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(ELEC4810)[2010](f)final~=idkeaej^_65495.pdf
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1. Solution: (4)

The membranes resting potential at room temperature can be determined by Goldman equation:




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Because the concentration of Ca2+ is much smaller than the other considered ions, so we neglect the effect of such ion.
2. Solution
(i) (3)


(ii)For example: Lead II signal (3)
P wave is produced by atrial depolarization, the QRS complex primarily by ventricular depolarization, and the T wave by ventricular repolarization. The P-R and S-T intervals are normally at zero potential, the P-R interval being caused mainly by conduction delay in the AV node. The S-T segment is related to the average duration of the plateau region of individual ventricular cells.




(iii) Montage means the placement of the electrodes. The EEG can be monitored with either a bipolar montage or a referential one. Bipolar means that you have two electrodes per one channel, so you have a reference electrode for each channel. The referential montage means that you have a common reference electrode for all the channels. (3)
(iv) The potential induced by an electrical dipole with current source can be estimated as: (3)
....cos422.....rVaeie

When , we have maximum :
..90.
e.

uVe6.05)7050(2.04)2/1.0(22(max)......


3. Solution:
(i) The function of electrical isolation is against the flow of hazard DC and low-frequency currents (power line) from the main unit to the patient. Take patient-ground isolator for an example; (3)

(ii) Raw EMG spikes are of stochastic shape, which means one raw recording burst cannot be precisely reproduced in exact shape. This is due to the fact that the actual set of recruited motor units constantly changes within the matrix/diameter of available motor units: If occasionally two or more motor units fire at the same time and they are located near the electrodes, they produce a strong superposition spike! (2)

(iii) For modern electrocardiographic system, the patient is not grounded at all. The reference potential of right leg is generated by so-called driven right leg circuit to reduce the common-mode voltage. (3)


Main purposes:
(1) Average the voltage at IN- and IN+ and feeds it back, inverted and amplified, to the right-leg electrode.

(2) Driving the common-mode voltage on the body to a low value. The feedback is usually- but not always- applied to the right leg.

(3) Reducing the common-mode noise from say the power line and providing a measure of safety against harmful voltages that may develop between the patient and ground.



4.
(i) (4)
Oscillometric method employs a calibrated semiconductor pressure sensor to transfer the pressure signal to electronic signal. Then a differential amplifier is used to enhance the SNR of the recorded s