Controls and indicators

Controls and instruments are the main interface between the operator and the machine or plant and it is important that it fits the operator s physical and mental capabilihes. Getting it wrong can be fatal. The pilot of a BA helicopter fhaf crashed info the sea off the Isles of Scilly claimed he did not see the warning light on the altimeter because, for his physique, the joystick obscured his view. 

The t)q)e of display must meet the needs of the human being operating the machine or equipment and the display itself must be clear and as easy to read as possible. It should not overload the operator with too much data but must take into accoxmt the information needed and how quickly it has to be assimilated. The importance of getting this right is underlined by the fact that poor display design was a contributory factor in the nuclear power stahon incident at Three Mile Island. 

Controls - i.e. levers, buttons, switches, foot pedals, etc. - represent the other half of the man-machine interface. To optimise a design it is necessary to take into account factors such as  

Points to take into account in the design and layout of controls and instruments include  

---

Fire detection and fire alarm systems. Control and indicating equipment. With BS EN 54-4 1997, superseded BS 5839 Part 4 1998 which remains cuiTcnt... 

Edeleanu made use of potentiostatic curves to determine the optimum conditions for the protection of stainless steel in sulphuric acid. A pilot plant was then used to determine the practicability of anodic protection at a constant potential. He pointed out several factors necessary for proper control and indicated the spectacular results obtained. 

Control stations perform the function of a controller and provide additional controls and indicators to allow an operator to manually adjust the controller output to the final control element. 

The self-balancing M-A control station shown in Figure 34 has several controls and indicators that are basically the same as those shown on the M-A control station in Figure 32. However, there are some which differ. In addition, the controller does not require a balancing procedure prior to shifting from one mode (manual or automatic) to another. 

The deviation indicator, setpoint indicator, setpoint adjustment thumbwheel, and output meter of the controller in Figure 34 function essentially the same as those in Figure 32. The remaining controls and indicators are quite different. Therefore, each will be discussed. 

Pressure detection shall be used for closed enclosure applications. Threshold detectors provide an electric signal when a preset overpressure is exceeded. Dynamic detectors provide an electric signal to the control and indicating equipment (CIE). Typically they have both rate-of-rise and pressure threshold triggering points that can be configured specifically to the application conditions. Although this type of detector minimizes spurious activation of the isolation system (due to pressure fluctuations other than explosion pressure rise), care shall be taken to set up such detectors to meet appropriate detection response criteria for the particular application and protected enclosure geometry. 

Fig 1, Photoelectric Cell Impulse Tube in Aberdeen Fuze Chronograph Fig 2, Recorder-Aberdeen Fuze Chronograph Fig 3, Mirror Mound - Jefferson Fuze Chronograph Fig 4, Tripod Assembly - Burst Time Indicator and Fig 5, Control and Indicator Assembly -Burst Time Indicator... 

Controls and indicators, such as power, humidification/dehumidification, and refrigeration switches... 

Individual temperalure control and indication of column, ovens, detectors, and sample inlets... 

Verification of test equipment calibration Verification of controls and indicators Computer control system testing Verification of sequence of operations Verification of major components operation Verification of alarms Power failure/recovery testing... 

If the candidate compound does not relax the tissue, then addition of a standard, such as cromakalim (1), at the end of the experiment can serve two purposes. Firstly, if cromakalim (1) relaxes the tissue, it acts as a positive control, and indicates that the test compound is inactive. Secondly, if cromakalim (1) does not induce a good relaxation, it suggests that the test compound may be a K channel blocker. BRL 31660 was found to block cromakalim-induced relaxations following this protocol, and as outlined above, has proved to be a very useful pharmacological tool. 

Measuring, control and indicating devices should be calibrated against appropriate national or international standards, which are traceable. 

PID The Piping and Instrumentation Diagram (P ID) shows in detail all the equipment, how it is connected with piping, where and what type of instrumentation and valves are used, the location of temperature, pressure, level and flow controllers (and indicators). Further it will show all the safety devices and alarms. The PI Ds give a comprehensive overview over the plant or the unit and it is a common document for mechanical, process, and instrumentation engineers in the downstream activities [851]. 

Table 2-3, List of Procedure Elements, lists the elements related to procedures and procedure control and indicates which guideline(s) and/or regulation(s) identify the element. It is intended to be used as a checklist to help you determine which elements are appUcable or required for your facility. Methods for addressing the elements required to design an effective procedure management system are discussed in Chapter 3.

Safety Interlocking Devices Control and Indication Devices... 

Numbering System for Protective Devices, Control and Indication Devices for Power Systems... 

NUMBERING SYSTEM FOR PROTECTIVE, CONTROL AND INDICATION DEVICES 535... 

Narrative for describing the interfacing of control and indication with other disciplines. 

Schedules of switchboard control and indication requirements, optional. 

In the alarm concentrated systems the supervisory lines are introduced directly to suitable control and indicating equipment. Also other different lines feeding the acoustic, optical, acoustic - optical signalizers. 

Distracted alarm systems are systems in which supervisory tines can, but they do not have to be introduced direetly to the control and indicating equipment. Usually the eontrol and indieating equipment is there eonneeted to the transmission line to whieh are also eonneeted the elosely defined modules e.g. expanding modules, the modules of printers, the modules of the power. 

---