Table of contents

By means of silicon planar technology it is possible to make not only integrated circuits but also integrated sensors and actuators. This paper gives a comprehensive review of research work in the sensor area. It also includes some general considerations with respect to measurement systems and signal conversion as well as some conclusions and comments on a future outlook.

Of the many tasks confided to the computer in electron optics and electron microscopy, lens and system design are examined in some detail, with particular attention to the methods employed. Optimisation is also considered. The use of computer algebra rather than arithmetic is discussed for the derivation of aberration formulae in unfamiliar or complex situations. In addition, many other applications of digital methods are described more briefly, in particular, image processing and data handling.

An apparatus is described for determining internal stress by the dip test method during creep testing in the plastic microstrain range. Tubular samples are twisted with high stability of the stress during a creep test. The lowest strain level detected by this apparatus is about 10^-7 under the best conditions. Some examples of internal stress determination by Ahlquist and Nix's method are shown for iron alloys at room temperature.

Smits and Perry (1980) state that dependence of CTA behaviour on overheat seems to have received little attention for low resistance ratios. This author would like to bring to attention that dependence of frequency optimised anemometers. In this note, pertinent results will be drawn together and the discussion will be expanded.

Measurements are presented of the detection efficiency of Johnston multipliers (type MM1-1SG) for positive and negative atomic ions. The results obtained with several multipliers and twenty different ion species fall about a smooth curve which relates detection efficiency to the velocity with which ions strike the first dynode.

A rapid acting gas valve is described. The opening and closing motions of the valve are under separate electrical control and the opening time of the valve can be varied over the range 10 to 100 mu s. At moderate opening times, 20-30 mu s, the valve produces high intensity pulsed beams of various molecular species with narrow velocity distributions.

A two-terminal capacitance method has been devised to measure the coefficient of linear thermal expansion ( alpha ) of thin films as conventional methods are unsuitable. The formula to evaluate the observed value of the thermal expansion coefficient ( alpha _obs) has been obtained and the relevant correction factor has been incorporated in the final formula alpha _true= alpha _obs+ alpha _el where alpha _el and alpha _true are the thermal expansion coefficients of electrode film and sample thin film respectively. The design of the dilatometric cell, the preparation of the thin-film specimen and the electrode film configuration are described. The change in capacitance with temperature of the vacuum capacitor, where the specimen film is the spacer, is used to evaluate alpha _obs. This technique has been standardised using thin platelets ( approximately 100 mu m) of a single crystal of NaCl. The other considerations which are important for the precision of this measurement technique are also discussed.

A new optical method to determine the shape of liquid surfaces is developed using the principles of schlieren technique. Measurements of surface shape were made on turbulent open channels and also on surface tension driven Genard cells to obtain hydrodynamic data. These measurements cover a range of 0.65 mm to 1.5*10^-4 mm vertical surface deflections induced by the fluid motion underneath. Measurements on the channel flow were highly precise and more than sufficient to characterise the surface shape. The Benard cells were near but within the practical limits of the optical system.

For pt.I see ibid., vol.8, no.7, p.600-2 (1975). An interferometer has been constructed to measure the thermal expansion of solids. The useful resolution is limited to 0.3 nm change in length by the sensitivity of the polarimeter or to about 5 parts in 10⁹ in relative length change by the stability of the laser. Because the divided beams are close together everywhere, the instrument is particularly insensitive to vibration and changes in ambient temperature compared to many other interferometers. No special devices are required to compensate for shear, and readout is completely automatic. Measurements on a sample of titanium silicate glass in the range from -100 to +200 degrees C are reported. Modifications to the sample chamber are expected to extend the operating range to 1500 degrees C.

The axial flux density distribution of single pole-piece magnetic electron lenses differ from those of conventional design. An experimental investigation has been carried out concerning the effect of the bore size on the shape of the field distribution of single pole-piece lenses. The size of the axial bore in the cylindrical pole-piece of an experimental lens was varied over a wide range and the axial flux density distribution was measured for each bore size. The characteristic features of the field distribution such as its peak value, its penetration inside the lens structure and its mathematical representation by an analytical function were studied in detail. The effect of the bore size on the magnetic asymmetry was also considered. Empirical equations concerning the properties of the field distribution are put forward. The results should be useful in the optimisation of lens design and in field distribution modelling.

In order to rationalise data acquisition from standard stopped-flow apparatus, a system has been implemented around an inexpensive yet powerful and flexible microcomputer controlling a 12-bit 25 mu s A/D converter and a paper-tape punch unit. BASIC and assembler ROMs available on microcomputer board provide the system with on-line data preprocessing and I/O flexibility. The data stored are visualised by a standard non-storage oscilloscope via D/A conversion, and they can be printed and/or punched for further off-line computer processing. Because of the wide range of time base for data sampling which can be obtained by proper loading of the microcomputer timers, the system may be profitably used in a number of cases other than stopped flow.

A four-channel photon counting system for Raman spectroscopy is described. It is capable of performing simultaneous measurements of four different Raman signals and thus makes it possible, for example, to combine difference Raman spectroscopy with polarisation measurements (I/sub ///, I_{perpendicular to} ) or to compare directly the Raman signals of a species in two different solvents. The instrument is also of value to researchers in other areas of spectroscopy such as fluorescence, absorption or emission.

The energy distribution of the primary electron beam effective when using the RPD method for cross section measurements is calculated from the difference of the electronic velocity distribution functions. Due to the difference method the shape of the distribution function changes from that of an accelerated Maxwellian to that of a true exponential function. Thus the energy halfwidth decreases from 2.47 kT to 0.69 kT (T, electronic temperature), when the difference voltage approaches zero, i.e. the energy width is not proportional to the difference voltage but to the temperature of the cathode.

A wire probe for measuring high frequency sea waves is described. Static and dynamic calibrations of the total system consisting of the probe itself and the electronics were conducted. They prove that the probe has full flat response to 50 Hz (limited by the wave generator). It is also insensitive to changes in water temperature or salinity. It is shown that the system can be successfully used for field experiments.

A 16 kV krypton pulse generator and a 30 kV krypton activated spark gap are developed to operate a Kerr cell shutter. The shutter is used to select single picosecond light pulses from a mode locked laser and to separate nanosecond light signals from a free running laser.

An open path CO₂ analyser is described for measuring CO₂ fluxes over crop canopies by the eddy correlation technique. The analyser measures CO₂ concentration within 0.3 ppm by volume with a time constant of 0.075 s. The CO₂ concentration is determined from a comparison of the absorption of infrared radiation in the 3.7 mu m and 4.3 mu m bands over a 1.5 m path.

The design, construction and performance of two types of miniature ceramic hydrophones are described, which are intended for acoustic pressure measurements in liquids at low megahertz frequencies. One of the devices has a 1.6 mm diameter cylindrical element with good directional characteristics and a sensitivity of approximately -224 dB re 1 V mu Pa^-1 up to 0.7 MHz. The other probe uses a 0.5 mm disc showing a sensitivity of -245 dB re 1 V mu Pa^-1 from 0.5 to 6 MHz and diminishing uniformity of directional response with increasing frequency. The stability of the probes is also discussed.

A fluorescence detection system for biological EXAFS experiments has been set up at the EMBL Outstation, Hamburg. An array of ten NaI(Tl) scintillation counters is used. The total counting rate of the system is 1.4 MHz. Data collection and reduction procedures were developed and are described. Examples of spectra obtained are presented. The system makes possible studies of samples in the sub-millimolar concentration range in the most favourable spectral region.

For pt.2 see ibid., vol.14, p.1260 (1981). A comparison is made of the results of the previously carried out analysis of the errors in total reflection TDS with the errors identified in the results of measurements performed on ethanediol and formamide in the frequency range 10⁷-10¹⁰ Hz. It is shown that the magnitudes of the random errors are reasonably well predicted as is the level of the unwanted reflection errors. A discussion is also given of the relative importances of the different sources of error and it is concluded that the main limitation in performance of the present system is due to random electrical noise emphasising the importance of very careful averaging of the TDS waveforms.

An apparatus for precise and absolute measurement of the thermal conductivity of electrically conducting liquids using the transient hot-wire method has been developed. In the present apparatus, a metallic wire coated with a thin electrical insulation layer has been used as a heating element and a resistance thermometer instead of a bare metallic wire. The effects on the thermal conductivity measurement caused by the thin insulation layer have been analysed. In the analysis, it was found that the effects can be negligibly small if the instrument is adequately designed. The usability of the method for electrically conducting liquids has been tested to measure the thermal conductivity of an aqueous NaCl solution in the temperature range 0 to 45 degrees C at atmospheric pressure. The accuracy of the present measurement was estimated to be +or-0.5%.

A piece of apparatus is described which allows fast and accurate energy barrier height measurements in metal-semiconductor Schottky diodes, by means of the capacitive method, during thermal cycles which may cause interdiffusions or reactions. A small diode holder, with a mobile electrical contact allowing compensation for parasitic capacitances, rapidly raises the temperature of the sample at a constant preselected value, in an inert atmosphere. The voltage-capacitance data are measured and processed automatically.

An anemometer for the measurement of the velocity of particles of different components in a flow, separate and apart from that of the flow itself, is described. As a component-selective mechanism Raman scattering is used. The velocity is measured by relating the autocorrelated scattering signal to the known laser beam profile.