Electric control signals

A positioner is a device that regulates the supply air pressure to a pneumatic actuator. It does this by comparing the actuator s demanded position with the control valve s actual position. The demanded position is transmitted by a pneumatic or electrical control signal from a controller to the positioner. The pneumatic actuator in Figure 35 is shown in Figure 36 with a controller and positioner added. 

The E/E/PE control system determines, in real time, the specific amount of mine hoist brake force required and sends electrical control signals to the electrically operated hydrauhc proportional valve, which in turn adjusts the hydraulic pressure supplied to the brake calipers and ultimately the braking force of the brake system. 

Reliable and highly accurate conversion of electrical control signals into specific process values. 

Proportional and dynamic conversion of electrical control signals (0/4... 20) mA into power, regulating pressure, regulating stroke and rpm is achieved with highly versatile modular component technology ... 

FIG. A-29 Modular component units used for conversion of electrical control signals. (Source J.M. Voith GmbH.)... 

Marine toxins modify the functions of many different types of ion channels in animal cell membranes. These channels may be important for maintaining the cell s resting potential, for generating electrical membrane signals, such as impulses, and for controlling hormonally triggered or metabolic responses. Thus toxins may depolarize membranes, leading to a (sometimes transient) increase in cellular activities, or they may... 

On working flowsheets the detectors, transmitters, and controllers are identified individually by appropriate letters and serial numbers in circles. Control valves are identified by the letters CV- followed by a serial number. When the intent is to show only in general the kind of control system, no special symbol is used for detectors, but simply a point of contact of the signal line with the equipment or process line. Transmitters are devices that convert the measured variable into air pressure for pneumatic controllers or units appropriate for electrical controllers. Temperature, for instance, may be detected with thermocouples or electrical resistance or height of a liquid column or radiant flux, etc., but the controller can accept only pneumatic or electrical signals depending on its type. When the nature of the transmitter is clear, it may be represented by an encircled cross or left out entirely. For clarity, the flowsheet can include only the most essential information. In an actual design... 

The importance of the characterization of the ambient, in terms of the measurements of those parameters capable of describing and/or controlling the ambient, is commonly recognized. These measurements can be done by special devices able to sense the physical or chemical quantities and possibly give an electric output signal. 

Computer-controlled automatic profile dies with electrical controlled sensors in closed-loop control systems have developed greater efficiency and accuracy to extrusion coating, cast film, and sheet lines. A scanner measures the web thickness and signals the computer, which then converts the readings to act on thermally actuated die bolts. The individual adjusting bolts expand or contract as ordered by the computer to control the profile. The more sophisticated systems measure adjusting bolt temperature and provide faster response time with less scrap and quicker startups. The scanner is typically an infrared, nuclear, or caliper-type gauge. 

The electrical section contains all electrical controls and components (e.g., programmable controllers, relays, contacts, and fuses), the signal wire distribution, and the integrated or remote force control systems. On many machines the electrical section is connected to the front of the press, thus minimizing space requirements. However, modern fully automated machines use computers that may be sensitive to machine vibration, dust, and heat. Therefore, these electronics should be located remotely from the machine. 

Electrical System. The conductors in the hose-cable carry power and control signals down to the underwater vehicle and return information. The drive-pump motor is powered by three-phase, 220 V carried down three paired conductors. The solenoid valve, which controls the clean pump, is energized by 24 V direct current (DC), which is controlled on deck. The submersible pump that circulates water through in situ sensors uses 110 V alternating current (AC) power from the hose-cable. 

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