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 a physical variable to which an instrument can respond; the ratio of the change in output magnitude to the change of the input which causes it after the steady-state has been reached.
Sensor: An element or device that detects a variable by receiving information in the form of one quantity and converting it to information in the form of that or another quantity.
Setpoint: A variable, expressed in the same units as the measurement, which sets either the desired target for a controller, or the condition at which alarms or safety interlocks are to be energized.
Settling time: The time required after a stimulus for the output to center and remain within a specified narrow band centered on its steady-state value.
Signal: A variable that carries information about another variable that it represents.
Signal-to-noise ratio: Ratio of signal amplitude to noise amplitude. The ratio of overall rms signal level to rms noise level, expressed in dB. For sinusoidal signals, amplitude may be peak or rms.
Span: The algebraic difference between the upper and lower range values expressed in the same units as the range.
Span shift: Any change in slope of the input-output curve.
Stability: The ability of an instrument or sensor to maintain a consistent output when a constant input is applied.
Steady-state: A characteristic of a condition, such as value, rate, periodicity, or amplitude, exhibiting only negligible change over an arbitrary, long period of time.
Stiffness: The ratio of change of force (or torque) to the resulting change in deflection of a spring-like element, the opposite of compliance.
Strain: The ratio of the change in length to the initial unstressed reference length of an element under stress.
Subsidence: The progressive reduction or suppression of oscillation in a device or system.
Suppressed range: A range in which the zero value of a measured variable is greater than the lower-range value (LRV). The terms “elevated zero,” “suppression” or “suppressed span” are also used to express the condition when the zero of the measured variable is greater than the LRV.
Suppressed span: The span in which the zero of the measured variable is greater than the LRV.
Suppressed zero: The range in which the zero value of a measured variable is less than the lower range value. The terms “elevation,” “elevated range” and “elevated span” are frequently used to express the condition in which the zero of the measured variable is less than the lower range value.
Suppression ratio: The ration of the lower-range value to the span. If range is 20-100 and, therefore, span is 80 and LRV is 20, the suppression ratio is 20/80 = 0.25 or 25%.
Synchronous: An event or action that is synchronized to a reference clock.
System noise: Measure of the amount of noise seen by an analog circuit or an ADC when the analog inputs are grounded.