New types of transformer frequency dividers

Conclusions The dividers described above can be made for dividing high voltages (2–3.5 kV) over a wide frequency range (20 Hz–200 kHz). The divider with its variable input resistance provides a convenient and rapid reading of the input voltage for a known output voltage and, owing to this, it can be used in thermoelectric voltage comparators.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 59–61, January, 1972.     

A Method of Checking High-Voltage DC Potential Dividers

A method of checking high-voltage dc potential dividers based on the use of a supplementary dc potential divider and a voltage comparator as standard means of measurement is considered. The method provides a constructive simplification of the checking system and enables high-voltage dc potential dividers to be checked at voltages of up to 100 kV.     

Low-value UHF film resistors

Conclusion The application of the technique described above for determining coefficienta of the frequency characteristic and the use of appropriate corrections for the effect of the external temperature and for the aging of resistors made it possible to determine the value of |¯Z_H| with an error not exceeding ±(2–3)% at a frequency of 1000 Mc.The UHF film resistors made in the manner described above have values between 0.1·10^–3 and 10·10^–3 ohm. and are suitable for use in instruments measuring small voltages at radio and ultrahigh frequencies.     

Two-channel frequency converter with quartz filters

Conclusion The method described for reproducing phase shifts between two voltages at elevated and high frequencies can be recommended as a beginning in constructing standard phase measuring apparatus.Theoretical investigations have shown that the error in the method can be reduced to 0.04–0.05°.Translated from Izmeritel'naya Tekhnika, No. 3, pp. 60–62, March, 1969.     

Adjustment of division factors of step voltage dividers

Conclusions The suggested method of adjusting step voltage dividers consists in successively equalizing the divider resistors switched in a definite order and introduces no systematic error. Conditions have been formalized for the applicability of the method. Relations between the voltage transfer ratios of the divider after adjustment and the accuracy of resistance equalization have been derived.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 49–53, September, 1977.     

Obtaining a given phase shift between voltages by the beating method

Conclusions The tests carried out by us have shown that it is possible with the above beating method circuit to set a given phase difference between voltages with an error not exceeding 0.1–0.3°, providing the described precautionary measures are observed. The above method can find wide application in producing reference phase-difference generators used for checking electronic phasemeters.The majority of phasemeters intended for measuring phase differences between two voltages have a linear scale and incorporate devices for setting the zero value of the phase. In such meters only the linearity of their scale need be checked. This circumstance makes considerably less stringent the requirements for the identity of the phasedifference generator amplifying channels, since the setting of the zero value of the phase can be made by means of the tested phasemeter.If the output of one of the channels is fitted with a calibrated potential divider it also becomes possible to use the device for measuring voltages by the compensation method.Phase-difference generators with a continuous adjustment of the phase angle in a given frequency range can be used widely not only for testing purposes but also for measuring phase characteristics of amplifiers, filters, and other radio equipment, as well as for adjusting components of tracking systems, computers, and other automatic equipment.     

Measuring the root-mean-square values of random voltages with tube voltmeters

Conclusions The above examples indicate that in using standard tube voltmeters for measuring root-mean-square values of noise voltages it is necessary to take into account the distribution laws of their instantaneous values. Otherwise substantial errors can be made. By using the above technique it is possible to find the required corrections for every type of voltmeter and any kind of distribution law of a stationary random process.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 49–51, October, 1970.     

Determining the short-term instability of quartz oscillator frequencies

Summary The measurement results show that phase shift in the instrument depends but very little on the voltages of the frequencies being compared or the sources of supply, thus providing the possibility of using the above instrument for comparing frequencies of crystal oscillators continuously throughout the day and night with great precision.This instrument in conjunction with the phase shifter can also be used as a phase meter for measuring phase shift with great precision. Thus, the error in measuring a phase difference at 60 kc does not exceed 1 · 10^–4 rad.If required it is possible to raise the precision of frequency deviation measurements by either increasing the sensitivity of the discriminators by means of larger input voltages to the discriminator, or by multiplying the frequencies under comparison.     

Improvement of the Voltage Dependence of High-Voltage AC–DC Transfer Differences at the NMIJ

A new ac–dc comparator system of 20–1000 V has been developed at the National Metrology Institute of Japan (NMIJ) for the calibration of ac–dc thermal voltage converters (TVCs), which are used as national ac–dc transfer standards. The ac–dc transfer differences of high-voltage transfer standards were evaluated by a traditional step-up procedure. The voltage dependence of the ac–dc transfer difference was observed in the earlier step-up procedures over 300 V, as reported by the latest international intercomparison. The experimental results for high-voltage TVCs with several different range resistors at the NMIJ suggest that the voltage dependence may primarily be caused by input connectors of range resistors and the change in the resistance value of the resistor and TVC modules due to heating from resistors. This paper describes the voltage dependence improvement of ac–dc transfer differences over 300 V at the NMIJ.      

Digital voltmeter measuring circuits with parallel potential dividers

Summary The methods examined in this article for compensating the temperature error in supply sources and for stabilizing the input resistance of parallel potential dividers open up new possibilities for the application of these dividers in digital voltmeters with a range of 1–1000 V. Parallel potential dividers with a decimal scale made according to [5] are more suitable for use with low-resistance multivoltmeters.The processing of the readings of each decade in this instance can be carried out in four steps by the method illustrated in Fig. 6.     

Application of electrolytic capacitors in measuring circuits

Conclusions Mass-produced electrolytic, and above all tantalum capacitors approach paper capacitors in many of their characteristics, and are superior to them with respect to their specific charges. In the range of –5 to +50C the electrolytic capacitors' values vary almost linearly with temperature. Moreover, capacitors designed for higher working voltages have a minimum instability. Aluminum capacitors type éM have the maximum instability, amounting approximately to 5–10% per 10C. Capacitors in hermetically-sealed casings types KéG and éGTs, groups OM and PM are 2–3 times more stable than the éM capacitors. Tantalum electrolytic capacitors have a stability 5–10 or more times greater than that of the éM capacitors.The storage of éM capacitors at room temperature for 10,000 h changes their values by 6% towards the end of that time. Aluminum capacitors in hermetically-sealed casings after 2000–4000 h of preliminary storage provide a more stable capacitance, and tantalum capacitors then obtain virtually constant values.It is possible to arrive at the conclusion from the measurement results that electrolytic capacitors, and above all tantalum capacitors, can be used successfully, in many instances, in various measuring circuits. Preliminarytesting and selection of capacitors, as well as the application of thermal compensating elements in measuring circuits with electrolytic capacitors will provide a higher precision of measurements.     

Infrared absorption in thick film resistors

Infrared absorption in polymer and glass-based thick film resistors has been measured between 400 and 1500 cm^–1. Sample structures are discussed on the basis of X-ray, Fourier transform-infrared and resistance-temperature data. It is shown that in polymer-based thick film resistors, the particulate phase is mostly responsible for the infrared absorption between 400 and 900 cm^–1, whereas the infrared absorption at higher wave numbers is related to the continuous phase. In glass-based thick film resistors, absorption is mostly determined by the highly doped glass. The results indicate that thick film resistors can be used as an absorbent coating in the 400–1500 cm^–1 region by suitable selection of the continuous and particulate phases.     

Potential dividers with a constant output resistance

Conclusions Above wye and chain-connected potential dividers can be used in all cases when normal dividers with discrete scales are used, if the condition of their use does not require a strictly constant input resistance. Such dividers can be successfully used in various automatic compensation measuring instruments with digital recording [5] and in devices which convert discrete coded information into voltages [4]. In these instruments the simple switching consisting of separate two-position elements is effectively used.The possibility of reducing to a minimum the number of precision resistances in the composition of the divider and less strict requirement for the quality of contacts is of undoubted interest for metrology. Although in normal circuits for measuring emf these dividers cannot be used owing to their variable input resistance, they can still be used for comparative precision measurements.These dividers will find wide and diverse application in cases when a constant output resistance is required, and the use of normal dividers involves inevitable errors; for instance, in two-stage potentiometer circuits, electronic models, grid electrical integrators, and various electrical checking devices.     

Measuring the diameter of a moving microwire conductor

Conclusions The dynamic properties of the automatic equipment model make it possible to measure the conductor diameters of the above microwires with an error of 0.5–0.7 for a wire propulsion speed of 2.5 mm/sec.Such systems are suitable for application in special measuring laboratories. If the measuring channels' operating speed of the polar-coordinate autocompensators is improved it will be possible to use them for manufacturing microwires with stable diameters.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 39–41, November, 1974.     

Microsecond-resolution electrical measurements in high-current discharges

The instrumentation and operation of an accurate technique for electrical measurements in a capacitor discharge system are described. Capable of measuring currents up to about 50 kA at voltages up to 10 kV, the system uses commercially available current transformers to measure both current and voltage. The measurement system was evaluated by performing experiments on a calibrated Inconel resistor. The results indicate that electrical resistance and imparted electrical energy can be measured with an uncertainly of less than 1.5%.Paper presented at the First Workshop on Subsecond Thermophysics, June 20–21, 1988, Gaithersburg, Maryland, U.S.A.Formerly National Bureau of Standards     

Precision comparator for measuring in the range 1–10 mV

Conclusions Investigations of the cascade comparator have shown that the error in measuring the ratio of the SS emf to the JJ voltage (1 mV) does not exceed 4·10^–7. For larger JJ voltages the error decreases, and for 8 mV it does not exceed 5·10^–8. This error is determined mainly by the response threshold of the NFK-2 nanovoltmeter which serves as a null detector in comparing the measured voltage to voltage drops across the comparator lower arm. When this voltmeter is replaced by more sensitive instruments the above error can be reduced to 10^–7 and 2·10^–8, respectively.The comparator can be used for precise measurements in various physical investigations, e.g., in measuring temperature by means of platinum resistance thermometers, etc., when the error must not exceed 10^–7.Deceased.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 53–56, May, 1980.     

Dual Highly Stable 150-kV Divider

A highly stable (± 1-ppm) 500-kV power supply is being developed for use in a high-resolution (~1-?) electron microscope. One of the critical components in such a power supply is, of course, the feedback element, which, in this case, is a resistive voltage divider. A dual 150-kV divider has been constructed to determine the stability of such devices. The dividers are compared in a guarded Wheatstone bridge circuit and appear to be stable to within a few parts in 108 when operating at 150 kV. The high-voltage section of each divider consists of 150 1-M? resistors.     

Dielectric properties of vanadium phosphate glasses in a combined electric field

The dielectric properties of vanadium phosphate glasses, composed of 70 mol% V2O5 and 30 mol% P2O5 with an addition of 1 wt% of CuO, have been measured under combined voltages simultaneously composed of dc voltages of 0, 30, 45 and 65 V, and an ac voltage of 0.5 V. Measurements were taken over a temperature range of 20–110°C and a frequency range of 10–105 Hz. The NiCr alloy electrodes used in this study were prepared by chemical vapour deposition techniques. The results of the measurements show that the conductivity and dielectric properties of the glasses could be described by a mechanism of electron hopping between energy states of the chain of molecules or by a tunneling effect. The transport of the electric charges involves movement across a potential barrier and the movement could be improved if the barrier was deformed by the dc voltage.     

Potential dividers in automatic AC digital voltmeters

Conclusions The application of ac compensation circuits provided with double and double shunting decades is limited by the frequency range within which the precision of modulo division and the given minimum phase shift between the reference and compensation voltages is maintained. These limitations can be evaluated from (11) and (12), remembering that the phase shift is affected substantially by the capacitance of switching contacts.Ac compensators with star-connected dividers are subject to easier requirements with respect to the capacitance of their switching elements. The division-ratio precision and minimum phase shift are fully determined only by the quality of the resistors in the circuit, i.e., by their meeting condition (7), which facilitates considerably the design of such dividers.