Fourier Systems

ECG DT189
Type: R ange:
ELECTROCARDIOGRAM 0 – 5V
Sensor description
The ECG (Electrocardiogram) measures
cardiac electrical potential waveforms
(voltages produced during contractions of
the heart).
This product is to be used for educational
purposes only. It is not appropriate for
medical or research applications.
Specifically, it may not be used for patient
diagnosis.
The sensor comes with a package of one
hundred silver/silver chloride electrode
patches that can be attached to the skin.
The sensor consists of Fourier’s egg-shaped sensor case and three electrode
leads. The sensor's circuitry isolates the user from the possibility of electrical shock
in two ways:
• The sensor signal is transmitted through an opto-isolation circuit.
• Power for the sensor is transferred through a transformer. The circuitry
protects against accidental over-voltages of up to 4,000 volts.
Note: As this sensor is current consuming, it is highly recommended to operate it
while the AC/DC adapter powers the MultiLog.

How it Works
Heart muscle cells are polarized at rest. This
means the cells have slightly unequal
concentrations of ions across their cell
membranes. An excess of positive sodium ions
on the outside of the membrane causes the
outside of the membrane to have a positive
charge relative to the inside of the membrane.
The inside of the cell is at a potential of about
90 millivolts (mV) less than the outside of the cell
membrane. The 90 mV difference is called the
resting potential. The typical cell membrane is
relatively impermeable to the entry of sodium.
However, stimulation of a muscle cell causes
an increase in its permeability to sodium.
Sodium ions migrate into the cell through the
opening of voltage-gated sodium channels.
This causes a change (depolarization) in the
electrical field around the cell. This change in
cell potential from negative to positive and
back is a voltage pulse called the action potential. In muscle cells, the action
potential causes a muscle contraction.

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Other ions and charged molecules are involved in the depolarization and
repolarization of the cardiac muscle. These include potassium, calcium, chlorine,
and charged protein molecules. The sum action potential generated during the
depolarization and repolarization of the cardiac muscle can be recorded by
electrodes at the surface of the skin. A recording of the heart's electrical activity is
called an electrocardiogram (ECG). The depolarization of cardiac-muscle cells
triggers the contraction.
The cells of the heart's conducting system will depolarize spontaneously. This
spontaneous depolarization is most apparent in a cluster of cardiac-muscle cells
embedded in the upper wall of the right atrium. This group of cells is called the
pacemaker (also known as the sinoatrial or SA node). Depolarization of the
pacemaker generates a current that leads to the depolarization of all other
cardiac-muscle cells. The wave of depolarization travels from the right atrium to
the left atrium quickly enough so that both atria contract at essentially the same
time.

The atria and the ventricles are isolated from each other electrically by
connective tissue that acts like the insulation on an electric wire. The
depolarization of the atria does not directly affect the ventricles. There is another
group of cells in the right
atria, called the
atrioventricular or AV node,
that will conduct the
depolarization of the atria
down a special bundle of
conducting fibers (called the
Bundle of His) to the
ventricles. In the muscle wall
of the ventricles are the
Purkinje Fibers, which are a
special system of muscle
fibers that bring
depolarization to all parts of
the ventricles almost
simultaneously. This process
causes a small time delay,
so there is a short pause after
the atria contract and
before the ventricles
contract. Because the cells of the heart muscle are interconnected, this wave of
depolarization, contraction, and repolarization spreads across all of the
connected muscle of the heart.

When a portion of the heart is polarized and the adjacent portion is depolarized,
an electrical current is created going through the body. This current is greatest
when one half of the connected portion of the heart is polarized and the adjacent
half is not polarized. The current decreases when the ratio of polarized tissue to
non-polarized tissue is less than one to one. The changes in these currents can be
measured, amplified, and plotted over time. The ECG represents the summation of
all the action potentials from the heart, as detected on the surface of the body. It
does not measure the mechanical contractions of the heart directly.
The impulse originating at the SA node causes the atria to contract, forcing blood
into the ventricles. Shortly after this contraction, the ventricles contract due to the
signal conducted to them from the atria. The blood leaves the ventricles through

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the aorta and pulmonary artery. The polarity of the cardiac muscle cells returns to
normal and the heart cycle starts again.

The Electrocardiogram

The electrocardiogram (ECG) is a graphic tracing of the heart's electrical activity.

A typical tracing consists of a series of waveforms occurring in a repetitive order.
These waveforms arise from a flat baseline called the isoelectric line. Any
deflection from the isoelectric line denotes electrical activity
The letters P, Q, R, S, and T designate the five major deflections on a normal ECG.
One heart cycle is represented
by a group of waveforms R
beginning with the P wave,
followed by the QRS wave
complex, and ending with the T
wave. The P wave represents the T
depolarization of the atria and is P
associated with their contraction.
The QRS wave complex consists Q
of three waves. The first negative
deflection is the Q wave and is
followed by a positive deflection S
called the R wave. The complex
ends with a negative deflection
known as the S wave. The QRS
wave complex denotes
depolarization of the ventricles
and is associated with their contraction. Atrial re-polarization occurs during the
depolarization of the ventricles. For this reason, the waveform associated with
atrial re-polarization is undetectable on an ECG. The last wave is called the T
wave, and is usually represented by a positive deflection. The T wave indicates
ventricular re-polarization
Electrical energy is also generated by skeletal muscle, and can be seen as
muscle artifacts if your arm is moved while the ECG is attached. The sequence
from P wave to T wave represents one heart cycle the number of cycles in a
minute is called the heart rare and is typically 70-80 beats per minute at rest.
Some typical times for portions of the ECG are:
P-R interval 0.12 to 0.20 seconds
QRS interval less than 0.i seconds
Q-T interval less than 0.38 seconds
If your ECG does not correspond to the above numbers, DO NOT BE ALARMED!
These numbers represent typical averages and many healthy hearts have data
that fall outside of these parameters. To read an ECG effectively takes
considerable training and skill.
PLEAE BE AWARE: This sensor is NOT intended for medical diagnoses!!!

Connecting the ECG Sensor to a Person

Use three electrode patches per subject. The electrodes can be reused, but since
they tend to absorb moisture (they are very hygroscopic), reuse is not
recommended. Note: Once opened, the electrodes should be kept refrigerated in
a clean, dry, airtight container for storage. Even with airtight storage, opened
electrode packages cannot be stored from one year to the next.

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• Because the electrical signal produced by the heart and detected at the
body's surface is so small, it is very important that the electrode patch makes
good contact with the skin. Scrub the areas of skin where the patches will be
attached with a paper towel to remove dead skin and oil.
• Peel three electrode patches from the backing paper. Firmly place the first
electrode on the right wrist.
• Place a second electrode a few
centimeters above the first one.
• Place a third electrode on the inside of
the left wrist.
• Place each electrode so it is on the
inside part of the arm (closer to the
body) and the tab on the edge of the
electrode patch is pointing down. This
way, the wire of the sensor can hang
freely without twisting the edge of the
electrode patch.
• Connect the micro alligator clips of the
three sensor’s leads to the tabs on the
edges of the electrode patches:
• Connect the two leads labeled R.A. (right arm) to the right arm electrode
patches.
• Connect the lead labeled L.A. (left arm) to the left arm electrode patch.

Calibration
The DT048 is shipped fully calibrated and no further calibration is needed.

What is it used for

ECG is usually used for measurements of the heart activity and response in various
human body modes like, rest and active, standing up and sitting down, etc…
The measurement parameters are the following intervals:
P-Q, QRS, Q-T, and heart rate.

Specifications
• Range: 0 - 5V
• 12-bit Resolution (TriLog):
1.25mV
• 10-bit Resolution
(MultiLogPRO, MultiLog):
5mV
• Offset: ~1 V (±0.3V)
• Gain: 1000
• Voltage protection: 4kV

Simultaneous ECG and respiration graphs

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