Abstract: An electromagnetic flowmeter is tested and calibrated in situ by measuring the impedance of the drive coil, and the isolation to ground impedance of the coil and of the flowmeter sensor electrodes. Testing is effected by portable field equipment or by a built-in test equipment facility with the flowmeter transmitter.

Abstract: Impedance between potential sensing electrodes of a high impedance meter is measured by applying a ramp waveform through a capacitor coupled to one of the electrodes to generate a substantially constant current, a measure of impedance being obtained by comparing this to the potential developed across the electrodes when a different current is flowing.

Abstract: In a coriolis flow meter, two drivers are provided and a measure of mass flow rate derived from the adjustment of the input signals to each driver required to achieve a desired phase shift in the output. This may give higher accuracy compared to conventional meters in which the phase shift is simply measured, and may also enable determination of other characteristics of the fluid.

Abstract: A method of measuring a characteristic of a flowing fluid comprising measuring said characteristic by means of two or more sensors which have differing responses to a variable affecting said measurement, and combining the outputs (as herein defined) of the sensors, so that the differences in the responses thereof cancel each other and the combined output is substantially independent of said variable.

Abstract: A method of assembling an electromagnetic flow sensor which includes a length of tubular material (referred to herein as a “spool”) (1) intended to be fitted with a tubular insert (2) that is anchored relative to the spool once the spool is fitted into the pipeline. Sealing is preferably achieved by means of extensions of the insert material (typically elastomer) intended to be trapped between end fittings of the spool and abutting ends of the pipeline and secured when the spool is connected in fluid-tight manner to the pipeline. The insert is preferably reinforced against deformation under the application of pressure, and this can be achieved by incorporating one or more bands (4) of suitable material into the insert.

Abstract: A chart recorder method and apparatus wherein a recording head records a plurality of different colored line segments on a recording medium, a head drive moves the recording head and the recording medium reciprocally relative to each other in a scanning direction, a recording medium drive moves the recording medium and the recording head relative to each other in a sub-scanning direction, a component receives a plurality of signals to be recorded on the recording medium as a corresponding plurality of traces to be recorded by the recording head, and a control circuit controls the recording head so that at least one of the traces is formed by line segments which change color cyclically.

Abstract: A sensor for measuring sulphur dioxide in flue gases comprises a sensing electrolyte of doped .beta.-alumina or doped NASICON. The dopant serves to increase conductivity at grain boundaries in the sensing element or at the electrode interface, thereby to increase the rate of depolarisation. Preferred dopants are copper silver and nickel.