Following is a definition of terms frequently used in the instrumentation, industrial automation and test & measurement communities.
Background Noise: The total noise floor from all sources of interference in a measurement system, independent of the presence of a data signal.
Backup: A system, device, file or facility that can be used as an alternative in case of a malfunction or loss of data.
Bandwidth: A symmetrical region around the set point in which proportional control occurs.
Basic Transportation Reference: The basic transportation section of the U.S. Government Test Specification MIL-STD-810D, Method 514.3, Paragraph I-3.2.1, Page 514.3-5. Basic transportation defines the test profiles that have been defined for equipment that is shipped as secured cargo; by land, by sea or by air. The test levels are based upon land transport stress levels because these are higher than stresses imposed by air or sea transportation environments.
Basic: A high-level programming language designed at Dartmouth College as a learning tool. Acronym for Beginner’s All-purpose Symbolic Instruction Code.
Baud: A unit of data transmission speed equal to the number of bits (or signal events) per second; 300 baud = 300 bits per second.
BCD, Buffered: Binary-coded decimal output with output drivers, to increase line-drive capability.
BCD, Parallel: A digital data output format where every decimal digit is represented by binary signals on four lines and all digits are presented in parallel. The total number of lines is 4 times the number of decimal digits.
BCD, Serial: A digital data output format where every decimal digit is represented by binary signals on four lines and up to five decimal digits are presented sequentially. The total number of lines is four data lines plus one strobe line per digit.
BCD, Three-State: An implementation of parallel BCD, which has 0, 1 and high-impedance output states. The high-impedance state is used when the BCD output is not addressed in parallel connect applications.
Bearing: A part which supports a journal and in which a journal revolves.
Beat Frequency: Beat frequencies are periodic vibrations that result from the addition and subtraction of two or more sinusoids. For example, in the case of two turbine aircraft engines that are rotating at nearly the same frequency but not precisely at the same frequency; Four frequencies are generated:(f1) the rotational frequency of turbine one, (f2) the rotational frequency of turbine two, (f1 + f2) the sum of turbine rotational frequencies one and two, and (f1 – f2) which is the difference or “beat” frequency of turbines one and two. The difference of the two frequencies is the lower frequency and is the one that is “felt” as a beat or “wow” in this case.
Beryllia: BeO (Beryllium Oxide) A high-temperature mineral insulation material; toxic when in powder form.
Best Fit Straight Line (BFSL): A line midway between two parallel straight lines enclosing all output vs. pressure values.
Beta Ratio: The ratio of the diameter of a pipeline constriction to the unconstricted pipe diameter.
BIAS Current: A very low-level DC current generated by the panel meter and superimposed on the signal. This current may introduce a measurable offset across a very high source impedance.
Binary Coded Decimal (BCD): The representation of a decimal number (base 10, 0 through 9) by means of a 4 bit binary nibble.
Binary: Refers to base 2 numbering system, in which the only allowable digits are 0 and 1. Pertaining to a condition that has only two possible values or states.
BIOS: Acronym for basic input/output system. The commands used to tell a CPU how it will communicate with the rest of the computer.
Bipolar: The ability of a panel meter to display both positive and negative readings.
Bit: Acronym for binary digit. The smallest unit of computer information, it is either a binary 0 or 1.
Blackbody: A theoretical object that radiates the maximum amount of energy at a given temperature, and absorbs all the energy incident upon it. A blackbody is not necessarily black. (The name blackbody was chosen because the color black is defined as the total absorption of light energy.)
BNC: A quick disconnect electrical connector used to inter-connect and/or terminate coaxial cables.
Boiling Point: The temperature at which a substance in the liquid phase transforms to the gaseous phase; commonly refers to the boiling point of water which is 100°C (212°F) at sea level.
BPS: Bits per second.
Breakdown Voltage Rating: The dc or ac voltage which can be applied across insulation portions of a transducer without arcing or conduction above a specific current value.
Bridge Resistance: Please see Input impedance and Output impedance.
BTU: British thermal units. The quantity of thermal energy required to raise one pound of water at its maximum density, 1 °F. One BTU is equivalent to 0.293 watt hours, or 252 calories. One kilowatt hour is equivalent to 3412 BTU.
Buffer Capacity (B): A measure of the ability of the solution to resist pH change when a strong acid or base is added.
Buffer: (1) A storage area for data that is used to compensate for a 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.(2) Any substance or combination of substances which, when dissolved in water, produces a solution which resists a change in its hydrogen ion concentration on the addition of an acid or alkali.
Bulb (Liquid-in-Glass Thermometer): The area at the tip of a liquid-in-glass thermometer containing the liquid reservoir.
Burn-In: A long term screening test (either vibration, temperature or combined test) that is effective in weeding out infant mortalities because it simulates actual or worst case operation of the device, accelerated through a time, power, and temperature relationship.
Burst Pressure: The maximum pressure applied to a transducer sensing element or case without causing leakage.
Burst Proportioning: A fast-cycling output form on a time proportioning controller (typically adjustable from 2 to 4 seconds) used in conjunction with a solid state relay to prolong the life of heaters by minimizing thermal stress.
Bus: Parallel lines used to transfer signals between devices or components. Computers are often described by their bus structure (i.e., S-100, IBM PC).
Byte: The representation of a character in binary. Eight bits.