The dependence of the signal from an ionization gage on the geometry of the system being measured when an organic vapor is present in the vacuum; the effect can falsify measurement results by up to an order of magnitude.



Related Terms

BASELINE DELAY

The time interval needed for the signal from a master station of a hyperbolic radionavigation system to travel the length of the baseline, introduced as a delay between transmission of the master and slave (or secondary) signals to make it possible to distinguish between the signals and to permit measurement of time differences.

PRIMARY GREAT CIRCLE

A great circle used as the origin of measurement of a coordinate; particularly such a circle 90° from the poles of a SYSTEM of spherical coordinates, as the equator. Also called PRIMARY CIRCLE, FUNDAMENTAL CIRCLE.

CONTACTOR CONTROL SYSTEM

A feedback control system in which the control signal is a discontinuous function of the sensed error and may therefore assume one of a limited number of discrete values.

RESTRICTED GAUGING

A system employing a device, which penetrates the tank and which, when in use, permits a small quantity of cargo vapor or liquid to be expelled to the atmosphere. When not in use, the device is kept completely closed.

CONTROL-SYSTEM FEEDBACK

A signal obtained by comparing the output of a control system with the input, which is used to diminish the difference between them.

ACOUSTIC POSITION REFERENCE SYSTEM

An acoustic system used in offshore oil drilling to provide continuous information on ship position with respect to an ocean-floor acoustic beacon transmitting an ultrasonic signal to three hydrophones on the bottom of the drilling ship.

DEAD TIME

  1. The time interval between a change in the input signal to a process control system and the response to the signal. 2. The time interval, after a response to one signal or event, during which a system is unable to respond to another. Also known as insensitive time.

REID VAPOR PRESSURE

a measurement of the amount of flammable vapor given off by a liquid of a certain temperature.

COMPUTER-CONTROLLED SYSTEM

A feedback control system in which a computer operates on both the input signal and the feedback signal to effect control.

AIDED TRACKING

A system of radar-tracking a target signal in bearing, elevation, or range, or any combination of these variables, in which the rate of motion of the tracking equipment is machine-controlled in collaboration with an operator so as to minimize tracking error.

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