Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
absolute --- not limited by restrictions or exceptions; unconditional.
A/D converter --- a device that changes an analog signal (such as voltage) into a digital signal (discrete data values).
accelerometer --- a sensor that measures acceleration. Acceleration can be due to gravity or changing motion. Acceleration is measured in units of earth¡¯s gravity (g¡¯s) or meters per second squared.
accuracy --- a comparison of the actual output signal of a device to the true value of the input. The various errors (such as Linearity, hysteresis, repeatability and temperature shift) attributing to the accuracy of a device are usually expressed as a percent of full-scale output (FSO.)
algorithm --- a set of well-defined rules or processes for solving a problem in a finite number of steps..
aliasing --- distortion due to sampling a continuous signal at too low a rate.
aliasing noise --- distortion component created when frequencies present in a sampled signal are greater than one-half the sample rate.
alignment --- the angle between the sensor's sensitive axis and the nominal package axis; measure in degrees.
ALU (arithmetic logic unit) --- the unit of a computing system containing circuits that perform arithmetic and logical operations.
analog output --- an electrical output from a sensor that changes proportionally with any change in input.
angular rate sensor --- a sensor that measures rotational velocity around its sensitive axis; measured in degrees per second.
anneal --- heat process used to remove stress, especially in surface micromachining.
anisotropic --- etching that is dependent on crystallographic orientation.
anti-aliasing filter --- normally a lowpass filter that band-limits an input signal before sampling to prevent aliasing noise
ASIC (application-specific integrated circuit) --- an IC designed for a custom requirement, frequently a gate array or programmable logic device.
attenuation --- decrease in magnitude of communication signal.
bandgap reference --- forward-biased emitter junction characteristics of transistor used to provide an output voltage with zero temperature coefficient.
bandpass filter --- filter designed to transmit a band of frequencies while rejecting all others.
bandwidth --- the frequency range within which the product will be able to accurately measure signals. Specified in Hz.
baseband --- frequency band occupied by information --- bearing signals before combining with a carrier in the modulation process.
baud --- unit of signaling speed equal to the number of discrete signal conditions or events per second. Refers to the physical symbols/second used within a transmission channel.
bias stability --- the maximum expected drift in a sensors output. This can be measured as a function of time or as a function of temperature.
bulk micromachining --- a process for making microstructures in which a masked (silicon) wafer is etched in orientation-dependant etching solutions.
calibration --- a resetting process of modifying sensor output to improve output accuracy.
chip --- a die (unpackaged semiconductor device) cut from a silicon wafer, incorporating semiconductor circuit elements such as a sensor, actuator, resistor, diode, transistor, and/or capacitor.
closed loop --- control system that utilizes a sensing device for measuring a process variable and making control decisions based on that feedback
CMOS --- complementary metal oxide semiconductor
common-mode rejection (ratio) - CMR or CMRR; the ratio of the common-mode input voltage to output voltage commonly expressed in dB (i.e., the extent to which a differential amplifier rejects an output when the same signal is applied to both inputs).
compensation --- added circuitry or materials designed to counteract known source of error.
convolution --- mathematical process that describes the operation of filters.
CPU (central processing unit) - the portion of the computer that includes the circuits that control the interpretation and execution of instructions.
D/A converter --- converts a digital signal (discrete values) to an analog voltage.
digital output --- transducer output that represents the magnitude of the measure and in the form of a series of discrete quantities coded in a system of notation.
digital tilt switch --- a tilt sensor that triggers relay outputs when tilted past a set angle
dissipation constant --- the dissipation constant is the ratio, (in milliwatts per ¡ãC) at a specified ambient temperature, of a change in power dissipation in a thermistor to the resultant body temperature change.
DMU (dynamic measurement unit) - provides measurements of accelerations along three orthogonal axes and rotation rates around three orthogonal axes.
DSP (digital signal processing) --- a process by which a sampled and digitized data stream is modified in order to extract relevant information. Also, a digital signal processor.
dynamic range --- the ratio of the largest to the smallest values of a range, often expressed in decibels.
EDP (ethylene diamine pyrocatechol) --- an etchant for bulk micromachining
end-point straight-line fit --- the maximum deviation of any data point on a sensor output curve from a straight line drawn between the end data points on the output curve.
EEPROM (electrically erasable programmable read only memory) --- a semiconductor technique used for permanent storage. It can be reprogrammed in the system.
EMI --- electromagnetic interference; see RFI.
epitaxial or epi --- a single-crystal semiconductor layer grown upon a single-crystal substrate and having the same crystallographic characteristics as the substrate material.
EPROM (erasable programmable read only memory) --- a semiconductor technique used for permanent storage, but can be erased by ultraviolet light.
error --- the algebraic difference between the indicated value and the true value of the input. Error is usually expressed in percent of full-scale span and sometimes expressed in percent of the sensor output reading.
error band --- the band of maximum deviations of the output values from a specified reference line or curve due to those causes attributable to the sensor. Usually expressed as "+/- % of full-scale output." The error band should be specified as applicable over at least two calibration cycles, so as to include repeatability, and verified accordingly.
ESD (electrostatic discharge) - an electrical discharge usually of high voltage and low current.
fiber optic gyro --- a high accuracy rate sensor that uses a laser and fiber optic ring to determine angular rate.
filter --- a circuit that reduces noise and other unwanted elements of a signal.
firmware --- computer program or instructions stored in ROM instead of in the software.
flash --- semiconductor memory that can be used for permanent storage and is easily electrically reprogrammed in the system; faster than EEPROM.
frequency range --- see "bandwidth"
GPS --- global positioning system.
gyro (gyroscope) --- device which can detect angular momentum in space.
high temperature casing --- an aluminum sensor casing for high temperature environments
hysteresis --- refers to a transducer's ability to reproduce the same output for the same input, regardless of whether the input is increasing or decreasing. Also, see temperature hysteresis.
IC (integrated circuit) --- a semiconductor that has several hundred or more transistors designed into it.
infrared --- area in the electromagnetic spectrum ranging from 1 to 1,000 microns.
input impedance (resistance) --- the impedance (resistance) measured between the positive and negative (ground) input terminals at a specified frequency with the output terminals open.
integrated --- the combined design and fabrication of interconnected components. An integrated circuit contains a multiplicity of transistors as well as diodes, resistors, sensor(s), and so forth.
I/O --- input/output for a semiconductor or circuit.
ion beam milling --- a dry-etching process that uses an ion beam to remove material through a sputtering action.
ion implantation --- a process whereby impurity ions are accelerated to a specific energy level and impinged upon the silicon wafer. The energy level determines the depth to which the impurity ions penetrate the silicon. Impingement time determines the impurity concentration.
maximum operating temperature --- the maximum body temperature at which the sensor will operate for an extended period of time with acceptable stability of its characteristics. This temperature is the result of the internal or external heating, or both, and should not exceed the maximum value specified.
maximum power rating --- the maximum power that a sensor will dissipate for an extended period of time with acceptable stability of its characteristics.
MCU (microcontrol unit) --- a semiconductor that has a CPU, memory, oscillator, and I/O capability on the same chip.
MEMS - microelectromechanical systems
micromachining --- the chemical etching of mechanical structure in silicon or other semiconductor material, usually to produce a sensor or actuator.
MIPS (millions of instructions per second) --- a measurement of microprocessor throughput.
MTBF (mean time between failure) - indication of the reliability of a product in normal use.
noise --- additional signals, coming from the product itself or other electronic equipment, that interfere with output signals trying to be measured
noise density --- a measure of noise as a function of frequency (e.g. mg/sqrt(Hz)). Generally, the larger the bandwidth of your measurement, the more noise you include in your measurement.
nonlinearity --- the deviation from a best fit straight line at full scale of true output verses actual.
null offset --- the electrical output present when the sensor is at null.
null temperature shift --- the change in null output value due to a change in temperature.
OEM --- original equipment manufacturer.
open loop --- system with no sensory feedback.
operating impedance --- the impedance measured between the positive and negative (ground) output terminals at a specific frequency with the input open.
operating temperature range --- the range of temperature between minimum and maximum temperature at which the output will meet the specified operating characteristics.
output loading --- the output characteristics of the device.
peripherals --- external circuit components necessary to achieve desired functionality, usually for an MCU or MPU.
PID (proportional integral derivative) --- control technique commonly used in servo systems.
piezoelectric effect --- the ability of certain materials to become electrically polarized in response to applied strain or to be strained in response to applied voltage.
piezoresistor --- a resistor that changes resistance in response to applied strain.
pitch --- rotation around the Y-Axis (for an airplane this is the rotation around the axis defined by the wings).
plasma etching --- an etching process that uses an etching gas instead of a liquid to chemically etch a structure.
PLC --- programmable logic control.
PLL (phase locked loop) --- a major component in a frequency synthesizer.
polysilicon (poly) - silicon composed of randomly arranged crystal unit cells.
random walk --- term used to describe the random bias of angular rate sensors.
ratiometric (ratiometricity error) --- at a given voltage, sensor output is a proportional value of the supply voltage. Ratiometricity error is the change in this proportion resulting from any change to the supply voltage. (Usually expressed as a percent of full-scale output.)
reactive ion etching (RIE) --- a dry-etching process that combines plasma etching and ion beam removal of the surface layer.
repeatability --- the maximum variation between repeated measurements under the same conditions.
resolution --- the smallest change that a sensor can measure.
response time --- time required for a sensor output to change from its previous state to a final state within an error tolerance band of the new correct value.
RFI (radio frequency interference) --- (usually) unintentionally radiated energy that may interfere with the operation of, or even damage, electronic equipment.
roll --- rotation around the X-Axis (for an airplane, roll is rotation about the axis defined by the fuselage).
sampling rate --- the number or readings an A/D converter takes per amount of time (i.e., 50 readings per second).
Sematech --- consortium of United States semiconductor and equipment manufacturers.
semiconductor sensor --- sensor manufactured using silicon, GaAs, SiC, or other semiconductor materials.
self-heating --- internal heating resulting from electrical energy dissipated within the unit.
sensitivity --- the change in output per unit change in input for a specified supply or current.
sensitivity shift --- a change in sensitivity resulting from an environmental change, such as temperature.
shock --- a short, sharp acceleration.
slew rate --- maximum rate of change of voltage with time.
smart sensor --- a device with built-in intelligence, whether apparent to the user or not (IEEE-proposed definition).
SMD --- surface mount device; see SMT.
SMT (surface mount technology) --- method of attaching components, both electrically and mechanically, to the surface of a conductive pattern.
span output --- the value of the output in each direction from the zero sensor output. (i.e., in an accelerometer, if the zero g output is 2.5V, and the span output is 2V, then the output will range from 0.5V to 4.5V).
spin-on --- semiconductor process to deposit films and coatings.
sputter --- semiconductor process to deposit a thin film of material, typically a metal, on the surface.
stability --- the ability of a sensor to retain specified characteristics after being subjected to designated environmental or electrical test conditions.
state machine --- logic circuitry that, when clocked, sequences through logical operations and can be a preprogrammed set of instructions or logic states.
storage temperature range --- the range of temperature between minimum and maximum that can be applied without causing the sensor (unit) to fail to meet the specified operating characteristics.
submicron --- measurement of the geometries or critical spacing used for complex, highly integrated circuits.
supply current --- the typical current that must be supplied to a sensor along with the supply voltage.
supply voltage --- the amount of voltage the user must supply the sensor for the sensor to work properly.
surface micromachining --- a process for depositing and etching multiple layers of sacrificial and structural thin films to build complex microstructures.
temperature coefficient of full-scale span --- the percent change in the full-scale span per unit change in temperature relative to the full-scale span at a specified temperature.
temperature coefficient of resistance --- the percent change in the dc input impedance per unit change in temperature relative to the dc input impedance at a specified temperature.
temperature error --- the maximum change in output at any input value in the operating range when the temperature is changed over a specified temperature range.
temperature hysteresis --- the difference in output at any temperature in the operating temperature range when the temperature is approached from the minimum operating temperature and when approached from the maximum operating temperature with zero input applied.
temperature range --- the temperatures between which the sensor will operate accurately.
temperature-wattage characteristic --- the relationship, at a specified ambient temperature, between the thermistor temperature and a the applied steady-state wattage.
thermal time constant --- the time required for a thermistor to change to 63.2 percent of the total difference between its initial and final body temperature when subjected to a step function change in temperature under zero-power components.
thermistor --- a thermally sensitive resistor whose primary function is to exhibit a change in electrical resistance with a change in body temperature.
torr --- pressure unit equivalent to 1 mm of mercury (mmHg).
transducer --- a device converting energy from one domain into another and calibrated to minimize the errors in the conversion process.
transfer function --- a mathematical, graphical, or tabular statement of the influence that a system or element has on the output compared at the input and output terminals.
transverse sensitivity --- the error in one axis expressed as a percentage of the output in the orthogonal axis (i.e., the amount of signal on the X-axis as a function of acceleration along the Y-axis).
vertical gyro --- a gyroscope whose spin axis is "stabilized" or gimbaled to remain vertical with respect to gravity; the vertical gyro is used to measure rotations away from vertical relative to the fixed earth reference frame
yaw --- rotation around the Z-axis (for an airplane, this would be the lateral (left/right) pointing direction of the head for the plane).
zero g output --- the output that will be read when the module is not accelerating.
zero offset --- the output at zero input for a specified supply voltage or current.
