Glossary of Terms: G

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Gage Factor
Measure of the ration of the relative change of resistance to the relative change in length of a resistive strain sensor (strain gage).
Gage Pressure
Form of differential pressure measurement in which atmospheric pressure is used as a reference.
Gain
Ratio of change in output to change in input that caused the change. Reciprocal of Proportional Band. Amplification of a circuit. Gain in the process is defined as the change in input divided by the change in output. A process with high gain will react more to the controller output changing.
Gain (of the controller)
Another way of expressing the "P" part of the PID controller. GAIN = 100/(Proportional Band). The more gain a controller has the faster the loop response and more oscillatory the process.
Gain Margin
The difference in the logarithms of the amplitude ratios at the frequency where the combined phase angle is 180 degrees lag is the gain margin.
Gain Range
The maximum and minimum voltage that will be digitized by the A-D converter is sometimes called the gain range.
Gain Scheduling
Predefined separate GAIN tuning values automatically applied to predefined process variable regions.
Glass Cover
Glass covers may protect a sensor against mechanical or chemical damage, such as welding sparks or strong solvents. .
Gravity Unit
One gravity unit (abbreviated g) is an acceleration of 32.2 feet per second per second.
Ground
(1) A conducting path, intentional or accidental, between an electric circuit or equipment and the earth, or some large conducting body serving in place of the earth (a voltage reference). (2) An electrical line with the same electrical potential as the surrounding earth. Electrical systems are usually grounded to protect people and equipment from shocks due to malfunctions. Also called safety ground.
Ground Loop
A condition created when two or more paths for electricity are created in a ground line, or when one or more paths are created in a shield. Ground loops can create undesirable noise.
Ground Potential
The electrical potential of the earth. A circuit, terminal or chassis is said to be at ground potential when it is used as a reference point for other potentials in the system.
Grounded Thermocouple
A thermocouple constructed in such a way that the measuring junction is an integral part of the sheath material. Electrical isolation is not provided in this type of construction.
Guaranteed Soak
Guarantees a setpoint programming segment’s process variable is within deviation for configured soak time. When deviation is exceeded, soak timing is frozen.
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