Metrology Glossary – D

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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D’Arsonval Movement

A meter movement based upon the permanent-magnet DC motor principle: a small coil of wire supported on jewel bearings or taut band between the poles of a permanent magnet. The magnetic field of the DC current passing through the coil interacts with the magnet’s field, causing rotation of the coil and an attached pointer against the restoring force of coil springs

Dashpot

A damping device which resists motion with viscous friction. The resulting force is proportional to velocity, but acts in the opposite direction.

Data Logger

An electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors

Decibel (dB)

A logarithmic measurement scale of the ratio of two voltages. Every 20dBs correspond to a voltage ratio of 10, every 10 dBs to voltage ratio of 3.162. Often used to measure sound or relative power in microwave frequency circuits.

Dead Load

An immovable, constant load. In structural engineering, refers to the weight of the structure itself and any immovable fixtures such as carpet or drywall. In calibration, refers to any pre-existing mass on a scale that cannot be removed prior to calibration such as the tank on a tank scale.

Dead Weight Tester

A calibration standard that uses the principle of a pressure balance to calibrate pressure measuring instruments. Deadweight systems consist of weights stacked on a piston which floats when hydraulic pressure is applied with a pump.

Deadband (Hysteresis)

In a digital controller, there may be one switching point at which the signal increases and another switching point at which the signal decreases. The difference between the two switching points is called hysteresis or deadband.

Decade boxes 

A box with a series of resistors, capacitors, or inductors which allows the user to select specific values. In calibration, decade boxes are often high-precision, allowing them to be used to calibrate a variety of electrical testers and meters.

Decimal Point

A small dot (point) used to separate the whole number part of a figure from the fractional part. Numbers to the right of this point are referred to as decimals. For example 48.2 uses the decimal point to separate 42 (the whole number part) from .2 (the decimal or fractional part, which is actually two tenths).

Deflection

The movement of a needle or the change in a digital display which indicates a change in the measured value. For example, a scale deflects to indicate a change in weight on its pan.

Delta Connection

A circuit formed by connecting three electrical devices in series to form a closed loop; most often used in three-phase connections.

Demand (active, real or true power)

The power which is actually consumed by the load. This measurement takes the power factor into account.

Demand Mode

How often a safety precautions are needed to respond to a certain event. Low demand mode (the most common mode in process applications) means less than one response per year.

Depth Gauge

Any of a variety of gauges used for measuring the depth of grooves, holes or other concavities.

Diameter Tape

Measuring tape used for determining the diameter of a cylindrical object.

Dielectric Strength

The maximum electrical field that an insulating material may be exposed to before its insulating properties break down.

Differential Input

A signal-input circuit where SIG LO and SIG HI are electrically floating with respect to ANALOG GND (METERGND, which is normally tied to DIGGND). This allows the measurement of the voltage difference between two signals tied to the same ground and provides superior common-mode noise rejection.

Differential Pressure Gauge

A visual indicator, designed to measure and illustrate the difference between two input pressures.

Differential Probe

Any of a variety of probes used for measuring the electrical voltage or current difference between two test points where neither test point is at ground.

Digit

A measure of the display span of a digital panel meter. By convention, a full digit can assume any value from 0 through 9, a 1/2 digit will display a 1 and overload at 2, a 3/4 digit will display digits up to 3 and overload at 4, etc.

Digital

Any device which displays a reading in digits rather than using a pointer. Also, any signal expressed as a series of the digits 0 or 1 as represented by physical values such as voltage.

Digital Averaging

A signal processing technique applied in the time domain and used to clarify a signal subject to noise by averaging a number of readings.

Digital Filtering

A signal processing technique which performs mathematical operations on a signal to reduce or enhance certain aspects of that signal.

DIN (Deutsche Industrie Norm)

A set of German standards recognized throughout the world. The 1/8 DIN standard for panel meters specifies an outer bezel dimension of 96 x 48 mm and a panel cutout of 92 x 45 mm.

Diode

An electrical component that allows current to flow in only one direction.

Distortion Factor (%DF)

Total difference between apparent power and true power at all harmonic frequencies.

Distortion Meter

A type of electronic test equipment used to determine specific frequencies that cause distortion in electronic devices.

Divisions (Display)

The maximum the scale can read divided by the minimum it can read is the number of divisions.

Dormant Scale

A scale whose base is embedded in a floor to bring the surface of the pan level with the floor.

Draft Shield (Weight and Scale)

A part of an analytical balance or mass comparator which keeps airflow from affecting readings

Drift

The continuous, slow change in a reading, especially on a digital device. Drift may cause a device to show readings above or below the actual value of the measurand.

Dropout

A momentary loss of signal in a communications system, usually caused by noise, propagation anomalies, or system malfunctions.

Dry Block

A versatile temperature calibrator that works by heating or cooling a metal block to a specific temperature and maintaining that temperature

Dual Inline Package (DIP)

An integrated circuit constructed with a plastic or ceramic case with metal pins running along each side.

Dual-Slope Conversion

A digital technique for converting a measured analog quantity to a precise digital equivalent, for display as a numerical value. During a fixed interval of time, the output of an integrating circuit rises linearly at a rate proportional to the measured analog input quantity. The circuit input is then switched to a precise reference-voltage source of opposite polarity, causing the output to descend at a fixed rate, while a counting circuit counts clock pulses delivered by an internal pulse generator. As the integrator output reaches its base level, the count is terminated; the total count (numerically equivalent to the analog input quantity) is then displayed in a digital readout as a voltage, current, resistance, or other parametric quantity.

Duplex Sensor

A dual element RTD or thermocouple wherein the elements are isolated from each other and contained in the same housing or sheath.

Durometer

An instrument used for determining the hardness of plastics and rubber.

 


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