Measurement-computing CIO-DAS160x/1x Instrukcja Użytkownika Pobierz pdf (Strona 13)

Figure 5-1b. Single-Ended Voltage Input Theory

Differential Inputs

Differential inputs measure the voltage between two distinct input signals. Within a certain range

(referred to as the common mode range), the measurement is almost independent of signal source to

CIO-DAS1600 ground variations. A differential input is also much more immune to EMI than a

single-ended one. Most EMI noise induced in one lead is also induced in the other, the input only

measures the difference between the two leads, and the EMI common to both is ignored. This effect is a

major reason there is twisted pair wire as the twisting assures that both wires are subject to virtually

identical external influence. Figure 5-2a and 5-2b below show a typical differential input configuration.

Figure 5-2a . Differential Input Theory

Input

Amp

To A /D

LL GND

CH IN

Vs + Vg2 - Vg1

Any voltage differential between grounds

g1 and g2 shows up as an error signal

at the input amplifier

Single-ended input with Common Mode Voltage

Input

Amp

To A /D

Differential Input

I/O

Connector

LL GND

CH High

CH Low

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 43 44

Brak uwag

Measurement-computing CIO-DAS160x/1x Instrukcja Użytkownika Strona 13