Abstract: There is disclosed an apparatus and method for detecting cavitation in fluid machines, for example pumps (100). In one embodiment a piezoelectric gasket (102) is used as a sensor to sense cavitation. In some embodiments highpass filters (302), (501) are used to detect ultrasonic acoustic signals in about the MHz range. If the energy in the MHz range is excessive then cavitation is deemed to be occurring and the speed of a motor (110) may be reduced in proportion to the degree of cavitation deemed to be occurring. In another embodiment (FIG. 5) the energy in the MHz range is normalized against the energy in the kHz range. Other sensors (600, 701) are also disclosed.

Abstract: A calibration device and method for lateral force calibration in small force measuring devices such as atomic force microscopes is disclosed. A platform has a substantially planar surface including a slot for accommodating at least part of the AFM cantilever tip, one or more supporting legs arranged to provide sprung resistance to the platform and a capacitive drive means for driving the platform laterally with respect to the AFM cantilever tip.

Abstract: A calibration device is disclosed. A platform has a substantially planar surface suitable for the landing of an AFM cantilever tip, one or more supporting legs arranged to provide sprung resistance to the platform and a capacitive sensor for measuring the combined spring constant of the one or more supporting legs with respect to displacement substantially perpendicular to said substantially planar surface.

Abstract: A calibration device and method for lateral force calibration in small force measuring devices such as atomic force microscopes is disclosed. A platform has a substantially planar surface including a slot for accommodating at least part of the AFM cantilever tip, one or more supporting legs arranged to provide sprung resistance to the platform and a capacitive drive means for driving the platform laterally with respect to the AFM cantilever tip.

Abstract: An ultrasonic power meter is provided for measuring ultrasonic power emitted by a device (18) under test. The meter includes a casing forming a chamber (16) within which an ultrasonic absorber (14) formed from polyurethane material is located. Overlying the absorber (14) is a membrane (12) of polyvinylidene fluoride which acts as a pyroelectric detector. The meter also includes a transfer medium (10), typically water, for allowing the transfer of ultrasonic energy emitted from a device (18) under test to the meter.

Abstract: An injection moulding system optimises the injection moulding process by removing selected articles (100) from a plurality of articles produced cyclically and tests a plurality of physical properties (105) of the removed articles including dimensions (106), weight (108) and gloss (107), together with a plurality of process parameters (109, 110) such as nozzle pressure and nozzle temperature. Adjustment of the process (121) is made automatically on the basis of up to three optimisers (114), including a case based reasoning optimiser (115), a fuzzy optimiser (116) and a rule based reasoning optimiser (117), in order to achieve pre-set article properties. The optimisers (114) can have confidence factors associated therewith, determined on the effect of previous process adjustments.

Abstract: A cavitation sensor includes an ultrasonically absorbent coating (20) disposed around a piezoelectric element (30) and a conduit (25). The conduit (25) includes a boundary delimited by the piezoelectric element (30), while the ultrasonically absorbent coating (20) is substantially transparent to acoustic driving field frequencies. The sensor is more accurate than prior art sensors.

Abstract: An NMR level gauging device comprising two sets of coils (2, 3) would ortonal to one another about a tank (1). Each set is spaced apart about the tank (1) so as to be capable of providing a substantially uniform magnetic field through the tank when an electric current passes through them. A steady dc current being supplied to coils (2) from a supply (4) and an oscillating electromagnetic field at one or more fixed frequencies is supplied to coils (3) from supply (5); the sets of coils (2, 3) together providing for a substantially position independent sampling of a substance of interest i.eg. fuel, within the tank (1). Detection means (6, 7) are provided for detecting the amplitude of an induced resonance signal in the substance of interest and to provide an amplitude dependent output as a gauge of the amount of substance in the tank (1).

Abstract: A tracking system is provided for tracking while determining the position of a point relative to a datum and includes a carriage (4) rotatably mounted on a frame (1) and which can rotate around a precision sphere (2). An interferometer (16) is mounted so as to rotate with the carriage (4), such that a mechanical center of rotation of the device and the measurement datum of the interferometer coincide at the same point.

Abstract: A method of determining a response characteristic of a microwave device includes coupling a microwave resonator to the device, loading the resonator with microwave radiation, monitoring the time decay of power from the resonator, and comparing the monitored time decay with a known characteristic of the time decay of radiation in the microwave resonator when loaded with radiation.

Abstract: A radiation resistant meter for use in intense ionising radiation fields ludes a meter unit (10) coupled to a separate processing and indicating unit (50) by means of a radio link (24,35). Radiation sensitive components in the voltage amplifier (14) and low frequency oscillator (16) are replaced by valves. Certain radiation sensitive components are covered in a potting compound. A calibration system formed from five zener voltage references (28) is located close to the sensor (12) and coupled to the same circuitry by a multiplexer (30), as is a thermistor (24) the signals from the components (12,26,28) are fed to the amplifier (14) in cyclical manner and processed by a computer (40) in the receiving unit (50). From the calibration voltages (28), the computer determines a calibration curve used for determining the magnitude of the parameter sensed by the sensor (12). The meter can operate at and measure radiation levels far higher than previously known equipment.

Abstract: Apparatus (2) for verifying the performance of optical fibre measurement equipment, comprising a housing (4), a length of optical fibre (6) in a main storage compartment (8), a first compartment (10) containing a first end (12) of the optical fibre (6) that is in the main storage compartment (8), and a second compartment (14) containing a second end (16) of the optical fibre (6) that is in the main storage compartment (8), the optical fibre (6) being stored under substantially zero tension, the first end (12) of the optical fibre (6) being a source end of the optical fibre (6), and the second end (16) of the optical fibre (6) being a detector end of the optical fibre (6).

Abstract: Optical long-path gas monitoring apparatus (2) comprising means (4) for providing a radiation beam, a modulator (10) for modulating the wavelength of the radiation beam such as to produce amplitude modulation of the beam in the presence of the gas being monitored, a radiation detector (12) for conversion of the radiation beam into an electrical signal, and a signal processor (PSD 1,PSD 2) for demodulating the electrical signal to provide a signal dependent upon the gas.

Abstract: A source of seismic waves operable within a borehole filled with liquid crises a module supported by a cable. The module includes means to generate a high voltage and to charge a bank of capacitors, and means to connect the capacitors across a pair of electrodes forming a spark gap. The electrodes are immersed in liquid at the same pressure as the borehole liquid and acoustically continuous with it, and are separated by a gap of width between 0.5 and 20 mm. If the gap is greater than about 5 mm, both the electrodes should be covered with insulation except at the positions where the spark is to be formed. The module can operate automatically at considerable depths and at high pressures.

Abstract: A heat exchanger including a plurality of fluid pathways (13, 15, 16, 17, ) in which at least some are defined between surfaces of unperforated primary plates (10). Between the primary plates (10) are at least two secondary perforated plates (12) extending along the fluid pathway (13, 15, 16, 17, 18) with perforations (11) in adjacent plates (12) being staggered. Adjacent secondary (12) and primary (10) sheets are in contact such that conducting pathways (19) are formed extending between the two primary surfaces while areas of secondary plates (12) not in contact with other secondary plates (12) constitute secondary surfaces (22).

Abstract: Disclosed is a device for lifting a single layer of fabric or fiber reinfed plastic sheets from a stack of such sheets with minimal damage to the structure of the fabric. A frame and a flexible base plate are provided with a plurality of individual needle gripper devices located at opposite ends of the base plate. Each needle gripper device includes a needle of arcuate form rotatably mounted about an axis of its arc so that when the needle rotates, the tip of the needle will penetrate a fabric sheet upon which the apparatus is placed and then roll the sheet relative to the frame so that the sheet is peeled away from its original position without stretching or deformation of the fabric.

Abstract: A flow meter for measuring liquid and gaseous flow rates in a mixed fluid ow has one or more helical fins (17) positioned between a cylindrical sleeve (10) and a core member (11). Centrifugal effects resulting from fluid flow though channels (29) defined between fins (17) sleeve (10) and core (11) separate liquid and gaseous phases, and the gaseous phase passes through bores (28) in the core member (11) to a central cavity (19) substantially closed at an upstream end (12). Liquid flow rate is measured in a channel (16) between the sleeve (10) and core member (11) after removal therefrom of gas, and gaseous flow is measured at an open downstream end (14) of the cavity (19). Flow rates may be measured using, for example, venturis (16,32,33,27,30,31). After measurement of the flow rates the liquid and gaseous phases are allowed to remix.

Abstract: A stabilized helium-neon laser emits radiation in the ranges of ultra-violet, infra-red and visible other than red in at least two modes. A stabilizing system consists of an alignment heater (19) which bends the laser tubes toward optimum alignment, a coil heater (20) which cyclically varies the tube length and permanent magnets (24,25) which reduce instability of mode polarizations and to optimize relative intensities of the modes. The transmitted output is stabilized in frequency by control of the laser tube length, with the stabilization signal derived from the steady or varying intensity of intensities of one or both of two orthogonally polarized optical outputs. There are many potential uses for non-red helium-neon lasers in applications where non-red light is required, for example, in multi-wavelength interferometry.

Abstract: In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.

Abstract: A plain bearing slide system has a carriage mounted on a slide by use of bearing pads. Each bearing pad is coated with a layer of polymeric material having a convex surface, and is arranged to ride on a counterface. The combined thickness of the layer and a layer providing the counterface is such that the difference between the static and dynamic coefficients of friction is substantially less than the difference associated with the material when used in bulk bearings. A slide system using PTFE, and with a combined thickness of the layers of 2 to 3 micrometers, operated as a measuring instrument under ambient conditions such that the PTFE is substantially non-eroding, has proved capable of providing measurements to an accuracy of 0.05 nanometers.