Glossary of Terms

Glossary of Terms for the Scale Industry

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D

D/A Converter
Short for digital-to-analog converter. This is a device that changes a digitally coded word into its equivalent quantized analog voltage or current. Just like the A/D device, there are very high-speed D/A's available, capable of converting at data rates up to 1 GHz.

Dash Pot
A damping device used to reduce scale oscillations.

Data Base
A large amount of data stored in a well-organized manner. A data base management system (DBMS) is a program that allows access to the information.

Data Display Module
Device which stores computer output and translates this output into signals that are distributed to program determined groups of lights, annunciators, and numerical indicators in operator consoles and remote stations.

DC
Direct current; an electrical current flowing in one direction only and substantially constant in value.

Dead Load
Empty weight of vessel or fixed force of platform and load-supporting structures on scale that must be cancelled out by weight measuring system.

Dead Time
Interval of time between initiation of input change or stimulus and start of resulting response.

Default
The value(s) or option(s) that are assumed during operation when not specified.

Deflection
In weigh-equipment, total measured displacement at point of load sensing in going from zero or no-load condition to full scale or rated load condition.

Density
Mass per volume. Often approximated as weight per unit.

Deviation
Difference between instantaneous value of controlled variable and desired value of controlled variable corresponding to set point. See error.

Digit
A measure of the display span of a 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. For example, a meter with a display span of ±3999 counts is said to be a 3-3/4 digit meter.

Digital
Pertaining to data in form of digits. Contrast with analog.

Digital Averaging
The ability of a digital indicator to smooth bouncy or erratic readings by taking several readings and averaging them together before sending the signal to the display. In creasing the digital averaging slows the indicator's update rate.

Digital Filtering
The process of smoothing, or removing noise from a signal via mathematical functions that are performed on the digital data stream.

Digital Gage
Measuring device that indicates measurement result via digital signal. Contrast with analog gage.

Digital Output
An output signal which represents the size of an input in the form of a series of discrete quantities.

Digital-to-Analog Conversion (D/A Conversion)
Production of analog signal whose instantaneous magnitude is proportional to magnitude of digital value.

Display
1) Image that appears on CRT screen or on other image projection systems. 2) Graphic representation of process variables or conditions.

Display Menu
List of displays from which you select specific information for viewing.

Dribble
In batching, reduction of rate of material flow near batch completion to avoid overshooting of desired batch weight or volume.

Drift
In weighing systems a random change in signal under constant load conditions. 2)The natural tendency of a device, circuit, or system to alter its characteristics with time and environmental changes. There is a change in the output characteristics while the inputs to the device have not changed, which affects accuracy.

Drift occurs over different time scales for different reasons. One of the most common and influential drift inducing effects is a change in ambient temperature. This is why the specifications of many sensors state the effect of temperature on various characteristics of the device. On an older device, drift may be caused by ageing affects on the materials it is made of, such as oxidation of metal elements. It can also be caused by the mechanical

Dust-Tight Construction
Classification of control and equipment construction which requires such devices be sealed sufficiently to prevent escape or intrusion of dust.

Dynamic Calibration
Calibration in which the input varies over a specific length of time and the output is recorded vs. time.

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