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Keysight Technologies
Generating Complex ECG Patterns with an
Arbitrary Waveform Generator
Measurement Tips
Volume 10, Number 3

Application Note
Introduction

Using an electrocardiogram (ECG) is an invaluable way to identify various physical ailments. To
conduct an ECG, medical personnel place leads on a patient's skin and measure the electrical
activity of the heart over one beat cycle. The outputs of the leads are combined to create an ECG
signal. Variations in the signal amplitude and timing provide indications of various ailments such
as myocardial infarction, hypocalcaemia, and emphysema. Today there is a wide array of cardiac
equipment that displays and interprets ECG signal patterns. Medical equipment designers need a
lexible way to seamlessly generate accurate ECG signal patterns to verify and test their designs.
In this measurement brief, we will discuss how to generate complex ECG signal patterns with an
arbitrary waveform generator (AWG).

Snapshot
A maker of cardiac monitoring equipment needed to test its latest design's ability to capture and
interpret ECG signals. The company's design engineers wanted to simulate gradually changing
sequences of normal and abnormal ECG signals to test and
tune the design's input signal condit-ioning hardware and
the irmware interpretation algorithms to ensure their design
did not produce false positives or life-threatening false
negatives. To simulate the ECG signals, the engineers used
the Keysight Technologies, Inc. 33521A function/arbitrary
waveform generator. They chose the 33521A because of its
arbitrary waveform sequencing feature. This feature allowed
them to seamlessly switch across various ECG signals stored
in arbitrary waveform memory. With this functionality, they
were able to simulate the gradual onset of various ECG signal
abnormalities without any discontinuities in their test. Also,
the 33521A's 1-million-point arbitrary waveform memory
allowed them to store a large library of various ECG signals.
ECG waveform
A typical 12-lead ECG waveform is shown in Figure 1. The example ECG waveforms used later in this measurement brief
Key waves and intervals are labeled. were based on the 33521A's built-in ECG waveform, which is shown
in Figure 2. An easy way to create a whole library of different ECG
QRS waveforms is to combine method 1 and 2 or method 3 and 2 together.
Complex You can access and manipulate the points in the built-in ECG waveform
(method 3) to create other non-typical or abnormal ECG signals
R for testing cardiac monitoring equipment. One way to do this on the
33521A is directly on the instrument using the large, front-panel
display. Another way is to use a mathematical software tool
(method 2). That is how methods 2 and 3 can be combined to create
a library of different ECG waveforms, and of course, methods 1 and
2 could be combined in the same manner.

ST
PR Segment
P Segment T

PR Interval Q
S
QT Interval

Figure 1. 12-lead ECG waveform Figure 2. Built-in ECG waveform

In this measurement brief, we will use the 12-lead ECG waveform
as an example to show you how you can use an AWG to create Measurement Tip
complex cardiac signal patterns. Of course, an AWG can be used
to simulate other lead-count ECG waveforms or to simulate a single- You can download and use an ECG simulator program
lead signal. The purpose here is to show how an AWG can be used created in MATLAB. You can find the ECG simulator download
to create complex cardiac signal patterns. and instructions at http://www.mathworks.com/matlabcentral/
ileexchange/10858-ecg-simulation-using-matlab or type "ECG
MATLAB" into a search engine and it should be at the top of the
ECG waveform results. The program creates ECG waveforms using multiple Fourier
series summed together. A Fourier series is used for each distinct
There are three methods to create and store an ECG on an AWG:
wave shape in the ECG waveform, such as the P wave,
1. You can use a device such as a digitizer or oscilloscope to capture T wave, etc. The program allows you to adjust various ECG
an actual ECG signal from a patient. Then you upload the digitized waveform parameters to simulate various cardiac conditions.
points to the AWG. With modern AWGs, there are many ways
to accomplish this, including using a .csv file and a memory stick.
2. You can use mathematical software to create an ECG signal. There
may be custom software for the AWG that can do this, or you could
use a standard software package, such as MATLAB .
3. If your instrument has this capability, you can use your AWG's built-in
typical ECG waveform. The Keysight 33521A has this capability.

3
Using an AWG's arb sequencing capability
Measurement Tip
to simulate complex ECG patterns
Real-world cardiac signals are typically very low in amplitude,
AWGs that have arb sequencing ability, like the 33521A function/arb often only a couple of millivolts or even less. This poses a problem
waveform generator, can seamlessly transition from one arb waveform for simulation using AWGs because typically their lowest
stored in memory to another without any discontinuities in the output. amplitude setting is between 10 mV and 1 mV (the 33521A's
Figure 3 shows an example using the 33521A's arb sequencing feature on lowest amplitude is 1 mV), and when they are used at their lowest
three different ECG waveforms stored in different places in memory. amplitude, the AWG's signal-to-noise ratio can become a problem.
One way to overcome these drawbacks is to use a voltage
divider at the output of the AWG. Since ECG signals are at such
low frequencies, the divider only needs resistors, as reactive
effects can be ignored. When you construct the voltage divider,
remember the amplitude accuracy of the divider's output signal
is dependent on the precision of the resistors used in the divider.
For example, a voltage divider that uses a 10-kohm resistor and
a 10-ohm resistor will reduce amplitude of 1 V down to 1 mV,
Figure 3. Example ECG waveform sequence as shown in Figure 4.
The first ECG waveform cycle is the 33521A's built-in ECG waveform.
The other two were based on the first one but were changed in a ECG in
systematic way using MATLAB software. Notice the second ECG 1 V max
waveform has a flattened T wave. In the third ECG waveform,
the T wave is inverted.
10 k
The 33521A's sequencing capability provides flexibility for controlling ECG out
when it sequences from one waveform to another. One way to control 1 mV max
sequencing is to specify how many cycles each waveform is run before
sequencing to the next. Sequences can also return to a waveform that
was used previously in that sequence. 10
Combining the 33521A's arb sequencing feature with its large arb
memory, 1 million points per channel standard with 16 million optional,
gives you the ability to simulate complex ECG patterns for thorough Figure 4. Simple voltage divider
testing of your cardiac monitoring equipment design. For example,
the three waveforms shown in Figure 3 each were created with about
500 points. You could store up to 2,000 different ECG waveforms of Conclusion
this size in the 33521A's standard arb memory. The 33521A allows arb
sequences to contain up to 512 steps, allowing you to create complex Human lives are at stake, so thorough testing of cardiac monitoring
ECG patterns for thorough testing. equipment designs is critical. To ensure your design properly
characterizes and interprets various ECG waveform conditions, you
need accurate testing simulations of complex ECG signal patterns.
Measurement Tip AWGs, like the 33521A, that have arb sequencing capability and
deep arb memory provide an excellent solution for ECG simulation.
You can control arb sequences on the 33521A asynchronously by The sequencing provides the ability to seamlessly transition through
using triggers to control waveform transitions instead of cycle counts. various ECG signal conditions. The deep arb memory complements the
This provides you with the ability to continuously cycle a waveform for sequencing capability by allowing you to store a large library of ECG
some undetermined time period until it receives a software trigger or waveforms. This allows you to add subtle changes from waveform to
external trigger or front-panel trigger. Once it receives the trigger, the waveform for high-resolution testing of your design.
33521A transitions to the next waveform in the sequence. You can
also mix the two ways of transitioning through a sequence, specifying
a count and using triggers.

Learn more about Keysight's function/
arbitrary waveform generator solutions
at www.keysight.com/find/
FunctionGeneratorSpotlight

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