Metrology Glossary – C

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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Calibration

The act of comparing an unknown quantity or value with a known quantity or value. It includes checking, adjusting, or systematically aligning a test instrument to a known standard.

Calibration Curve

A process model that is constructed primarily for the purpose of calibration, describing the relationship between two measurement scales and providing the means for conversion.

Calibration Error

The difference between the reading and actual measurement within a calibrated device. Also, errors in a reading caused specifically by misalignment of an instrument’s calibration constants.

Caliper

A handheld precision measurement tool used to determine a variety of measurements such as an internal diameter, outsite diameter, depth, or step of an object. Calipers are made in a variety of models such as vernier, dial, digital, or traditional inside/outside and divider calipers.

Capability Study

A set of calculations used to assess whether a system is statistically able to meet a set of specifications or requirements.

Capacitance

The potential of a system to hold electric charge, measured in Farads.

Capacitance Meter

A piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors.

Capacitor

An object or system which can store electrical energy. Typically, a component in an electrical circuit rated in Farads for its potential to hold a charge.

Capacity (Scale)

The upper end of the range for a scale or load cell. Many scales and load cells have an actual capacity much greater than the printed or published capacity (usually 1.5 or even 2 times) This is to avoid a potential blowout which can occur when the device is overloaded.

Centrifuge

A machine that uses a centrifugal force to separate liquids and solids, or to separate liquids of different densities.

Certificate of Conformance (NTEP Certificate of Conformance)

Certificate offered by the National Conference of Weights and Measurements which states that equipment complies with national standards

Chain Hoist

A lifting or hoisting apparatus in which the stress of lifting the load is borne by a chain over pulley mechanisms. Frequently used to lift and hold extreme loads over extended periods of time, chain hoists can experience slip, where gravity over time forces hoisted loads to lose clearance.

Chamfer Gage

A precision instrument designed specifically to measure the top (major) diameter of a chamfer, countersink, center drill, or tapered hole.

Chart Recorder

An instrument used to record various process and electrical signals. Traditionally, a paper chart with a marker or pen tip has been used to record such conditions as temperature, pressure and relative humidity over time, however newer versions are digital and can be remotely monitored with computer interfacing hardware and software.

Checkweigher

An automatic or manual scale used for checking the weight of packaged commodities, usually in some form of high speed or motion-based process. It is normally found at the off-going end of a production process and is used to ensure that the weight of a pack of the commodity is within specified limits.

Clamp Meter

An electrical tester that combines a basic digital multimeter with a current sensor designed to clamp around a conductor.

Class III

Accuracy class for commercial items

Class IIIL

Accuracy class for vehicles and items over 30,000 pounds

CMR (Common-Mode Rejection)

The ability of a differential amplifier to not pass (reject) the portion of the signal common to both the + and – inputs.

CMV (Common-Mode Voltage)

The voltage between neutral point of the load and the system ground. Also, the voltage between neutral point of the load and the dc midpoint.

Coaxiality

The tolerance for how closely the axis of one cylinder conforms to the axis of another cylinder.

Cold Junction Compensation

When measuring temperature using thermocouples, the process of compensating for the voltage created when the cold junction is not at 0°C.

Combination Square

An adjustable device used as a tri-square, miter square, or level.

Combined Error

Maximum possible deviation from all the factors that can cause error

Commercially Pure (CP)

Usually considered to have impurities of not more than 1 part in 10,000.

Comp Loop

An extra pair of wires going to the tip of an RTD but not connected to the element, a novel way of lead wire resistance compensation.

Compound Pressure Gauge

A pressure measurement device that can display both positive and negative (vacuum) pressures.

Compression

A reduction of volume without a reduction of mass.

Compression Tester

A device used used to establish the compressive force or crush resistance of a material and the ability of the material to recover after a specified compressive force is applied. Compression testers can be manual or automatic and some feature high accuracy load cell units to measure load over time.

Concentrated Load Capacity (CLC)

The maximum amount of weight a weighbridge can have on it within a certain area.

Concentricity

The 2D tolerance that controls how closely a cross-section of a cylinder, sphere, or cone is to a mathematically perfect circle.

Conductivity( Electrical)

The measure of how well a material can conduct electricity. It is the inverse of resistivity.

Conductivity (Thermal)

The measure of how well a material can conduct heat.

Conductivity Meter

A device that measures the amount of electrical current or conductance in a solution.

Connection Head (Environmental Monitoring Systems)

The link between the Process (conduit) and the Sensor, containing a terminal block for lead connections.

Control Drawing

A basic outline with engineering description, qualification requirements and equipment drawings.

Controller (Temperature/Pressure or other Process)

A device capable of receiving a signal from a sensing probe (temperature, pressure, humidity, etc.) within a process and regulating an input to that process in order to maintain selected environmental conditions (control point).

Conversion Rate

The number of analog-to-digital conversions performed per second by a Data Processing Machine.

Coordinate Measuring Machine (CMM)

A device that dimensionally measures 3-D components with an accuracy approaching 0.0001 inches. They typically consist of a large granite or hard surface platform connected to an elevated crossbar which holds a probe that travels in three dimensions around an object placed on the platform.

Copper-Accelerated Acetic Acid Salt Spray (CASS)

A method of corrosion resistance testing that involves adding acetic acid to a solution with salt used in salt spray tests. This method is much more corrosive than the ordinary salt spray method of testing.

Cornerload

The load on an individual corner of a scale with multiple load cells.

Cornerload Error

The error associated with putting a weight on the corner or away from the center of a scale.

Corruccini Technique

A method of interpolation for a platinum RTD. This method is based on the measurement of two or three fixed points and their correlation to an NIST calibrated reference thermometer, essentially fitting the slope of the reference thermometer to the calibrated thermometer

Count/Counts (Scales and Scale Systems)

The number of time intervals counted by the dual-slope A/D converter and displayed as the reading of the decimal point.

Counting Scale

A scale, often of the benchtop variety, which has the capability to count individual pieces or units by weight.

Crane Scale

A scale or load cell attached in line to the lifting mechanism of a crane or hoist for determining lift load.

Creep

The slight loss of tension (in-line) or clearance (hanging) when load is applied over time.

Creep Recovery

The gradual recovery of tension or clearance which has experienced creep.

Crest Factor

The ratio of the maximum (crest) value of a periodic function (AC voltage or current) to its RMS value.

Current

The rate of flow of electricity. Usually measured in Amperes.

Current Loop

An electrical setup that uses two conductors to send signals to a device. It can be used for analog signaling or supplying

Current Probe

Any of a variety of probes that senses the current flowing through a conductor and converts it to a voltage that can be viewed and measured on an oscilloscope or meter.

Current Shunt

A low-value resistive load with a known resistance value through which current flows. Voltage is measured across the shunt and used (along with the known resistance value) to calculate the current in a circuit using Ohm’s Law.

Current Transformer (CT)

An instrument accessory which detects current flow without breaking the circuit under test. An AC transformer, usually step-down; typical ratio listing would be 1000:1. This would indicate 1000A on the primary and 1A on the secondary. Also called Toroidal coil for process applications. Typical output is 5 AAC when full load current is applied to the system.

Cylindricity

Assesses how closely an object comes to a perfect cylinder, meaning that it is not only round, but also straight along its axis


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