Table of contents

The principles of aircraft thermometer design are reviewed, from which it is deduced that the conical head design possesses distinct advantages over other kinds of thermometer head in high-speed flight. The construction of the thermometer is described and the results of wind-tunnel tests are quoted and discussed. The lag and radiation errors are calculated and the extension of the use of the thermometer to supersonic flight is discussed. An outstanding feature of this thermometer is the remarkable constancy of the recovery factor over a range of Mach numbers from 0.2 to 0.9 and its rapid response to temperature changes, the lag coefficient being of the order of 2 s.

A simple container which has proved suitable for the measurement of the dielectric properties of liquids in an H₀₁ resonator is described, together with a method of correcting for the meniscus.

A unit is described which automatically adjusts the value of a continuous current passing through a coil placed in a chamber so that the rate of heat dissipation duplicates that released by a small animal in a similar chamber.

At high relative humidities a current of 30 mA through a 38 s.w.g. chromel-p/constantan thermocouple produces sufficient Peltier cooling to form a film of water on the junction which may then be used as the wet-bulb of a psychrometer. The wet-bulb depression can be read to 0.001° C and in the range 97-100% changes of 0.01% relative humidity can be detected.

After calibration over sodium chloride solutions the psychrometer has been used to determine the water content/free energy curves of two soils, and good agreement has been obtained with previous determinations by other methods.

The contractor uses a small thyratron to control the current in a coil around the betatron flux of the machine, the current being supplied by the changing betatron flux. The X-ray yield is increased by a factor varying from three to twenty.

The measuring element in the instrument described is a photomultiplier tube operated in a logarithmic difference circuit which views, alternately through red and blue filters, a diffuser illuminated by the lamp which is being calibrated. The output from the circuit is linearly proportional to the reciprocal of the colour temperature of the lamp and is independent of its brightness. Readings can be made with an accuracy of approximately ±5° K over the colour temperature range from 2200 to 3200° K.

An instrument for recording temperature, chlorinity and depth in the upper 1000 metres of the sea is described. The temperature range is 0-30° C, with an accuracy of ±0 15° C. The chlorinity range spans about seven parts per thousand of chlorinity, the accuracy being ±0.03 parts per thousand. The accuracy in depth is ±10 m. The three quantities are recorded sequentially by a single-pen strip-chart recorder, each quantity being recorded for five seconds at a time. The underwater unit is suspended by means of an armoured steel cable, which has a single electrically-insulated core. This core carries power down to the underwater unit, and brings up the signals from the measuring elements. A simple frequency-modulation method of telemetering is used.

A diffusion method is described in which two columns of molten salt to be interdiffused, initially separated by a gas bubble at reduced pressure, are joined by breaking a capillary and allowing external pressure to eliminate the bubble. After a period of diffusion, the salt distribution is preserved by causing the glass diffusion tube to break at the point of initial junction while the tube is still in position in the high temperature zone of the furnace. The method has been tested with a 1: 1 CdCl₂-KCl mixture. The self-diffusion coefficient of cadmium is found to be 1.40 cm.²sec^-1 at 470° C, with a probable error of 2.5%. The method is applicable up to temperatures of the order of 1000° C.

A simple electrocardioscope with a cathode-ray tube and an electrocardiophone are described for use in lectures and during surgical operations. The electrocardiophone can be attached to the cardioscope amplifier and converts the amplified bioelectric potentials into signals of constant audio frequency and of variable intensity.

A galvanometer relay is described which consists of a mirror galvanometer with limited deflexion, an optical system, a photoconductive cell, a Wheatstone bridge and a polarized relay. The input is a small d.c. current supplied to the galvanometer coil. The output is the energy available at the switch contacts of the polarized relay. The power amplification, i.e. the ratio between minimum input energy necessary to actuate the relay and maximum output energy available at the contacts of the polarized relay, is, in the simple prototype, 1: 10¹³; the figure for a commercially produced version could be much higher. Large input overloading is allowable, e.g. a current 100 000 times greater than the minimum failed to damage the instrument. The instrument described is already quite small (4 × 4 × 6 in.), but improvements in its design could reduce the size still further.

An image intensifier is described in which a thin layer of selenium is placed in the electron microscope. The imaging beam causes the selenium to become conducting and potential restoration is provided by an auxiliary scanning beam which produces a television display signal. The device is extremely sensitive and useful images can be obtained with electron microscope beam current densities of the order of 10^-11 A/cm².