Smoothing EKG Data
The PASPORT EKG Sensor can be a greate resource to get your students interested in the heart cycle. After collecting data they can use the annotation and analysis tools to label the different waves and calculate the intervals between them. In the example below, raw data has been collected and annotated by students.
The data is certainly usable, but the P-wave is a little hard to differentiate from background noise. Fortunately, SPARKvue™ and PASCO Capstone™ both support calculators with a selection of built in functions that can help us process the data. To create a calculation build a new page with two graphs, one displaying the output voltage of the EKG sensor.
On the second graph, instead of selecting a sensor measurement, choose the user-entered tab at the top of the page and then create/edit calculation.
The final step is to create a calculation using the smooth function which is in the special functions list. I’ve chosen to call my output EKG with the units still in mV. The smooth function takes three variables SMOOTH( number of data points, measurement(y), measurement (x)) and outputs an average for the number of data points entered. The cost of this processing is fewer data points, which with the very short intervals of the QRS complex can reduce the resolution of the sensor. The best results of this calculation will be at the highest sample rates, where it has more data to process.
In the formula box add the following equation.
Now return to the graph and choose the calculated data for the second display.
With the graphs scaled exactly the same it’s easy to see how the noise has been reduced as a result of the smooth function. It’s also important to note that the amplitude of the QRS waves have been reduced. Depending on the type of analysis your students will be doing the number of data points being smoothed should be adjusted in the calculation. Here are some examples with 3, 6, and 12 data points being smoothed.
Having students collect and analyze data on themselves can be a great way to keep them engaged and curious. But please remember that PASCO sensors are an educational tool and not intended for medical diagnostics.