Measurement-computing DaqBook 2000 Series Manuel d'utilisateur télécharger pdf (Page 88)

G-2 959395 Glossary

Digital-to-Analog

Converter (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 between 2 signal lines for a single channel. (Also see

ngle-ended mode).

Differential mode

vol

tage

Differential mode voltage refers to a voltage difference between two signals that are referenced

o a common point. Example: Signal 1 is +5 VDC referenced to common. Signal 2 is +6 VDC

referenced to common.

If the +5 VDC signal is used as the reference, the differential mode voltage is +1 VDC

(+ 6 VDC - +5 VDC = +1 VDC).

If the +6 VDC signal is used as the reference, the differential mode voltage is -1 VDC

(+ 5 VDC - +6 VDC = -1 VDC).

ESD

Electrostatic discharge (ESD) is the transfer of an electrostatic charge between bodies having

fferent electrostatic potentials. This transfer occurs during direct contact of the bodies, or

when induced by an electrostatic field. ESD energy can damage an integrated circuit (IC).

Excitation

Some transducers [e.g. strain gages, thermistors, and resistance tem

perature detectors (RTDs)]

require a known voltage or current. Typically, the variation of this signal through the

transducer corresponds to the condition measured.

Gain

The degree to which an input signal is amplified (or attenuated) to allow greater accuracy and

resol

ution; can be expressed as ×n or ±dB.

Isolation

The arrangement or operation of a circuit so that

signals from another circuit or device do not

affect the isolated circuit.

In reference to Daq devices, iso

lation usually refers to a separation of the direct link between the

signal source and the analog-to-digital converter (ADC). Isolation is necessary when

measuring high common-mode voltage.

Linearization

Some transducers produce a voltage in linear proportion to the condition m

easured. Other

transducers (e.g., thermocouples) have a nonlinear response. To convert nonlinear signals into

accurate readings requires software to calibrate several points in the range used and then

interpolate values between these points.

Multiplexer (MUX)

A device that collects signals from several inputs and outputs them on a single channel.

Sample (reading)

The value of a signal on a channel at an instant in

time. When triggered, the ADC reads the

channel and converts the sampled value into a 12- or 16-bit value.

Scan

A series of measurements across a pre-selected sequence of channels.

Sequencer

A programmable device that manages channels and channel-specific settings.

Simultaneous

Sample-and-Hold

An operation that gathers samples from multiple channels at the same instant and holds these

values until all are sequentially converted to digital values.

Single-ended mode

The single-ended mode measures a voltage between a signal line and a common reference that

ay be shared with other channels. (Also see differential mode).

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Measurement-computing DaqBook 2000 Series Manuel d'utilisateur Page 88

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