Abstract: Measurement apparatus performs a measurement of insulation resistance of an electrical insulator by applying a voltage to the electrical insulator, increasing the voltage with time, and measuring the resulting current through the electrical insulator. An output from an electrical circuit for measuring current through the electrical insulator is sampled by iteratively performing steps of producing samples representing currents measured when the voltage applied to the electrical insulator is increased by successive increments. For each iteration, a threshold is determined for the current measured in the iteration by processing at least one sample measured for the respective iteration and samples measured for a plurality of previous iterations. Increasing the voltage applied to the electrical insulator is stopped in response to the current measured in the iteration exceeding the determined threshold.

Abstract: Measurement apparatus performs a measurement of a quality indicator for an electrical insulator comprising a ratio of a first value of an electrical parameter at a first time to a second value at a second time. An output from an electrical circuit for measuring the electrical parameter for the electrical insulator is sampled to produce at least one sample and steps of sampling the output from the electrical circuit are performed to produce one or more further samples at successive increments in time and at least some of the samples are processed to generate an approximate function relating the measured electrical parameter to time. A predicted value is calculated for the quality indicator on a basis comprising the electrical parameter indicated by the approximate function for the second time and an electrical signal is generated indicating a state of the measurement based on at least the predicted value of the quality indicator.

Abstract: Loop resistance is measured in a live-earth conductor loop comprising a residual current device powered by an alternating current mains supply. A measurement circuit having a low-pass filter characteristic arranged to substantially remove signal components at the frequency of the alternating current mains supply is used to measure, in a first period, a voltage across live and earth conductors of the live-earth conductor loop to determine a first voltage. A current application circuit is used to apply a unipolar test current having a magnitude below a trip current value of the residual current device for a second period and the measurement circuit is used to measure a second voltage between the live and earth conductors. Based on a difference in test current between the first and second periods and a difference in voltage between the first voltage and the second voltage, the resistance of the live-earth conductor loop is calculated.

Abstract: In a meter for performing a measurement of an electrical parameter, an output from a sensor is sampled to produce at least one sample, and an iterative method is performed comprising: producing further samples; holding in memory a stored array of samples comprising the at least one sample and each of the further samples from each iteration; determining a measure of statistical variability of a mean for the respective iteration from a measure of statistical variability and from the number of samples used to generate the measure of statistical variability; comparing the measure of statistical variability of the mean with a pre-determined threshold; and generating an electrical signal indicating a state of the measurement if the measure of statistical variability of the mean of the samples taken during the measurement is less than or equal to the pre-determined threshold.

Abstract: In a meter for performing a measurement of an electrical parameter, an output from a sensor is sampled to produce at least one sample, and an iterative method is performed comprising: producing further samples; holding in memory a stored array of samples comprising the at least one sample and each of the further samples from each iteration; determining a measure of statistical variability of a mean for the respective iteration from a measure of statistical variability and from the number of samples used to generate the measure of statistical variability; comparing the measure of statistical variability of the mean with a pre-determined threshold; and generating an electrical signal indicating a state of the measurement if the measure of statistical variability of the mean of the samples taken during the measurement is less than or equal to the pre-determined threshold.

Abstract: In a meter for performing a measurement of an electrical parameter, an output from a sensor is sampled to produce at least one sample, and an iterative method is performed comprising: producing further samples; holding in memory a stored array of samples comprising the at least one sample and each of the further samples from each iteration; determining a measure of statistical variability of a mean for the respective iteration from a measure of statistical variability and from the number of samples used to generate the measure of statistical variability; comparing the measure of statistical variability of the mean with a pre-determined threshold; and generating an electrical signal indicating a state of the measurement if the measure of statistical variability of the mean of the samples taken during the measurement is less than or equal to the pre-determined threshold.

Abstract: Loop resistance is measured in a live-earth conductor loop comprising a residual current device powered by an alternating current mains supply. A measurement circuit having a low-pass filter characteristic arranged to substantially remove signal components at the frequency of the alternating current mains supply is used to measure, in a first period, a voltage across live and earth conductors of the live-earth conductor loop to determine a first voltage. A current application circuit is used to apply a unipolar test current having a magnitude below a trip current value of the residual current device for a second period and the measurement circuit is used to measure a second voltage between the live and earth conductors. Based on a difference in test current between the first and second periods and a difference in voltage between the first voltage and the second voltage, the resistance of the live-earth conductor loop is calculated.

Abstract: An electrical plug for testing an electrical mains socket is provided. The plug comprises a pin for engagement with a pin receptor of the mains socket. The pin comprises first and second electrical contacts, each comprising a surface portion to engage with a different respective region of the receptor. The first and second contacts are electrically isolated from one another at the pin. An electrical testing system and a method of testing an electrical mains socket is provided. The testing system comprises the electrical plug and a first circuit connected to the contacts and configured to measure an electrical resistance therebetween. The method includes providing the electrical plug and measuring an electrical resistance between the electrical contacts. A further method is provided for testing an electrical mains plug comprising a pin, by providing an electrical socket with a pin receptor having first and second regions electrically isolated from one another.

Abstract: A test lead for an electrical meter is provided. The test lead comprises a flexible elongate member comprising a current sensing coil at least partially disposed about a flexible core along the length of the member. A first connector is disposed at one end of the member for coupling a respective end of the current sensing coil to a test port of an electrical meter. A second connector is disposed at an opposing end of the member for coupling a respective end of the current sensing coil to an electrically conductive member, to provide an electrical path, via the sensing coil, from the electrically conductive member to the first connector.

Abstract: A flexible electrical current sensor is provided, the flexible electrical current sensor comprising a solenoid disposed about an at least partially magnetic core. The at least partially magnetic core comprises at least one magnetic element. The at least one magnetic element is configured to provide one or more regions of overlap such that a respective gap is provided in each region of overlap. Each respective gap is configured such that the effective magnetic permeability of the at least partially magnetic core is maintained during flexing.

Abstract: An electrical plug for testing an electrical mains socket is provided. The plug comprises a pin for engagement with a pin receptor of the mains socket. The pin comprises first and second electrical contacts, each comprising a surface portion to engage with a different respective region of the receptor. The first and second contacts are electrically isolated from one another at the pin. An electrical testing system and a method of testing an electrical mains socket is provided. The testing system comprises the electrical plug and a first circuit connected to the contacts and configured to measure an electrical resistance therebetween. The method includes providing the electrical plug and measuring an electrical resistance between the electrical contacts. A further method is provided for testing an electrical mains plug comprising a pin, by providing an electrical socket with a pin receptor having first and second regions electrically isolated from one another.

Abstract: A test lead for an electrical meter is provided. The test lead comprises a flexible elongate member comprising a current sensing coil at least partially disposed about a flexible core along the length of the member. A first connector is disposed at one end of the member for coupling a respective end of the current sensing coil to a test port of an electrical meter. A second connector is disposed at an opposing end of the member for coupling a respective end of the current sensing coil to an electrically conductive member, to provide an electrical path, via the sensing coil, from the electrically conductive member to the first connector.

Abstract: In a meter for performing a measurement of an electrical parameter, an output from a sensor is sampled to produce at least one sample, and an iterative method is performed comprising: producing further samples; holding in memory a stored array of samples comprising the at least one sample and each of the further samples from each iteration; determining a measure of statistical variability of a mean for the respective iteration from a measure of statistical variability and from the number of samples used to generate the measure of statistical variability; comparing the measure of statistical variability of the mean with a pre-determined threshold; and generating an electrical signal indicating a state of the measurement if the measure of statistical variability of the mean of the samples taken during the measurement is less than or equal to the pre-determined threshold.

Abstract: A flexible electrical current sensor is provided, the flexible electrical current sensor comprising a solenoid disposed about an at least partially magnetic core. The at least partially magnetic core comprises at least one magnetic element. The at least one magnetic element is configured to provide one or more regions of overlap such that a respective gap is provided in each region of overlap. Each respective gap is configured such that the effective magnetic permeability of the at least partially magnetic core is maintained during flexing.

Abstract: Test apparatus is provided for testing an electrical property of a fluid. The apparatus comprises an electrically conductive container (1) forming an outer electrode of a test cell for containing the fluid, an inner electrode (2) of the test cell, an inductive heating assembly (3) and a cooling means. The inner electrode (2) of the test cell is arranged, when mounted relative to the electrically conductive container (1), to project into, and remain electrically isolated from, the electrically conductive container (1). The inductive heating assembly (3) comprises an inductive heating coil (4), which surrounds the electrically conductive container (1), for heating the electrically conductive container (1) and the inner electrode (2). The cooling means comprises an air channel (9) to allow passage of air across a surface of the electrically conductive container (1), for cooling of the electrically conductive container (1).

Abstract: Test apparatus is provided for testing an electrical property of a fluid. The apparatus comprises an electrically conductive container (1) forming an outer electrode of a test cell for containing the fluid, an inner electrode (2) of the test cell, an inductive heating assembly (3) and a cooling means. The inner electrode (2) of the test cell is arranged, when mounted relative to the electrically conductive container (1), to project into, and remain electrically isolated from, the electrically conductive container (1). The inductive heating assembly (3) comprises an inductive heating coil (4), which surrounds the electrically conductive container (1), for heating the electrically conductive container (1) and the inner electrode (2). The cooling means comprises an air channel (9) to allow passage of air across a surface of the electrically conductive container (1), for cooling of the electrically conductive container (1).

Abstract: A double-clamp earth tester device, having a voltage-inducing transformer (VT) (30), a current-sensing transformer (CT) (32), a voltage source adapted to supply a voltage across a primary winding (31) on the VT core (44) and a signal processing unit (35) adapted to measure a resultant signal output from a secondary winding (33) on the CT core (46), is susceptible to errors induced by electromagnetic interference between the cores (44, 46) of the two transformers. Previously, the effects of this interference have been mitigated by surrounding one or both cores (44, 46) with electromagnetic shielding (42). This had lead to devices having a bulky head portion and attendant difficulties in accessing sites having restricted access (52). These problems have been overcome by providing means to modify the signal output form the secondary winding (33).