2 analog input signal connection – ADLINK cPCI-9116 User Manual

Page 26

Advertising
background image

16

• Signal Connections

3.2

Analog Input Signal Connection

The 9116 series provides up to 64 single-ended or 32 differential analog input
channels. You can set and fill the Channel Gain Queue to get the desired
combination of the input signal types. The analog signals can be converted to
digital value by the A/D converter. To avoid ground loops and to obtain
accurate measurements from the A/D conversion, it is quite important to
understand the signal source type and how to choose the analog input modes:
Single-ended, Differential, or User Common Mode.

3.2.1

Types of signal sources

Floating Signal Sources

A floating signal source means it is not connected in any way to the buildings
ground system. A device with an isolated output is a floating signal source,
such as optical isolator outputs, transformer outputs, and thermocouples

Ground-Referenced Signal Sources

A ground-referenced signal means it is connected in some way to the buildings
system. That is, the signal source is already connected to a common ground
point with respect to the 9116 card, assuming that the computer is plugged into
the same power system. Non- isolated outputs of instruments and devices that
plug into the buildings power system are ground-referenced signal sources.

3.2.2 Input

Configurations

Single-ended Mode

In single-ended mode, all input signals are connected to ground provided by
the 9116 card. It is suitable for connections with floating signal sources. Figure
4 illustrates single-ended connection. Note that when more than two floating
sources are connected, these sources will be referenced to the same common
ground.

AIn

AGND

n = 0, ...,63

Floating
Signal
Source

Instrumentation
Amplifier

To A/D
Converter

Input Multipexer

V1

V2

+

-

+

-

J1

Figure 4: Single-ended Mode and Floating sources

Advertising