Metrology Glossary – T

At J.A. King, we strive to educate our team and our customers so we can all make informed decisions and improve quality. Having information at our fingertips is the best way to do that. We have compiled a list of the most common terminology within the precision measurement industry, backed by our experts with years within our industry.


Precision Measurement Glossary of Terms

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Tachometer

An instrument that measures angular velocity (speed) of a rotating object, typically in revolutions per minute.

Tape Measure

A flexible ruler used to measure distance, consisting of a ribbon of cloth, plastic, fiberglass, or metal strip with linear-measurement markings.

Tare

A deduction from the gross weight of a substance and its container made in allowance for the weight of the container

Temperature Coefficient

A numerical value indicating the relation between a change in temperature and a simultaneous change in some other property, often the physical length of an object.

Temperature Controller

An instrument used to control temperatures, mainly without extensive operator involvement

Temperature Data Logger

A measurement instrument that is capable of autonomously recording temperatures over a defined period of time

Temperature Limit

The full capability of the system from the lowest point to the highest point; limited by the sensor.

Temperature Probe

Any of a variety of devices which convert temperatures to electrical signals.

Tensile Tester

A device used to perform a test in which a sample is subjected to a controlled tension until failure.

Tension meter

A tension meter is a device used to measure tension in wires, cables, textiles, belts and more.

THD (% THD, Total Harmonic Distortion)

The contribution of all harmonic frequency currents or voltages to the fundamental current or voltage, expressed as a percentage of the fundamental

Thermal Shock

Occurs when a thermal gradient causes different parts of an object to expand by different amounts. This differential expansion can be understood in terms of stress or of strain, equivalently

Thermistor

A temperature sensitive passive semiconductor which exhibits a large change in electrical resistance when subjected to a small change in temperature. Usually with negative temperature coefficient.

Thermocouple (TC)

A sensor for measuring temperature that consists of two dissimilar metals that are joined together at the sensing end.

Thermocouple Break Protection

A Safety feature to indicate when a thermocouple has failed in an open circuit condition. Its purpose is to eliminate the possibility of an ambiguous reading. In the case of a temperature controller, it eliminates the dangerous condition of thermal runaway.

Thermocouple Calibrator

Any of a variety of devices used to simulate the presence of a thermocouple probe in an electrical circuit. Most models can simulate a variety of thermocouple types by sourcing a scaled voltage which represents a known temperature.

Thermocouple Loop Resistance

The total resistance of the thermocouple and its extension wire.

Thermometer

Any of a variety of instruments used to measure temperature. Thermometers may be digital (thermocouple or RTD), analog (bimetal), or liquid-in-glass and vary widely in temperature limits and accuracy.

Thermopile

A number of thermocouples connected in series, arranged so that alternate junctions are at the reference temperature and at the measured temperature, to increase the output for a given temperature difference between the measuring and reference junctions.

Thermowell

The pressure vessel into which an RTD or thermocouple is inserted for easy removal and/or replacement purposes.

Thread Gauge

Also known as a screw gauge or pitch gauge, is used to measure the pitch or lead of a screw thread.

Thread Profile Gage

These precision gages are ideal for quickly identifying each of the different tapered thread forms named in the API Std. 5B and Specification 7. Thread profile gages can also be used to perform a visual inspection of a thread form for detecting chipped inserts, stretched threads, wide first threads, or rolled over threads

Torque Analyzer (Torque Tester)

Any of a variety of devices which measure and analyze torque characteristics on a number of different torque tools such as electronic torque wrenches, dial torque wrenches, click torque wrenches, electric screwdrivers, air screwdrivers, pulse tools, cordless screwdrivers, torque screwdrivers and nutrunners. Most torque testers consist of a digital display and one or more torque transducers, sometimes with a loading system to apply the torque or a rundown fixture to simulate a torque joint. Some torque testers are analog models that rely on mechanical linkage to deflect a needle.

Torque Wheel (Torque Arm)

A tool used for the calibration of torque transducers, consisting of a rigid arc of a known radius and a suspension cable from which weights are hung. The cable rests against the arc so that the angle of force produced by the weights is always 90° to the torque length as the transducer turns with increasing weight. This reduces mechanical cosine error, allowing for a more precise application of known torque.

Torque Multiplier

A tool used to provide a mechanical advantage in applying torque to turn bolts, nuts or other items designed to be actuated by application of torque, such as the actuation of valves, particularly where there are relatively high torque requirements.

Torque Screwdriver

A screwdriver with components that ensure tightening to a specified torque, ensuring tightening which is sufficient, but not excessive.

Torque Transducer

A device for measuring and recording the torque on a rotating system, such as an engine, crankshaft, gearbox, transmission, rotor, a bicycle crank or cap torque tester.

Torque Watch

A measuring tool for measuring very low torque values, usually consisting of a chuck for mounting small parts or screwdriver bits and a dial face for reading the torque value.

Torque Wrench

Any of a variety of tools used to apply a known amount of torque when tightening a joint (usually a nut). Torque wrenches may have a dial face or digital readout which reports the amount of torque applied, or they may be micrometer-based wrenches which are set to a known torque and click when that torque is reached.

Total Runout

A 3D measurement which takes into account the entire surface of a part. Where runout measures only one cross-section relative to an axis, total runout takes the entire part into consideration

Tracking

The ability of an instrument to indicate at the scale mark being checked when energized by the proportional value of actual end-scale excitation.

Tracking Error

The error in indication at a scale mark, expressed in percentage of fiducial value, when the instrument is energized by the proportional value of the actual end-scale excitation.

Triac

A three-electrode semiconductor switching device that can switch either alternating or direct currents.

Trim

To make a slight change in a strain gauge system by means of a potentiometer or other adjustment point. In multiple load cell systems, a small adjustment to help balance the input from the different cells.

Triple Point

The Temperature at which the solid, liquid and vapor phases of a pure substance co-exist in equilibrium.

True RMS (Root Mean Square)

The true root-mean-square value of an AC or AC-plus-DC signal, often used to determine power of a signal. For a perfect sine wave, the RMS value is 1.11071 times the rectified average value, which is utilized for low-cost metering. For significantly non-sinusoidal signals, a true RMS converter is required.

Truck Scale

A large set of scales, usually mounted permanently on a concrete foundation, that is used to weigh entire rail or road vehicles and their contents

Two Wire Transmitter

Transmitters which provide a two-wire output with the same wiring used for power and output in order to reduce the number of wires running to the control enclosure. The load resistance is connected in series with a dc power supply, and the current drawn from the supply is a 4-20 mA or output signal which is proportional to the input signal.


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