Small Vane Research Articles

A resonant-cavity torque-operated wattmeter for microwave power

A sensitive method of microwave power measurement is described which makes use of the mechanical force exerted by the electromagnetic field on a small vane in a resonant cavity. It is shown that the force on the vane is a simple function of the Q-factor of the cavity, the power absorbed in it and the perturbation of its resonant frequency caused by the vane. The results of a comparison between an experimental wattmeter based on this principle and a water calorimeter are given, and the requirements of a practical instrument are discussed.

Tools for the Workshop

The Fielden Servograph is operated by a servo motorized mechanism which is controlled by a moving coil, moving iron, dynamometer or electrostatic movement, the pointer of the normal movement being replaced by a small light vane which acts as one plate of a variable condenser. Another similar vane arranged to be turned by the servo mechanism moves in the same are as the meter operated vane, and the two are maintained at a constant spacing by an electronic capacity relay which controls the servo motor. It is only necessary to provide enough energy to deflect a normal indicating meter movement, and the servo mechanism locates the pen arm with precision, being positionally controlled by this movement. The electronic relay circuit is present at works and needs no re‐adjustment.

A Self-Compensating Temperature Indicator

The following paper describes a unique adaptation of the temperature sensitive magnetic alloys known as ``calmaloy'' to the cold junction compensation of thermocouple temperature indicators. It has been known for some time that certain specially prepared copper-nickel alloys possess the property of changing permeability linearly with temperature over very wide ranges. This peculiar function of permeability has been advantageously used for effecting temperature compensation on different devices, particularly watthour meters. The need has recently arisen of providing suitable compensation for millivolt meters used in connection with thermocouples for determining the temperatures of air cooled aircraft motors. It is shown that by employing the restoring torque on the instrument produced by a small vane of calmaloy in addition to the usual restoring torque of the spring, a very satisfactory compensation results. Curves are shown which illustrate the accuracy of compensation obtained and a detailed explanation of just how it is accomplished is also given.

A self-compensating temperature indicator

The following paper describes a unique adaptation of the temperature sensitive magnetic alloys known as “calmaloy” to the cold junction compensation of thermocouple temperature indicators. It has been known for some time that certain specially prepared copper-nickel alloys possess the property of changing permeability linearly with temperature over very wide ranges. This peculiar function of permeability has been advantageously used for effecting temperature compensation on different devices, particularly watthour meters. The need has recently arisen of providing suitable compensation for millivolt meters used in connection with thermocouples for determining the temperatures of air cooled aircraft motors. It is shown that by employing the restoring torque on the instrument produced by a small vane of calmaloy in addition to the usual restoring torque of the spring, a very satisfactory compensation results. Curves are shown which illustrate the accuracy of compensation obtained and a detailed explanation of just how it is accomplished is also given.

A new portable electrocardiograph

This instrument was developed in collaboration with L. T. Robinson, H. B. Marvin and J. K. Leibing of the General Engineering Laboratory of the General Electric Company at Schenectady, N. Y. It consists essentially of a special three stage amplifier, a special mirror galvanometer and a camera which is operated by a modified phonograph mechanism. The total weight of the instrument with batteries and all accessories in two carrying cases of rugged construction is seventy-eight pounds.Amplification of the action current of the heart is obtained by an amplifier which resembles a radio amplifier. Two tubes of type PR-1-C and one tube of type 201-A are employed. There are special resistances so constructed as to be unaffected by temperature changes and to permit accurate standardization of the electrocardiogram. The batteries consist of a six volt storage battery and seven 22-volt dry cells.The galvanometer consists of a small iron vane ruggedly suspended in a cell full of a clear oil of appropriate viscosity a...

A New Type of Thermogalvanometer

The puff of air from an orifice in an air chamber when the air within is suddenly heated is utilised in this instrument to deflect a small suspended vane. The current to be measured is made or broken through a heater of small thermal capacity in the air chamber and the outrush or inrush of air through the orifice delivers an impulse to the vane. The disturbing effects of extraneous heat and pulsations of external pressure are eliminated by a compensation method. In one instrument of this type the sensibility was 4 mm. per microwatt and the extremity of the throw of the vane was attained in 2 seconds.