Isolation Amplifier Research Articles

電極法による管内粒子の局所平均流速の測定

An electric probe for measuring local velocity of particles in solid-liquid mixtures has been constructed and tested for its performance using four kinds of glass spheres, sand, and an oxidized iron powder.The probe is composed of a supporting bakelite tube (dia. 4mm), a ceramic tube, and three ringlet electrodes made of Pt wire (dia. 0.3mm).The electrodes are axially placed on the surface of the ceramic tube at intervals of 10mm.The fluctuations of differential voltage between the middle and the upstream electrode were cross-correlated with those between the middle and the downstream electrode to determine the transit time in conjunction with the local velocity of particles.Volumetric flow rates calculated from particle velocity distributions of upward flows in a vertical pipeline were compared with those obtained from an electric magnetic flow meter.The accuracy of 6% in the sand and the glass sphere and 8% in the oxidized iron powder was achieved at the discharge velocity of about 3m/s.A comparison of velocity distributions between the probe and the pitot tube in a horizontal pipeline revealed that the pitot tube measurement was insufficient in the region of high solid concentration.Some difficulty was encountered in the measurement of velocity distributions in a steel pipeline due to the electric effect of the steel pipe. It was, however, solved by means of isolation amplifiers introduced into the measuring system.

Magnet Current Bypass Shunt

A precision active shunt has been developed for fine tuning of individual magnet fields in a series magnet string operated from a single power supply. The shunt uses power transistors operated in linear mode to regulate the bypass current in the range 0 to 50 A with precision of ±10 mA. Communication with and control of shunt which may be floating 1000 V or more above earth ground, is by means of transformer coupled isolation amplifiers. Because of reliability requirements, 7 transistors, mounted on demountable water cooled copper plate are used. Low level electronics and current sensing resistor are mounted on the same plate. This paper presents system description and preliminary results.

A channel electron multiplier and optically coupled amplifier used as an incident flux monitor

A system is described that performs monitoring of the incident photon flux for synchrotron radiation experiments. The system uses a channel electron multiplier whose output signal current in the high voltage line is accurately measured with an optically coupled isolation amplifier.

Auger Electron Spectroscopy by the Use of an Isolation Amplifier

An isolation amplifier was used to detect Auger electrons in a commercial type Auger electron spectroscopy (AES) system with a cylindrical mirror analyzer (CMA). Auger spectra of energy distribution type and of differentiated type were obtained simultaneously. The versatility of the isolation amplifier was demonstrated and discussed.

Design considerations for linear optically coupled isolation amplifiers

A hybrid optically coupled isolation amplifier is described which optimizes DC performance, bandwidth, physical size, and cost. The design utilizes a blend of monolithic and hybrid technologies to achieve this unique set of characteristics. The development of the linear optical coupler is traced. Optical and electronic circuit techniques are presented that combine, for the first time, precision performance with miniature packaging. Optional connections allow unipolar/bipolar and inverting/noninverting operation with both voltage and current inputs. Typical performance, based upon production runs, includes: 1000 V isolation voltage, 10 nA offset current, 1 pA//spl deg/C offset drift, 0.3 /spl mu/A barrier leakage at 60 Hz, 0.05 percent nonlinearity, and a bandwidth of over 60 kHz.

Discrete devices: Fabrication and processing techniques, borrowed from LSI technology, play major roles in new component designs

Describes how materials processing and fabrication techniques, have made possible the production of denser, smaller, and faster components during the past year. Among the components were high-frequency power-switching devices, microwave devices for communications, solid-state relays, and isolation amplifier transformers. Solid-state devices can now handle over 10 million watts. In the laboratory GaAs FETs have moved to even higher frequencies and even lower noise figures. The state of the art is an 8-gigahertz FET fabricated with electron-beam lithography with a 1.1-decibel noise figure and 14-dB associated gain.

A new 2-kV common-mode voltage wide-band isolation amplifier

Describes a new modulation-demodulation technique for isolation amplifiers, particularly useful for multichannel data acquisition systems. Input and output stages are transformer coupled using an improved version of the amplitude-modulation technique of a symmetric square wave, which requires a simple rectifier bridge for demodulation. Characteristics of the isolation stage obtained in this way are excellent linearity and gain stability, typical of magnetic coupling, and a frequency bandwidth ranging from DC to an upper limit which, at least in principle, is not fixed by the demodulation technique; moreover, common-mode voltages in the kilovolt range are obtainable. Details of an amplifier are given, designed as the analog input stage of a multichannel data acquisition system.

Backscattering spectra of medium energy electrons

Backscattering spectra of medium energy electrons (1–10 keV) are very important in Auger electron spectroscopy. Backscattered electrons compose the background and contribute to the excitation of Auger transitions. TheN(E) backscattering spectra were determined by an Auger spectrometer with a CMA analyzer operated in DC mode using an isolation amplifier system. TheN(E) backscattering spectra of electrons were studied on graphite, Si, stainless steel, Ge, Mo, W and Au in the 0.7–3 keV range. The backscattering spectra are presented. Our main results can be summarized as follows:

A SQUID Magnetometer for Simultaneous Measurements of Spontaneous Magnetization and AC Susceptibility around the Magnetic Phase Transition Point

A cryostat for simultaneous measurements of spontaneous magnetization and AC susceptibility by using a SQUID with a temperature control system was constructed. The temperature of samples can be controlled to an accuracy of 1.2×10-5 at temperatures from 1.6 K to 6.5 K during measurements. This accuracy is obtained by good thermal isolation from their surroundings and use of an isolation amplifier which breaks ground loop currents interfering with the detection of temperature. The SQUID magnetometer consists of a flux locked loop followed by another phase-sensitive detector referenced to the frequency of AC susceptibility. The frequency range of AC susceptibility is from 1 Hz to about 200 Hz and the sensitivity is 2×10-10 emu at 10 Hz with a time constant of 3 seconds, which corresponds to 10-4 of the flux quantum at a SQUID.

The Hybrid Compatible Transformer

In the past, hybrids containing transformers were hard and costly to produce because of difficulties with size, uneven mounting surfaces, and substrate to magnet wire interconnections. A new but simple toroid transformer assembly implemented on a hybrid substrate using standard printed conductors and gold wires is described. This innovation, called the hybrid compatible transformer [1], has recently progressed from the prototype stage to full scale production. It opens up numerous possibilities for improving the performance of hybrid circuits and for producing low-cost hybrid versions of products previously available only in discrete form. The biggest benefit in the form of lower cost and smaller size is anticipated for low power (1-25 W) dc/dc converters [2]. However, other products easily hybridized using this technique are isolation amplifier, RF-receivers, high-speed sample and hold circuits, 4/20 mA loop isolators, ac/dc converters, and EMI filters.

Optically coupled wide bandwidth dc isolation amplifier

We describe a general purpose optically coupled dc isolation amplifier with voltage gain of 100, 20-V peak-to-peak output swing, and response from dc to well over 250 kHz. Components used are all standard, commercially available items.

Optically coupled high-voltage isolation amplifier

A common and persistent problem in modern instrumentation is the observation and recording of small signal waveforms that are removed from ground by very high voltages. Examples of this are the instrumentation of neutral particle injectors used in controlled thermonuclear research and the construction of safety breaks for air core toroidal devices. To overcome this problem a very high voltage isolation amplifier was designed. It employs analog-to-digital conversion with serial data transmission on a fiber optic cable.

Removal of AC interference from the electrocardiogram.

A method is described for the removal of AC interference from the electrocardiogram in monitors which do not have isolated inputs. The patient's leads are connected to an isolation amplifier which provides isolation between the input and the output and has a high common mode rejection ratio. The output from the isolation amplifier is taken to the electrocardiographic monitor. The isolation amplifier not only provides additional patient safety but also reduces the level of AC interference without interfering with any frequency components in the electrocardiogram.

An automatically balancing isolation amplifier for the decoupling of measuring systems with high impedances.

It is theoretically shown that different conditions of coupling and grounding cause error voltages with the simultaneous use of two high-impedance measuring systems (e.g. pH electrodes). By the use of special amplifiers using optical transmission systems these error voltages are prevented. The transmission characteristics of the couplers are sensitive to changes in temperature due to the incorporation of infrared emitters in the system. An amplifying equipment with high d. c. stability was developed. The temperature drift was suppressed by the use of a special chopper stabilisation.

Correction to “Isolation amplifier with combined magnetic and optical coupling”

In the above paper,1 there were two misprints. The first appears in (1), in which the minus sign should be a multiplication sign. The second is in the formula page 116, where + must be read instead of ÷.

A practical design for insensitive RC-active filters

A systematic RC -active network synthesis procedure for the realization of second-order transfer functions is proposed. The realization employs three operational amplifiers and no isolation amplifiers are necessary. The sensitivity of the resulting networks to passive element variations has been found to be low. The sensitivity to variations in the active elements has been made very low. A design is given in which tuning can be achieved by trimming only resistors. The design is particularly attractive for high- Q realizations. The stability properties and the influence of the finite bandwidth of the amplifiers are examined. The proposed realization has been compared with those of Kerwin, Huelsman, and Newcomb, of Tarmi and Ghausi, and of Thomas, and found to offer several attractive features as compared to these realizations. The design procedure was used to obtain a sixth-order elliptic bandpass filter. Experimental results show close agreement between theory and practice. Further, these results indicate that these realizations are insensitive to temperature and power supply variations.

Isolation Amplifier with Combined Magnetic and Optical Coupling

The amplifier presented in this paper is suitable for isolated acquisition of analog signals in the frequency range from dc to more than 10 MHz. It employs a combination of magnetic and optical isolation techniques which gives to the circuit good features of speed and precision.

A canonical realization of active RC filters†

A canonical structure of an RC active filter is presented which can realize any transfer function. It consists of a fixed passive part and an active part that is computed from two triangular systems of linear equations. The solution vectors are the gain values of the active part and can be implemented as input resistances of summing amplifiers. The equations are generated systematically from the given passive part and the required transfer function. The realization requires at most n isolation amplifiers and two operational amplifiers to obtain any transfer function of degree n. An extra amplifier is added to minimize the sensitivity.

Isolation amplifier energized by ultrasound.

A power supply energized by ultrasound has been developed and investigated. The supply can be used in medical applications where a high isolation from earth is essential, for example in the protection of a patient from the hazards of electric shock caused by medical instrumentation. The ultrasound energy is generated by a transmitting piezoelectric crystal (transducer) and sent to a receiving transducer via a glass rod 20 mm long. At the receiving transducer the acoustic energy is converted back to electric energy. The power transmission has been measured at different resonances of the glass rod-transducer combination. The radial mode resonance of the transducer seems to give the largest power transfer and the highest efficiency.

Recent advances in microwave integrated-circuit solid-state source design

Microwave integrated-circuit techniques have been applied to the design of solid-state signal sources. These sources use such circuits as varactor-tuned transistor oscillators, resistive isolation pads, amplifiers, and frequency multipliers. Using these circuits, a millimeter wave voltage-tunable source with an output of 10 mW from 31.8 to 33.4 GHz was made. A second source that was constructed was voltage tunable from 8.7 to 9.7 GHz with an output power greater than 10 mW.