| OCR: Optical Character Recognition.
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| Octal: Pertaining to a base 8 number system.
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| Offset: The difference in temperature between the set point and the actual process temperature. Also, referred to as droop.
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| Ohmmeter: An instrument used to measure electrical resistance.
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| Ohms law: V = IR, where V is the potential across a circuit element, I is the current through it, and R is its resistance. This is not a generally applicable definition of resistance. It is only applicable to ohmic resistors, those whose resistance R is constant over the range of interest and V obeys a strictly linear relation to I.
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| Oil Free Compressor: A positive displacement air compressor which has no oil injected into the compression chamber for lubrication, cooling or sealing. |
| Olsen (Ductility) Test A method of measuring the ductility and drawing properties of strip or sheet metal which involves determination of the width and depth of impression. The test simulating a deep drawing operation is made by a standard steel ball under pressure, continuing until the cup formed from the metal sample fractures. Readings are in thousandths of an inch. This test is sometimes used to detect stretcher straining and indicates the surface finish after drawing, similar to the Erichsen ductility test.
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| On/off Controller: A controller whose action is fully on or fully off. |
| Op Amp: The Operational Amplifier is a general purpose integrated circuit used as a basic building block for the implementation of linear functions. Op amps form the "front end" or sensory apparatus of many electronics systems, capturing weak signals emanating from the real world and amplifying and filtering them for processing. A typical use of an op amp is to take a smaller signal and increase it by a specific amount to become a larger signal.
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| Open Circuit: The lack of electrical contact in any part of the measuring circuit. An open circuit is usually characterized by rapid large jumps in displayed potential, followed by an off-scale reading.
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| Operating System: Software which acts as an interface between the user of a computer and the computer hardware and its BIOS. The purpose of the operating system is to provide an environment in which a user may run other programs and manage files. Windows is an operating system developed by Microsoft for PCs. |
| Optical Isolation: Two networks which are connected only through an LED transmitter and photoelectric receiver with no electrical continuity between the two networks.
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| Optical or Infrared Resolution: The ratio of the distance to the target divided by the diameter of the circular (or spot) for which the energy received by the thermometer is a specified percent age of the total energy that would be collected by an instrument viewing a calibration source at the same temperature. The distance to the target is generally the focal distance of the instrument. The percentage energy is generally 90?95%. |
| Optical Pyrometer: A system that, by comparing a source whose temperature is to be measured to a standardized source of illumination (usually compared to the human eye), determines the temperature of the former source. |
| Optical Time Domain Reflectometer (OTDR) An instrument used to measure optical transmission characteristics. The instrument accomplishes this by sending short pulses of light, in a series, down a fiber and then giving a graphic representation of the backscattered light.
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| Orifice Plate: A flow measurement device for liquids or gases that uses a restrictive orifice plate consisting of a machined hole that produces a jet effect. Typically the orifice meter consists of thin plate with a square edged, concentric, and circular orifice. The pressure drop of the jet effect across the orifice is proportional to the flow rate. The pressure drop can be measured with a manometer or differential pressure gauge.
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| OSHA: Occupational and Safety Hazard Organization.
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| Outlet Check Valve/ Haskel The check valve located in the hydraulic body/ gas end cap, that permits fluids/gasses to go into the downstream system during a pumping stroke and closes to prevent return of the system fluid/gas during the suction stroke. |
| Output Impedance: The resistance as measured on the output terminals of a pressure transducer at standard temperature, with no measured applied, and with the excitation terminals open-circuited.
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| Output Noise: The RMS, peak-to-peak (as specified) AC component of a transducer?s DC output in the absence of a measurand variation.
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| Output: The electrical signal measured at the output terminals which is produced by an applied input to a transducer.
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| Overload Protection : A circuit that protects the instrument against excessive current at the input terminals. |
| Overrange, Safe: The maximum pressure or load which may be applied to the transducer without causing a permanent change in the performance specifications.
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| Overshoot: The number of degrees that a process exceeds the set point temperature when coming up to the set point temperature. |
| Oxidation-Reduction (redox): A chemical reaction consisting of an oxidation reaction in which a substance loses or donates electrons, and a reduction reaction in which a substance gains or accepts electrons. Redox reactions are always coupled because free electrons cannot exist in solution and electrons must be conserved.
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| Oxidation-Reduction: In its most basic form Oxidation is a chemical reaction with oxygen. Example: the oxidation of Methane (formula). In this example, molecular Oxygen is the oxidizing agent and the substance reacting with oxygen (methane) is called the reducing agent. Confusingly the reducing agent (Methane) can also be called an oxidizable gas. Compounds containing oxygen can yield oxygen in a reaction and are also called oxidizing agents. Oxidation is a reciprocal process in which one agent is reduced and one oxidized. A more complete way of describing oxidation is through the transfer of electrons. The substance oxidized loses electrons. The substance reduced gains electrons. Under suitable conditions, the oxidation-reduction reaction produces a flow of current. |
| Oxidation: A reaction in which there is an increase in valence resulting from a loss of electrons; often associated with the corrosion of metals, where the corroded metal forms an oxide; elevated temperatures increase the rate of oxidation.
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