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Amplicon - Tech glossary Category: Technical and IT Date & country: 25/11/2007, UK Words: 107

Calibration Period
Instruments should be periodically checked for calibration accuracy. How often will depend on how much usage and how the instrument is treated. Instruments should be checked each year and if the utilisation is severe a calibration period of 6 months or 3 months should be observed

Channel
One of several signal/data paths that may be selected

Character
A letter, figure, number, punctuation or other symbol contained in a message or used in a control function

Character Set
The set of characters that can be coded and/or printed by a particular machine

Clear
Restore a device to a prescribed initial state, usually the zero state

Clock
A device that generates accurate, periodic signals for synchronisation purposes

CMR (Common Mode Rejection Ratio)
Common Mode Rejection states the ability of the equipment to reject noise which appears between the input terminals (high and low) and ground CMR is needed only when the equipment ground is different than the ground of the source being measured. When the equipment is operated from a line source of power or when both high and low inputs are raised a…

CMV (Common Mode Voltage)
This specifies the DC voltage which is tolerable between input low and power ground. When the equipment is operated from logic level power the CMV is apt to be in the order of 0.5 VDC or less. Using batteries or a transformer-isolated power supply permits an instrument to be operated at a higher CMV, usually in the order of 100 VDC when related to …

Code
A set of unambiguous rules specifying the way in which characters may be represented. It is also another term for the text of computer software

Cold Junction
The junction of a thermocouple (see thermocouple) to a measuring instrument, as opposed to the Hot Junction which is used to measure the temperature

Cold Junction Compensation (CJC)
A technique to compensate for thermocouple errors made when the reference or cold junction is at a temperature other than 0° C. Generally the instrument cold junction will be at room temperature or higher depending on internal heating. An internal sensor is used to measure this temperature to compensate for the thermocouple junction offset

Communication Turnaround
Changeover from transmit to receive or vice versa in a half duplex system

Conversion Rate
Conversion rate specifies the number of readings per second the A-to-D converter can produce. In many cases the conversion rate may be faster than the settling time and therefore the digital meter may be able to produce several readings before settling to full accuracy. Usually for a few digits change in reading, the settling and conversion times a…

Conversion Time
The time required, in an analog/digital input/output system, from the instant that a channel is interrogated (such as with a read instruction) to the moment that an accurate representation of the data is available. This could include switching time, settling time, acquisition time, converter processing time etc. Crest Factor: When making true RMS A…

CTS (Clear To Send)
A control signal, defined in the RS-232 standard, to indicate that Data Communication Equipment (DCE) is ready to transmit

Data Acquisition or Data Collection
Gathering information from sources such as sensors and transducers in an accurate, timely and organised manner

dB (Decibel)
A logarithmic representation of the ratio between two signal levels

DCD (Data Carrier Detect)
A control signal, defined in the RS-232 standard, generated by DCE to indicate that it is receiving a valid signal

DCE (Data Communication Equipment)
The equipment that provides the functions required to establish, maintain and terminate a connection, and provides the signal conversion required for communication between data terminal equipment and the telephone line or data circuit. See Modem

Default
The values or options that are assumed when not specified

Digit
Digit is a word with more than one meaning in discussing digital voltmeters. A four-digit panel meter is one having four decimal decades eg 9999. Accuracy of one digit implies an accuracy of one count in the least significant decade

Digital Signal
A discrete or discontinuous signal; one whose various states are identified with discrete levels or values

DIP Switch
A set of switches contained in a 'Dual In-line Package' for mounting on a printed circuit board

DMA (Direct Memory Access)
This is a process whereby the I/O controller gains temporary control over the CPU's memory, while the program is running, to allow a single word or a group of words to be read or written. The I/O process obtains direct access to the memory

DMM (Digital Multimeter)
A multi range analog input, analog to digital converter and digital display

DPM
(Digital Panel Meter): A single range analog input, analog to digital converter and digital display

Drift
Small variations in a measured parameter over a period of time

Drivers
Part of the software that is used to control a specific hardware device

DSR (Data Set Ready)
A control signal, defined in the RS-232 standard, to indicate the status of DCE

DTE (Data Terminal Equipment)
A computer or other terminal that provides data in the form of digital signals at its output

DTR (Data Terminal Ready)
A control signal defined, in the RS-232 standard, to indicate the status of DTE

Dual-Slope Conversion
The dual-slope A/D conversion technique or variations thereof is the most common used in digital meters. The technique uses an operational amplifier connected as an integrator, and a digital counter-timer. There are two steps to the conversion. The input is connected to the integrator and the feedback capacitor is charged for a fixed period of time…

DVD-R
DVD-ROM that can be written to once, much like CD-R

DVD-RAM
Re-writable version of DVD, Drives can also read DVD-ROM and CDs

DVD-ROM
Read only DVD media, Drives can also read CDs

DVD-RW
Re-writable version of DVD

Dynamic Link Library (DLL)
A library of functions used by Windows© programmers

EIDE
Enhanced integrated drive electronics, Common data interface between PC and Data storage devices

Enable-Disable
To enable a circuit prepares it to perform the intended function

File
A set of related records or data treated as a unit

Fortran
(FORmula TRANslation): This a high level programming language for scientific computation

Full Duplex
Refers to a communications system or equipment capable of simultaneous two-way communications

Ground
An electrically neutral wire having the same potential as the surrounding earth. Provides a reference point for an electrical system. Half Duplex: Refers to a communications system or equipment capable of communications in both directions, but only one at a time

Handshaking
Exchange of predetermined codes and signals between two data devices to establish and control a connection

Hardware
The visible parts of a computer system such as the circuit boards, chassis, peripherals, cables etc. It does not include data or computer programs

Hertz
A unit of frequency equating to one cycle per second

Hex (Hexadecimal)
This is a numbering system which uses a base of 16. The symbols used to represent the digits are 0,1 ,2,3,4,5,6,7,8,9,A,B,C,D,E,F (F = 15 in decimal). For example the value FF hex = 255 decimal = 11111111 binary. The numbering system to base sixteen

Host
The controlling computer

Input Impedance
Instruments often require a high input impedance to prevent their high sensitivity and accuracy from being affected by loading errors. In DPMs 1Megohms input impedance is not unusual

Interface
A shared boundary defined by common physical interconnection characteristics, signal characteristics and meanings of interchanged signals

Interrupt
An interrupt breaks into the computers program of instructions to carry out a particular routine. It is a way of controlling input/output activity in which a peripheral device sends a signal to interrupt the programme in order to send or receive data. To signal a process to take a specific action

IP camera
An IP camera is an image recording device comprising lens, image sensor and image processor capable of transmitting video across an IP-based network, typically Ethernet in a LAN environment

Isolation Voltage
The voltage which an isolated circuit can withstand. Isolation voltage is specified between two or more points

LCD (Liquid Crystal Display)
Digital instruments employ LCD readouts because they utilize miniscule amounts of power making them excellent for battery operated instruments. LCDs are best in high ambient light levels as they do not wash out but instead gain greater contrast in bright light

Leading Zero Suppression (Blanking)
Some digital panel meters have a control output line which permits leading zero suppression. This is accomplished by connecting a decimal point select line to the suppression control. Zeros to the left of the decimal point selected will be blanked. Digits other than zero will not be suppressed

LED (Light Emitting Diode)
LED displays provide a bright clear numeric presentation of readings in digital instruments. They are generally best for indoors environments and can be viewed from a greater distance in normal lighting conditions. Most LED displays are red but are also available in yellow and green

Linearity
The linearity of a digital voltmeter is the inaccuracy in reading which results when reading of the instrument is plotted against the actual absolute voltage input, from zero to full scale. For a perfect DPM the function is a straight line. Linearity is the greatest deviation from a straight line expressed as a percentage of full scale

Logic Gate
An electronic device which implements an elementary logic function. The functions are OR, AND, NOR, NAND, XOR and NOT. A high voltage level output from the gate normally indicates a TRUE state (1) and a low voltage level output indicates a FALSE state (0)

Loop-back Test
A test of a communications link performed by connecting the equipment output of one direction to the equipment input of the other direction and testing the quality of the received signal

LSB (Least Significant Bit)
In a system in which a numerical magnitude is represented by a series of digits, the least significant bit (binary digit) is the digit that carries the smallest value or weight

Modem (MOdulator-DEModulator)
A type of DCE that converts digital data to an analog signal for transmission on telephone circuits. A modem at the receiving end converts the analog signal to digital form

Monotonic
A DAC is said to be monotonic if the output increases as the digital input increases, with the result that the output is always a single valued function of the input

MPEG4
Moving Picture Experts Group Compression Standard Version 4. MPEG4 is a technology for compressing voice, video and related control data and is one of the MPEG international standards

MSB (Most Significant Bit)
In a system in which a numerical magnitude is represented by a series of digits, the most significant bit (binary digit) is the digit that carries the greatest value or weight

Multi-drop
A system of serial communication that allows multiple transmitter/receiver combinations to be connected to a single transmission line

Multiplexer
A multiple way analog switch q.v., where a single path through the switch is selected by the value of a digital control word

NMR (Normal-Mode Rejection)
This is the amount of noise superimposed on the input signal of a DC digital voltmeter which the instrument is capable of rejecting. It is expressed in decibels. NMR is enhanced by passive and active filters as well as integrating techniques of ND conversion. It is not a good policy to rely on a DPM to reject noise. A good clean signal should be ob…

NMS (Normal Mode Signal)
Aka Series mode signal. In a differential analog measuring system, the normal mode signal is the required signal and is the difference between the voltages on the two input signal lines with respect to ground level of the measuring system

Noise
An undesirable electrical interference to a signal

NVR (Networked Video Recorder)
An NVR is a video recording platform designed to work exclusively with IP video feeds from IP cameras and video servers on an Ethernet backbone

Octal
A numbering system which uses a base of 8. The symbols used to represent a numerical value are 0, 1, 2, 3, 4, 5, 6 and 7. For example the value 23 decimal is 27 octal

Offset
(a) A fixed, known voltage added to a signal. (b) The location of a register above the base address

Optical Isolation
Two networks coupled only through an opto-electronic sender and receiver with no electrical conductivity between the two networks

Optoisolator
A type of semiconductor which achieves electrical isolation by transmitting signals by light pulses

Over-Range
An input device with a measurement range of 0-10V may be able to read above this value by a small amount. After a nominal amount the instrument is said to be 'over-range' and this may be indicated by flashing digits on a panel meter for example

Overload Protection
Input overload protection is provided in digital instruments to protect the meter from damage whenever voltages in excess of the measuring range are applied to the input. In measuring voltage, the intrinsic high input impedance provides protection in most cases

PAL (Programmable Array Logic)
This is an Integrated Circuit (IC) with an array of interconnected logic gates. The interconnections between logic gates are removed by blowing fusible links in order to produce the required final logic

Parity Bit
One of the bits that may be incorporated in a character to be used as a simple form of error detection

Pascal
A high level programming language originally developed as a tool for teaching the concepts of structured programming. It has evolved into a powerful general-purpose language popular for writing scientific and business programs. Borland Turbo Pascal is a dialect of Pascal

Polarity Inhibit (Blanking)
In some applications of bipolar digital panel meters it is desirable not to display the polarity sign. Such is the case for AC or ohms measurements. In many digital panel meters a control line is provided for blanking the polarity sign from a remote contact-closure or logic-level change

Port
An interface on a computer capable of communication with another device

Protocol
The rules for communication between like processes, giving a means to control the orderly communication of information between linked stations

Range
Refers to the maximum allowable full-scale input or output signal for a specified performance

Resolution
A binary converter is said to have a resolution of n-bits when it is able to relate 2n distinct analog values to the set of n-bit binary words

RI (Ring Indicator)
A control signal, defined in the RS-232 standard, to indicate that DCE is receiving a ringing signal

RS (Reference Standard) 232-422-485
Designations of various recommendations formulated to standardise the application of serial communication between connected computers, terminals, modems, instruments etc

RTS (Request To Send)
A control signal, defined in the RS-232 standard, generated by DTE to instruct DCE to transmit

Sample and Hold
Sample and hold signal conditioners are used in conjunction with digital panel meters to acquire fast instantaneous voltage readings which are programmed in time at any position of a waveform. A typical sample and hold measures amplitudes up to ±10 volts. Upon application of a logic one to a control line, the sample and hold acquires and its outpu…

Scroll
To move the display so that new information may appear

Serial Transmission
A method of information transfer in which the bits comprising a character are sent in sequence one at a time

Settling Time
The time taken for the signal appearing at the output of a device to settle to a new value caused by a change of input signal

Software
The non-physical parts of a computer system that includes computer programs such as the operating system, high level languages, applications program etc

Source Code
A non-executable program written in a high level language. The source code must be translated by a compiler or assembler into object code that is understood by the computer

Space
One of two possible states of a binary information element

Start Bit
The first bit transmitted in the asynchronous transmission of a character to synchronise the receiver

Stop Bit
The last bit transmitted in the asynchronous transmission of a character to return the circuit to the at-rest condition

Symbol
The graphical representation of some idea. Letters and numerals are symbols

Thermocouple
A thermocouple is made up of two dissimilar metal conductors, known as thermoelements, joined so as to produce a thermal EMF which varies with temperature

Thermocouple Measuring Junction
The junction of a thermocouple which is subjected to the temperature being measured (aka Hot Junction)

Thermocouple Reference Junction
The junction of a thermocouple which is at a known temperature( aka Cold Junction)