Glossary of Terms: O

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Object Distance
The object distance is defined as the distance between the front end of the sensor and the object itself.
Occupational Safety and Health Administration (OSHA)
The United States governmental agency that establishes and enforces safety standards in the workplace.
Off Delay Logic
Adjustable delay (after input signal stops) before output is de-energized.
Off State Current
Supply or bias current flowing into a solid state device when it is in the un-actuated state (see Leakage Current).
Sustained deviation between actual control point and setpoint under stable conditions.
Unit of electrical resistance. Resistance through which a current of one ampere will flow when one volt signal is applied.
Ohm's Law
Current in a circuit is directly proportional to the voltage, and inversely proportional to resistance. The complete Ohm's Law also includes the relationships of watts to amps, volts and ohms.  Stated as: E = IR Where: I = Amps, I = E/R, E = Volts, R = E/I, R= Ohms
Oil Resistant
The standard PVC cables are not made to operate continuously within an oily environment. PUR and Teflon covered cables are available.
OLE for Process Control (OPC)
A standard set by the OPC Foundation for fast and easy connections to controllers.
On Delay Logic
Adjustable delay (after onset of input signal) before output is energized.
On/Off Control
A method of control in which the controller acts as a switch, turning the final control element either ON or OFF, depending on the value of the setpoint.
Characteristic of an object that prevents light from passing through. The opposite of translucent. Opaque objects are easy to detect since they block light almost entirely.
Open Loop
Control system with no self-correcting action for misses of desired operational condition, as there is in a closed-loop system. Also refers to a controller in manual mode.
Open Loop Control
A control system with no feedback signal from the sensor.
Operating Characteristics of a Switch
The commonly specified force, torque and linear or angular travel properties of a switch. Examples: operating or release force, operating point, differential, overtravel.
Operated Contact Position
Position to which the contacts move when the plunger is traveled to the operating point or into the overtravel range.
Operating Force
The force which must be applied to the plunger to cause the moving contact to snap from the normal contact position to the operated contact position.
Operating Temperature
Actual range over which sensors can be operated. Usage outside the temperature limits will result in loss of stability, change in operate point and possible permanent damage to the sensor. Nominal sensing distance is determined at 25 Degrees C.
Optical Isolation
Two electronic networks that are connected through an LED (light emitting diode) and a photoelectric receiver. There is no electrical continuity between the two networks.
Optical Power
Power or intensity of the projected light available from a particular emitter; beam intensity.
OR Logic
Output is produced when any one or more inputs are present.
Original Equipment Manufacturer (OEM)
A company that makes basic hardware for other manufacturers to build into their products.
(1) Information leaving a device. (2) Useful energy delivered by a circuit or device. Can be energy produced at the output terminals of an amplifier, a source of energy. (3) Control signal action in response to the difference between setpoint and process variable. (4) Output of the PID controller. In auto mode the controller calculates the output based its calculation using the error signal (difference between setpoint and PV). In manual mode, the user sets the output.
Output Impedance
Impedance across the output terminals of a sensor presented by the sensor to the associated external circuitry.
Output Noise
RMS, peak-to-peak (as specified) AC component of a sensors DC output in the absence of a change in input pressure.
Output Resistance
3-wire proximity switches have a built-in load resistance. In case of high frequency switching an external load resistance can be connected in parallel in order to reduce the time constant.
Output Type
The form of control output, such as time proportioning, distributed zero crossing, serial digital-to-analog converter or analog. Also the description of the electrical hardware that makes up the output, such as relay, voltage pulse, or analog.
Outside Air
Modern building codes require certain amounts of fresh air be forced through public use buildings at all times when occupied to promote good indoor air quality. This fresh air intake is called outside air. A building that has 30% outside air means that for each time 100% of the air in the building is re-circulated, 30% of the re-circulated air is exhausted from the building and replaced with fresh air from outside. This improves indoor air quality, but results in an efficiency penalty since the outside air must be heated or cooled, and humidified or de-humidified to the desired building conditions.
The maximum specified pressure which may be applied to the sensing element of a sensor without causing a permanent change in the output characteristics.
The amount a process variable exceeds the setpoint during a change in the system load or change in the setpoint before stabilizing. The opposite condition is called "undershoot".
As an operating characteristic of a switch, overtravel is the distance through which the plunger moves when traveled from the operating point to the full overtravel point. As a characteristic of the actuation applied to the switch, overtravel is the distance the plunger is driven past the operating point.
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