Null Shift Research Articles

Magnetometric sensors with improved functional parameters

A functional study of TFS-3 fluxgate sensors developed for the INTERBALL space missions is presented. Good sensitivity and thermostability, a low offset of 0–2 nT, a thermal null shift of 0.04 nT/°C and a peak-to-peak magnetic noise level of < 0.2 nT were obtained for a field frequency range of 0–1 kHz in the −70 to +70°C temperature interval using special thermostabilization procedures.

Null shift and beam squint in circularly polarized offset-reflector antenna

A formula for the null shift of the difference mode pattern of an offset-reflector antenna is derived. It is shown that this null shift and the beam squint of the sum mode pattern have different values. Such a phenomenon must be considered in the design of a two-channel tracking system.

不均等負重合案内弁を用いた空気圧案内弁・シリンダの周波数特性

Measurements of the underlap for four-way valves gave results that the underlap was not only uneven but also geometrically asymmetric for some four-way valves. Both the unevenness and the asymmetricity have considerable influence on the characteristics of the valve-controlled cylinder. In addition to the unevennesses i=(Δ1/Δ)- 1, i= (Δ'1/Δ')-1, the asymmetricity η=Δ'1/Δ is introduced for a valve, where Δ, Δ' are the mean underlaps of the left side and the right side three-way valves and Δ1, Δ'1 are the underlaps on the supply sides. represents the right side. Considering i, η and Δ of a valve, the frequency response of a valve-controlled cylinder with viscous friction, Coulomb friction and mass load was theoretically analyzed where the flow versus pressure characteristic curves were approximated partially as polynomials of degree 3 of the pressure. The tendency shown by the theoretical results agreed fairly well with that of the experimental results. The frequency characteristics of (piston velocity)/(spool displacement) = V(jω)/ Y(jω)show the same tendency for an asymmetric valve as that for a symmetric valve. But, for the case where an asymmetric valve is used, there is null shift of the valve ( δο) for avoiding the piston drift. δο changes in proportion to i, and |δο| becomes larger according to the increase in η (for η>1) or 1/η (for η <1).δο changes little for the changes in Δ and frequency ω.

Single-isotope Laser Gyro

A single-isotope He-Ne laser gyro has been constructed and operated, and the results have been compared with those obtained from a multi-isotope system. Strong mode competition in the single-isotope ring laser has been found in a region 10-30 MHz near line center. The sense of the mode competition has been found to depend on the direction of rotation of the laser cavity. Hence, by mechanical dithering of the laser, the time-averaged effect of the mode competition can be zero. However, with a current unbalance, a large dispersion-type null shift is found near line center. Unlike the linear laser and the multi-isotope ring laser, the single-isotope ring laser is characterized by strong mode competition such that only a single longitudinal mode oscillates over most of the free spectral range.

Single-isotope laser gyro

A single-isotope He–Ne laser gyro has been constructed and operated, and the results have been compared with those obtained from a multi-isotope system. Strong mode competition in the single-isotope ring laser has been found in a region 10–30 MHz near line center. The sense of the mode competition has been found to depend on the direction of rotation of the laser cavity. Hence, by mechanical dithering of the laser, the time-averaged effect of the mode competition can be zero. However, with a current unbalance, a large dispersion-type null shift is found near line center. Unlike the linear laser and the multi-isotope ring laser, the single-isotope ring laser is characterized by strong mode competition such that only a single longitudinal mode oscillates over most of the free spectral range.

Langmuir flow effects in the laser gyro

Langmuir flow effects have been investigated in the laser gyro by measuring the integral of the beat frequency while tuning the frequency of oscillation. The results are in agreement with the traveling-wave Lamb model. The presence of the dc discharge tube walls gives rise to gas circulation in the laser gyro cavity. If the oppositely directed traveling waves see a net gas flow the gyro exhibits a null shift which depends on the magnitude and direction of the discharge current unbalance causing the net gas flow. The null shift is shown to be due to the mode pulling and pushing associated with the anomalous dispersion exhibited by the gain atoms.

Effects on Inertial Guidance Systems of Random Error Sources

Random process theory is applied to a number of typical problems encountered in the error analysis of inertial guidance systems and in the design of optimum error predicting filters for such systems. The applications of random process theory include: Measurement of system error autocovariance functions. An example of the measurement of a random drift rate process, constructed by the uniformly distributed sampling of a deterministic periodic function, is treated in detail. Estimation of velocity and position errors due to such basic error sources as gyro drift rate and accelerometer null shift. Design of optimum prediction filters for drift rate, attitude, velocity and position and for minimization of target miss distance. Treatment of hybrid inertial system error as a gated random process. The specific example is taken of drift angle increase between Poisson-distributed correction intervals for a Doppler inertial system.