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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




A


Absolute Encoder
An absolute encoder provides information in the form of unique output for every resolvable movement of motion or shaft rotation.

Accuracy
Related to the incremental encoding disk. It is the difference between the theoretical position of one increment or bit edge and the actual position of the edge.

Ambient Temperature
The average or mean temperature of the surrounding air that comes in contact with the equipment and instruments under test.

Axial Loading
The force applied to a shaft end surface directed along the axis of rotation.

Axial Load (maximum)
Maximum axial load is the maximum force that may be applied to the shaft without reducing the rated operating life or causing deviation from the rated performance.

Advanced display
PicoScope software dedicates almost all of the display area to the waveform. This ensures that the maximum amount of data is seen at once.

Analog offset
Also called DC offset, this is a valuable feature available on many PicoScope oscilloscopes. Analog offset adds a DC voltage to the input signal.

Arbitrary waveform generator (AWG)
An arbitrary waveform generator (AWG) is used to generate electrical waveforms. The waveforms can be either repetitive or single-shot. An AWG can generate any arbitrarily defined waveshape as its output.

ARINC 429 - introduction
ARINC 429, also known as the Mark 33 DITS specification, was developed to provide interchangeability and interoperability of line replaceable units (LRUs) in commercial aircraft.

Auto-arrange axes
If you have lots of input channels, reference channels and math channels enabled, it can take time to move them around and scale them so that they are all clearly visible.





B


Bandwidth
Oscilloscope bandwidth is defined as the frequency at which a sine wave input signal is attenuated to 70.7% of the signal’s true amplitude, known as the –3 dB point, a term based on a logarithmic scale.

Bi-directional
Bi-directional refers to an encoder output code format from which direction of travel can be determined.

Block capture mode
This is the default mode used by PicoScope software. The scope stores data in internal buffer memory, then processes it and transfers it to the PC before starting the next block.

Buffer sizes
PicoScope buffer sizes are specified in kS (kilosamples), MS (megasamples) or GS (gigasamples). The makers of the memory chips that we use in PicoScope oscilloscopes usually state memory sizes as powers of 2, and we follow this convention in our specifications.





C


Calibration
Calibration is checking the accuracy of a measurement instrument by comparing it to reference standards. The result of equipment calibration is higher accuracy.

CAN and CAN FD bus decoding
CAN bus (Controller Area Network) is a serial data standard originally developed in the 1980s by Robert Bosch GmbH for use in automotive applications.

CE (European Compliance)
Sets essential electromagnetic compatibility, within the European markets, for all electrical and electronic equipment that may interfere with other equipment, or that may be interfered with other equipment.

Channel
Each channel is a unique incremental output of the encoder.

Complementary
Complementary is the term for two identical periodic signals where one signal is electrically inverted from the other. Example of single channel electrically inverted. Complementary signals are typically generated by inversion of the electrical output from a single channel.

Current Sinking Output
A logic form that requires current flow out of the input of the PLC or counter and back to the output of the encoder. The encoder sinks this current, which is sourced by the input circuitry. This is the most common output circuit configuration. It uses an NPN output transistor in the encoder.

Current Sourcing Output
A logic form that requires current flow from the output of the encoder to the input of the counter or PLC. The encoder sources the current and the input circuitry of the counter or PLC sinks this current. This output circuit is seldom used. It usually requires a PNP output transistor in the encoder.

Cycles Per Revolution (CPR)
The number of increments on the disk of an incremental encoder. A one-thousand-increment encoder has a CPR of 1000.





D


Differential Line Driver
Output stage of the encoder that produces two "complementary" pulse trains per output channel. These complementary outputs can be transmitted through long cables with minimal loss of signal integrity. Electrical noise effects are reduced when the signals are compared by the "differential line receiver". Receiver input impedance should be matched to the line driver output and the transmission line for best noise immunity.

Digital Command Control (DCC) protocol decoding
Is a standard defined by the National Model Railroad Association (NMRA) DCC Working Group and is a standard for manufacturers to allow the independent control of multiple locomotives and accessories on a train set.

Digital triggering
The majority of digital oscilloscopes still use an analog triggering architecture based on comparators. This causes time and amplitude errors that cannot always be calibrated out and often limits the trigger sensitivity at high bandwidths.

Disk
Typically made of glass, metal or plastic with precise position incremental lines. These lines are also known as increments. The number of increments determines the resolution, or CPR, of the encoder.

Dual Channel
A dual-channel encoder produces two incremental outputs. These two outputs are generally in quadrature (90° phase separation) relationship to each other. They are typically referred to as Channel A and Channel B.

Duty Cycle
The total time to complete one on/off cycle.





E


Encoder (shaft type)
An encoder is an electro-mechanical device that translates mechanical motion (such as position, velocity, acceleration, speed, or direction) into electrical signals.

Equivalent time sampling
Equivalent-time sampling builds a picture of a repetitive signal by capturing small parts of the waveform from successive triggered acquisitions.





F


Frequency Response
Frequency response for an incremental encoder is the maximum frequency of the output signal in Hertz.





I


Incremental Encoder
An incremental encoder is a device that provides a series of periodic signals due to mechanical motion. The number of successive cycles corresponds to the resolvable mechanical increments of motion.

Index Reference
The index is a separate output generated by a special track that produces a single cycle (or transition change) at a unique position or positions such as center, home, zero, or reset point. Sometimes referred to as a "marker pulse."

IP 50
Protected against dust. Limited ingress (no harmful deposit).

IP 64
Totally protected against dust. Protected against water sprayed from all directions. Limited ingress permitted.

IP 65
Totally protected against dust. Protected against low pressure jets of water from all directions. Limited ingress permitted.

IP 66

Totally protected against dust. Protected against strong jets of water. Limited ingress permitted.

IP 67

Totally protected against dust. Protected against the effect of immersion between 15cm and 1m.

IP 69K

Totally protected against dust. Protected from steam-jet cleaning.

I2C serial bus decoding

The I2C (Inter Integrated Circuit) bus is a low-speed serial data protocol commonly used to transfer data between components and modules within a single device.





J


Jitter
Is uncertainty in the timing of a signal edge. The signal being measured by the oscilloscope may have jitter of its own, caused by unstable frequency, amplitude or pulse width. This is added to the oscilloscope’s intrinsic jitter caused by imperfections in its triggering and timing circuits.





L


Line Count
The number of equally spaced radial lines per 360 mechanical degrees on the incremental encoder code disk.

Line Driver
A circuit that provides error-free output pulses in electrically noisy environments or over long transmission lines when used with a line receiver.





M


Mask limit testing
Mask limit testing allows you to compare live signals against known good signals, and is designed for production and debugging environments. Simply capture a known good signal, draw a mask around it, and then attach the system under test.

Mixed-signal oscilloscope (MSO)
A type of digital oscilloscope that combines the basic functions of a 16-channel logic analyzer with the functionality of a 2- or 4-channel digital oscilloscope.

Modbus serial protocol decoding
Modbus is a low-speed serial data protocol, commonly used in industrial applications where a supervisory computer (master) controls or monitors multiple remote devices (slaves).





N


NEMA 4
Enclosure rating intended for indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, and hose directed water; undamaged by the formation of ice on the enclosure.

NEMA 13
Enclosure rating intended for indoor use primarily to provide a degree of protection against dust, spraying of water, oil and noncorrosive coolants.

Negative Going Pulse
When activated, the pulse goes low (logic 0) or in a negative direction. Do not be confused by negative going, meaning the pulse goes negative in relationship to the signal common or reference level. These statements are for positive logic only. All shaft encoders are based on positive logic.

Noise
An undesirable electrical signal from an external source such as an AC power line, motors, generators, transformers, fluorescent lights, CRT displays, computers, radio transmitters, and others.





O


1-Wire
1-Wire is a serial communications bus system developed by Dallas Semiconductor Corp (now Maxim Integrated Products, Inc.) It provides low-speed data, signaling, and power over a single line. 1-Wire is similar in concept to I²C, but with lower data rates and longer range.

Open Collector Output
When the signal is taken directly off the collector element of the output transistor, no pull-up is used. This is the electronic equivalent of a mechanical switch closure to common. The input device of the PLC or counter is effectively placed in a series circuit that includes the output transistor and input device, which is often an optoisolator and the positive voltage supply. When the output transistor turns on, the circuit is completed and current will flow. The output signal can not be observed unless the circuit is completed externally.





P


Persistence modes
Advanced display modes allow you to collect thousands of waveforms per second. New or more frequent data can be displayed in a brighter color or shade. This makes it easy to see glitches and dropouts and to estimate their relative frequency.

Phase
Phase is electrical degrees of displacement between two encoder outputs, typically 90° in quadrature encoders.

Probe compensation
To minimize capacitive loading on the device under test, most probes use a 10:1 attenuator. This can often be adjusted, or compensated, to improve the frequency response.

Position Error
Position error is the difference between the theoretically correct shaft position and its position as indicated by the encoder cycle count.

Positive Going Pulse
In the low or logic 0 state, it is in the quiescent state. It goes high or logic 1 when activated. This is a transition in the positive going direction.

Pulses Per Revolution
Number of pulses occurring in one revolution of the encoder shaft.

Pulse Polarity
Either positive going or negative going. A pulse has two logic states: activated or inactivated. These two states are opposite. When the pulse is in its quiescent state (high or low), it is at one particular logic level (1 or 0). When the pulse hits or is in the activated state, this logic level reverses itself for the duration of the pulse.

Pulse Width
The actual real time between identical points on the leading or trailing edge of a pulse to the next successive leading or trailing pulse edge. The pulse width of the output signal of most encoders is a 50% duty cycle on the clock outputs. Some models utilize a timed or "one shot" output. This provides a constant pulse width irrespective of the pulse repetition rate or shaft speed.

Pull-Up Resistor
When added inside the encoder between the positive voltage and the collector element of the output transistor, it becomes a pull-up circuit. This is also known as a pulse output.

Push-Pull Output
An output circuit that will both sink and source current.





Q


Quadrature
A dual output encoder used for bi-directional motion control. One channel leads the other by 90 electrical degrees. By monitoring the phase shift of both channel A and B, direction can be determined. Another benefit of a quadrature encoder is count multiplication. With an appropriate counter, resolution can be multiplied up to four times. For instance, by using this technique, an encoder with CPR of 1000 can provide a resolution of up to 4000 pulses per shaft revolution.

Quadrature Error
Quadrature error is the phase error when the specified phase relationship between two channels is nominally 90 electrical degrees.





R


Radial Load
The force applied at a specific point to the encoder shaft perpendicular to the axis of rotation. Note: It is important to note where the force is being applied along the shaft, due to the cantilever effect.

Radial Load (maximum)
The maximum force that may be applied perpendicularly to the shaft without reducing the rated operating life or causing deviation from the rated performance.

Resolution
The number of increments on the encoder disk. For incremental encoders, resolution is defined as cycles per revolution (CPR).

RS-232
Is a standard for serial data communication first defined in 1962 by the Electronic Industries Alliance for use with data communication devices such as teletypewriters.





S


SENT bus
SENT (Single Edge Nibble Transmission), SAE standard J2716, is a one way, point-to-point protocol for transmission of signal values from sensors to a controller. It is used mainly in automotive applications and enables reliable transmission of high-resolution data with lower cost than standards such as CAN, and higher bit rate than LIN.

Shaft Run Out
Amount of shaft movement while spinning.

Signal generator
A signal generator is an invaluable piece of test equipment. The output from a signal generator is a repeating waveform whose characteristics are set by the user. Signal generators can be used for research and development purposes, along with the servicing and repair of electronic equipment.

Single Channel
A single channel encoder produces one incremental output. They are often used for tachometry applications.

Solder Terminals
For applications that require direct solder connections to the shaft encoder.

FFT spectrum analyzer
The spectrum view plots amplitude against frequency and is ideal for finding noise, crosstalk or distortion in signals.

SPI bus
SPI (Serial Peripheral Interface) bus was originally developed by Motorola for use with their microcontrollers. Due to the simplicity of the bus, other manufacturers adopted it and it has become widely available in components used in embedded system designs.

Streaming mode
This enables long periods of slow data collection for chart recorder and data-logging applications as well as fast USB streaming.

Symmetry
Symmetry is the ratio of the ON time to the OFF time of the output signal for one channel. This ratio is optimally 50-50.





T


TIR
Total Indicator Reading

Torque (running)
Running torque is the rotary force required to keep an encoder shaft turning. It is typically expressed in ounce-inches.

Torque, Starting
Starting (breakaway) torque is the rotary force required to overcome static friction and cause the encoder shaft to begin rotating.


U


Unidirectional
An encoder output code format from which direction of travel cannot be determined.

USB
(Universal Serial Bus) is widely adopted in today’s personal computers and tablets for communication and power to printers, keyboard, mice, memory devices and many other peripherals. It is also used for chip-to-chip and module-to-module communication in many other types of electronic devices and embedded systems.

USB flexible power
Many models can be powered directly from the USB connection, while the highest-performance models require an external AC adaptor. Some models can operate with USB power with two channels turned on, but require an AC adaptor to support four-channel operation.


V


Vibration analysis

Vibration in mechanical systems, particularly with rotating machinery, can be very problematic, creating unwanted noise or introducing stresses that can lead to catastrophic failures. Analysing vibration can help to identify root causes and allow corrections to be made to improve reliability.


W


XY display mode
An XY view, in its simplest form, shows a graph of one channel plotted against another. XY display mode is useful for showing relationships between periodic signals (using Lissajous figures) and for plotting I–V (current-voltage) characteristics of electronic components.