impedance


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Related to impedance: impedance matching, inductance, acoustic impedance

impedance

 [im-pe´dans]
1. obstruction or opposition to passage or flow, as of an electric current or other form of energy.
2. the resistance in alternating current circuits, represented by the letter Z in mathematical formulas. Medical equipment is often rated according to impedance to allow for optimum performance by matching impedance ratings. A transformer can be used between components to cause the impedances of unequal systems to match.
acoustic impedance an expression of the opposition to passage of sound waves, being the product of the density of a substance and the velocity of sound in it.

im·ped·ance

(im-pē'dăns),
1. Total opposition to flow. In electricity, when flow is steady, impedance is simply the resistance, for example, the driving pressure per unit flow; when flow is changing, impedance also includes the factors that oppose changes in flow. Thus, deviations of impedance, from simple ohmic resistance because of the effects of capacitance and inductance, become more important in alternating current as the frequency of oscillations increases. In fluid analogies (for example, pulsatile flow of blood, to-and-fro flow of respiratory gas), impedance depends not only on viscous resistance but also on compressibility, compliance, inertance, and the frequency of imposed oscillations.
2. Resistance of an acoustic system to being set in motion.

impedance

/im·ped·ance/ (im-pēd´ans) obstruction or opposition to passage or flow, as of an electric current or other form of energy. Symbol Z .
acoustic impedance  an expression of the opposition to passage of sound waves, being the product of the density of a substance and the velocity of sound in it.
aortic impedance  the sum of the external factors that resist ventricular ejection.

impedance

[impē′dəns]
Etymology: L, impedire, to entangle
a form of electric resistance observed in an alternating current that is analogous to the classic electric resistance that occurs in a direct current circuit. It is expressed as a ratio of voltage applied to a circuit to the current it produces, as an alternating current oscillates ahead of or behind the voltage.

Impedance

Cardiac pacing The total opposition that a circuit presents to alternating electrical current. Cf Resistance.

im·ped·ance

(im-pē'dăns)
1. Opposition to flow of gases, liquids, or electrical current.
2. Resistance of an acoustic system to being set in motion.

impedance

any resistance to the flow of fluids moved by a series of pulses, such as blood flow.

impedance

obstruction or opposition to passage or flow, as of an electric current or other form of energy.

acoustic impedance
an expression of the opposition to passage of sound waves, being the product of the density of a substance and the velocity of sound in it.
References in periodicals archive ?
EIS measurements were carried out for coated panels using Gamry EIS 300 electrochemical impedance analyzer connected to a femtostat.
Both impedance and weight monitoring set off many false alarms.
This model is typically sufficient to describe the polymer impedance response in the dry electrode method.
2002), Cartesian Impedance Control Techniques for Torque Controlled Light-Weight Robots, Proceedings of 2002 IEEE International Conference on Robotics and Automation, Washington, DC, May, 2002
3), which gives an acceptable fit of the investigated impedance measurements.
As long as every pair on a layer is always "riding this line," the differential impedance will be constant.
Automatic impedance matching greatly reduces ringing and thus settling time.
The effective equivalent input impedance which will be connected to the input of a second stage transfer resistance amplifier (not shown in Fig.
Alternatively, it may also be possible that an end-of-cure indication in the impedance curves could be successfully correlated to a final cure state after self-heating is complete.
Impedance, return loss, and other data that relate to system performance were measured for each manufacturer's premise system.