Metrology Glossary – A

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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Absolute Pressure

Zero referenced to a perfect vacuum, equaling the sum of gauge pressure plus atmospheric pressure

Absolute Zero (Temperature)

Theoretically the lowest temperature possible, at which atoms would stop moving. Equivalent to 0°K, -273.15°C, and -459.97°F

Accelerometer

An instrument used for measuring acceleration, typically that of the vibration of a machine, building, or other structure. Accelerometers may measure one axis of movement or three axes of movement.

Accreditation Body

An organization that provides accreditation services. Most often this is an outside or third party that provides individuals with recognition of the ability to perform specific task. Usually delivered in the form of a certificate or diploma which defines the scope of the accreditation.

Accumulator

An energy storage device, which accepts, stores, and releases energy. Devices can store various types of energy including, thermal, mechanical, and electrical.

Accuracy

The degree of exactness to which the final product of a measurement corresponds to the measurement standard. Accuracy of a device is specified by the manufacturer to indicate the degree to which the readings provided by the device may deviate from the actual value.

Air Sampler

A device or equipment used to sample a measured amount of air in a specified time to quantify the particulate or microbiological content of air within a controlled environment.

Aircraft Weighing Scale

A device used to weigh aircraft. Typically, comprised of a series of three load cell units connected to a central control unit and readout. Each load cell is placed below a contact point with the ground and simultaneously reports load to measure weight of an aircraft.

Alpha

Temperature coefficient of resistance expressed in ohm/ohm/°C. Defines the average resistance/temperature relationship over the fundamental interval of 0 to 100°C.

Alternating Current (AC)

An electrical current within a circuit which reverses the direction of flow of electrons continuously at regular intervals.

Ambient Conditions

The surrounding conditions (temperature, humidity, air pressure, etc.) that are taken in to consideration when systems are commissioned or tested.

American Association for Laboratory Accreditation (A2LA)

A non-profit, internationally-recognized accreditation organization that offers a full range of comprehensive laboratory and laboratory-related accreditation services and training.

American National Standards Institute (ANSI)

The primary organization for fostering the development of technology standards in the United States. ANSI works with industry groups and is the U.S. member of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC)

American Standard Code for Information Interchange (ASCII)

The most common format for text files on a computer. Created by using binary numbers to represent upper and lower case letters, numbers, and special characters.

American Wire Gauge (AWG)

The American Wire Gage is an index which shows, indirectly (inversely and logarithmically), the cross-sectional area of a round wire.

Ammeter

A device that measures the electric current in a circuit.

Ampere

The base unit of an electric current in the International Systems of Units, equivalent to a flow of one coulomb per second

Analog

Signals or information represented by a continuously variable physical quantity such as spatial position (as an analog pressure gauge), voltage (as a needle-and-scale panel meter), etc.

Analytical Balance

A device used to weight materials, often in the milligram or sub-milligram range. Typically analytical balances house enclosed weighing environments as to not affect the material weight by air particles such as dust or other debris. Often called a draft shield, these enclosure also protect the weighing area from any cross drafts or airflow that would affect readings.

Anemometer

An instrument used for measuring the speed of wind or the current of a gas.

Angle Block

A device used in dimensional metrology as a base standard for a particular angle. Typically angle blocks come in a set ranging from 1 degree up to 45 degrees and can be stacked to build specific angles for references.

Angular Load – Concentric (Common Center)

A load applied concentric with the primary axis at the point of application and at some angle with respect to the primary axis

Angular Load – Eccentric (Off Center)

A load applied eccentric with the primary axis at the point of application and at some angle with respect to the primary axis

Aperture

The opening of a lens’s diaphragm that controls the amount of light that can pass through – in metrology this is relevant in equipment such as optical comparators and vision systems where lighting can affect a measurement.

Apparent Power

a measure of alternating current (AC) power that is computed by multiplying the root-mean-square (rms) current by the root-mean-square voltage.

Associated Apparatus

A device used in intrinsically safe circuits which serves to limit the energy available in order to maintain the intrinsic safety of the circuit under prescribed conditions. Typically a “safety barrier” and is usually required to be installed in a non-hazardous location.

Asynchronous Transmission

Describes a process where transmitted data is encoded to include start and stop bits to inform the receiver where each character begins and ends. Also called start/stop transmission.

Attenuator

An electronic device that reduces the power of a signal while not distorting its waveform.

Auto Ignition Temperature (AIT)

The lowest temperature at which a material will spontaneously combust in a normal atmosphere without an external source of ignition, such as a flame.

Auto-Polarity

Automatic interchanging of connections to a digital meter when polarity is wrong; a minus sign appears ahead of the value on the digital display if the reading is negative.

Autoclave

A device that uses pressure and temperature to reach and maintain a particular environment. They are used frequently within the life sciences or chemical industry to produce environments inhabitable for any microorganisms or their spores. Other uses include production of carbon fiber components for the aerospace and motorized vehicles industry. Chambers can range in size from small table top units to industrial units sometimes up to 100 feet in length and 15 feet in diameter.

Automatic Shut Off

A mechanism that has the ability to shut off a system or device without the need for any human interaction. Often automatic shutoff mechanisms are attached to pressure or temperature systems and require calibration in order to properly trigger when conditions are met. Similar to a pressure relief valve, an automatic shutoff mechanism keeps conditions from reaching dangerous levels even with no human interaction.

Automatic Zero / Automatic Zero Maintenance (AZM)

Electronically compensates for numerous conditions that cause minor variations around zero, providing a means to have a “true zero” at all times on a digital scale or device.

Average Piece Weight (APW)

Used by counting scales to count pieces by taking the amount of weight and dividing it by the number of samples.

Avoirdupois Units

A system of measuring weight that uses pounds and ounces.

Axial Load

Force administered along the lines of an axis.

Axle Scale

A device used to weigh vehicles based on the load at each axle where each axle is weighed individually and then all weights are added for a full measured value. Often axle scales are used in place of full vehicle scales due to space and budget restrictions.


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