Measurement-computing CIO-DAS08-PGH User Manual download pdf (Page 13)

3.1.9 Board and Signal Source Have Isolated Grounds

Some signal sources will already be electrically isolated from the board. Figure 3-4 shows a typical isolated ground system. These

signal sources are often battery powered, or are fairly expensive pieces of equipment (since isolation can be expensive), isolated

ground systems provide excellent performance, but require some extra effort during connections to assure optimum performance

is obtained. Please refer to the following sections for further details.

3.2 WIRING CONFIGURATIONS

Combining all the grounding and input type possibilities provides us with the following potential connection configurations. The

combinations along with our recommendations on usage are shown in Table 3-1 below.

Table 3-1. Analog Input Configuration Recommendations

RecommendedDifferential Inputs

Already Isolated

Grounds

AcceptableSingle-ended InputsAlready Isolated Grounds

Unacceptable without

adding Isolation

Differential Inputs

Common Mode

Voltage > +/-10V

Unacceptable without

adding Isolation

Single-Ended Inputs

Common Mode

Voltage > +/- 10V

RecommendedDifferential Inputs

Common Mode

Voltage < +/-10V

Not RecommendedSingle-Ended Inputs

Common Mode

Voltage < +/-10V

AcceptableDifferential InputsCommon Ground

RecommendedSingle-Ended InputsCommon Ground

OUR VIEW

INPUT

CONFIGURATION

GROUND

CATEGORY

The following sections depicts recommended input wiring schemes for each of the seven possible input configuration/grounding

combinations.

3.2.1 Common Ground / Single-Ended Inputs

Single-ended is the recommended configuration for common ground connections. However, if some of your inputs are common

ground and some are not, we recommend you use the differential mode. There is no performance penalty (other than loss of

channels) for using a differential input to measure a common ground signal source. However the reverse is not true. Figure 3-4

below shows a recommended connection diagram for a common ground / single-ended input system.

Figure 3-4. Common Ground / Single-Ended Inputs

Input

Amp

To A /D

A/D Board

I/O

Connector

LL GND

CH IN

Signal

Source with

Common Gnd

Optional wire

since signal source

and A/D board share

common ground

nal source and A/D board

sharin

common

round connected

to sin

le-ended input.

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 27 28

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