National Instruments Network Card SCC CO20 User Manual

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.  
 
 
Tools  
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 ni.com/manuals. To download  
the latest version of NI-DAQmx, click Download Software at ni.com.  
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 ni.com/manuals.  
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.  
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.  
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.  
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  
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SCC-CO20 Isolated Current Output Module User Guide  
 
 
E/M Series  
DAQ Device  
SCC-CO20  
3
+
15 V iso  
2
1
AO (X )  
AO GND  
I
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  
SCC-CO20  
3
2
3
2
SUPPLY  
SUPPLY  
+
+
Load  
Load  
15 V iso  
15 V iso  
0–  
20 mA  
020 mA  
SINK  
SINK  
+
High  
CMV  
1
1
I
I
Figure 2. Connecting the SCC-CO20 Using the Internal Loop Supply  
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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  
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SCC-CO20 Isolated Current Output Module User Guide  
 
SCC-CO20  
3
SUPPLY  
+
15 V iso  
2
1
ISO GND  
I
SCC-CO20  
3
SUPPLY  
SINK  
+
15 V iso  
Load  
2
1
I
Figure 3. Connecting Two SCC-CO20 Modules to a Higher-Resistance Load  
SCC-CO20 Isolated Current Output Module User Guide  
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Using an External Loop Supply  
In order for the current sink to operate properly with an external loop  
supply, the voltage must be within the range of 3 to 42 V. If the voltage is  
too high, overheating can occur and damage the module. Figure 4 shows  
four configurations using an external loop supply.  
SCC-CO20  
SCC-CO20  
2
SINK  
2
SINK  
+
Load  
0–20 mA  
0–20 mA  
+
Load  
1
1
ISO GND  
ISO GND  
I
I
a. Nonreferenced load and external voltage supply (two circuits)  
SCC-CO20  
SCC-CO20  
2
SINK  
2
SINK  
+
Load  
0–20 mA  
0–20 mA  
+
Load  
1
1
ISO GND  
ISO GND  
High  
CMV  
High  
CMV  
I
I
+
+
b. Referenced load and external voltage supply (two circuits)  
Figure 4. Connecting the SCC-CO20 Using an External Loop Supply  
When you use an external loop supply, the order of the supply and load does  
not matter as long as you do not create a second loop through which current  
flows. If both the supply and the load are grounded, connect the signals as  
shown in Figure 5.  
© National Instruments Corporation  
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SCC-CO20 Isolated Current Output Module User Guide  
 
 
SCC-CO20  
2
SINK  
+
0
20 mA  
1
ISO GND  
Load  
I
Figure 5. Connecting the SCC-CO20 to a Grounded External Loop Supply  
and a Grounded Load  
For information about how to configure the SCC-CO20 module using  
NI-DAQmx, refer to the SCC Quick Start Guide.  
Calibrating Gain and Offset Errors  
The SCC-CO20 is calibrated at the factory before shipment. If you want  
to adjust the gain and offset of the SCC-CO20 in your system using an  
E/M Series DAQ device, you need a current meter (ammeter) with an  
accuracy of at least 2 μA.  
To adjust the gain and offset of the SCC-CO20, complete the following  
steps:  
1. Disconnect the load from the SCC-CO20 you want to calibrate.  
2. Set an output range of 0 to 10 V for AO (X), the E/M Series DAQ  
device channel connected to the SCC-CO20.  
3. Connect the negative lead of the ammeter to the current sink (pin 2)  
and the positive lead to the current supply (pin 3) of the SCC-CO20.  
4. Using your software, have AO (X) output 10 mVDC.  
5. Adjust the offset potentiometer on the top of the SCC-CO20 until the  
ammeter reads 20 μA. The offset is now calibrated.  
6. Using your software, have AO (X) output 9 VDC.  
7. Adjust the gain potentiometer on the top of the SCC-CO20 until the  
ammeter reads 18 mA. The gain is now calibrated.  
SCC-CO20 Isolated Current Output Module User Guide  
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Note Normally you would adjust to 0 μA in order to calibrate the offset, but because  
the SCC-CO20 cannot source current, it is impossible to know when you have adjusted  
past 0 μA.  
Using the SCC-CO20  
The SCC-CO20 is a 0 to 20 mA programmable current sink. The current  
output is controlled by AO (X), a 0 to 10 V unipolar DAC output channel  
of an E/M Series DAQ device. The relationship between the AO (X)  
voltage level and the current output of the SCC-CO20 is linear and is  
described by the following equation:  
VAO(X)  
--------------- = ICO20  
500  
where  
V
AO (X) is the AO (X) voltage level.  
ICO20 is the SCC-CO20 current output in amperes.  
The current sink is an N-channel power MOSFET sink to an isolated  
ground reference. You can use the SCC-CO20 with industry-standard  
0 to 20 or 4 to 20 mA current loops.  
Note The current sink does not source current. If the input voltage is 0 V or less,  
the module sinks 0 mA.  
Isolated Ground Reference  
Each SCC-CO20 module is referenced to its own isolated ground. Each  
isolated ground can have up to 60 VDC of common-mode voltage between  
itself and any other channel ground or chassis ground. Refer to the  
Connecting the SCC-CO20 to a Load section for different ways to use  
the isolated ground in signal connections.  
© National Instruments Corporation  
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SCC-CO20 Isolated Current Output Module User Guide  
 
Specifications  
These ratings are typical at 25 °C unless otherwise stated.  
Electrical  
Number of output channels.....................1  
Output referencing..................................Nonreferenced (floating)  
Input range..............................................0 to 10 V  
Output range ...........................................0 to 20 mA  
Voltage compliance ................................12.5 V  
Maximum load resistance  
5 mA................................................2,500 Ω  
10 mA..............................................1,250 Ω  
15 mA..............................................830 Ω  
20 mA..............................................625 Ω  
Absolute accuracy...................................0.1% of full-scale output range  
Temperature drift....................................0.5 μA/°C typ  
1 μA/°C max  
Power Requirement  
Analog power .........................................175 mW max  
+15 V...............................................5.8 mA max  
–15 V ...............................................5.8 mA max  
Digital power (+5 V) ..............................645 mW  
+5 V.................................................129 mA max  
SCC-CO20 Isolated Current Output Module User Guide  
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Physical  
1.87 cm  
(0.74 in.)  
7.93 cm  
(3.12 in.)  
3.55 cm  
(1.4 in.)  
Figure 6. SCC-CO20 Dimensions  
Weight.................................................... 28 g (1.0 oz)  
I/O connectors........................................ One 20-pin right-angle male  
connector  
One 3-pin screw terminal  
Field-wiring diameter............................. 28 to 16 AWG  
Maximum Working Voltage  
(Signal + common-mode) each input should remain within 42.4 Vpeak or  
60 VDC of ground.  
Maximum working voltage refers to the signal voltage plus the CMV.  
Channel-to-earth (inputs) ....................... 42.4 Vpeak or 60 VDC,  
Measurement Category I  
Caution This device is rated for Measurement Category I and is intended to carry signal  
voltages no greater than 42.4 Vpeak or 60 VDC. Do not use this device for connection to  
signals or for measurements within Categories II, III, or IV.  
Isolation Voltage  
Channel-to-earth isolation  
Continuous...................................... 60 VDC,  
Measurement Category I  
Withstand........................................ 2300 Vrms verified by a 5 s  
dielectric withstand type test  
© National Instruments Corporation  
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SCC-CO20 Isolated Current Output Module User Guide  
 
Environmental  
Operating temperature ............................0 to 50 °C  
Storage temperature................................–20 to 70 °C  
Humidity.................................................10 to 90% RH, noncondensing  
Maximum altitude...................................2,000 m  
Pollution Degree (indoor use only) ........2  
Safety  
This product meets the requirements of the following standards of safety  
for electrical equipment for measurement, control, and laboratory use:  
IEC 61010-1, EN 61010-1  
UL 61010-1, CSA 61010-1  
Note For UL and other safety certifications, refer to the product label or the Online  
Product Certification section.  
Electromagnetic Compatibility  
This product meets the requirements of the following EMC standards for  
electrical equipment for measurement, control, and laboratory use:  
EN 61326 (IEC 61326): Class A emissions; Basic immunity  
EN 55011 (CISPR 11): Group 1, Class A emissions  
AS/NZS CISPR 11: Group 1, Class A emissions  
FCC 47 CFR Part 15B: Class A emissions  
ICES-001: Class A emissions  
Note For the standards applied to assess the EMC of this product, refer to the Online  
Product Certification section.  
Note For EMC compliance, operate this product according to the documentation.  
Note For EMC compliance, operate this device with shielded cables.  
CE Compliance  
This product meets the essential requirements of applicable European  
Directives as follows:  
2006/95/EC; Low-Voltage Directive (safety)  
2004/108/EC; Electromagnetic Compatibility Directive (EMC)  
SCC-CO20 Isolated Current Output Module User Guide  
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Online Product Certification  
Refer to the product Declaration of Conformity (DoC) for additional  
regulatory compliance information. To obtain product certifications and  
the DoC for this product, visit ni.com/certification, search by model  
number or product line, and click the appropriate link in the Certification  
column.  
Environmental Management  
NI is committed to designing and manufacturing products in an  
environmentally responsible manner. NI recognizes that eliminating  
certain hazardous substances from our products is beneficial to the  
environment and to NI customers.  
For additional environmental information, refer to the NI and the  
Environment Web page at ni.com/environment. This page contains the  
environmental regulations and directives with which NI complies, as well  
as other environmental information not included in this document.  
Waste Electrical and Electronic Equipment (WEEE)  
EU Customers At the end of the life cycle, all products must be sent to a WEEE recycling  
center. For more information about WEEE recycling centers and National Instruments  
WEEE initiatives, visit ni.com/environment/weee.  
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(For information about China RoHS compliance, go to  
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SCC-CO20 Isolated Current Output Module User Guide  
 
 
SCC-CO20 Module Pin Assignments  
Figure 7 shows the I/O connector pins on the bottom of the module.  
4
1
2
5
3
1 Pin 1  
2
Pin 2  
3
PWB Key  
4
Pin 19  
5 Pin 20  
Figure 7. SCC-CO20 Bottom View  
Table 1 lists the signal connection corresponding to each pin.  
Table 1. SCC-CO20 Pin Signal Connections  
Pin Number  
Signal  
1
2
E/M Series AO (X)  
E/M Series AO GND  
3
4
E/M Series AO GND  
5
6
7
8
9
+5 V  
GND  
10  
11  
12  
13  
+5 V REF  
+15 V  
SCC-CO20 Isolated Current Output Module User Guide  
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Table 1. SCC-CO20 Pin Signal Connections (Continued)  
Pin Number  
Signal  
–15 V  
14  
15  
16  
17  
18  
19  
20  
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Refer to the Terms of Use section on ni.com/legal for more information about National  
Instruments trademarks. Other product and company names mentioned herein are trademarks or trade  
names of their respective companies. For patents covering National Instruments products/technology,  
refer to the appropriate location: Help»Patents in your software, the patents.txt file on your  
media, or the National Instruments Patent Notice at ni.com/patents.  
© 2002–2008 National Instruments Corporation. All rights reserved.  
371078D-01  
Aug08  
 

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