Abstract: An apparatus for detecting and measuring changes in the shape of a wall of a body includes a detector capsule adapted for attachment to the wall and pneumatically connected to a volume transducer responsive to changes in the internal volume of the apparatus produced by changes in the shape of the wall. The internal volume of the capsule is partially defined by a flexible diaphragm for engagement and complementary movement with the wall. The capsule contains a resiliently deformable material which presses the diaphragm into contact with the wall regardless of the convex or concave shape of the wall.

Abstract: A cam and follower arrangement in which the cam consists of a track carried by a rotatable member. The track has one or more abrupt directional transitions (17) and the follower (17) is biassed to engage one wall or the other (21) of the track (21) appropriate to the direction of rotation of the member by means including a direct-current electric motor operated in a stalled condition. The arrangement may be employed in a monochromator for spectrophotometric apparatus to drive a filter-holder to position one of a number of optical filters arranged in the incoming beam of light.

Abstract: A panel-mountable fuseholder for a cartridge fuse comprises a substantially cylindrical body open at one end and closed at the other end. The fuseholder is provided with an electrical contact comprising an annular first portion, a second portion extending substantially perpendicular to the plane of the annulus and having a terminal outside the body of the fuseholder, and a third portion extending substantially perpendicular to the plane of the annulus on the same side of the plane as the second portion. The second portion has a projecting tongue which engages the fuseholder body to retain the contact therein. The third portion resists the tendency of the contact to tip and become dislodged when the terminal of the second portion is bent away from the fuseholder body to facilitate soldering of a lead to such terminal.

Abstract: A device for maintaining the temperature of a body at a desired value comprises a thermo-electric heat pump sandwiched between a thermally conductive member and a heat sink. The heat sink is maintained at a substantially constant temperature above the ambient temperature by an electrical heating element. This arrangement reduces the effect of changes in ambient temperature and enables the heat pump to work across a substantially constant temperature differential.

Abstract: A dual beam spectrophotometer includes a radiation chopper, a monochrometer, and a diffraction grating moved by a stepper motor. The chopper includes a gate pulse generator which produces gate pulses G.sub.S and G.sub.R corresponding to periods during which radiation from the source passes through a sample cell and a reference cell respectively. A stepper motor drive circuit produces pulses to step the stepper motor which are synchronized with the chopping cycle by means of the G.sub.R and G.sub.S pulses. The stepper motor is arranged to step an equal number of times in each half of a chopping cycle. A further condition which is preferably satisfied is that the first pulse of a sequence should start in the opposite half of the chopping cycle from that in which the first pulse started in a previous chopping cycle. At low stepping rates the motor will step twice in one chopping cycle and then pause for several cycles before again stepping twice.

Abstract: An automatic sample supply apparatus is provided with a delivery tube which aspirates liquid samples from sample containers mounted on a turntable and delivers the samples to a dosing aperture of a graphite tube of an atomic absorption spectrophotometer or to the sample input of other analytical instruments. The turntable also carries at least one flushing discharge container which is of similar form to the sample container, but has an aperture in the side wall. When the turntable is indexed so that the delivery tube enters the flushing discharge container, a solenoid valve is opened to allow a flushing liquid from a container to flow through the delivery tube and into the flushing discharge container. The aperture in the wall of the flushing discharge container is dimensioned so that the flushing liquid will only flow through it when a given head of liquid exists above the top of the aperture.

Abstract: A dual beam spectrophotometer includes signal processing circuitry for producing sample-dark and reference-dark signals. The dark signals substracted from the sample and reference signals are the average of the dark signals produced on each side of the sample and reference pulses. The signal processing circuitry may comprise four sample and hold circuits which store the sample signal, reference signal and first and second dark signals, a resistive combining network for the two dark signals and first and second substractor circuits. The first substractor circuit provides the sample-dark signal at its output while the second substractor circuit provides the reference-dark signal at its output.

Abstract: A displaceable combination of a sample solution cell and a one-piece plastic stirrer is provided for spectrophotometry. The cell has an opening at one end through which the stirrer is inserted and arranged for reciprocation in the cell by engagement of a portion outside the cell. The stirrer is also arranged to sit in the cell during passage of radiation therethrough upon spectrophotographic measurement of the sample.

Abstract: An apparatus is provided for detecting trace quantities of chemical species in the form of a vapor by subjecting ions produced in a sample of the mixed gas under flow to an ion repulsive electric field which is directed in the opposite direction to the flow of the gases, and comprises a fan for drawing the sample through a hollow body, having an inlet, a first region containing means for ionizing at least a proportion of the molecules of the sample by a corona discharge, a second region in which the sample is subjected to an oppositely directed ion repulsive electric field and a third region having an electrode for collecting ions of selected polarity. Ions of a selected polarity whose ionic mobilities exceed a value dependent on the strength of the ion repulsive electric field and the velocity of the gas flow are prevented from entering the third region. A resistor may be provided to limit the current of the corona electric discharge to a value not greater than 100 nanoamps.

Abstract: A load weighing system for a fork lift truck uses load cell transducers to measure the compressive forces exerted between a supporting chain or chains which support(s) the load forks and an anchorage point for the chain(s).

Abstract: An apparatus for detecting the presence of explosives by screening subjects passing through a controlled axis tunnel, the apparatus comprising a substantially open ended tunnel having a cross-section so that subjects can proceed in a single file through the tunnel. The apparatus further comprises a first pair of apertures, one in each side wall of the tunnel located at a first distance from an entrance to the tunnel, and a second pair of apertures, one in each side wall of the tunnel, located at a second distance greater than the first distance from the entrance to the tunnel. Air duct means extend between the various apertures. Also included are means for inducing a circulatory flow of air through the air duct means and across the tunnel between the apertures and, further, means for detecting the vapor of an explosive substance in the air in such duct means.

Abstract: A transport mechanism for transporting a series of carrier members carrying a plurality of receptacles through a processing zone wherein the carrier members are sequentially driven in a first passageway and are passed to a second and optionally to athird passageway by (a) angled guide grooves in the base of each member and pivots in the floor of the passageway and (b) angled camming surfaces respectively at the leading edge of each carrier member and at an appropriate corner between the first passageway and the second passageway. Each carrier member may contain materials in the receptacles for sampling, analysing or for automatic laboratory testing in the processing zone.

Abstract: An apparatus for delivering fluid at a controlled rate of flow wherein fluid is forced from a container by the piston of a vacuum cylinder. A flow restricting valve is provided, either at the output of the container or at the output of a second cylinder which is coupled to the piston of the vacuum cylinder.