Accuracy: The nearness of a measured value compared to the actual value. Usually expressed as a maximum deviation from the correct value; e.g., ±1% indicates the measured value will be between 99 and 101% of the actual value.
Analog Output: A continuous electrical signal used to provide a linear representation of the level of material.
Blanking Distance: The minimum operating distance of a sensor that operates by measuring time-of-flight (e.g., ultrasonic, radar) to allow the transducer to receive an echo from the target; blanking is used to ignore strong, close reflections that are usually not the intended target.
Deadband: A region with a measurable distance but with no change in output (see hysteresis).
Differential Pressure: The variation in pressure between two separate points.
Float: Any device with a less specific gravity than the surrounding fluid thereby allowing the device to maintain buoyancy.
Hydrostatic Pressure: The pressure exerted at a known depth by a column of liquid with a consistent density.
Hysteresis: The property of an output that differs between increasing and decreasing values based on the same deadband.
Zero Offset: The divergence of a sensor’s output from the recognized zero reference point.
PSIA: Unit of pressure as pounds per square inch absolute, which places the zero reference at full vacuum; measured by the sum of gauge (see PSIG) and atmospheric pressures.
PSIG: Unit of pressure as pounds per square inch gauge, which places the zero reference at ambient atmospheric pressure.
Repeatability: The ability of a sensor to reproduce a consistent output. Usually expressed as a maximum deviation from the actual value; e.g., ±1% indicates repeatable value of between 99 and 101% of the actual value.
Resolution: The minimum change in level that a sensor is able to detect.
Response Time: The time required for an output to react to a given input.
Signal: A variation in electron flow that conveys information from one location to another.
Span: The distance or correlating output between two measureable points.
Specific Gravity (SG): A dimensionless ratio of the density of a particular material to the density of water at 4°C (39.2°F).
Submersible: Any object with the ability to operate under water.
Switch Point Output: A discrete mechanical or electronic signal that indicates a state of being opened or closed. Typically used as high or low alarm conditions.
Transducer: A device used to convert energy from one form into a different form.
This glossary of terms was contributed to Flow Control magazine by Jacob Bingham, applications engineer for Automation Products Group (www.apgsensors.com).