Measurement-computing DaqBoard 3000USB Series Instrukcja Użytkownika Pobierz pdf (Strona 127)

Glossary 887194 G-1

Glossary

Acquisition

A collection of scans acquired at a specified rate as controlled by the sequencer.

alog

A signal of varying voltage or current that communicates data.

Analog-to-Digital

Converter (ADC)

A circuit or device that converts analog values into digital values, such as binary bits, for use in digital

computer processing.

Application Program Interface. The interface program w

ithin the Daq sy

stem’s driver that includes function

calls specific to Daq hardware and can be used with user-written programs (several languages supported).

Bipolar

A range of analog signals with positive and negative values (e.g., -5 to +5 V); see unipolar.

Buffer

Buffer refers to a circuit or device that allow

s a signal to pass through it, w

hile providing isolation, or another

function, without altering the signal. Buffer usually refers to:

(a) A device or circuit that allows for the temporary

storage of data during data transfers. Such storage can

compensate for differences in data flow

rates. In a FIFO (First In - First Out) buffer, the data that is

stored first is also the first data to leave the buffer.

(b)

A follower stage used to drive a number of gates w

ithout overloading the preceding stage.

(c)

An amplifier which accepts high source impedance input and results in low source impedance output

(effectively, an impedance buffer).

Buffer A

mplifier

An amplifier used primarily to match two different impedance points, and isolate one stage from a succeeding

stage in order to prevent an undesirable interaction betw

een the tw

o stages. (Also see, Buffer).

Channel

In reference to Daq devices, channel simply

refers to a single input, or output entity.

In a broader sense, an input channel is a signal path between the transducer at the point of measurement and

the data acquisition system. A channel can go through various stages (buffers, multiplexers, or signal

conditioning amplifiers and filters). Input channels are periodically

sampled for readings.

An output channel from a device can be digital or analog. Output

s can vary in a programmed w

ay in response

to an input channel signal.

Common mode

Common mode pertains to signals that are identical in amplitude and duration; also can be used in reference

to signal components.

Common mode voltage

Common mode voltage refers to a voltage magnitude (referenced to a common point) that is shared by two or

more signals. Exam

ple: referenced to common, Signal 1 is +5

VDC and Signal 2 is +6 VDC. The common

mode voltage for the two signals is +5.5 VDC [(5 + 6)/2].

Crosstalk

An undesired transfer of signals between systems or sy

stem components. Crosstalk causes signal

interference, more commonly referred to as noise.

Digital

A digital signal is one of discrete value, in contrast to a vary

ing signal. Combinations of binary digits (0s and

1s) represent digital data.

Digital-to-A

nalog

Conv

erter (DAC)

A circuit or device that conv

erts digital values (binary

bits), into analog signals.

DIP switch

A DIP switch is a group of miniature switches in a small Dual In-line Package (DIP). Typically, users set these

itches to configure their particular application.

Differential mode

The differential mode measures a voltage between 2 signal lines for a single channel. (Also see single-ended

mode).

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