cryostat must be used-at 70°K the loss is low enough for operation of a useful delay line.

The transmission loss for the 3~s delay is about 6dB. Acous- tic mismatch to the sapphire rod causes minima of insertion loss at one quarter and three-quarter wavelength frequencies, and the band-pass characteristic is almost flat for 1GHz bandwidth about mid-band.

Standard Telecommunication Laboratories Limited, London Road, Harlow, Essex (shown al The Physics Exhibition 1968)

LEAK DETECTOR

Permanently tuned solid state circuit elements are used in the design of the new leak detector El-100 from Protech Advisory Services Ltd. The detector (shown in Fig 2) con- verts the ultrasound produced by gas leaks into audible sounds.

The instrument measures 9in x l$in diameter (229 x 32mm) and weighs 802 (22’7g) complete with headset. It can detect leaks down to 0. OOlin (0.025mm) and with pressures as low as 61bf/in2 (41 X 103N/m2). A standard 9V radio type bat- tery is used, giving a battery life in excess of lyr with an 8hr- day cycle of duty.

Protech Advisory Services Ltd, 21 High Street, Rickmans- worth, Hertfordshire, England

THICKNESS METER

A new ultrasonic thickness meter is available for measure- ments on engineering metals, glass, ceramics and plastics. The instrument (shown in Fig 3) is the Krautkramer ‘Cor-

rosion meter’. It contains a shock-resistant moving coil gal- vanometer with a 5.5in scale; this covers two ranges, either O-0.6in (steel) (accuracy f. 0.005in) and O-2.4in (f0.015in) or alternatively O-15mm (kO.lmm) and O-60mm (kO.3mm).

The meter weighs 5.51b (2kg) and is contained in an oil-resis- tant plastic case measuring 8.1 X 6.9 x 5.lin (205.7 X 1’75.3 X 129.5mm); there are self-contained calibration blocks. The hinged meter lid serves as a variable position stand; alterna- tively the instrument can be used with a carrying strap, as shown in the illustration. Power is supplied by dry batteries. Special ‘fail-safe’ circuitry prevents reading if coupling is inadequate or if an unsuitable meter range is selected.

The instrument was designed for industrial requirements of thickness measurement where more sophisticated instrumen- tation, with flaw detection, would be unnecessary. It is sup- plied with two probes, a tube of high temperature coupling paste, a carrying strap and an operating manual.

Krautkramer Ultrasonics, Inc, One Research Drive, Stratford, Connecticut 06497, USA; Wells-Krautkramer Ltd, Blackhorse Road, Letchworth, Hertfordshire, England

GENERATOR

The high frequency generator (Fig 4) has been developed for processing in the upper region of the ultrasonic spectrum by Macrosonics Corporation.

The new generator has an output of 150W at 800kHz and drives a ll/,in piezoceramic submersible transducer which has an output in water up to 85W. The transducer can oper- ate continuously for more than 5000h at temperatures up to 100°C. Model 180VF, as it is known, has these applications: creation of micronic aerosols, accelerations of chemical reactions, extractions, destruction of cells, emulsification. It may also be used for chemical biosynthesis,flame spec- trophotometry, ageing of alcohols and humidification. 180VF is housed in a cabinet 12 x 63/q X 19in and weighs 331b.

Macrosonics Corporation, 880 Elston Street, Rahway, New Jersey, USA

FULLY PROGRAMMABLE PULSE GENERATOR

A fully programmable pulse generator, designed to be con- nected directly to a process control computer, is now avail- able from E-H Research Laboratories UK Ltd. It consists of two units, the 1420 timing unit and the 1139 pulse driver (a and b in Fig 5). All pulse parameters on both units are programmable by three digit BCD logic. Parameters con- trolled on the tuning unit include: repetition rate (IkHz-1OMHz) delay (lOns-lOOtis); width (lOns-AOO@s).

The output from the timing unit is fed to the 1139 unit on which amplitude and attenuation, baseline offset, and rise and fall times can be programmed. The output from the 1139 is f_lOV, and the maximum uncalibrated risetime about 2.5ns.

138 ULTRASONICS July 1968