Glossary of Terms: T

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Target
The part or piece being detected.
TCP/IP
Transmission Control Protocol/Internet Protocol. Communications protocols used to connect hosts on the internet.
Temperature, Ambient
The temperature of the air or other medium that surrounds the components of a thermal system.
Temperature Calibration Point
A temperature at which the output of a sensor is compared against a standard.
Temperature Drift
The speed of sound depends on temperature. Deviation can be up to 0.18%/K. Temperature drift of the ambient air is mostly compensated within the sensor itself. The specification for temperature compensation is valid for stationary conditions.
Temperature Error
Maximum change in output, at any input pressure within the specified range, resulting from a change in temperature.
Temperature Limit Switch
Factory Mutual (FM) Standard 3545. See also Limit Controller.
Temperature Range
The temperature range indicated under ambient conditions corresponds to the operating temperature range.
Terminal Base Linearity (TBL)
(aka End Point Linearity) A method of defining linearity. The maximum deviation of any data point on a sensor output curve from a straight line drawn between the end data points on that output curve.
Terminal Line
Theoretical slope for which the theoretical end points are normalized at 0 and 100% of both measurand and output. Interchangeability error is referenced to this line.
Text Format
Text format refers to information in the ASCII character set. It is unformatted. Each byte in the file contains one character that conforms to the standard ASCII code.
Thermal
Coefficient of Resistance The change in resistance of a semiconductor per unit change in temperature, over a specific range of temperature.
Thermal Conductivity
A measure of the rate of flow of thermal energy through a material in the presence of a temperature gradient. Materials with high electrical conductivities tend to have high thermal conductivities.
Thermal Drift Chart
Chart illustrating sensor operating variance due to changes in temperature.
Thermal Efficiency
Ratio of available energy to captured energy.
Thermistor
A temperature sensor. The name comes from thermal resistor. It is a semiconductor that exhibits a large change in resistance as a function of temperature. Most thermistors exhibit a negative temperature coefficient, where resistance decreases as temperature rises. These are referred to as NTC thermistors.
Thermistor
A temperature-sensitive passive semiconductor which exhibits a large change in electrical resistance when subjected to a small change in temperature, usually with a negative temperature coefficient.
Thermocouple
Popular temperature sensor because of its low cost, wide operating range and ruggedness. Consists of two dissimilar metals joined together, making a continuous loop. When one junction has a different temperature from the other an electromotive force (voltage) occurs. There are several types of thermocouples, constructed from different metals and with differing temperature ranges and accuracies.
Thermocouple Break Protection
The ability of a control to detect a break in the thermocouple circuit and take a predetermined action.
Thermocouple Extension Wire
A pair of wires connecting a thermocouple sensor to its reference junction or instrumentation. The electromotive force (EMF) characteristics of the extension wire must be similar to the EMF characteristics of the thermocouple.
Thick Film
Technology using silk screened pastes to form conductor, resistor, thermistors, and insulator patterns; screened onto the substrate (usually ceramic) and cured by firing at elevated temperatures.
Thin Film
Technology using vacuum deposition of conductors and dielectric materials onto a substrate (frequently silicon) to form an electrical circuit.
Three Position Step Control
Algorithm that is an extension of ON/OFF Duplex control and includes internal feedback of the state of the relays. Effect of control action is that ON and OFF time of output relay changes in proportion to error signal and the Gain and reset time settings.
Three-Wire Switching Output
Sensors with three leads. Two for the power supply (+Vcc/gnd) and one for the digital output signal.
Threshold Response
Control type that responds to the change in input signal level. Plug-in amplifiers are either threshold or transition responsive.
Throughput
Number of results produced per unit of time.
Throw
Number of circuits that each individual pole of a switch can control. The number of throws is completely independent of the number of poles and number of breaks. A single-pole double-throw single-break switch connects the common terminal of the switch to the normally closed terminal when the plunger is free, but connects the common terminal to the normally open terminal when the plunger is depressed. A single-pole single-throw single-break switch has a common terminal and either a normally open terminal or a normally closed terminal but not both.
Time Constant
Time required for output of a "First Order Lag" device to reach a percentage of its final value for a step change in input.
Time\Current Duplex
Variation of duplex with Current active for 50 to 100% output and Time active for 010 50% output.
Time Delay
A time delay is used to delay the output of the sensor. There is a response as well as a release delay. The response time delay changes the time period between closing the light beam and the output switching. The release time delay enlarges the time between interrupting the light beam and the output switching.
Time Proportioning Duplex
Algorithm that uses two SPDT relays for Time Duplex Proportional Control. Normally open (NO) or normally closed (NC) contacts selected by positioning an internal jumper.
Time Proportioning Simplex
Output algorithm that uses one SPDT relay for Time Proportional Control. Normally open (NO) or normally closed (NC) contacts are selected by positioning an internal jumper.
Time Stamp
Information added to data to indicate the time at which it was collected.
Total Travel
Distance from the plunger free position to the full overtravel point.
Totalizer
Calculates and displays the total flow volume as measured by input or derived by input algorithm.
Transducer
A fully packaged, signal conditioned, compensated and calibrated sensor. Device that converts an input signal of one form (physical quantity) to an output signal of another form (usually electric). Examples include thermocouples and photocells. Most sensors are also transducers.
Transient
A short surge of current or voltage, often occurring before steady-state conditions have become established. In electronic usage, usually refers to an unwanted, temporary, large increase or decrease in a current or supply voltage that only occurs occasionally. Almost always due to reactive components during rapid changes in voltage or current.
Transient Protection
Circuitry to guard against spikes induced on the supply lines by inductive sources such as heavy motors or solenoids turning On and Off.
Transistor-Transistor Logic (TTL)
Refers to logic circuits consisting of two or more directly interconnected transistors, to provide conditional switching capability.
Translucent
Allows light to pass through. Detecting translucent objects is often best done with retroreflective scan, during which the light must pass through the object twice, thereby causing more of a signal change (larger signal ratio).
Transmitter
A primary device that translates a process measurement into a current/voltage signal for long-distance transmission. A transducer with a current loop output, typically 4 to 20 mA, enabling transmission of a signal over a longer distance.
Triac
A solid-state device used to switch alternating currents.
Trigger
A trigger is something that causes a data acquisition system to start collecting data. It may be as simple as pressing a software button or a set of conditions which when met trigger data capture (internal triggers), or an externally generated, hardware signal (an external trigger).
Truncation
Rejection of the final digits in a number, thus lessening the precision but not necessarily the accuracy.
TTL Compatibility
TTL (transistor-transistor-logic) requires NPN (current sinking) input signals. Reliable operation demands maximum input sensor voltage drop of 0.8 V. Most TTL compatible interface devices have voltage drops of less than 0.7V.
T-Type Thermocouple
Copper-constantan thermocouple with a temperature range of -200 to 400 Degrees C.
Tuning
Adjustment of control constants in algorithms or analog controllers to produce control effect.
Twisted Pair
Cable that consists of individual wires wrapped around each other for carrying telephone or computer data. Reduces pickup noise levels in signals.
Typical
Refers to the target value or where a range is given, represents an estimate of where 2/3 of the total population of several production runs would be.
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