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DT048 EKG

Type:
ELECTROCARDIOGRAM

Range:
0 - 5V


Sensor Description:

The EKG (Elecrocardiogram or ECG) measures cardiac electrical potential waveforms (voltages produced during the contraction of the heart). NOTE: 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 the electronics box with a cable for connecting to a MultiLog interface via a DIN plug connector. Three electrode leads enter the EKG Sensor box on the side opposite the cable that attaches to the interface. 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.

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.
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 (EKG). 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 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 pro-cess 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 EKG 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 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 (EKG) 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 five major deflections on a normal EKG are designated by the letters P, Q, R, S, and T. One heart cycle is represented by a group of waveforms beginning with the P wave, followed by the QRS wave complex, and ending with the T wave. The P wave represents the depolarization of the atria and is associated with their contraction. The QRS wave complex consists of three waves. The first negative deflection is the Q wave and is followed by a positive deflection 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 repolarization occurs during the depolarization of the ventricles. For this reason, the waveform associated with atrial repolarization is undetectable on an EKG. The last wave is called the T wave, and is usually represented by a positive deflection. The T wave indicates ventricular repolarization.

Electrical energy is also generated by skeletal muscle, and can be seen as muscle artifacts if your arm is moved while the EKG 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 EKG 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 EKG 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 EKG effectively takes considerable training and skill.
Note: This sensor is NOT intended for medical diagnoses !!!

Connecting the EKG Sensor to a Person

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

Calibration:

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

What is it used for:

EKG 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: