Instrumentation relay controllers

Fig. 9-20, Classification of automatic controllers (a) self-operated controller, using energy only from controlled medium through primary element (6) relay-operated controller with self-operated measuring means and relay-operated controlling means (c) relay-operated controller. with relay-operated measuring means and relay-operated controlling means. [G. A. Hall, Jr. by permission from Process Instruments and Controls Handbook, Douglas M. Considine (ed.), McQraw-Hill Book Company, Inc., New York, 1957.]...

S.3 Second and Third Ploors. The layout of the second and third floors is shown in Fig. 9.2.C, as mentioned in the discussion of the first floor the instrument and control rooms are on the second and third floor levels. These two rooms operate much.as a unit with the instrument room having the amplifiers and relays and the control room having the indicating and recording instruments for reactor operation. The control room is at the higher level so that conduits and raceways do nq.t come from an overhead position. /... 

For instrument modules, relay and control modules or control panels or all power modules, where an interlock with the door is not possible or is not provided, a proper shroud or shutter must be provided on all exposed live parts rated above 240 V. 

Alarms are used to alert operators of serious, and potentially hazardous, deviations in process conditions. Key instruments are fitted with switches and relays to operate audible and visual alarms on the control panels and annunciator panels. Where delay, or lack of response, by the operator is likely to lead to the rapid development of a hazardous situation, the instrument would be fitted with a trip system to take action automatically to avert the hazard such as shutting down pumps, closing valves, operating emergency systems. 

All alarm and shutdown signals are relayed to the main control pannel where the instruments are clearly labeled with plant instrument... 

Current laboratory robot operations use many of the instrument modules familiar in conventional automation syringe drives, relay drivers, current and/or voltage sensors (including A/ D conversion) etc. The uniquely robotic component is a "pick and place" arm which serves as a "mass mover" of sample, solution etc. from one unit operation to the next. The robot controller functions to control both the pick-and-place component and the separate unit operations. Actually it is poor practice to separate any of the... 

Jacket temperature was controlled by connecting the thermoregulator and the heater to an American Instrument Co. relay model No. 4-5300. Power to the heater was supplied by a 60-cycle variable transformer normally operated at about 10 volts. Jacket temperature was recorded by feeding the thermocouple output through a Leeds and Northrup d.c. amplifier (No. 9835-B) to a Speedomax H Azar strip chart recorder. 

Booster relays are designed to provide extra flow capacity for the instrument air system, which decreases the dynamic response time of the control valve (i.e., the time for most of a change to occur). Booster relays are used on valve actuators for large valves that require a large volume of instrument air to move the valve stem. Booster relays use the pneumatic signal as input and adjust the pressure of a high flow rate capacity instrument air system that provides pressure directly to the diaphragm of the valve actuator. 

Figure 2.5 Integrated analytical system. A nine-position microfabricated device was coupled to an ITMS instrument via a transfer capillary and a microESI ion source. The inner surface of the transfer capillary (15 cm long, 75 pm i.d., 150 pm o.d.) was derivatized with 3-aminopropylsilane. The etched channels were 30 pm deep and 72-73 pm wide. The diameter of the reservoirs was 1mm. The sample flow was controlled by an array of computer-controlled high-voltage relays which are also schematically represented. The software controlled the sample flow from the different reservoirs, the generation of MS spectra, the selection of potential peptides, the generation of MS-MS spectra and the matching of the MS-MS spectra against a protein sequence database. (Adapted with permission from Ref. 6).

Fig. 13.5 Instrumentation for critical evaluation of the Karl Fischer water method, (a) Amperometric circuit (b) relay circuit for automatic burette control (c) potentiometric circuit. (Reproduced from [58] with permission of the American Chemical Society).

Such double beam instruments can be controlled more easily in processes by relays or microprocessors. No mechanics for automatic exchange of sample and reference cells have to be included. The energetic efficiency of the light paths is lower. A double monochromator supplies higher quality photometry. The spectral resolution can be increased and the amount of stray light is drastically decreased. The slit in-between the two monochromator parts is essential. A high performance instrument is shown in Fig. 4.3. Such spectrometers are rather expensive but are very useful in the examination of complex photoreactions as well as in the measurement of problematic samples such as turbid solutions, viscous samples, or thin films. 

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