Time Proportioning Computer Control of Resistive Heating

ABSTRACT

The design and construction of an interface to regulate electrical power to a heater (resistive load) for temperature control is described. An overview of various techniques is presented and a specific approach to heater power control is described in detail. The method, however, can be easily adapted to other applications, for example, the manipulation of a solenoid valve to control an average fluid flow rate. The interface described here has a linear relation between the numerical computer output value and the power delivered to the load. This is convenient for both calibration and scaling purposes.     

McKee-Pedersen Instruments

ABSTRACT

A simple and inexpensive emulator interface for replacing ROM with memory programmable from a host computer is described. The unit can be used with any commercial micro- or minicomputer with a parallel output port. The emulator interface was developed for running a dedicated Z80 based system on an Apple II+ computer.     

A Versatile Potentiostat With Optional Computer Control

ABSTRACT

A versatile potentiostat which can supply a maximum of 125 ma is described. The potentiostat uses readily available electronic components and an interface is detailed which allows the potentiostat optional computer control.     

Computer Control for the Study of Reactor Dynamics

ABSTRACT

The key elements in the study of chemical reaction transients are generation of forcing functions, rapid measurement of process variables and reliable computer control system. A multicomponent reaction involving propene metathesis was studied under computer control. The real-time control of the inlet gas concentrations to a Berty reactor, reactor temperature measurement and control, and acquisition of reactor effluent composition via rapid analysis in a gas chromatograph are described. The time intervals for servicing the interfaced devices were generated by hardware interrupts. The multitasking computer control program with interrupt servicing was written in FORTH.     

Experimental and Computational Methods for Studying Multicomponent Equilibria. II. An Automated System for Precision emf Titrations

ABSTRACT

A potentiometric titrator designed mainly for complex formation investigations is described. The titrator is constructed from electronic building blocks, without a computer. The functioning of the titrator may be described by a rigid cyclic program with the possibility of adapting the titrator to the actual chemical system by varying a few key parameters on thumbwheel switches. Before the titration, the experimenter makes the decisions necessary. The titrator has no inherent facilities to decide whether equilibrium has been attained. Experiences gained with this titrator and the advantages over a computer-based system are discussed.     

An Automated Dual-Wavelength Spectrophotometer Optimized for Phytochrome Assay

ABSTRACT

A microcomputer-controlled dual-wavelength spectrophotometer suitable for automated phytochrome assay is described. The optomechanical unit provides for sequential irradiation of the sample by the two measuring wavelengths with intervening dark intervals and for actinic irradiation to inter-convert phytochrome between its two forms. Photomultiplier current is amplified, converted to a digital value and transferred into the computer using a custom-designed IEEE-488 bus interface. The microcomputer calculates mathematically both absorbance and absorbance difference values with dynamic correction for photomultiplier dark current. In addition, the computer controls the operating parameters of the spectrophotometer via a separate interface. These parameters include control of the durations of measuring and actinic irradiation intervals and their sequence. Because the data are processed solely within the microcomputer, except for the initial linear amplification, any output desired can be obtained, including automated determination of not only total phytochrome content, but also of the proportions present in the far-red- and red-absorbing forms.     

Scanning Electrode System for Surface Studies

Abstract

The construction of a scanning electrode system is described. The system is designed to measure chemical and electrical parameters above surfaces. It was tested with scanning reference and scanning pH electrodes on a steel coupon which contains a weld, several artificial corrosion pits of different depths and diameters, and an artificial crack of varying depth. The apparatus is computer controlled; the program for control of the apparatus is provided. A stationary electrode is utilized with a moved examined surface (a coupon). The apparatus is capable of determining surface dimensions of pits, but not pit depths. The artificial pits and crack were shown to be anodic locations. The solution above the pits and crack was more acidic than the solution above the remainder of the coupon.     

Accurate Molten Salt Viscometry

SUMMARY

The viscometer described in this note is of general applicability but its features are particularly suited for measurements with molten salts having appreciable vapor pressures and/or chemical reactivity to atmospheric moisture. While sealed viscometers are not unknown [1, 2], the present design ensures a constant starting volume and minimizes some of the inherent experimental difficulties, for example, calibration, repeated measurements, and kinetic energy and surface tension corrections. Magnitude and sources of errors are briefly considered, and results with this viscometer for KN0₃ (mp, 337°C), HgCl₂ (mp, 277° C; bp, 304°C), and CsN0₃ (mp, 414°C) are reported.     

Research on method of constraint conversion in feature-based data exchange between heterogeneous CAD systems

Data exchange between heterogeneous CAD systems is the key problem in the field of CAD, and the popular solution to this problem is a feature-based method. Aiming at keeping the consistency of design intent in data exchange between heterogeneous CAD systems, this research focuses on the method of constraint conversion. First, two kinds of basic feature transformation ways are summarized, and this is the foundation of constraint conversion. Second, a novel identification of geometric elements based on the improved geometric certificate is proposed, and the identifier of geometric element is used to recognize the acting object of constraint. Third, the principles of constraint conversion are put forward, and the method of constraint conversion for a single feature is proposed according to the principles. Fourth, an algorithm of constraint conversion for the whole process of CAD data exchange is designed. Finally, the contrast experiment of CAD data exchange is completed, and the result of the experiment shows that the approach mentioned above is effective. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Sun Wei is a professor and the deputy dean of school of mechanical engineering at Dalian University of Technology. His research interests include knowledge-based product digital design, computer supported collaborative design, analysis and optimization of product. He received a BS, a MS and a Ph.D in mechanical manufacturing and automation from Dalian University of Technology, P. R. China. Ma Tie-Qiang is a Ph.D. candidate in school of mechanical engineering at the Dalian University of Technology. He received a BS and a MS from Dalian JiaoTong University P. R. China. His research interests include computer graphics & computer aided design, product data management, computer supported collaborative design. Huang Yu-Jun is a graduate in School of mechanical engineering at the Dalian University of Technology. He received a BS from Wuhan University of Science and Technology P.R. China. His research interests include product data exchange and computer graphics     

Automatic Absorbance Calibration Routine for a Computerized Uv-Visible Rapid Scanning Spectrophotometer

Sir:

A Fortran IV computer program is used to calculate absorbance at varying wavelengths in a UV-visible rapid scanning spectrophotometer. Using the program eliminates the necessity of calibrating the absorbance axis in the usual manner using standard solutions or filters and plotting calibration curves, because the voltage output of the computer is automatically identical to the actual absorbance of a sample.     

Computer Analysis of High Resolution Mass Spectral Data from Mixtures of Organic Compounds

ABSTRACT

The operation of a set of computer programs for the reduction and qualitative analysis of mass spectral data from mixtures of organic compounds is described. The routines were developed for the analysis of data from fossil fuel materials but are applicable to any mixture of organic species. Data is processed by first sorting masses into homologous series and then placing the homologous series into groups which contain the same heteroatomic species. Within these groups series are ordered according to degree of unsaturation. Empirical formula possibilities are determined and plots of intensity versus mass are made for each homologous series. The routines are very general and can be used with any type of ionization process and with a wide variety of heteroatomic species. An example of the application of these routines to an aromatic nitrogen concentrate from shale oil is presented.     

Computerized Phosphorescence Decay Measurements

ABSTRACT

An on-line digital computer has been applied to phosphorescence decay studies. The computer controlled excitation timing and provided data acquisition, smoothing, and data reduction functions. Phosphorescence decay steps for mixtures could be observed over a wide time domain.     

High Speed Parallel Interface for a PAR Multichannel Detector Controller and a HP9845T Minicomputer

ABSTRACT

The design and construction of a high speed parallel interface between a Hewlett-Packard 9845T minicomputer and an E G&G Princeton Applied Research Corporation (PAR) model 1216 multichannel detector controller is described. The hardware as well as the software necessary to implement this interface is discussed.     

A Scheme for Serial Communications Among Small Computers

ABSTRACT

An approach to experimental control and data logging for multiple analytical stations is considered. A very economical, yet reliable, scheme uses a host computer to serve a number of less powerful satellite systems which control individual experiments and can be operated temporarily independently of the host. An example of communications between systems is detailed in which machine language subroutines called by high level languages provide reliable data transfer and control flexibility for special needs.     

On-Line Computer Control of a Luminescent Spectrometer with Off-Line Computer Data Processing and Display

SUMMARY

A luminescent spectrometer has been interfaced with a general purpose digital computer operated in a time-share mode. The computer controls both monochromators and logs the data on magnetic tape. By means of its constituent mode subroutines, the computer controls the spectrometer in any of six modes for the acquisition of luminescent information. It will record the excitation, emission or detailed three-dimensional spectra, integrate luminescent intensity at fixed wavelength coordinates, locate the wavelength region and general form of an unknown spectrum, and record luminescent intensity at fixed wavelength coordinates at selected time intervals, or oscillate either one or both monochromators between two fixed points so that the change of luminescence at either one or two points of the emission and excitation wavelengths can be monitored as a function of time.

The data are processed off-line with a CDC 6600 computer that permits the data to be portrayed in several graphic forms. The raw data can be corrected for instrumental response, smoothed, differentiated; data arrays can be either magnified or eliminated by masking.     

Versatile Pump Controller for Continuous Flow Methods

ABSTRACT

A computer-driven pump controller capable of providing voltage, current and pulsed outputs for up to five pumps in analytical systems is described. The controller is ideal for situations which require remote control of speed and direction for many pumps of different types. The design is based on the Advanced Micro Devices 9513 system timer chip and provides 0-10 V, 0-25 mA and pulsed TTL outputs to control each pump. In addition, phase-locked loop circuitry allows feedback for speed regulation of certain pumps. For control of stop/start, direction or other functions, eight independently programmable TTL outputs are provided. The controller is inexpensive and designed to be driven from the parallel printer port of an IBM PC compatible computer for maximum portability. Other uses of the interface are also possible.     

A Precision Audio-Frequency Voltage Regulator

SUMMARY

A circuit is described which, when fed with an alternating voltage whose amplitude may vary, produces an accurately settable, continuously variable output amplitude. The error in the output amplitude is within 0.1% for inputs from 3 V to 7 V rms, between 30 Hz and 4 kHz, and within 1% between 16 Hz and 10 kHz. By connection to this inexpensive circuit, any simple, inexpensive audio oscillator is effectively converted into a multirange, precision-amplitude ac source.     

Construction and Evaluation of an Opto-Coupled Potentiostat with a PC/PDA Interface

Abstract

The design, construction, and characterization of a portable opto-coupled potentiostat are presented. The potentiostat is battery-powered, managed by a microcontroller, which implements cyclic voltammetry (CV) using suitable sensor electrodes. Its opto-coupling permits a wide range of current measurements, varying from mA to nA. Two software interfaces were developed to perform the CV measurement: a virtual instrument for a personal computer (PC) and a C-base interface for personal digital assistant (PDA). The potentiostat has been evaluated by detection of potassium ferrocyanide in KCl medium, both with macro and microelectrodes. There was good agreement between the instrumental results and those from commercial equipment.     

A Computer-Controlled Mass Spectrometer System

SUMMARY

A computer has been incorporated as the main control element in two thermal ionization mass spectrometers used for the routine isotopic analysis of uranium. The operational logic is contained in the software, rather than in the hardware, providing broad versatility in the implementation of operational modes, and greatly simplified hardware. An operational mode was developed which was optimum for the particular mass spectrometer and the type of sample to be analyzed. The system has been used for the analysis of over 1600 samples in the first 10 months of operation, and has proven its value in reduced manpower requirements arid improved quality control.

Two thermal ionization mass spectrometers have been used for routine analysis of uranium isotopic composition and isotope dilution analysis at the AEC's Idaho Chemical Processing Plant for many years. The basic instruments have been described elsewhere [1, 2], and have proved well suited to the job after 34 years of combined service and tens of thousands of samples.     

A Generalized Interface for 16-Bit Computers

ABSTRACT

Most peripherals used by chemists for on-line experiments can be interfaced quickly and relatively inexpensively by taking a modular approach to the interface. The usual interface has been divided into three parts: a bus which distributes standardized signals for control and data, a module for the computer, and a module for each peripheral attached to the bus. Furthermore, the number of peripherals that can be attached to a computer can be easily expanded. Transistor-transistor logic and TTL-compatible circuitry have been used throughout.