Glossary of EE Terms
-
D/A Converter (also D/A or DAC)
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.
-
DAC Gain Error
The measure of the span error of the DAC. It is the deviation in slope of the actual DAC transfer characteristic from the ideal. Gain Error is usually expressed as a percentage of the full-scale range.
-
Data Acquisition
Data acquisition is the process of sampling signals that measure real world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems (abbreviated with the acronym DAS or DAQ) typically convert analog waveforms into digital values for processing.
-
dB FS
These are decibels relative to full scale amplitude (digital microphones)
-
dB SPL
Sound pressure level in decibel, relative to 20 µPa (20 µPa = 0 dB SPL, 1 Pa = 94 dB SPL).
-
dBA
dBA are decibels A-weighted.
-
dBV
A decibel relative 1V reference (1V = 0dBV)
-
DCS – Distributed Control System
Process Management is synonymous with what is commonly known as Distributed Control Systems (DCS). Within the system the process controller elements are not centrally located, but are distributed throughout the system with each component sub-system controlled by one or more controllers. They are used to control manufacturing processes that are continuous or batch-oriented. These processes can be very complex and expensive, particularly if downtime is experienced. DCS requires high-accuracy and complex controller solutions with advanced processing and network capability with a large focus on reliability.
-
Dead Reckoning
Dead Reckoning is a method of determining position using a combination of previous position, direction, and acceleration. A gyroscope can be used to measure rate of rotation, which is integrated once to obtain heading information. An accelerometer can be used to measure acceleration, which is integrated twice to obtain distance traveled.
-
Degrees of Freedom
Degrees of freedom (DoF) are the set of displacements and rotations along which an object can move. 6 degrees of freedom (x, y, z translational; pitch, roll, yaw rotational) are sufficient to fully define motion in free space.
-
Diaphragm
A diaphragm is the same as a membrane. It is the moving part of the condenser.
-
Differential Analog Input Voltage Range
The peak to peak differential voltage that must be applied to the converter to generate a full scale response. Peak differential voltage is computed by observing the voltage on a single pin and subtracting the voltage from the other pin, which is 180 degrees out of phase. Peak to peak differential is computed by rotating the inputs phase 180 degrees and taking the peak measurement again. Then the difference is computed between both peak measurements.
-
Differential Linearity (DNL)
The difference between the measured and the ideal 1 LSB change between any two adjacent codes in a converter’s transfer function. It is an important specification for measuring error in converters; the DC accuracy of a converter is mainly determined by this specification. DNL is defined the same for precision and high-speed data converters.
-
Digital Downconversion (also direct-IF-to-digital conversion)
This refers to a demodulation technique for sampling an intermediate frequency (IF) signal with a wide-bandwidth A/D whose sampling rate is equivalent to the local oscillator frequency (< IF frequency). In this super-Nyquist application, the A/D serves as the mixer stage and its digital output data is a beat frequency; the modulation data can be recovered with a DSP stage.
-
Digital Feedthrough
Digital feedthrough is a measure of the impulse injected into the analog output of the DAC from the digital inputs of the DAC but is measured when the DAC output is not updated. It is specified in nV-sec and measured with a full-scale code change on the data bus, that is, from all 0s to all 1s, and vice versa.
-
Digital Filtering
The process of smoothing, spectrally shaping, or removing noise from a signal has traditionally been accomplished with analog components. With the advent of high-speed DSP products, now filtering can effectively and economically be accomplished in the digital domain. Digital filters are basically mathematical functions that are performed on the digital data stream and their characteristics can be altered under software control, which adds to their overall flexibility. Finite Impulse Response (FIR) and Infinite Inpulse Response (IIR) are examples of digital filter functions.
-
Digital Isolator (from definition in iCoupler Quick Sales Reference)
A device that separates two electrical systems for safety and circuit functional requirements.
-
Digital Output Sensor
A digital output sensor provides a discrete binary code that is proportional to its input stimulus.
-
Digital Potentiometer -- DigiPOT, VR, Variable Resistor
The Digital Potentiometer is an integrated circuit that performs the same resistance adjustment as a mechanical trimmer or Rheostat. In addition, it can be configured to perform the three-terminal mechanical potentiometer voltage divider function. Digital Potentiometer are known by several abbreviated names: E2POT, DACPOT, VR, variable resistor, RDAC, Rheostat, etc.
-
Digital RF memory (DRFM)
DRFM systems digitize incoming RF input signals at a frequency and with sufficient bandwidth to adequately represent the signal to enable reconstruction and retransmission of the RF signal as and when required. Low latency between digitization and reconstruction are typically a requirement for such systems as they are used for jamming and Radar simulation systems. A DRFM may also modify the signal prior to retransmission to alter the signature and create false targets; adjusting its apparent radar cross section, range, velocity, and angle.
-
Digital to Analog Converter (DAC, D/A Converter)
An digital to analog converter is a device that changes a digitally coded word into its "equivalent" quantized analog voltage or current.
-
Digital-to-Analog Glitch Impulse
Digital-to-analog glitch impulse is the impulse injected into the analog output when the input code in the DAC register changes state. It is generally specified as the area of the glitch in nV-sec and is measured when the digital input code is changed by 1 LSB at the major carry transition.
-
Direct Digital Synthesis (DDS)
A process by which you can digitally generate a frequency-agile, highly-pure sinewave, or arbitrary waveform, from an accurate reference clock. The digital output waveform is typically tuned by a 32-bit digital word that allows sub-Hz frequency agility. The DDS's frequency output is normally reconstructed with a high-speed, high-performance D/A to generate an analog output signal. The ability to add internal functions such as phase modulation, amplitude modulation, digital filtering, and I&Q outputs, are making DDS devices attractive for digital communication applications. They serve in capacities such as modulators, local oscillators, and clock detect/recovery circuits.
-
Directionality
Directionality is the way a microphone responds to sounds coming from different directions. There are three basic types of microphones by directionality:
- Omnidirectional, or Omni – responds equally to sounds coming from all directions
- Unidirectional – responds primarily to sounds coming from one direction. Most common unidirectional microphones are cardioid microphones.
- Bi-directional, or Figure-eight – responds to sounds coming from two opposite directions, with a null in between.
Note: all ADI microphone models are Omnidirectional.
-
Displacement Damage (DD)
Non-ionizing radiation induced device degradation. The damage mechanism is as a result of collisions with atoms to displace them from lattice positions creating interstitials and vacancies. The overall effect of displacement damage (DD) is a change in the minority carrier lifetimes of semiconductors, and increased light absorption and coloration in crystalline optical materials.
-
Dither
The technique of adding controlled amounts of noise to a signal to improve overall system loop control, or to smear quantizing error in an A/D converter application.
-
Double Tap
A double tap refers to two taps in close succession.
-
DSP
DSPs or Digital Signal Processors take real-world signals like voice, audio, video, temperature, pressure, or position that have been digitized and then mathematically manipulate them. A DSP is designed for performing mathematical functions like "add", "subtract", "multiply" and "divide" very quickly.
Learn more about Digital Signal Processors.
Searching Resources...
