There are several ways to calculate an integral in LabChart. Two of the simplest are using the integral channel calculation or the cyclic measurements channel calculation.
Using the Integral Channel Calculation
The Integral channel calculation provides a method of computing time-integrals with various reset methods. Integral works in real time during sampling and on pre-recorded data. The Integral dialog allows you to set up the Integral channel calculation.
1. Open the Integral dialog by selecting "Integral..." from any Channel Calculation pop-up menu.
2. In the dialog that appears, select the source channel for the calculation from the Source pop-up menu.
3. Select the Integral Type you would like to calculate:
- Standard Integral: use all data points.
- Absolute Value: integrate absolute values of data points.
- Positive Only: use only data points whose values are greater than 0.
- Negative Only: use only data points whose values are less than 0.
4. Set up the Reset type and any additional parameters this may require:
- No Reset: integral is not reset, and the integrated signal is summed indefinitely.
- Timed Reset: integral is reset periodically, at intervals specified in the text box to the right of the reset type menu.
- Reset Each Cycle: integral is reset each time the source signal passes through zero to a positive value.
- Time Constant Decay: In this mode, input samples are summed to generate the output, as for the standard integral mode. However, each time a new sample is added the sum is multiplied by a positive constant that is a little less than 1. For a constant input voltage Vmax, the resulting sum – namely, the integral output – approaches a maximum (Vmax.?) with the time constant (tau, ?) that is entered by the user. In electronic terms, this mode approximates the behavior of a 'leaky' analog integrator, or 'RC' low pass filter. Unlike a filter, the integral multiplies the output values by the sample period in seconds and correspondingly changes the units to V.s.
- Reset By Event: use a specific event to trigger the reset (this uses the options set in the Event Options Dialogue).
5. Set up the Integral
limits (optional) for the time the integral is to be
calculated from.
6. Set up the scaling for the displayed data.
- Set Scale top and Scale bottom for the calculated data in terms of the source channel units or select Auto scale to automatically generate a suitable scale for the displayed data (Recommended if performing subsequent channel calculations, on the display channel.).Choose the number of Decimal places to show in the Range/Amplitude display.
7. Upon clicking "Okay", the continuous integral will appear in the channel you selected.
Using Cyclic Measurements
Cyclic Measurements will calculate the integral for the region between each detected cycle of a cyclic waveform. This can be run in real time during sampling or on pre-recorded data.
1. Open the Cyclic Measurements dialog by selecting "Cyclic Measurements..." from any Channel Function pop-up menu. on a blank channel that you intend to use for calculation.
