Glossary of Terms: U

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Ultrasonic
Sensing technique using high frequency sound waves as the sensing medium. It can be used in either through beam or proximity configurations.
Undershoot
The amount by which a process variable falls below the setpoint before stabilizing.
Underwriter's Laboratories, Inc. (UL)
A non-profit organization that establishes, maintains and operates laboratories for the examination and testing of devices, systems and materials primarily for safety.
Ungrounded Thermocouple
A thermocouple construction in which the measuring junction is enclosed in a protective layer and electrically isolated from the sheath.
Unidirectional Differential Pressure Sensor
A differential pressure sensor requiring the greater input pressure to be applied to a specified pressure port.
Uninterruptible Power Supply (UPS)
Battery-backed device used to keep critical equipment, including computers, running in the event of a mains power failure.
Unipolar
A signal range that is always positive or always negative, for example 0 to +10 V.
Universal Asynchronous Receiver/Transmitter (UART)
In serial communications, the UART takes bytes of data and transmits the individual bits sequentially. Adds Start, Stop and sometimes Parity bits before and after the transmitted word.
Universal Serial Bus (USB)
A serial bus gradually replacing RS232 on PCs because of its higher speed. Standard interface for most computers.
Unshielded
Inductive sensor in which the coil is sensitive to surrounding metal. For a given coil size, an unshielded design has a longer sensing distance than a shielded one. Note, when mounting an unshielded sensor in metal, there must be a minimum space of one housing diameter (D) surrounding the sensor head.
Unshielded Sensor
A sensor with limited side and front sensing capabilities.
Upscale Break Protection
A form of break detection for burned-out thermocouples. Signals the operator that the thermocouple has burned out.
Usable Sensing Distance
Sensing distance after temperature range tolerance and manufacturer's tolerance are taken into account.
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