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A-B

A Accuracy: Degree of conformity of a measured value to an accepted standard value; or closeness of a reading or indication of a sensor to the actual value of the quantity being measured. Accuracy rating: A number that defines a limit that the measurement errors will not exceed under some reference operating conditions. It includes …

C

Calibrate: To ascertain that the output of a device properly corresponds to the information it is measuring, receiving or transmitting. This might involve the location of scale graduations, adjustment to bring the output within specified tolerance or ascertaining the error by comparing the output to a reference standard. Calibration: The process of adjusting an instrument …

D Damping: The suppression of oscillation. The viscosity of a fluid is used in viscous damping, while the induced current in electrical conductors is used to effect magnetic damping. Deadband: The range through which an input can be changed without causing an observable response. Dead time: The interval between the initiation of a change in …

G Gain (magnitude ratio): For a linear system or element, the ratio of the magnitude (amplitude) of a steady-state sinusoidal output relative to a causal input. In an electrical circuit, the amount of amplification used, sometime expressed in decibels (dB). Gain accuracy: Measure of deviation of the gain (of an amplifier or other device) from …

O Ohmmeter: A device used to measure electrical resistance. One-to-one repeater: A diaphragm-operated device which detects process pressure and generates an air (or nitrogen) output signal of equal pressure. Optical isolation: Two networks or circuits in which an LED transmitter and receiver are used to maintain electrical discontinuity between the circuits. Output settling time: The …

R

R Radio frequency: The frequency range between ultrasonic and infrared. AM broadcast frequencies range from 540 to 1,800 kHz, while FM broadcasts from 88 to 108 MHz. Radio frequency interference (RFI): Noise induced upon signal wires by ambient radio-frequency electromagnetic radiation with the effect of obscuring an instrument signal. Ramp: The total (transient plus steady-state) …

S

Sampling period: The time interval between observations. Scale factor: The factor by which the number of scale divisions indicated or recorded by an instrument must be multiplied to compute the value of a measured variable. Sensing element: The element that is directly responsive to the value of a measured variable. Sensitivity: The minimum change in …

T Temperature coefficient: The amount of drift, in percent of full scale output, that might result from a 1°C change in ambient temperature. Thermal shock: An abrupt temperature change applied to a device. Time constant: The value “T” in an exponential term A(-t/T). For the output of a first-order system forced by a step or …