Electrical input signals

Where possible, each alarm and safeguard feature should be challenged by simulation of actual alarm conditions within the sterilizer equipment system. Where simulation of physical alarm conditions would be impractical, alarm circuitry may be challenged by use of electrical input signals. 

Equivalent circuit (formal or mathematical) modeling presents the system in hypothetical electrical circuits consisting of well-defined ideal and sometimes nonideal electrical elements. Measurement modeling explains the experimental impedances in terms of mathematical functions in order to obtain a good fit between the calculated and experimental impedances. In the latter case the parameters obtained do not necessarily have clear physicochemical significance. Such a model describes the system s response to various possible electrical input signals. 

Proportional pressure valves convert an electrical input signal in the form of a voltage from 0.. . lOV proportional to a hydraulic pressure. In principle, they are electrically controlled pressure valves in which the manual setting device is replaced by an electrical setting actuator called the proportional solenoid. This is shown in the bottom drawing in Figure 5.9. 

On the analog side, tbe filter is often the conventional resistor-capacitor or RC filter. However, other possibihties exist. For example, one type of A/D converter is called an integrating A/D because the converter basically integrates the input signal over a fixed intei val of time. By making the intei val I/60th second, this approach provides excellent rejection of any 60-Hz electrical noise. 

The centrifugal pump directly driven by a variable-speed electric motor is the most commonly used hardware comoination for adjustable speed pumping. The motor is operated by an electronic-motor speed controller whose function is to generate the voltage or current waveform required by the motor to make the speed of the motor track the input command input signal from the process controller. 

The lock-in has two (electrical) inputs the first consists of the signal s(t) to be measured with noise n(t) the second is the square wave reference signal r(t). 

Time-domain reflectometry (TDR) involves the use of two or more substantial metal rods inserted into soil. The rods are parallel and are attached to a signal generator that sends an electrical input down the rods. The time it takes the signal to travel down the rods is dependent on the soil s apparent dielectric constant, which, in turn, is proportional to the amount of water in the soil. Upon reaching the end of the rods, the signal is dissipated and the amount of... 

The optical fibers connect the two longest links of a typical optical fiber communications system. In brief, an input signal enters an encoder generally in an electrical form with the... 

As described in section 2.4.2, an impedance experiment involves the application of an electrical signal (E or O) and the measurement of an electrical current or a potential. Consider that a potentiostatic experiment (application of a potential) with three types of input signals can be used for determination of the impedance49. 

Loop checking includes both dry and wet loop checks. Dry loop checking includes verifying that power is available at the field device, verifying the field device input signal electrical continuity through the Input/Output (I/O) device to the operator interface (reversed for output devices), and verifying the baseline software. 

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