Abstract: The detector elements are sensitive to the target presence in their respective vicinities and are distributed in the surveillance zone. First differences (S1-S2, S3-S2, S4-S2) are formed from outputs of the detector elements taken pairwise, and at least one other first difference (S3-S2, S4-S2) previously filtered in a filter (213, 213') is subtracted from each first difference (S1-S2) to form a second difference, where said filter is controlled to minimize the value of the second difference in the absence of a target, and the second differences so obtained are used (216) to detect the target. In particular the invention applies to detecting submarines using magnetometer buoys.

Abstract: An arc detection method and apparatus is provided for an electric circuit having an electrified conductor (46) connecting a voltage source (26) to a load (30). The arc detector includes a field sensor (62) sensing an electromagnetic field established about the conductor by the occurrence of an electrical arc in the circuit, and generating a field responsive signal in response thereto. Arc discrimination circuitry responds to the field sensor and generates a tentative arc signal in response to a given characteristic of the field responsive signal. Arc timing window circuitry responds to the arc discrimination circuitry and generates a confirmed arc signal in response to a given timing characteristic of the tentative arc signal.

Abstract: A system for detecting and positioning objects, the electric conductivity of which differs from the surrounding medium thereof by measuring variations in an electric field generated into the medium. More precisely, the invention concerns a method and assembly for detecting objects or objectives, for example vessels, in electrically conductive medium, for example sea, by measuring changes, disturbances, signs, indications or the like caused by the object or objective, especially for surveying water fairways and/or extent.

Abstract: Apparatus and method for measuring power density in an energized volume of water using either a measurement of voltage gradient or current density for use in determining optimal electrical power parameters for electrofishing, in-water electroshocking, electrical barrier control and the like. Specific probes for either measurement are disclosed. A calculator or programmed microprocessor receives measurements of current density or voltage gradient and water conductivity at a selected location within an energized liquid body and performs the mathematical operations necessary to calculate power density. Values on a graph of water conductivity, current density, voltage density and power density are used to determine how much electrical power to apply to a specific organism in a specific volume of liquid.

Abstract: A method of determining the percentage gas content of an insulating glass window unit or the like comprises the steps of applying a voltage to opposed panes of the unit, progressively increasing the voltage, monitoring the voltage and recording the magnitude of the voltage at which a continuous discharge occurs, or is about to occur, between the electrodes and converting the magnitude to a number indicative of the percentage gas content of the gas between the panes.

Abstract: Method and apparatus of charge distribution analysis insulating and semiconducting dielectric materials to measure by using a Coulomb Balance surface/subsurface space charge layers and the sign, mobility and polarizability of charge carriers. The technique includes measuring the force, attractive or repellent, between a bias electrode to which a voltage is applied and a dielectric material in a condensor half cell arrangement. An apparatus is provided for heating a sample for causing the generation of surface/subsurface charges, and then for applying an external potential while the sample is maintained at a high temperature. The effective mass of the sample is detected by determining the amount of force necessary to restore a balance arm, by which the sample is supported, to its original position, the alteration in position being due to attractive or repulsive electrostatic forces between the sample and the electrodes.

Abstract: An omnidirectional lightning ranging, identification and protection system having circuits that produce no false alarms or failures to alarm, responsive to cloud to ground and cloud discharges, capable of differentiating between cloud to ground and cloud discharges insensitive to background noise, autonomous with respect to power and communications conductors for operating reliably in the presence of nearby lightning discharges, requiring no field calibration, that provides local and remote lightning rate and range data, and that provides mechanisms for automatically signalling and disconnecting electrical equipment for the purpose of lightning protection. The system has circuits that are responsive to the electric field changes produced by lightning discharges in the frequency range between 2 khz and about 200 khz and to time coincident optical radiation in the 6000 to 9000 angstroms wavelength range.

Abstract: Method for determining the susceptibility of a protective device protected electronic assembly to electrostatic discharge events. The protective component is subjected to an electrostatic discharge event and the amount of kinetic energy transferred to the protective component during the electrostatic discharge event is determined. The susceptibility of the assembly to electrostatic discharge events is then determined based upon the amount of kinetic energy transferred to the protective component during the electrostatic discharge event.

Abstract: A method is described for determining the return stroke polarity of distant lightning for distances beyond 600 km by detecting the electric field associated with a return stroke of distant lightning, and processing the electric field signal to determine the polarity of the slow tail of the VLF waveform signal associated with the detected electric field. The polarity of the return stroke of distant lightning is determined based upon the polarity of the slow tail portion of the waveform.

Abstract: A meter (10) for measuring extremely-low-frequency radiation includes a coil circuit (22) whose output is filtered by a sharp-cut-off high-pass filter (24) to pass standard house-current frequencies but suppress the frequency components that would predominate as a result of movement of the meter with respect to the earth's magnetic field. An integrator (26) compensates for the frequency response of the coil circuit (22), an RMS circuit (35) converts the signal to its root-mean-square value, and a display circuit (28) provides a display determined by the resultant signal.

Abstract: A digital, high-voltage meter device is comprised of two poles, each having a probe connected to high-voltage resistors. The resistors are connected to supply low-voltage inputs to a digital voltmeter. In a modification, one of the poles including its probe and high-voltage resistor, is replaced by a connector, such as an alligator clip, adapted to be releasably connected to system ground.

Abstract: A method for measuring the field pattern of electrical or magnetic fields using a sensor arrangement, for determining the spatial position of a biological power source is disclosed which compensates for background activity. The method includes the steps of measuring the background activity at a time before the biological power source is stimulated, and the resultant signal vector of the background activity is formed. This signal vector of the background activity is vectorially subtracted from each resultant vector of the subsequently obtained values from the biological power source, so that a signal vector is obtained which is essentially caused only by the current from the power source. A weighting factor, which varies the length of the vector of the background field, is iteratively calculated together with the source parameters for the biological power source by error minimization, so that the parameters of the power source can be optimally portrayed.

Abstract: An integrated circuit (11) is tested at a high microwave frequency through the use of a laser beam (19) having a repetition rate much lower than the test frequency. Electric fields of the test signal extend into an electro-optic material (12) that modulates part of the laser beam. Another part of the laser beam is converted to an electrical pulsed signal that is applied to a microwave mixer (33) along with part of the test frequency signal. A harmonic of the pulsed signal mixes with the test frequency to yield a difference frequency that can be used as a phase reference for analyzing the phase of the test signal. The component pulses (30) of the laser beam have a pulse width which is much shorter than the separation of the pulses, which make it inherently rich in higher harmonics of the fundamental pulse repetition rate.

Abstract: The Stripline Fast Faraday Cup is a device which is used to quantitatively and qualitatively measure gigahertz time structure characteristics of ion beams with energies up to at least 30 Mev per nucleon. A stripline geometry is employed in conjunction with an electrostatic screen and a Faraday cup to provide for analysis of the structural characteristics of an ion beam. The stripline geometry allows for a large reduction in the size of the instrument while the electrostatic screen permits measurements of the properties associated with low speed ion beams.

Abstract: An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors.

Abstract: A current transformer detects a ground fault current and outputs a secondary current signal to heat a filament disposed in an airtight flash lamp upon the occurrence of a ground fault. With heating of the filament, an ignition material is ignited in the lamp and causes weakening of the glass bulb of the lamp. A moving member pressing against the lamp shatters the weakened lamp and is displaced, thus releasing an indicator to project from a holder to a ground fault indicating position.

Abstract: An optical transformer comprises at least two potential dividing capacitors connected in series to each other are connected between a high-voltage conductor and an intermediate electrode or between the intermediate electrode and the ground, and optical voltage sensors connected in parallel to the respective potential dividing capacitors and capable of modulating light in accordance with voltage. In another form, the optical transformer has a single potential dividing capacitor connected between a high-voltage conductor and an intermediate electrode or between the intermediate electrode and the ground, and at least two circuits connected in parallel with the potential dividing capacitor, each circuit including a series the connection of an optical voltage sensor for modulating light in accordance with the voltage and a resistor or an impedance.

Abstract: In an interferometric fiberoptic sensor with homodyne detection for measuring electrical fields or voltages, the measurement signal is compensated separately from operating point control. The measurement signal originating from the electrical field is compensated in a piezoelectric modulator (5) which consists of modulator elements which are identical with the at least one sensor element (3) with respect to material, geometric shape and crystal orientation. Additional separate apparatus (4) with a sufficiently large phase swing are provided for operating point control. Modulator element and sensor element (3) are essentially at the same temperature so that the temperature-dependence of the matter constants of the sensor element and the temperature-dependence of the fiber interferometer are eliminated. The sensor preferably operates in accordance with the principle of a fiberoptic two-mode interferometer.

Abstract: A device for measuring an electric field comprises three optical fiber sensors, which each have a piezoelectric sensor element, as well as an interferometer for generating a sensor signal. The optical fiber sensors have piezoelectric sensor elements that exclusively detect with the aid of the inverse piezoelectric effect a predetermined directional component, assigned in each case, of the electric field. The directional components of the different sensor elements are each aligned perpendicular to one another. An evaluation circuit determines the absolute value and direction of the electric field from the sensor signals generated.The sensor elements are preferably formed by a single piezoelectric body, on whose faces the sensor fibers are fixed.

Abstract: A system for detecting an arcing fault in a telephone central office DC power distribution conductor repeatedly measures the current flow in the distribution line, as with an inductive coupling, and derives a Fourier transform analysis spectrum from such measurements. The power values at intervals across the frequency spectrum are compared with recorded threshold template values encompassing the spectrum typical of an arcing event and an alarm condition is established when such threshold levels are exceeded.

Abstract: A lightning direction finder controller (LDFC) for use at remote sites in a Lightning Detection Network provides information on lightning return strokes to a network controller. The LDFC digitizes and processes return stroke data from an analogue direction finder unit, time tags each return stroke with an absolute time accurate to the nearest 10.sup.-4 second of NIST time, and provides an interface for satellite and/or land line communication of lightning flash data to the network controller. The LDFC includes a CPU board, a multi-function analogue and digital input/output board that provides an interface to the analog direction finder unit, and an Interface Facility that provides an interface for: satellite and/or bisynchronous communications, a local data storage device, diagnostic devices, and a satellite controlled clock. A watchdog timer on the Interface Facility resets the CPU of the LDFC when data communications cease, or the execution of the main program halts.

Abstract: A high-voltage measuring device includes a grounded, cylindrical outer electrode (1) and an inner coaxial electrode (2) which has an at least approximately cylindrical shape and carries a high-voltage potential. A non-flat high-voltage resistor (3) which is arranged coaxially with respect to the inner electrode and is connected thereto. This resistor extends at least as far as the vicinity of the outer electrode. The response bandwidth and the loadability of the device substantially improved in that the high-voltage resistor is a cone shape envelope of uniform thickness such that the potential variation in response to current flow through the resistor corresponds to the electrostatic potential variation at least at the area of the inner electrode.

Abstract: The turns of an optical fiber paid out from a canistor are counted, and the signature of the optical fiber is measured, by monitoring the electromagnetic field of the charge on the optical fiber as it moves past an antenna. The optical fiber follows a helical path as it is paid out. A stationary antenna located transversely proximate the payout region detects a periodic repeating variation of the bound and/or free electrical charge associated with the optical fiber, as the optical fiber periodically moves closer to and farther from the antenna along the helical path. Each period of the variation corresponds to one turn of optical fiber paid out from the canister.

Abstract: A system for predicting the occurence of microburst/windshear comprising at least one sensor for receiving lightning produced signals, a processor for processing those received signals to produce data and generate a warning when the processed data indicates that a microburst/windshear is about to occur.

Abstract: The detection of brief pulses generating high frequencies is carried out by a system including: sensor for detecting an electrostatic field and for detecting an electromagnetic field, such that the variation of the electrostatic field ocurring in a period of time of less than 1 millisecond may be identified. A signal activator for warning about the presence, in an interval of time of less than 1 millisecond, of the variation of the electrostatic field detected and of the electromagnetic field, allowing identification of a pulse due to an electrostatic discharge from furniture or human beings. The invention is applicable to the detection of pulses due to electrostatic discharges.

Abstract: The invention is an instrument for determining the work functions (unbiased) or absolute surface potentials (biased) of conducting sample surfaces. These values are inferred from measured surface potential differences between the sample and the instrument's non-contacting sensor. Charge incurred in the sensor by the proximity and surface potential of the sample surface alters the impedance of a semiconductor channel within the sensor. The deviation in the charge dependent impedance of the sensor from a calibrated zero-field reference is used by a feedback controller to alter the base potential of the sensor to eliminate the deviation signal. In this state, the surface potential of the sensor matches that of the sample thus forming a zero-field condition, as a result no charge is induced in the sensor. The surface potential difference between the sample and the sensor is then equal to the sensor base voltage, which is directly measured by a voltmeter.

Abstract: A device to remove the dead band in atmospheric electric potential measurements while maintaining a low leakage path to ground. In one embodiment the device comprises a AC high voltage source connected through a high ohm resistor and capacitor network to a sharp corona point and a means for measuring the current through the corona point.

Abstract: The performance of a device under test is observed with and without the presence of controlled EMI fields. Voltage signals from the device under test are transmitted to an oscilloscope by overdamped conductors, a hybrid electrical/optical transmitter, a fiber optic cable, a receiver and a conductor cable. The overdamped conductors are transparent to the EMI fields and the current in those conductors is kept very small by the use of a very high input impedance in the transmitter. The hybrid transmitter may be an analog or a digital transmitter.

Abstract: A fiber-optic voltage sensor comprises at least one fiber-optic, piezoelectric sensor element (2a, 2b, 2c, 2d), which measures a predeterminable directional component of a local electric field. One or more than one piezoelectric sensor elements (2a, 2b, 2c, 2d) are arranged serially between two ends of the fiber-optic voltage sensor, each piezoelectric sensor element (2a, 2b, 2c, 2d) respectively measuring a directional component of a local electric field, which component lies parallel to a path element assigned to it, the path elements as a whole forming an open polygon connecting the two ends of the fiber-optic voltage sensor. Each sensor element (2a, 2b, 2c, 2d) has a gain which is proportional to a length of the path element assigned to it. In a preferred embodiment, the piezoelectric sensor elements (2a, 2b, 2c, 2d) are connected by spacers (3a, 3b, 3c).

Abstract: A method and an apparatus for measuring a flight path parameter of a projectile (7) or parts thereof during flight possibly into the region of the target, with the electrical charge imparted to the projectile (7) or its part by friction with the air and/or by the gas fumes generated during ignition or detonation being detected by means of at least one inductively operating sensor (1) and the zero passage of the resulting signal is evaluated. The resulting signal can be utilized to measure time of flight, velocity, a time pattern for the distribution of fragments or the like.

Abstract: A sensor for measuring disturbances to an electrostatic field caused by the intrusion of a charged body or a charge producing body. The sensor employs at least two probes displaced from each other which have attached beads of radioactive material to provide free ions in the vicinity of the probe. The free ions enhance the signal created by each probe when it is affected by a disturbance in the electrostatic field in which it resides. The signals thus created are conditioned for transmission to a differential amplifier which combines them and produces an output signal which represents the detection of an intruding charged body, its distance, and its characteristics. The sensor can be configured with more than two probes seeded or placed in an array and a computer for real-time selection of the two yielding optimum signals for charged body location, velocity, direction of travel, and electrostatic signature.

Abstract: An apparatus for sensing the electrical potential of a positive electrostatic field which is primarily below the surface of the earth, and observing the changes in a series of each reading is accomplished by means of an instrument employing a column of mercury in a small-diametered quartz tube, which is open on its lower end with means connecting to the other end for changing the level of mercury within the tube. A conductive coating on the exterior of the tube is connected to an electrometer and the coating is arranged to be selectively grounded or ungrounded in conjunction with changing the level of the mercury column. The readings for the electrometer provide a measure of the electrostatic field.

Abstract: A non-contacting electrostatic voltage follower comprising a detector electrode sensitive to electrostatic quantities such as electrostatic fields, voltages, charges and the like, a modular coupled to the electrode for modulating the capacitance coupling between the electrode and a surface bearing an electrostatic quantity to which the electrode is exposed, a detector amplifier of the current summing type having the summing input thereof connected to the detector electrode, and a high bandwidth amplifier having an input connected to the output of the detector amplifier. A probe comprises a transparent carrier element coupled to the modulator, a first conductive and transparent film on a surface of the carrier and defining the detector electrode, and a second film of conductive and transparent material on the remainder of the surface of the carrier and spaced from the first film.

Abstract: A circuit for providing a scaled sinusoidal voltage proportional to a sinusoidal current referenced to a first reference potential. The scaled sinusoidal voltage is referenced to a second reference potential. A scaling resistor is connected between an operational amplifier inverting input terminal and the operational amplifier output terminal. A transformer has a primary winding in series with the sinusoidal current. A secondary winding has a first terminal coupled to the second reference potential and a second terminal coupled to the operational amplifier inverting input terminal. An integrator has an inverting input terminal coupled to the operational amplifier output terminal, a noninverting input terminal coupled to the second reference potential and an output terminal coupled to the operational amplifier noninverting input terminal.

Abstract: Detection of lightning, storms, or the like via sensing means connected between an external antenna and ground, plus alerting means including gate means and indicator means operatively connected to the sensing means. An unpowered cascaded emitter-follower arrangement of at least a Darlington pair of transistors triggers the gate means when lightning-induced or similar fluctuations in ambient electric field cause the sensing transistors to conduct. A pulse-stretcher between the sensing means and the gate means controls the duration of indication and includes a capacitor connected to discharge through a sensing transistor during conduction of the sensing means and to recharge through a gate transistor during actuation of the indicator means. Resistors between the antenna and ground and between the base and the emitter of the respective transistors in the sensing means preclude actuation by fluctuations characteristic of slower-acting phenomena.

Abstract: Flow measuring apparatus comprising a probe (1) coupled via a coaxial cable (2) to control circuitry with a current to voltage convertor (10), absolute value circuit (12), auto zero switch and integration (11, 27) and voltage to current circuit (18) yielding an analog output, corresponding to flow at the probe.

Abstract: An array of sensors responsive to atmospheric electrostatic fields is deployed, preferably with the sensors elevated above the ground. Suitable sensors are corona point sensors having a stainless steel needle. The corona current signals from the sensors are digitized and processed to determine the peak in the rate of sharp discontinuities in the electrostatic field. The peak in the rate of sharp discontinuities precedes a thunderstorm microburst by several minutes. The signal processing apparatus also generates equipotential contour maps of electrostatic field for spatially locating a microburst. The latter signal may also serve as a predictor for windshear since anomalous electric fields caused by charge carrying downdrafts may occur without lightning.

Abstract: A method and apparatus, including an opto-isolation coupler, for monitoring an electrical parameter of a high voltage circuit. The apparatus comprises monitoring circuitry, a pair of input conductors, and the opto-isolation coupler. The input conductors are coupled to the high voltage circuit. The coupler comprises a holder and a Neon or other glow tube located therein for producing light upon the passage very little electrical current, e.g., in the microamp range, therethrough. The coupler includes a very high resistivity resistor coupled to the input conductors for providing the very low current to the Neon tube, and a phototransistor located within the holder and coupled to the monitoring circuitry to provide an electrical signal in response to the receipt of light from the Neon tube. The holder is a tubular member having a glass barrier wall separating the Neon tube and phototransistor and is encapsulated in a light-tight structure to prevent ambient light from reaching the phototransistor.

Abstract: A ground based conductor motion sensing apparatus is provided for remotely sensing movement of electric power transmission lines, particularly as would occur during the wind induced condition known as galloping. The apparatus is comprised of a motion sensor and signal generating means which are placed underneath a transmission line and will sense changes in the electric field around the line due to excessive line motion. The detector then signals a remote station when a conditioning of galloping is sensed. The apparatus of the present invention is advantageous over the line mounted sensors of the prior art in that it is easier and less hazardous to install. The system can also be modified so that a signal will only be given when particular conditions, such as specific temperature range, large amplitude line motion, or excessive duration of the line motion, are occurring.

Abstract: Electrostatic discharge properties of materials are quantitatively measured and ranked. Samples (20) are rotated on a turntable (15) beneath selectable, co-available electrostatic chargers (30/40), one being a corona charging element (30) and the other a sample-engaging triboelectric charging element (40). They then pass under a voltage meter (25) to measure the amount of residual charge on the samples (20). After charging is discontinued, measurements are continued to record the charge decay history over time.

Abstract: The present invention relates to a system for acquisition and separation of the effects of simultaneous sources of electromagnetic field. According to the invention the system comprises an array of n pick-ups (1a . . . 1e) connected to registration means (2), the minimum number n of pick-ups per array being equal to 2s+2, where s is equal to a number of simultaneous sources to be analysed.

Abstract: The invention relates to an apparatus for detecting an electromagnetic pulse having a given origin, more particularly due to a nuclear explosion. This apparatus comprises means for sensing the electrical component of an electromagnetic pulse, means for differentiating a signal supplied by the sensing means from an electromagnetic pulse of a given origin from another pulse and means for taking note of the result of the detection. The differentiation means advantageously comprise means for detecting the passage of the signal supplied by the sensing means at a value exceeding a threshold value, a time counter started by the detection means during the detection of said passage, means for integrating the signal supplied by the sensing means and means for comparing the value of the integrated signal up to time t.sub.1 following the starting of the sensor with a reference value.

Abstract: An apparatus for providing a map-like display of weather phenomena such as lightning discharges, in which the distance from an observation location to the source of the discharge is determined from the ratio of the integrated intensity of two different components of lightning produced signals, the intensity of the first component varying as the inverse of the distance and the intensity of the second component varying as the inverse of the square of the distance.

Abstract: A voltage measurement circuit is provided which can be used in a single supply situation, which has a measurement range from rail to rail and which uses a reference voltage which can lie anywhere between the rails but not at the rail to which measurements are to be referenced. The unknown voltage is sampled to a first plate of a capacitor. The second plate of the capacitor is connected to ground. The first plate of the capacitor is then connected to the first input of a comparator, the second input being connected to receive the reference voltage. If the unknown voltage is less than the reference voltage, the second plate of the capacitor is disconnected from ground and then connected to receive the reference voltage. Otherwise it remains connected to ground. The first plate of the capacitor is then connected to a constant current source, causing the voltage at the first comparator input to decrease linearly with time.

Abstract: In a voltage detector using an electro-optic material whose refractive index is changed by a voltage developing in a selected area of an object under test, an end portion of the electro-optic material has a corner-cube shape, whereby the detection of the voltage can be accurately achieved substantially being free from the influence of the input light tilt to the optical axis.

Abstract: An electrical conductor is spaced close to an insulating web to detect electrostatic surface charges on the surface of the web.

Abstract: The measurement of slowly changing or static electric potential or dielectric polarization is effected by an input circuit which comprises a pair of diodes a pair of resistors and a pair of switches. The diodes are connected in reverse parallel between an input terminal and a pair of output terminals. The circuit detects when the potential rises above a first voltage level, changes the input impedance thereof from high to low, detects when the potential has fallen below a second voltage level, and changes the input impedance back to high. Summation means is provided for summing the above changes in input impedance from which a determination can be made as to whether the potential is steady, increasing or decreasing. The switches are preferably Schmitt triggers having a hysteresis which represents the two reference voltages.

Abstract: The installation comprises a certain number of measuring stations, represed here as three in number referenced respectively 1, 2 and 3, equipped respectively with antennae I.sub.1, I.sub.2, I.sub.3, which are connected by transmission lines L.sub.1, L.sub.2 and L.sub.3 to a central data acquisition unit 4, itself connected to a real time data processing unit 5. The central unit 4 comprises receiving means, means for sorting and associating the data and means for momentary storage of the sorted and associated data.

Abstract: A hermetically sealed, electrically insulative enclosure (A) is surrounded by a Faraday cage (B). At least one electrode (C) is disposed within the hermetically sealed enclosure. The volume of the enclosure is selectively altered such that an initial charge density in the neighborhood of electrod changes, which changes the electrode potential. The change causes a current to flow to or from the electrode which returns the electrode potential and the electrode surrounding space charge toward an equilibrium condition. In one embodiment, a current measuring circuit (D) is disposed between the electrode and the Faraday cage to derive a measure of the current flow therebetween. In another embodiment, a like electrode is disposed within another hermetically, sealed insulative enclosure which is shielded by the same or another Faraday cage. In the second embodiment, the measuring circuit measures the current flow between the two isolated electrodes.

Abstract: A cooled, temperature controlled electrometer for the measurement of small currents. The device employs a thermal transfer system to remove heat from the electrometer circuit and its environment and dissipate it to the external environment by means of a heat sink. The operation of the thermal transfer system is governed by a temperature regulation circuit which activates the thermal transfer system when the temperature of the electrometer circuit and its environment exceeds a level previously inputted to the external variable temperature control circuit. The variable temperature control circuit functions as subpart of the temperature control circuit. To provide temperature stability and uniformity, the electrometer circuit is enclosed by an insulated housing.