USER GUIDE
SCC-CO20 Isolated Current
Output Module
The SCC-CO20 is an isolated current output module that outputs up to
20 mA. The output current level is proportional to the voltage applied to
the module by an analog output channel of an E/M Series DAQ device.
Conventions
The following conventions are used in this guide:
<> Angle brackets that contain numbers separated by an ellipsis represent
a range of values associated with a bit or signal name—for example,
AO <3..0>.
» The » symbol leads you through nested menu items and dialog box options
to a final action. The sequence File»Page Setup»Options directs you to
pull down the File menu, select the Page Setup item, and select Options
from the last dialog box.
This icon denotes a note, which alerts you to important information.
This icon denotes a caution, which advises you of precautions to take to
avoid injury, data loss, or a system crash. When this symbol is marked on
the product, refer to the Read Me First: Safety and Radio-Frequency
Interference document, shipped with the product, for precautions to take.
When symbol is marked on a product, it denotes a warning advising you to
take precautions to avoid electrical shock.
When symbol is marked on a product, it denotes a component that may be
hot. Touching this component may result in bodily injury.
bold Bold text denotes items that you must select or click in the software, such
as menu items and dialog box options. Bold text also denotes parameter
names.
italic Italic text denotes variables, emphasis, a cross-reference, or an introduction
to a key concept. Italic text also denotes text that is a placeholder for a word
or value that you must supply.
monospace Text in this font denotes text or characters that you should enter from the
keyboard, sections of code, programming examples, and syntax examples.
This font is also used for the proper names of disk drives, paths, directories,
programs, subprograms, subroutines, device names, functions, operations,
variables, filenames, and extensions.
SC-2345 SC-2345 refers to both the SC-2345 connector block and the SC-2345 with
configurable connectors.
SCC SCC refers to any SCC Series signal conditioning module.
What You Need to Get Started
To set up and use the SCC-CO20, you need the following items:
❑ Hardware
– SC-2345/2350 with one of the following:
• SCC-PWR01
• SCC-PWR02 and the PS01 power supply
• SCC-PWR03 (requires a 7 to 42 VDC power supply,
not included)
– One or more SCC-CO20
– 68-pin E/M Series DAQ device
– 68-pin cable
– Quick Reference Label
❑ Software
– The latest version of NI-DAQmx
❑ Documentation
– SCC-CO20 Isolated Current Output Module User Guide
– SC-2345/2350 User Manual
– SCC Quick Start Guide
– Read Me First: Safety and Radio-Frequency Interference
– Documentation for your hardware
– Documentation for your software
SCC-CO20 Isolated Current Output Module User Guide 2 ni.com
❑ Tools
– 1/8 in. flathead screwdriver
– Numbers 1 and 2 Phillips screwdrivers
– Wire insulation stripper
Note Software scaling of measurements is not supported on the Macintosh operating
system. Refer to the SCC-CO20 Module Pin Assignments section.
You can download NI documents from
the latest version of NI-DAQmx, click Download Software at
Device Specific Information
Note For general SCC module installation and signal connection information, and
information about the SC-2345/2350 carrier, refer to the SCC Quick Start Guide, available
for download at
Installing the SCC-CO20
Caution Refer to the Read Me First: Safety and Radio-Frequency Interference document
before removing equipment covers or connecting/disconnecting any signal wires.
Connecting the SCC-CO20 to a Load
Note The signal names have changed. Refer to ni.com/info and enter rdtntg
to confirm the signal names.
ni.com/manuals.
Plug the SCC-CO20 into either SC-2345/2350 analog output socket
J(X+17), where X is 0 or 1. The SC-2345/2350 routes the voltage output of
E/M Series DAQ device analog output channel AO (X) to the SCC-CO20.
ni.com/manuals. To download
ni.com.
The screw terminals are labeled by pin number <1..3>. Pin 1 is the ground,
pin 2 is the current sink, and pin 3 is the isolated loop supply. Figure 1
shows how the ground, sink, and supply connect to the E/M Series DAQ
device.
© National Instruments Corporation 3 SCC-CO20 Isolated Current Output Module User Guide
E/M Series
DAQ Device
AO (X )
SCC-CO20
+
15 V iso
–
3
2
AO GND
Figure 1. SCC-CO20 Signal Connections to E/M Series DAQ Device
Using the Isolated Loop Supply of the SCC-CO20
You can connect the SCC-CO20 to a load using either the isolated internal
loop supply or an external supply. The internal loop supply outputs a
voltage of 15 V with respect to the isolated ground reference. When using
the internal loop supply, the compliance voltage is 12.5 V. This allows for
a maximum load resistance of 625 Ω at 20 mA. Figure 2 shows how to
connect the SCC-CO20, using the internal loop supply, to a nonreferenced
(floating) load and to a load with a high common-mode voltage.
SCC-CO20
+
15 V iso
–
3
SUPPLY
0–20 mA 0–20 mA
2
SINK
Load
SCC-CO20
+
15 V iso
–
3
SUPPLY
2
SINK
1
I
Load
+
High
CMV
–
1
I
I
1
Figure 2. Connecting the SCC-CO20 Using the Internal Loop Supply
SCC-CO20 Isolated Current Output Module User Guide 4 ni.com
Note If your load is grounded and you are using the internal supply, connect the load
ground to the current sink terminal at pin 2 on the SCC-CO20. Do not connect the load
ground to the isolated ground terminal because doing so could defeat the module isolation.
Driving Higher-Resistance Loads with the SCC-CO20
In order to calculate the supply voltage your application requires, multiply
the load resistance by the current you need to sink, then add 2.5 V for the
voltage drop across the protection diode and the current-sink MOSFET.
If you need a higher voltage than the 15 V provided by the internal loop
supply, you can either add a second SCC-CO20 module or provide an
external loop supply.
Adding a Second SCC-CO20 Module
You can add another SCC-CO20 loop supply to create a supply of 30 V,
as shown in Figure 3. Do not use more than two SCC-CO20 modules on
a single circuit, because the resulting voltage can cause overheating and
damage the modules and other equipment.
© National Instruments Corporation 5 SCC-CO20 Isolated Current Output Module User Guide
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