exhibitions: Seen at the Physics Exhibition, Alexandra Palace, March 11th – 14th, 1968

exhibitions Seen at the Physics Exhibition, Alexandra

Palace, March 11th - 14th, 1968

Vacuum gun producing muzzle velocities up to 1150 ft/s for impact tests. (Ether Engineering Ltd.).

Displacement transducer based on Thompson- Lampard capacitor arrangement working with auto- matic a.c. bridge. Range 0.25 m, resolution 0.1 pm, accuracy 0.5 pm, or range 0.25 in, resolution 1 pin, accuracy lopin. (Automatic Systems Laboratories Ltd.)

Universal testing machine, 25 kgf to 10,OOO kgf full range, lead screw operated with strain-gauge load cell and potentiometer operated extensometer. Self- balancing a.c. potentiometer chart recorder can be driven from cross-head or extensometer or time base. Digital display may cover load, extension or area of load-extension graph. (Tensometer Ltd.)

Piezoelectric accelerometer calibrator comparing the test accelerometer with a reference (titanium slug with crystal system) built into a magnetic vibrator driven at frequency variable from 3 Hz to 30 kHz. Reference gives 10 g at 70 Hz for vibration level of 1 mm checked by microscope during calibration adjustment. (Environmental Equipments Ltd.)

Automatic guidance of farm tractors by ultrasonic- pulse echoes scanning differences in soil level (ploughing furrow) ahead of tractor. The tractor is turned round at end of field by a fence reflecting pulsed beams of infra-red light emitted by gallium arsenide lamps on tractor. (National Institute of Agricultural Engineering.)

Low-fidelity holography by exposing series of photo- graphic transparencies to laser beam (A.W.R.E., Aldermaston). For the strain analyst, this overshoots the mark and is therefore of no use. However, wait for medium-fidelity holographs !

Piezoelectrically or magnetostrictively driven scan- ning interferometers to measure surface irregularities. (A.W.R.E., Aldermaston.)

Pressure transducer for 10,OOO to 120,000 lbf/in2 based on coiled-coil manganin resistor (10 Ohm) and dummy in an a.c. resistance comparison bridge de- tecting resistance ratios to 10-5 or less. (Shell Research Ltd.)

Vibrating-wire extensometers for measurement of propeller shaft torque and thrust with special wire clamps, integral hinge machined out of extensometer body and closed-crcuit wireless transmission of signal from shaft. (Shell Research Ltd.)

Imacon ultra-high-speed image converter camera giving up to 20 frames at rate of the order of 107 per second, and a cheaper single-picture camera with a biplanar image converter tube giving exposure in nano- second range. (John Hadland Ltd.)

10 Watt argon laser as a monochromatic light source for use with ultra-high-speed multi-frame cameras up to 4 x 107 pictures per second. (C.E.G.B., Marchwood)

High-accuracy differential pressure transducer on the differential transformer principle for 0 to 10 in water gauge or 0 to 60 lbf/in2 with linearity of 0.5% F.S.D., 0.25 % repeatability, static pressure capability &-5000 lbf/in2. (K.D.G. Instruments Ltd.)

Telemetry system for signal transmission from a rotating shaft with 5 kHz carrier system frequency modulated for signal transmission and accepting signals from d.c. to 2 kHz. Information from up to 16 channels can be transmitted by means of a scanner in the rotating electronics. (English Electric Ltd.)

Laser Doppler tracker to measure velocities. (Decca Radar Ltd.)

Analogue for the diffusion equation permitting a scan of, e.g., transient and steady-state thermal stresses at selected points of a component. (Salford University).

Automatic ellipsometry of an initially circularly polarised ray after traversal of an electric field (City University). At present of restricted applicability but perhaps of importance to three-dimensional photo- elasticity five years hence.

M.L.M.

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