Noise sampling period

All signals are ignored during the absolute refractory period, and noise sampling occurs within the relative refractory period. The purpose of the ARP is to prevent oversensing of the output pulse stimulus afterpotential, the atrial electrogram produced by the atrial stimulus, or ventricular depolarization. 

If measurement noise combined with a large ratio of derivative time to sampling period (Tjy/At) causes an overactive derivative mode, then the error signal must be filtered before calculating the derivative action (see Chapter 17). 

When a digital computer is used for process control, measurements of the process output are sampled and converted into digital form by an analog-to-digital converter (ADC). The sampling period Ar must be carefully selected. The choice of the sampling period should be based on the process dynamics, noise frequencies, signal-to-noise ratio, and the available computer control system. 

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