Measurement Computing CIO-DAS16 - Manual (Page 11)

FLOATING DIFFERENTIAL
A floating differential input is two wires from the signal source and a
10K ground reference resistor installed at the CIO-DAS16 input. The
two signals from the signal source are Signal High (CH# HI) and
Signal Low (CH# LO) (Figure 2-4).
The reference resistor is connected between the CIO-DAS16 CH# LO
and LLGND pins.
A floating differential hookup is useful when the signal source is
floating with respect to ground, such as a battery, 4-20 mA transmitter
or the lead lengths are long or subject to EMI.
The floating differential input will reject up to 10V of EMI.
Figure 2-4. Floating Differential Input
WARNING!
Verify that the signal source is floating. Check it with a voltmeter before risking the CIO-DAS16 and PC!
DIFFERENTIAL
A differential signal has three wires from the signal source. The signals are Signal High (CH# HI), Signal Low (CH# LO)
and Signal Ground (LLGND) (Figure 2-5).
A differential connection allows you to connect the CIO-DAS16 to a signal source with a ground that is different from
the PC ground, but less than 10V difference, and still make a true measurement of the signal between CH# HI and CH#
LO.
Figure 2-5. Differential Input
EXAMPLE:
A laboratory instrument with its own wall plug. There are sometimes voltages in wall GND between outlets.
7
LL GND
CH 0 HI
CH 0 LO
+
- 8
16
DIFFERENTIAL
AMP
TO A/D
10K OHM
+ -
BATTERY
19
18
17
16
15
37
36
35
34
CIO-DAS16 FLOATING DIFFERENTIAL - The two
signals from the signal source are Signal High
(CH 0 HI) and Signal Low (CH 0 LO).
GND
LL GND
CH 0 HI
CH 0 LO
+
- 8
16
DIFFERENTIAL
AMP
TO A/D
V+
V-
19
18
17
16
15
37
36
35
34
CIO-DAS16 DIFFERENTIAL - The signals are Signal High (CH 0 HI), Signal Low
(CH 0 LO), and Signal Ground (LLGND).