Sample-and-hold

In Table 7.3 the difference between Xo(kT) and Xo(t) is due to the sample and hold. It should also be noted that with the discrete response x kT), there is only knowledge of the output at the sampling instant. 

Assuming that a sample and hold device is in cascade with the transfer function G. s), determine G z) for the following... 

Figure 11.33 Schematic of the optoelectronic sensor scheme. Sample and hold devices.

The output of the lock-in amplifier is input to a sample-and-hold amplifier or directly to the analog-to-digital converter. This signal is converted to a digital and thus machine-readable form. 

Just as sample-and-hold amplifiers must be properly adjusted, so must ADCs both range and linearity are generally adjustable. As with sample-and-hold amplifiers, periodic validation of adjustment should be carried out. 

In this technique the excitation and fundamental system response is identical to that for dc polarography. The sample-and-hold measuring scheme is like that used to great advantage in LAPP (see Sec. III.F). 

Besides the elimination of the sample-and-hold, oversampling converters also reduce the complexity of the anti-aliasing filter. Previous anti-aliasing filters required the use of high order active filters (11th order elliptic for example) that resulted in phase... 

Sixteen groundwater samples were collected and analyzed for VOCs (EPA Method 8260), lead (EPA Method 6010), and nitrite (EPA Method 354.1). The intended use of all data is quarterly monitoring. The SAP states the sampling and holding time completeness goal of 100 percent analytical completeness goal is 90 percent. 

When the dead time has passed, the controller is switched back to automatic and its output (m) is adjusted based on the new measurement it "sees" at that time. A timer sets the period for which the controller is switched to manual, and that period is adjusted to exceed the dead time of the loop. This way, the sample-and-hold controller has less time to make the same amount of correction as the conventional PID would and therefore its integral setting must be increased in proportion to the ratio of cycle to automatic time periods (Figure 2.35). 

Sample and hold controllers are periodically switched from manual to automatic and back again. They are used mostly on dead-time processes. 

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