Automatic Control Circuit Research Articles

Monitored Geiger counter X-ray diffractometer with automatic recording

The equipment produces automatically a compact photographic record of a step-scan of a powder diffraction pattern in steps of 0.02° (2θ). It is arranged that movement over the background region between lines is rapid, so that only the line profile and the immediate background on either side are recorded in detail. The specialized electronic circuits and the relay-operated automatic sequence control circuits are described, together with a special automatic camera provided with various safety devices to protect the record. Facilities for other scanning procedures are also provided.

Automatic Beam Positioning for Mass Spectrometers

A system is described for the control of the position of the ion beam in a mass spectrometer. The instantaneous position of the beam with respect to the point of maximum collector current is presented on a cathoderay tube indicator. The beam can be held at this maximum point either manually using this indication, or by automatic control circuits. In automatic operation the beam first ``searches'' for the peak by sweeping slowly across the region of the collector plate. It is then ``locked in'' and hunts about the point of maximum current. The amplitude of the hunting can be made sufficiently small so that the average collector current does not differ greatly from the peak current. The beam remains locked in position during slow drifts of magnet current and acceleration voltages. After large sudden fluctuations it returns to search operation and locks in shortly thereafter. The method of control is an adaptation of principles used in automatic frequency control of radar receivers.

A Direct-Reading Acoustical Impedance Meter

A device for the measurement of acoustical impedance is described which employs a high impedance source, monitored by a ribbon element acting as an acoustical ammeter. The output of the ribbon acts through an automatic volume control circuit to maintain constant the volume current injected into the impedance under test. The sound pressure so developed is proportional to the absolute acoustical impedance and is measured by a high impedance probe microphone. The ribbon element also serves as a phase angle reference for the unknown impedance. The total acoustical path length from the ribbon to the diaphragm of the probe microphone is kept to an absolute minimum.

A Method for Vectorial Stability Criteria of Automatic Control Circuit and its Example

A Method for Vectorial Stability Criteria of Automatic Control Circuit and its Example

On the Stationary Oscillation Induced in the Control Circuit by the Non-linear Characteristics in the Relay

In case the non-linearities are kept containing in the control circuit elements, the stationary oscillation which has the circular frequency and the amplitude determined by the nonlinear characteristics and the chasacteristic value of the circuit occurs. We hereby consideded the dead zone and saturating characteristics in the relay of pilot valve type, and found, by means of analysis and experiment, the stationary oscillation induced in the control circuit by the above characteristics in the circuit having the controller of the three types ; that is, integral, proportional and proportionl integral action. Thus it will be possible to observed the effect of the non-linear characteritics on the stability of the automatic control circuit.

An Investigation of certain Properties of the Ionosphere by Means of a Rapid Frequency-Change Experiment

The paper is concerned with the recording of various characteristics of a radio wave reflected from the ionosphere as the frequency is altered rapidly An apparatus is described in which a receiver is kept in tune with a sender by means of automatic frequency control circuits operated by the direct pulse from the sender. The tuning is corrected by each pulse and remains fixed for the time between pulses. A frequency range of 1 Mc/s. can be covered in 1 sec. and may be selected anywhere in the range 2-20 Mc/s. A number of applications of the apparatus are described and typical records are reproduced. The irregularities of ionization present in the normal regions are investigated by the observation of the irregular variations of the amplitude of the reflected wave which are produced when the frequency is altered. Irregularities of ionization are sometimes found to be localized in height. Observations of the reflection coefficient of the abnormal region E suggest that there are two distinct types of region, one an irregular region consisting of scattering clouds, the other a coherent layer with a thickness of the order of 5 km. The apparatus is also used to study the behaviour of the subsidiary critical frequencies often present below the main critical frequency of region E. It is found that these are always decreasing in critical frequency whenever they are observed. Records of amplitude and group path near the critical frequency of a region can be used to determine the collision frequencies of electrons. The treatment is mainly descriptive, and a full discussion of those records which require a detailed quantitative analysis is reserved for a later paper.

Some automatic control circuits for radar receivers

Automatic control circuits developed for radar receivers include frequency control, gain control, gain equalization of two receiving channels, and rapid variation of gain with time in accordance with a predetermined law.This paper summarizes the various problems which have been encountered, under the above headings, and the techniques evolved for dealing with them. Examples are given of practical systems.A theoretical treatment of a.f.c. discriminators which combine the function of pulse integration is given in an Appendix.

Some automatic control circuits for radar receivers

Some automatic control circuits for radar receivers

Process Lags in Automatic-Control Circuits

Abstract Methods are given for quantitative determination of time lags in automatically controlled processes. The area under recovery curves is taken as a direct measure of process difficulty, and this area is shown to vary as the second power of the time lag. A “recovery-factor” term, part of a complete expression for controllability, is introduced which makes possible a classification of processes in dimensions of the process itself, regardless of controller or valve mechanism used. Values of this recovery factor from various industrial applications are given in tabular form. Several processes are examined for the time lag, and means of reducing this unfavorable characteristic are demonstrated. It is felt that this paper will be useful to engineers who are interested in improving the controllability of the processes which they design.

Closure to “Discussions of ‘Process Lags in Automatic-Control Circuits’” (1943, Trans. ASME, 65, pp. 440–443)

Closure to “Discussions of ‘Process Lags in Automatic-Control Circuits’” (1943, Trans. ASME, 65, pp. 440–443)

Rapid-Recording A-C Bridge

A power-factor and capacitance bridge capable of unattended recording has been described. Changes in the specimen may be fully recorded within one second of their occurrence. The bridge may be used in connection with life tests, during treating processes, and for recording tests on large numbers of nominally identical structures, in the process of production. The automatic control circuits described in this paper are not limited only to application to the Schering bridge, but may be used for automatic balancing of practically any other type of a-c bridge as well.

AUTOMATIC GAIN CONTROL

The simple, automatic volume control circuit of radio receivers has been adapted for use in the studio amplifier of a broadcasting station to give a semiautomatic control of programs. The circuit adjustments for optimum control action were determined experimentally, and then this control action was analyzed by means of oscillograms. The effects of different time constants and degrees of control were noted, and methods for varying the latter indicated. The circuit is shown to be distortionless, except in so far as manual control of amplifier gain may be said to introduce "distortion". The control action, while not fully automatic, is complete enough to be of real assistance to the operator.

Supervisory and Control Equipment for Audio-Frequency Amplifiers

This paper is divided into two parts: In the first part a new type of level indicator is presented, and in the second a device for controlling the output signal of an amplifier is described. Part I: Two types of level indicators in use at the present time on audio-frequency amplifiers are the r-m-s voltmeter and the average voltmeter. Neither of these will tell the operator how near the signal is to the overload point of the amplifier. A new type peak voltmeter is described that makes continuous measurements of the highest peak values attained by the signal. Part II: An automatic control circuit is described which reduces the amplification of a special amplifier when the output voltage reaches a certain amount, thereby keeping the subsequent equipment from being overloaded.