Measurement-computing StrainBook/616 Manual de usuario descargar pdf (Pagina 144)

G-2 Glossary 969597 Data Acquisition

Digital

A digital signal is one of discrete value, in contrast

to a varying signal. Combinations of binary

digits (0s and 1s) represent digital data.

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).

Encoder Mode

The encoder mode al

lows the WBK17 to make use of data from optical incremental quadrature

encoders. When in the encoder mode, the WBK17 accepts either differential or single-ended

inputs and provides power for up to four encoders. When reading phase A, phase B, and

index Z signals, the WBK17 provides positioning, direction, and velocity data.

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); so

safe handling is required.

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.

Gating

In relation to the WBK17, any counter can be gated by the mapped channel. When the mapped

channel is high, the counter will be allowed to count, when the m

apped channel is low, the

counter will not count but hold its value.

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 data acquisition, 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.

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