Measurement-computing CIO-EXP-GP Manuel d'utilisateur télécharger pdf (Page 16)

+P EXCITATION. VOLTS

−

SENSE

+ SENSE

(+)IEXC

−

VOLTS IN OR COMMON

+ VOLTS IN

SHORTING WIRE

INSTALLED

+EXCITATION CURRENT

+ SENSE

−

(

−

)

IEX

−

+ VOLTS IN

−EXCITATION CURRENT

Each input circuit has eight screw terminals associated

with it. These terminals are shown in Figure 4-4 to the

right.

To connect a voltage signal to the input circuit you

need only use three screw terminals. These are:

+SENSE Signal high, or CH HI on a DAS board

−

SENSE Signal low, or CH LO on a DAS board.

Must be jumpered to

−

P for single-ended

−

P Low Level Ground (LLGND)

Figure 4-4. Input Screw Terminals

4.7.1 Single-Ended Inputs

A single-ended input has two wires connected to the CIO-EXP-GP; a signal high and a Low Level

Ground (LLGND). The LLGND signal

must be the same ground the PC is on.

Single-ended mode is

selected by installing a jumper between the signal low (

−

SENSE) and ground (

−

P). The -SENSE

terminal is then connected to the signal ground and the +SENSE terminal is connected to the signal.

4.7.2 Floating Differential

A floating differential input has two wires from the signal source and a 10K ground reference resistor

installed at the CIO-EXP-GP input. The two signals from the signal source are Signal High and Signal

Low. The reference resistor is connected between the CIO-EXP-GP “

−

SENSE” and “-P” pins and the

Signal Low is connected to the -SENSE terminal. The +SENSE terminal is connected to the Signal High.

A floating differential hookup is handy when the signal source is floating with respect to ground, such as

a battery. The floating differential input will reject up to 10V of EMI energy on the signal wires.

CAUTION: Is the signal source really floating? Check it with a voltmeter before risking the

CIO-EXP-GP and PC.

4.7.3 Fully Differential

A differential signal has three wires from the signal source. The signals are Signal High, Signal Low and

Signal Ground (LLGND). Signal High is connected to the +SENSE terminal and Signal Low is

connected to the -SENSE terminal. The ground reference must be connected to the -P terminal.

A differential connection allows you to connect the CIO-EXP-GP to a signal source with a ground that is

different than the PC ground, but less than 10V difference, and still make a true measurement of the

signal. For example, a laboratory instrument with its own wall plug. Sometimes there is a voltage

between wall outlet grounds.

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Measurement-computing CIO-EXP-GP Manuel d'utilisateur Page 16

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