Instrumentation rotameters

Instrument Society of America 400 Stanwix Street Pittsburgh, Pa. 15222 Standards l ibrary for Measurement and Control, 12th ed., 1994. Instmmentation standards and recommended practices abstracted from those of 19 societies, the U.S. Government, the Canadian Standards Association, and the British Standards Institute. Covers control instmments, including rotameters, aimunciators, transducers, thermocouples, flow meters, and pneumatic systems (see... 

Many different techniques are available for flow measurement and for recording of respiratory functions or flow parameters in particular (e.g. [115,116]). However, not all methods are appropriate for measurement of inhalation flows, either because they have low frequency responses or they influence the shape of the inspiratory flow curve by a large volume or by the inertia of the measuring instrument (e.g. rotameters). They may also interfere with the aerosol cloud from the inhalation device during drug deposition studies. 

Trace element feed rotameter Indicates panel-mounted instruments. ... 

A new air-flow unit based on the ASTM D 3574 - Test G method is now available from Fluid Data, 1201 North Velasco, Angleton, TX 77515 (409-849-2344). This unit. Fluid Data s Model FPI Foam Porosity Instrument, is reported to be easy to read, computer-compatible, and more portable than its predecessors. It uses a digital electronic display instead of a rotameter, has automatic calibration, and prints out consecutively numbered results. An RS-232 serial port allows data to be transferred from the unit and stored in a computer. This unit is illustrated in Figure 10.1. 

Pumps should be cahbrated with a rotameter [27] prior to and after sampling. Analytical instruments must also be calibrated before measurements. For example, GC/MS must be cahbrated for mass and retention times using reference standard materials [70] and comparison made with the fragmentation patterns of known standards, usually a deuturated compound like toluene-dg. Similarly, the method detection limit must be determined by finding the standard deviation of seven replicate analyses and multiplying it by the f-test value for 99% confidence of seven values [30,62]. It is also usual for internal standards to be added to the samples and to evaluate the correlation coefficients of each standard used when multilevel calibration is employed. For automatic thermal desorption tubes, external and internal standardisations are achieved by injecting solutions of standards into the tubes [27,28] for canisters, solutions of standards are injected into the canisters followed by zero air. 

The types of instruments used in an industrial setting are often different from those used in the laboratory. The most common high precision laboratory instrument is the mass flow controller and rotameters are frequent for applications for both gases and liquids but are much less accurate. In industry, obstruction flow meters, Coriolis meters, and vortex shedders are more standard. 

Rotameters are most common in laboratories and for instrumentation in industrial processes. Their precision is perhaps no better than 2-5%. 

Conventional instrumentation is a rotameter on the demineralized water feed, with a manual valve for adjustment of the rate. Magnetically coupled flow indicators will not work properly in the strong electrical field of the cell room. The density of the caustic solution is measured with a nickel hydrometer. The hot, strong caustic would quickly destroy a conventional glass instrument. 

Each instrument has a rotameter equipped with a Optical Sensor which will cause contact closure (and annunciation at the control console) if flow deviates from the target band selected during calibration. The alarm will actuate on low flow (failed pump, clogged filter paper, frozen sample line) or on high flow (broken filter tape or out-of-tape). 

The apparatus consists of six components pump, heating system, test section, condensing systems, receiver, and instrumentation, A conventional centrifugal water pump is used to establish and maintain flow through the apparatus. The receiver is cooled with water to prevent cavitation in the pump. The flow rate through the pump is measured by means of a rotameter. 

As indicated in Figure 1, the instrumentation consists of three rotameters, one pressure gage, six mercury manometers, and one thermometer. In order to check the flow rates through the test section by a difference computation, the sight glass on the receiver and a stop watch were used to determine the accumulation of fluid in the receiver during the runs. All manometer systems in which liquid contacted the pressure tap were completely filled with liquid between the taps and the mercury menisci. 

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