral) The | (integral) measurement computes the integral value of the data samples between the endpoints of the selected area. This is essentially a running summation of the data. Max The maximum measurement finds the maximum amplitude value within the selected area (including the endpoints). Mean The mean measurement computes the mean amplitude value or average of the data samples between the endpoints of the selected area and displays the average value. min The minimum measurement finds the minimum amplitude value within the selected area (including the endpoints). none Selecting none turns off the measurement channel and no result is provided. none Selecting none turns off the measurement channel and no result is provided. P-P The p-p (peak-to-peak) finds the maximum value in the selected area and subtracts the minimum value found in the selected area. P-P shows the difference between the maximum amplitude value in the selected area and the minimum amplitude value in the selected area. Samples The Samples measurement shows the exact sample number of the selected waveform at the cursor position. Since the Biopac Student Lab handles the sampling rate automatically, this measurement is of little use for basic analysis. The slope measurement uses the endpoints of the selected area to determine the difference in magnitude divided by the time interval. The slope measurement returns the unstandardized regression coefficient, which describes the unit change in Y (vertical axis values) per unit change in X (horizontal axis). Slope stddev This value is normally expressed in unit change per second (rather than sample points) since high sampling rates can artificially deflate the value of the slope. When the horizontal axis is set to display either frequency or arbitrary units, the slope is expressed as a unit change in vertical axis values per change in Hertz or arbitrary units, respectively. When an area is selected, the slope measurement computes the slope of the line drawn as a best ft for all selected data points. Stddev (standard deviation) is a measure of the variability of data points. The stddev measurement computes the standard deviation value of the data samples in the selected range. The advantage of the stddev measurement is that extreme values or artifacts do not unduly influence the measurement. Time The Time measurement shows the exact time of the selected waveform at the cursor position. If a range of values is selected then the measurement will indicate the time at the last position of the cursor. Value The value measurement displays the amplitude value for the channel at the point selected by the I-beam cursor. If a single point is selected, the value is for that point, if an area is selected, the value is the endpoint of the selected area.