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Glossary of data acquisition terms.
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24-Hour Time-of-Day Mode: Counter/Timer circuits which may be used as real-time clocks. They are able to control triggering based on the time of day.

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 A 

A/D Conversion Time: This is the length of time an A/D converter requires to convert an analog signal into a digital value. The theoretical maximum speed (conversions/second) is the inverse of this value. The FAST 1611 high-speed A/D board is a highly efficient example, providing a full 1MHz speed from a micro's conversion time. See Speed/Typical Throughput

A/D Converter (ADC): A device (usually an IC chip on your data acquisition board) which accepts an analog signal and outputs a corresponding digital value.

A/D, D/A: Analog Input boards convert analog signals into digital values (A/D-Analog to Digital), allowing your PC to acquire data from analog sources; Analog Outputs convert D/A (Digital to Analog), usually supplying a voltage or current.

AGP: Accelerated Graphics Port. A video port design by Intel (R) to increase video data transfer performance up to 8x beyond the standard PCI bus. Slots come in standard AGP shapes, and in longer AGP PRO shapes.

ANSI: American National Standards Institute.

ASCII: American Standard Code for Information Interchange-numeric values assigned to letters, numbers, and other characters to enable exchange of information between devices. i.e. 'A'=65, 'B'=66, etc.

ASIC: Application Specific Integrated Circuit, an integrated circuit with a large number of logic gates that are connected to meet a specific application requirement.

AT Bus: Now commonly known as the ISA bus, the AT bus is the original 16-bit expansion bus featured in the IBM AT. See ISA Bus for more detailed info. Other bus types include PC, EISA, PCI.

ATM: Asynchronous Transfer Mode

Accuracy: The maximum deviation that can be expected between the meter reading and the actual value being measured, under specified conditions.

Alias: A false lower frequency component that appears in data sampled at too low a sampling rate. (See the Nyquist Sampling Theorem).

Analog: Having the property (electrical) of varying in continuous, rather than incremental or discrete steps.

Analog Slope Trigger: Sampling can be triggered at a user-selectable point on an incoming analog slope. Triggering can be set to occur at a specific threshold level, including select modes of +/- slope, level high, & level low. Our DAP, FAST, & HSDAS series boards all include this useful triggering option.

Asynchronous: A method of serial communication where data is sent when it is ready without being referenced to a timing clock, rather than waiting until the receiver signals that it is ready to receive.

Attenuation: Reducing the amplitude of a waveform without introducing distortion. An adjustable passive network (filter) may be used to reduce power level of a signal without introducing any appreciable distortion

Auto-Polarity: An ability of digital instruments to measure and display values of either polarity without the need to interchange test lead connections

Autoranging: When autoranging, a board can be set to monitor the incoming signal and automatically select an appropriate gain level based on the previous incoming signals.

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 B 

BIOS: Basic Input/Output System, a set of routines (usually loaded at startup) that support the transfer of information between elements of the system including disk drives, memory and displays.

BPS: Actual number of Bits Per Second--similar to Baud.

Background Acquisition: The collecting of data 'in the background' while other software is running.

Backplane: See Passive Backplane

Base Address: A memory address that serves as the starting address for programmable registers. All other addresses are located by adding to the base address. The default base address on most of our data acquisition boards is 300Hex.

Batch file: An ASCII text file containing a sequence of operating or system commands.

Baud Rate: This is the speed (in bits-per-second) at which data transfer can occur. 38.4 kilobaud is 38,400 bits of data per second. Since most data transfers involve an 8-bit character plus 1 or 2 additional bits, typically 10 baud equals 1 character per second. (14.4kbaud Ù 1440 characters/second.)

Benchmark: A standard to which similar products can be tested for the purpose of comparison.

Bias Current: Current that flows out of an amplifier's input terminals that will produce a voltage drop across the source impedance in a perfect amplifier this error term will be equal to zero.

Binary: Base 2 numbering system consisting of only 0 and 1. May be represented as a digital signal and referred to as True/False, High/Low, or On/Off.

Bipolar Inputs: Bipolar inputs are designed to accept voltages in the ±X Volts range, allowing positive or negative voltage inputs. (ex: ±5V). See Unipolar.

Bits & Bytes: One bit is one Binary digit, either a binary 0 or 1. One Byte is the amount of memory needed to store each character of information (text or numbers). There are eight bits to one Byte (or character); there are 1024 Bytes to one Kilobyte (K, KB), and 1024 Kilobytes to one Megabyte (MB, Meg). Our data acquisition boards typically take two-byte samples, so a board acquiring data at a 20kHz sample rate is actually gathering 40,000 bytes of data per second. See also Word.

Boolean Algebra:  form of algebra that uses logic, rather than numeric calculations. Some Boolean functions are AND, OR, and NOT.

Breakout Box: A device used to troubleshoot or test communications signals between two devices.

Brownout: A short-term decrease in voltage levels to below 80% of their nominal value.

Buffer: A storage area for data that is used to compensate for the speed difference when transferring data from one device to another. Usually refers to an area reserved for I/O operations, into which data is read, or from which data is written. Buffer Memory is usually stated either in bytes or in words (samples).

Burst-Mode:  high speed data transfer in which the address of the data is sent followed by back-to-back data words, minimizing channel-to-channel skew.

Bus: The expansion connector built into the computer. Boards are inserted into this connector, and all communication between the computer and your board occurs through the computer’s bus. There are several different expansion buses available, including the XT, AT, PCI, EISA, and VESA buses for IBM-compatible PCs, & NuBus or PCI for the Macintosh PC line.

Byte: See Bits & Bytes.

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 C 

CAD/CAM/CAE: Computer-Aided Design, Computer-Aided Manufacturing, Computer-Aided Engineering.

CD-ROM: Compact Disc-Read Only Memory, a high capacity (600 megabytes) storage media that uses laser optics to read data. Similar to standard 5" CDs.

CMRR (Common Mode Rejection Ratio): The board’s ability to measure only the difference between the leads of a transducer, rejecting what the leads have in common. The higher the CMRR, the better the accuracy.

Cache: High-speed processor memory that buffers commonly-used instructions or data to increase processing throughput.

Code: The text of a computer program. Also used as a verb; to code means to write a program.

Cold Junction Compensation (CJC): Thermocouple measurements require a reference to icepoint temperature (0°C), cold Junction Compensation circuitry measures the ambient temperature at the junction and provides necessary compensation. Our STT terminal panels feature a heavy isothermal plate for high-accuracy cold junction compensation.

Cold Junction Compensation Channel: An additional data acquisition input channel used exclusively for cold junction compensation, leaving the remaining input channels free for data acquisition. Our ACPC boards include this channel for increased accuracy and consistent temperature measurement. See Thermocouple.

Conversion Rate: The number of analog-to-digital conversions performed per second by an A/D device.

Counter/Timer Trigger: On-board Counter/Timer circuitry can be set to trigger data acquisition at a user-selectable rate and for a particular length of time.

Counter/Timers: User-accessible circuitry built into many of our DAS boards which can be used for event counting or frequency measurement.

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

Current Inputs: A board designed for current inputs can accept and convert analog current levels directly, without conversion to voltage. (Typ. 0-20 or 4-20ma).

Current Sink: This is the amount of current the board can supply for digital output signals. With 10-12mA or more of current sink capability, you can turn relays on and off. Digital I/O boards with less than 10-12mA of sink capability are designed for data transfer only, not power relay module switching.

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 D 

D/A: Digital to analog; See A/D.

DAC: Acronym for Digital-to-Analog Converter. See A/D.

DAS: Acronym for Data Acquisition System.

DDE: Dynamic Data Exchange, A form of interprocess communication implemented in Microsoft Windows and OS/2 which allows data from different applications to be easily shared.

DDL: Data Definition Language, used to define all attributes and properties of a database.

DIO, DI/O, Digital I/O: Digital Input and Output.

DLL: Dynamic Link Library–A Windows® software module composed of executable code and data that can be called from or used by applications or other DLLs; typically used to enhance software by adding functionality with very little programming required. Instructions and data in a DLL are loaded/run when they are called by an application or by other DLLs.

DDWG: Digital Display Working Group; a consortium that developed the DVI standard.

DOS: Disk Operating System

DSP: Digital Signal Processor, an integrated circuit designed for high speed data manipulations

DT-Connect: A board-to-board interconnect standard to facilitate high-speed data transfer by completely freeing the PC bus from data transfer overhead.

DVI: Digital Visual Interface; standard developed by the DDWG to direct the digital signal connection between a PC and a Display Device. See the DVI Technical Tutorial.

Daughterboard: A printed circuit board that attaches or “piggybacks” onto another to provide additional functionality or performance.

Delta-Sigma Modulating ADC: A high accuracy analog-to-digital converter circuit that samples at a higher rate and lower resolution than is needed, and (by means of feedback loops) pushes the quantization noise above the frequency range of interest. This out-of-band noise is typically removed by digital filters.

Differential (Diff): See Number of Channels.

Direct Memory Access (DMA): Allows a 64KByte block of memory to be set aside for high-speed transfer of data to PC system memory. Boards which support single DMA access can store up to 64KBytes of data (32K samples) at speeds which can reach 250KBytes per second on ISA-bus PCs. Dual DMA access means that a second 64KByte block is set up while the first is being filled, allowing unlimited sample sizes.

Drift: Meter reading or set point variations due to changes in component values, often due to external changes in ambient temperature or line voltage.

Dual-Ported RAM Memory: Allows acquired data to be transferred from on-board memory to the computer’s memory while data acquisition is occurring.

Dual-Scan Color Displays: A passive-matrix flat screen color display technology which is slower than a TFT display, and less expensive. See LCD, STN, TFT.

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 E 

EDID: Extended Display Identification Data; a standard data format containing monitor information such as vendor information, monitor timing, maximum image size, and color characteristics. Together with the DDC specification, this enables the PC system, display, and graphics adapter to communicate. This, in turn, allows the system to be configured to support specific features available to the display.

EEPROM: Electrically-Erasable Programmable Read-Only Memory, a nonvolatile memory chip which may be erased & reprogrammed electronically.

EMI: Electromagnetic Interference

EPP: Enhanced Parallel Port.

EPROM: Erasable Programmable Read Only Memory, a nonvolatile memory chip which may be erased only with exposure to ultraviolet light.

Electro-Luminescent (EL) Display: Monochrome flat-screen display with yellow-green text. (2 to 16 grays). Immune to vibration; offers a wide viewing angle.

Emulator: hardware or software designed to imitate another device, used in product development.

Encoder: See Optical Encoder

Excitation Power: Power required by a transducer to produce an output.

External Pulse Trigger: Almost all of our A/D boards allow sampling to be triggered by a voltage pulse from an external source.

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 F 

FFT: Fast Fourier Transform.

FIFO: A First In-First Out memory buffer; the first data received & stored is the first data sent out of the buffer.

File Server: A file storage device on a local area network (LAN) that is accessible to all users on the network. Often contains network administration files & software.

Flash ADC: An analog-to-digital converter whose output code is determined in a single step by a bank of comparators and encoding logic.

Flash EEPROM: Electrically Erasable Programmable Read Only Memory, a non-volatile memory chip which may be erased and reprogrammed electronically.

Full Duplex:  A type of communications that allows simultaneous data transfers in both directions. Half duplex transmissions alternate directions back & forth.

Function: A set of software instructions that returns a value when executed. e.g. Y= COS(x)

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 G 

GUI (Graphical User Interface): An intuitive, easy-to-use means of communicating information to and from a computer program by means of graphical screen displays. GUIs can resemble the front panels of instruments or other objects associated with a computer program.

Gain: Applied to the incoming signal, gain acts as a multiplication factor on the signal, increasing the number of ranges the board is designed to accept. For example, if you select the ±5V range and set the gain to 10, signals in the ±0.5V (500mV) range are usable; with a gain of 20, the range is ±250mV.

General Purpose Interface Bus (GPIB): The popular name for the IEEE-488 interface connection and communications standard.

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 H 

Half Duplex: See Full Duplex.

Handshake: A signal that acknowledges the transfer of information or communication.

Hertz (Hz): A unit of frequency equal to one cycle per second. Throughput rates of 1kHz (‘kiloHertz’, 1000Hz) imply the ability to handle 1,000 samples/second, while sampling rates of 1 million samples/second are referred to as 1 MHz (‘MegaHertz’).

Hexadecimal (H): Base 16 numbering system consisting of 0-9 and A-F. e.g. Fbase 16 is equivalent to 15base 10. Hex numbers are usually suffixed with an H. (i.e. 300H).

Hierarchical: A method of organizing a computer program or a system design with a series of levels; each level with further subdivisions, as in a pyramid or tree structure. (Most operating systems use a hierarchical file structure of directories and subdirectories.)

High Byte: In a two-byte group of bits, the high byte contains the most significant digits.

High-Level Language: A program to allow simplified creation of other programs. High-level languages allow specification of computer action through much smaller (and easier-to-read) steps than assembly-level code, by defining specific ‘Instructions’ in low-level machine code. Examples include BASIC, C, & Pascal.

Hot-Swappable: The ability to insert and remove PCMCIA cards, some hard drives, and some power supplies without first shutting off the power.

Hysteresis: An error resulting from the inability of an electrical signal to produce the same reading when approached slowly from either direction.

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 I 

IEEE-1394: FireWire

ISA Bus: Industry Standard Architecture, an expansion bus used in most IBM-compatible PCs. Also known as the AT bus

Icon: A graphic representation of a function or functions to be performed by the computer. For example, using a picture of a chess piece to represent a PC chess game.

Index: (Encoders) A single, separate output on an incremental encoder providing 1 count/revolution.

Individual Gain Per Channel: Allows you to select an individual gain level for each input channel, thereby allowing a much wider range of input levels and types without sacrificing accuracy on low-level signals. Our AC series boards support individual gain settings on each channel, thereby allowing you to connect a large variety of transducers to a single board.

Input Impedance: Resistance to electrical flow measured in Ohms (). Input impedance is the resistance due to inductive, capacitive, and resistive elements measured across the input lines of a board.

Integrating ADC: An analog to digital converter whose output code represents the average value of the input voltage over a given time interval.

Interlacing: a display method on a raster scan monitor that scans each even number scan line of the screen in one sweep of the screen, and the odd-numbered scan lines on the next sweep.

Internet: A global network of computer systems linked via high-speed telecommunications lines, with no centralized control. Many millions of users typically exchange information, correspondence, and data files.

Interrupt: To stop an execution of a program, then execute another subroutine, in such a way that the first program can be resumed normally after the execution of the interrupt service program. In an IBM-compatible computer there are eight or sixteen levels of hardware interrupts, (IRQ0 to IRQ7, or IRQ 15 in newer models), and 256 levels of software interrupts.

iSBX: An expansion bus/connector found on some advanced I/O cards. For use with iSBX expansion modules.

Isolation Voltage: The voltage that an isolated circuit can normally withstand, usually specified from input to input and/or from any input to the amplifier output, or to the computer bus.

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 K 

Kernel: The portion of the system software that manages memory, files and peripheral devices.

Kilo (K): 1,000. When referring to the memory capacity of a computer, it is equal to 210 or 1,024 bytes of data.

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 L 

LAN: Local Area Network, a group of computers and devices located in a limited area and connected by a communications link.

LCD (Liquid Crystal Display): A display that uses a liquid compound to display information, typically monochrome. Not designed for wide viewing angle. See TFT, STN.

LSB: Least Significant Bit.

LVDT: A differential output driver intended for use with a differential receiver; usually provided where long lines and high frequency are required.

Line Surge: A sudden transient increase in current or voltage carried by a line. See Surge, Spike.

Linearity: A measure of departure from a straight line response in the relationship between two quantities, where the change in one quantity is directly proportional to a change in the other quantity.

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 M 

MSB: Most Significant Bit.

Machine Language/Code: Instructions that are written in a binary or hexadecimal format that your computer can execute directly. Also: object code, object language.

Mega (M): 1,000,000. 1 Megabyte = 1,048,576 bytes.

Memory Buffer: See Buffer.

Microchannel Bus: An expansion bus used in many of IBM’s PS/2 PC systems starting in 1987. Very few peripherals were made for this bus, despite its superior specifications, and it has been mostly abandoned.

Microprocessor: The small central processing unit (CPU) that performs the logic operations in a micro-computer system. The CPU also decodes instructions from a stored program, performs arithmetic logic operations, generates timing signals, produces commands for external use in process control, instrumentation and data acquisition hardware control.

Microstepping: The ability to divide a full step of a stepping motor into smaller increments. Microstepping Drivers divide each full step of a motor into 10 or more microsteps for fine positioning and more smooth motor movement.

Modem: Modulator-Demodulator, a communications device that modulates digital data into audio signals for transmission over telephone lines, incoming audio signals are demodulated into digital data.

Motherboard: The main circuit board of a computer system, containing the main microprocessor (CPU), supporting circuitry, and expansion slots. Motherboard-based systems are by far the most common in desktop computers. However, they are harder to service or upgrade the CPU (must disassemble the system, not just replace a card). See Passive Backplane.

Multiplexer: A set of electro-mechanical or semiconductor switches with a common output that can select one of a number of input signals. With the addition of multiplexing panels, 64, 256, or more inputs can be fed to a single input channel. This usually results in a slower sample rate (throughput), but allows very large data acquisition systems to be constructed affordably. The WIN MUX16 offers both high-speed throughput and a high number of inputs.

Multitasking: A property of an operating system that allows several processes to be running simultaneously.

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 N 

NEMA: National Electrical Manufacturers Association. Defines size and level of environmental protection of an instrument or enclosure. NEMA 4 enclosures are suitable for indoor or outdoor use, as they provide protection against windblown dust or rain, splashing water, and hose-directed water. They are rust-resistant, and are designed to withstand external icing. They are not protected against internal icing or condensation. NEMA 12 enclosures are mainly for indoor use, designed to withstand dust, falling dirt, rust, and dripping non-corrosive liquids such as oil or coolants.

NMRR: Normal Mode Rejection Ratio. An indication of an instrument's ability to reject interference, usually power input line frequency, across its input terminals.

Noise: An undesirable electrical signal, noise comes from external sources such as AC power lines, motors, generators, transformers, fluorescent lights, CRT displays, computers, and from internal sources such as semiconductors, resistors, inductors, and capacitors. Can cause errors in readings of not filtered.

Non-interlaced: A display method on a raster scan monitor that scans each line of the screen once during a refresh cycle. A non-interlaced monitor will generally provide a more flicker-free picture. (See Interlacing.)

Number of Channels: This is the number of input or output lines of a board. Single-Ended inputs share the same ground connection, while Differential inputs have individual two-wire inputs for each incoming signal, allowing greater accuracy and signal isolation. See also Multiplexer.

Nyquist Sampling Theorem/Nyquist Frequency: A law of sampling theory that states: if a continuous bandwidth-limited signal contains no frequency components higher than half the frequency at which it is sampled, then the original signal can be recovered without distortion. To avoid accidental low-frequency aliasing while sampling a signal, you must take samples at two or more times the frequency of the signal being sampled. The Nyquist Frequency is equal to twice the frequency of the signal being sampled.

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 O 

OEM: Original Equipment Manufacturer

On-Board Memory: Incoming data is stored in on-board memory before being dumped into the PC’s memory. On a high-speed board, data is acquired at a much higher rate than can be written into PC memory, so it is stored in the on-board buffer memory.

Operating System: Base-level software that controls a computer, runs programs, interacts with users, and communicates with installed hardware or peripheral devices. i.e. DOS, OS/2, UNIX, or Macintosh MacOS.

Optical (Opto) Isolation: The technique of using an opto-electric transmitter and receiver to transfer data without electrical continuity. Provides an electrical barrier between related circuits to eliminate voltage differences and damages from transient power surges.

Optical Encoder: A device that provides a quadrature signal output for positioning information (position, direction, speed) of a rotating wheel.

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 P 

PC: Personal Computer.

PC Bus: The original expansion bus used in the IBM PC (and the IBM XT & compatibles). Known as an 8-bit expansion slot, a PC-bus slot can only accept those cards which do not require a 16-bit (AT) interface.

PC/104: A standard which defines a compact, modular form-factor version of the PC bus on 3.6" x 3.8" cards. Used in embedded computer systems.

PCI Bus: Peripheral Component Interconnect bus.

PCMCIA: Acronym for Personal Computer Memory Card International Association, a standards writing group which defined the specifications for a card slot typically found on portable computers.

PID: Proportional Integral Derivative, a method of process control combining Proportional, Integral, and Derivative control actions.

PPM: Parts Per Million. i.e. 100ppm = 0.01%

Parity Bit: An extra binary digit (bit) appended to a data byte to test for errors. IBM-compatible PCs use parity bits in all internal memory.

Passive Backplane: A circuit board with a row of connectors to accept other circuit boards. Most common would be a PC expansion bus (ISA or PCI-bus backplane) with several PC expansion slots. A backplane usually does not contain any circuitry except the conductors between the connectors. Passive Backplane units are easy to service since plug-in CPU cards can be easily replaced. See Motherboard.

Pixel: A single dot on a monitor or computer display.

Pretrigger: Boards with “Pretrigger” capability keep a continuous buffer filled with data, so when the trigger conditions are met, the sample includes the data leading up to the trigger condition.

Program I/O: The standard method of memory access, where each piece of data is assigned to a variable and stored individually by the PC’s processor.

Programmable Gain: See Gain.

Protocol: The exact sequence of bits, characters and control codes used to transfer data between computers and peripherals through a communications channel, such as GPIB (IEEE-488).

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 Q 

Quadrature: Two square wave signals out of electrical phase by 90°.

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 R 

RAM: Random Access Memory. The memory used by your PC to execute programs and store variables. With more RAM, larger programs can be run, and more data can be acquired & manipulated at high speed. See Bits & Bytes (above).

REP INSW: REPeat Input String

RFI: Radio Frequency Interference

RISC (Reduced Instruction Set Computing): A type of microprocessor design that that focuses on rapid and efficient processing of a relatively small set of instructions. RISC design is based on the premise that most of the instruction decodes and executes are simple. As a result, the RISC architecture limits the number of instructions that are built into the microprocessor but optimizes each instruction so that it can be carried out very rapidly.

RS-232: A standard for asynchronous serial communications. Used in most IBM-compatible PC systems for their COM: ports, as well as in most modems, printers, and terminals with serial interfaces.

RS-422: A standard for asynchronous serial communications. Designed for distances up to 4000+ feet.

RS-485: A serial communications standard that provides for addressing of devices, so multiple devices can co-exist at individual addresses on the same pair of wires.

RTD: resistance Temperature Detector, a device used to measure temperature. An RTD’s element changes resistance in proportion to the change in temperature.

Rack Space, Rack Unit: One Rack Unit (RU), also known as a rack space, is equal to 1.75" of vertical height in a standard EIA 19" equipment mounting rack. Screw holes in both racks and rack-mount equipment are placed in such a way as to line up in 1.75" increments. A unit which is 6RU high therefore requires 10.5" of vertical rack height.

Range Select: The full-scale range the board uses is selected by one of three methods: through the DAS software, by a hardware jumper on the board, or through the use of an external reference voltage.

Raster Scan Display: A display which is divided into lines of pixels. (In a 1024 x 768 display, each line is 1024 pixels across, and there are 768 lines.) On a typical monitor, each line is scanned many times each second, refreshing the pixels faster than the eye can perceive.

Real Time: A property of an event or system in which data is processed as it is acquired instead of being accumulated and processed at a later time. i.e. Real-time displays show incoming data as it is acquired.

Relay:  switch activated by electricity. A relay allows another signal to be controlled without the need to route the other signal the control point; it also allows a rela-tively low-power signal — the signal used to activate the relay — to control a high power (voltage) signal.

Repeatability: The ability of a device to return the same reading in successive measurements of the same signal. Usually written as a percentage of full scale, indicating the deviation between given readings or measurements taken under identical conditions

Resolution: The number of bits in which a digitized value will be stored. This represents the number of divisions into which the full-scale range will be divided. e.g. A 0-10V range with a 12-bit resolution will have 4096 (212) divisions of 2.44mV each (10V/212 or 10V/4096). Our ACPC 16 boards can resolve an incoming signal to .76µV (50mV/216 or 50mV/65,536).

Runtime System: The core programs/code of a large software package which allow you to execute pre-defined setups or sub-applications, without the ability to modify those setups, or generate new ones. For example, a Temperature Logger defined using LABTECH NOTEBOOK. You could operate the Logger with just a runtime version of NOTEBOOK, but you could not create another type of data acquisition setup. Only the code generator in the full NOTEBOOK package could create a new setup/application.

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 S 

SCSI: Small Computer System Interface, a high speed parallel interface defined by American National Standards Institute (ANSI). Commonly found on hard disk drives & PC peripheral devices.

SRAM: Static RAM

STN LCD Color Display: Super Twist Nemantic LCD Displays utilize a filtering scheme to generate colors. As a passive display technology, it does not respond as quickly as a TFT display, nor does it cost as much. Typically capable of 256 colors. See LCD, TFT.

Sample: One measurement by a data acquisition board, usually consisting of a number which corresponds to a specific reading. Most boards are compared by the number of samples they can measure each second. This Sample Rate is best explained below at Speed.

Sample-and-Hold (S/H, S&H): A circuit that acquires and stores an analog voltage on a capacitor for a short period of time. See Simultaneous Sampling.

Self-Calibrating: A self-calibrating board has an extremely stable on-board reference which is used to calibrate A/D and D/A circuits for higher accuracy.

Self-Diagnostics: Boards with this feature have an on-board testing routine which tests most, if not all, of the board’s functions at power-up or on request.

Sensitivity: The minimum change of signal level or strength that can be detected by an instrument.

Serial Port: A communication interface using one data line with all data bits transferred sequentially, one at a time. See also RS-232.

Signal Conditioner: A device that serves as an amplifier, filter, rectifier, or performs some other process that transforms a raw acquired signal into one more readily and accurately readable by an A/D converter board.

Simultaneous Sampling: The ability to acquire and store multiple signals at exactly the same moment. Sample-to-sample timing inaccuracy (skew) is typically measured in nanoseconds. Our WIN 30DS4 simultaneously samples 4 signals to within 300 picosec. (±0.3ns).

Single-Ended: See Number of Channels.

Skew: The difference in time between the acquisition of two samples. Any board offering Simultaneous Sampling will specify the skew to indicate the greatest amount of time between “simultaneous” samples. Channel-to-channel skew is the time between consecutive samples, while the maximum skew is the difference in time between the first and last sample in a particular group of acquired samples.

Software Drivers: Typically a set of programs or subroutines allowing the user to control basic board functions, such as setup and data acquisition. These can be incorporated into user-written programs to create a simple but functional DAS system.

Software Programmable: Features which may be accessed or controlled from within a computer program, without the need to set jumpers or switches on the hardware board or device

Software Trigger: Indicates the board allows software control of data acquisition triggering. All of our boards are designed for software control.

Source Code: non-executable program statements written in a high level language.

Speed/Typical Throughput: The maximum rate at which a board can sample and convert incoming signals. The typical throughput is divided by the number of channels being sampled to arrive at the typical number of samples-per-second on each channel. To avoid false readings, the number of samples-per-second on each channel needs to be greater than twice the frequency of the analog signal being measured. See the Nyquist Theorem.

Spike: An overvoltage of an amplitude at least 100% over peak line voltage for 0.5 to 100 microseconds.

Step: Stepping motors allow precise rotational positioning, with each increment of rotation being a step. Our ORM 200-series motors offer 200 steps per revolution, with each step a 1.8° movement. Half-stepping allows your motor to move in half-step increments (typically 0.9°/half-step).

Strain Gauge: A device used to measure strain. Usually designed to output a voltage relative to the strain placed on it. Popular for electronic scales.

Successive Approximation ADC: An analog-to-digital converter that sequentially compares a series of binary-weighted values from an analog input to produce an output digital word in n steps, where n is the resolu-tion of the converter in bits.

Surge: Line voltage exceeding 110% of nominal value.

Surge Protector or Suppressor: A device that prevents potentially damaging power surges from reaching a computer or any other device that is connected to it. Surge protectors work by collecting and diffusing excess power, sometimes within a few billionths of a second.

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 T 

TFT Color Display: Thin Film Transistor displays use a precise array of active light-emitting semiconductors to display a crisp, bright color picture, even in daylight and in darkness. Can typically display 512 colors.

TFT Color LCD Display: A low-power display design combining TFT and LCD display technology to provide crisp, bright color without generating much heat.

TTL (Transistor Transistor Logic): Circuits based on groups of transistors which respond to the presence of or lack of a low-voltage signal. TTL-level signals are usually 5-volt signals with little current-handling ability (1.7ma typ.) Many digital I/O lines are TTL-level, and therefore unable to switch power relays without the use of a buffered mounting panel like our CYSSR 24.

Thermistor: A resistive temperature device composed of metal oxides. A thermistor’s resistance changes in a predictable way with changes in temperature.

Thermocouple: A junction of two dissimilar metals used to measure temperature. The output is a non-linear millivolt signal proportional to the temperature differential between the junction and the point of voltage measurement. See also RTD, LVDT, and Cold Junction Compensation.

Throughput: A measure of data transfer rate; see Speed.

Transceiver: A device that will both transmit and receive signals.

Transducer: Any device which generates an electrical signal from real-world physical measurements, e.g. LVDTs, strain gauges, thermocouples, RTDs, etc.

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 U 

UART: Universal Asynchronous Receiver Transmitter, an integrated circuit that will receive and transmit serial data, most commonly found in modems.

Uninterruptible Power Supply (UPS): Commonly referred to as a “Battery Back-Up”, a UPS provides power for a short period of time after an AC power failure to allow organized shutdown and saving of your work.

Unipolar Inputs: When set to accept a unipolar signal, the channel detects and converts only positive voltages in the 0 to X Volts range. (ex: 0 to +10V). See Bipolar.

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 V 

VAR: Value-Added Reseller

VGA: Video Graphics Array, a video controller that generates the signals required for video display.

VESA DDC: VESA Display Data Channel; a standard communication channel between the display adapter and the monitor. Together with the EDID specification, it enables the PC system, display, and graphics adapter to communicate. This allows the system to be configured to support specific features available to the display.

Vaporware: A term used to describe software or hardware that has been announced or advertised by suppliers, but is not available, or doesn’t work. Most computer products spend 2 to 6 months in this state. Some a year or more, and some never get out of it.

Virus: A program that “infects” computer files by creating copies of itself on to the files. Many are designed to damage files and programs, all reduce system stability.

Voltage Regulator: A device that maintains a constant voltage output despite changes in load or input.

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 W 

Watchdog Timer: automatically re-starts system after a detection of software interruption.

Word: The number of bits or bytes required to represent a single piece of data. One sample from a 16-bit A/D board requires 16 bits, or two bytes. Most 12-bit samples are also 2 bytes long, with 4 bits left unused.

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