Measurement-computing Personal Daq/3000 Series Bedienungsanleitung PDF herunterladen (Seite 85)

Glossary 887194 G-1

Glossary

Acquisition

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

Analog

A signal of vary

ing 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.

API

Application Program Interface. The interface program w

thin the Daq system’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, while providing isolation, or another

function, w

ithout 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 follow

er stage used to drive a number of gates w

thout overloading the preceding stage.

hich accepts high source impedance input and results in low source impedance output

(effectively, an impedance buffer).

Buffer Amplifier

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 way

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

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 converts 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

switches to configure their particular application.

Differential mode

The differential mode measures a voltage betw

een 2 signal lines for a single channel. (Also see single-ended

mode).

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