Measurement-computing CIO-DAS6402/12 Instrukcja Użytkownika Pobierz pdf (Strona 16)

Systems with varying ground potentials should always be monitored in the differential mode. Care is required to assure that the sum

of the input signal and the ground differential (referred to as the common mode voltage) does not exceed the common mode range

of the A/D board (+/-10V on the CIO-DAS6402). Figure 4-6 below show recommended connections in this configuration.

Figure 4-6. Common Mode Voltage < +/-10V / Differential Inputs

4.2.5 COMMON MODE VOLTAGE > +/-10V

The CIO-DAS6402 will not directly monitor signals with common mode voltages greater than +/-10V. You will either need to alter

the system ground configuration to reduce the overall common mode voltage, or add isolated signal conditioning between the

source and your board. See Figure 4-7 and 4-8 below.

Figure 4-7. Common Mode Voltage > +/-10V. Single-Ended Input

Figure 4-8. Common Mode Voltage > +/-10V. Differential Input

4.2.6 ISOLATED GROUNDS / SINGLE-ENDED INPUTS

Single-ended inputs can be used to monitor isolated inputs, though the use of the differential mode will increase you system’s noise

immunity. Figure 4-9 below shows the recommended connections is this configuration.

Input

Amp

To A/D

A/D Board

I/O

Connector

LL GND

CH High

CH Low





Signal Source

with Common

M ode Voltage

Signal source and A/D board

with common mode voltage

connected to a differential input.

GND

The voltage differential

between these grounds,

added to the maximum

input signal must stay

within +/-10V

System with a Large Common Mode Voltage,

Connected to a Single-Ended Input

I/O

Connector

Input

Amp

To A/D

LL GND

CH IN

A/D Board

arge common

mode voltage

between signal

source & A/D board

GND

Isolation

Barrier

When the voltage difference

between signal source and

A/D board ground is large

enough so the A/D board’s

common mode range is

exceeded, isolated signal

conditioning must be added.

System with a Large Common Mode Voltage,

Connected to a Differential Input

arge common

mode voltage

between signal

source & A/D board

GND

Isolation

Barrier

When the voltage difference

between signal source and

A/D board ground is large

enough so the A/D board’s

common mode range is

exceeded, isolated signal

conditioning must be added.

Input

Amp

To A/D

A/D Board

I/O

Connector

LL GND

CH High

CH Low

10 K

10K is a recommended value. You may short LL GND to CH Low

instead, but this will reduce your system’s noise immunity.

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