Electronic balance control

Recent developments in electronic motor power and speed controls have provided the means to reduce the power input at normal speed to balance this reduced load requirement, and also to modulate both power and speed as a method of capacity reduction. It is improbable that electronic speed control will be economical for motors above 100 kW. 

Figure 16 shows the experimental arrangement for the measurement of the surface pressure. The trough (200 mm long, 50 mm wide and 10 mm deep) was coated with Teflon. The subphase temperature was controlled within 0.1 C by means of a jacket connected to a thermostated water circulator, and the environmental air temperature was kept at 18 °C. The surface tension was measured with a Wilhelmy plate of platinum(24.5 x 10.0 x 0.15 mm). The surface pressure monitored by an electronic balance was successively stored in a micro- computer, and then Fourier transformed to a frequency domain. The surface area was changed successively in a sinusoidal manner, between 37.5 A2/molecule and 62.5 A2/molecule. We have chosen an unsaturated phospholipid(l,2-dioleoyl-3-sn-phosphatidyI-choline DOPC) as a curious sample to measure the dynamic surface tension with this novel instrument, as the unsaturated lipids play an important role in biomembranes and, moreover, such a "fluid" lipid was expected to exhibit marked dynamic, nonlinear characteristics. The spreading solution was 0.133 mM chloroform solution of DOPC. The chloroform was purified with three consecutive distillations. 

Solution of the educts and catalyst are pumped through the system, which is controlled by electronic balances. The actual reaction is performed in 87 ml continuous-flow reactor, from which samples are taken automatically and analyzed by gas chromatography (GC). The analytical data are processed online. 

Tolbert L M etal., 2002, Charge Balance Control Schemes for Cascade Multilevel Converter in Hybrid Electric Vehicles. IEEE Transactions on Industrial Electronics, 49(5), 1058-1064. 

Labcon PI 14 computer system consists of an Epsom Pine computer mounted in a purpose made portable case containing the necessary power supplies and interface components to allow control of a sieve shaker and electronic balance. Firmware in Epsom is included to provide a variety of methods of data handling and presentation procedures. 

I) polyethylene wash bottle (m) single-pan electronic balance with automatic zeroing and digital readout, 100 g 0.001 g capacity (n) electric flask heater (o) solid-state control for electric flask heater (p) stainless steel spatula (q) Keck clamp. 

The continuous enzyme membrane reactor (CMR). (1) Temperature-controlled water-bath (2) Feed tanig (3) Stirrer motor for feed tank (4) Feed pump (5) Feed inlet line to the reaction vessel (6) Reaction vessel (7) Magnetic stirring table (8) Prefilter (9) Recycle pum (10) Flowmeter (11) Membrane inlet pressure gauge (12) Hollow fiber membrane cartridge (13) Membrane outlet pressure gaug (1 Pressure adjusbneut valve (15) Retentate recycle line (16) Air bath environment (17) Pemieate (product) line (18) Permeate collection vessel (19) Electronic balance... 

A third possibility is the use of an automatic valve combination together with a small intermediate vessel that is placed on an electronic balance coupled to a computer for control of the valves. This is a very accurate method that can be adjusted to very small feeding steps down to a minute range, resembling an almost continuous medium supply. 

Electronic balances generally feature an automatic taring control that causes the display to read zero with a container (such as a boat or weighing bottle) on the pan. Most balances permit taring up to 100% of the capacity of the balance. 

You wiU use either an electronic balance or a mechanical single-pan balance (if you have a double-pan balance, your instructor will provide instructions on its use). The electronic balance is set to zero using the zero (tare) control bar or button before weighing an unknown object. For mechanical balances, the zero point is determined before weighing. 

Almost the reverse evolution can be observed for the other field disturbance (right). The response of the electrons is controlled at the beginning by the short relaxation time of some 10 s, at around half the pulse duration by the long relaxation time of some 10 s, and close to the end of the pulse again by the short relaxation time. As a result, large deviations between gain and loss in the power balance slowly arise at the beginning, reach their maximum at about half the pulse duration, and vanish almost without any delay at the end of the field pulse. 

In a series of experiments to investigate the factors that control the rate of a reaction, aqueous hydrochloric acid was added to calcium carbonate in a conical flask placed on an electronic balance. The loss in mass of the flask and its contents was recorded for 15 minutes. 

Experimental Verification of Adsorption Isotherms and Linear Least-Squares Analysis. If gas A is exposed to a very high surface area solid catalyst (i.e., sslOO m /g) in a closed chamber, then a sensitive electronic balance should provide measurements of the increase in catalyst mass at a given gas pressure pa as active sites become occupied. A flow control valve is necessary to maintain constant pressure pa while measurements are made, because adsorption of gas molecules on the catalytic surface will cause a decrease in gas pressure if additional gas is not introduced into the system. Knowledge of the gas density at STP conditions and the additional mass of gas from the flow control valve required to maintain constant pressure pa allows one to calculate the volume of adsorbed gas per initial mass of catalyst, va- Experiments are repeated at different gas pressures. The raw data correspond to pa va pairs that can be modeled via the Langmuir isotherm to extract two important parameters of the adsorption process. 

The purpose of this chapter is to give an overview of the chemical and biological processes that control the reactivity of Fe(II) in heterogeneous aqueous systems with respect to pollutant transformation. To this end, we will evaluate data collected in various laboratory systems as well as field studies. Two classes of model compounds with complementary properties will be used to monitor the reactivity of Fe(II) species in the various systems. Nitroaromatic compounds (NACs) primarily served to characterize the systems in terms of mass and electron balances. Reduction of NACs by Fe(II) species results in only a few major products (aromatic amines and hydroxy-lamines) which can be easily quantified by standard HPLC-UV methods in the low liM range. Polyhalogenated aliphatic compounds (PHAs) were used if little perturbation of the systems in terms of electron transfer to the organic substrates was crucial. Reduction of PHAs requires fewer electrons than nitro reduction and PHAs can be quantified by standard GC-ECD methods in the low ppb range. 

The use of an electronic balance offers the possibility to record the result of a weighing objectively, by connecting to a printer or a computer programme (in-process control). 

Figure 4.19 shows a schematic representation of state-of-the-art expression apparatus. The more conventional piston press apparatus described in Section 4.5.1 is augmented with the addition of a computer driven pressure regulator which allows the pressure applied to the piston to be carefully controlled and varied according to a preset pattern (e.g. ramp, sinusoidal etc.). The interfaced rotary or linear encoder, force transducer and electronic balance allow semi-continuous measurements of piston displacement, transmitted pressure and... 

Many industrial filtrations are performed under variable rather than constant pressure conditions and Chapter 4 describes how sequences of constant pressure experiments can be used to provide scale-up constants that are valid for other pressure/flow regimes. Figure E.3 shows some experimental data for constant rate calcite filtrations where the pressure changes and flow measurements for the filtration have been provided by a software controlled pressure regulator and an electronic balance, respectively. In accordance with theory, a near linear relation is shown between pressure and time. The theoretical predictions also shown on Figure E.3 were produced using... 

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