National Instruments SCC-CI20 User manual

USER GUIDE
SCC-CI20 Current Input Module
USER GUIDESCC-CI20 Current Input Module
The SCC-CI20 converts current to voltage by passing it through a precision
249 Ωresistor and sending the resulting voltage to the E Series DAQ device
as a 0 to +5 V signal. The SCC-CI20 accepts up to two current sources at a
maximum of 20 mA. A differential instrumentation amplifier buffers each
input signal.
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,
P1.<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 in software, such as menu
items and dialog box options. Bold text also denotes parameter names.

SCC-CI20 Current Input Module User Guide 2 ni.com
italic Italic text denotes variables, emphasis, a cross reference, or an introduction
to a key concept. This font 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 configurable
connector.
SCC SCC refers to any SCC Series signal conditioning module.
What You Need to Get Started
To set up and use the SCC-CI20, you need the following items:
❑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-CI20 modules
❑SC-2345/2350 User Manual, available at ni.com
❑SCC-CI20 Current Input Module User Guide
❑SCC Quick Start Guide, available at ni.com
❑Read Me First: Safety and Radio-Frequency Interference
❑SC-2345 Quick Reference Label
❑68-pin E Series DAQ device, documentation, and 68-pin cable
❑1/8 in. flathead screwdriver
❑Numbers 1 and 2 Phillips-head screwdrivers
❑Wire insulation strippers
❑NI-DAQ (current version) for Windows 2000/NT/XP/Me

©National Instruments Corporation 3 SCC-CI20 Current Input Module User Guide
Note Software scaling of measurements is not supported on the Macintosh operating
system. Refer to the Specifications section for more information.
Device Specific Information
Note For general SCC module installation and signal connection information, and
information about the SC-2350 carrier, refer to the SCC Quick Start Guide, available for
download at ni.com/manuals.
Installing the Module
Caution Refer to the Read Me First: Safety and Radio-Frequency Interference document
before removing equipment covers or connecting/disconnecting any signal wires.
You can plug the SCC-CI20 into any analog input socket on the SC-2345.
It can function either as a single-stage module or as the first stage of a
dual-stage signal conditioning configuration. The socket you choose
determines which E Series DAQ device channels receive the SCC-CI20
signals.
For single-stage input conditioning, plug the SCC-CI20 into any socket
J(X+1), where Xis 0 to 7, and connect the input signals to the module as
describedinthe Connecting the InputSignalssection.
If you use the SCC-CI20 in a dual-stage configuration, you must use it as
the first stage. Plug the SCC-CI20 into any socket J(X+9) and plug the
second-stage SCC into socket J(X+1), where Xis 0 to 7. Connect the input
signals to the SCC-CI20as describedin the Connecting the InputSignals
section. The SC-2345 connects the output signals of the SCC-CI20 to the
inputs of the second-stage SCC. One example of a second-stage module
compatible with the SCC-CI20 is a lowpass filter module (SCC-LPXX).
Sockets J9 to J16 are also available for digital input/output (DIO)
conditioning or control. Refer to the SC-2345/2350 User Manual for more
information on configuring, connecting, and installing SCC modules.
Connecting the Input Signals
Note The signal names have changed. Refer to ni.com/info and enter rdtntg to
confirm the signal names.
Each screw terminal is labeled by pin number <1..4>. Pins 1 and 2 form a
differential channel routed to E Series DAQ device channel X+8, and pins
3 and 4 form a second differential channel routed to E Series DAQ device

SCC-CI20 Current Input Module User Guide 4 ni.com
channel X. The value of Xis determined by the number of the SC-2345
socket, J(X+1) or J(X+9), where you plug in the SCC-CI20. Figure 1 shows
the SCC-CI20 signal connections.
Figure 1. SCC-CI20 Signal Connections
The input signal source can be floating or ground-referenced. The
SCC-CI20 has high-impedance bias resistors typically required for floating
sources, so you do not need external bias resistors referenced to ground.
Replacing the Input Resistors
Incorrect connections can damage the input resistors and possibly other
components of the module. Spare 249 Ωresistors are available inside the
SCC-CI20. To open the SCC-CI20, complete the following steps:
1. Remove the screw from the back (wide unlabeled side).
2. Turn the front (wide labeled side) toward you.
3. Place the screw-terminal receptacle to the left.
4. Slide the top cover to the right.
5. Lift off the cover.
Signal
Source
AI (X )
AI (X+8)
SCC-C120 E Series DAQ Device
Overvoltage
Protection
Overvoltage
Protection
+
–
Overvoltage
Protection
Overvoltage
Protection
+
–
Signal source may be floating or ground-referenced.
AI SENSE
1
3
4
2
AI GND
10 MΩ
10 MΩ
R3
R2

©National Instruments Corporation 5 SCC-CI20 Current Input Module User Guide
The input resistors are socketed so that you can replace them when
necessary. Figure 2 shows the locations of the input and spare resistors.
Figure 2. SCC-CI20 Parts Locator Diagram
For information about how to configure the SCC-CI20 module using
NI-DAQmx, refer to the SCC Quick Start Guide.
Using the SC-C120 when Scaling Voltage Measurements
If you configured the SCC-CI20 using Measurement & Automation
Explorer (MAX) and you are using NI-DAQ, the reading you get from the
E Series DAQ device accounts for the voltage-to-current conversion and
returns milliamps, not volts. Otherwise you must convert the raw voltage
measurement to a current measurement. To make this conversion, use the
following formula:
where Iis in milliamps and Vis in volts.
1 Input Resistor for AI (X )
2ProductName
3AssemblyNumber
4 Spare Resistors
5 Input Resistor for AI (X+8)
13
2
4
5
IV
0.249
-------------=

SCC-CI20 Current Input Module User Guide 6 ni.com
Specifications
These ratings are typical at 25 °C unless otherwise stated.
Analog Input
Number of input channels.......................2 DIFF
Input range ..............................................0 to 20 mA
Input resistor
Value................................................249 Ω
Tolerance .........................................0.05%
Temperature coefficient
of resistance .....................................10 ppm/°C
Maximum power dissipation ...........0.25 W
Maximum input current ..........................32 mA
Output range ...........................................0 to +5 V
Output slew rate......................................0.75 V/µs min
Gain error................................................±0.1% max1
Temperature stability of gain error.........±0.006%/°C max
Offset error .............................................±0.6 mV max1
Temperature stability of offset error.......±21 µV/°C max
Dynamic Response
Bandwidth (–3 dB, amplitude ≤4 mA) ...10 kHz
Output slew rate......................................0.75 V/µs min
1 Temperature range is 23 °C ±5 °C.

©National Instruments Corporation 7 SCC-CI20 Current Input Module User Guide
Power Requirement
Analog power ......................................... 100 mW max
+15 V .............................................. 3.2 mA max
–15 V............................................... 3.2 mA max
Digital power (+5 V).............................. 0.0 mW
Operating voltage range
+15 V .............................................. ±10%
–15 V............................................... ±10%
Physical
Dimensions............................................. 8.89 cm ×2.92 cm ×1.85 cm
(3.50 in. ×1.15 in. ×0.73 in.)
I/O connectors........................................ One 20-pin right-angle
male connector,
one 4-pin screw terminal
Wire gauge range ................................... 28 to 16 AWG
Maximum Working Voltage
Maximum working voltage refers to the signal voltage (I×249 Ω) plus the
common-mode voltage.
Channel-to-earth..................................... ±15 V, Installation Category I
Channel-to-channel ................................ ±15 V, Installation Category I
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

SCC-CI20 Current Input Module User Guide 8 ni.com
Safety
The SCC-CI20 is designed to meet the requirements of the following
standards of safety for electrical equipment for measurement, control,
and laboratory use:
• IEC 61010-1, EN 61010-1
• UL 3111-1, UL 61010B-01
• CAN/CSA C22.2 No. 1010.1
Note For UL and other safety certifications, refer to the product label, or visit
ni.com/hardref.nsf, search by model number or product line and click the appropriate
link in the Certification column.
Electromagnetic Compatibility
Emissions................................................EN 55011 Class A at 10 m
FCC Part 15A above 1 GHz
Immunity ................................................EN 61326:1997 + A2:2001,
Table 1
CE, C-Tick, and FCC Part 15 (Class A) Compliant
Note For EMC compliance, operate this device with shielded cabling.
CE Compliance
This product meets the essential requirements of applicable European
directives, as amended for CE marking, as follows:
Low-Voltage Directive (safety)..............73/23/EEC
Electromagnetic Compatibility
Directive (EMC) .....................................89/336/EEC
Note Refer to the Declaration of Conformity (DoC) for this product for any additional
regulatory compliance information. To obtain the DoC for this product, visit
ni.com/hardref.nsf, search by model number or product line, and click the
appropriate link in the Certification column.

©National Instruments Corporation 9 SCC-CI20 Current Input Module User Guide
SCC-CI20 Module Pin Assignments
Figure 3 shows the I/O connector pins on the bottom of the module.
Figure 3. SCC Module Bottom View
Table 1 lists the signal connection corresponding to each pin. AI (X) and
AI (X+8) are the analog input signal channels of the E Series DAQ device.
AI GND is the analog input ground signal and is the reference for AI (X)
and AI (X+8). A GND is the reference for the ±15V supplies. AI GND and
A GND connect to the SC-2345 at the SCC-PWR connector. Pins 17 to 20
accept signals from a first-stage module if you are cascading two modules.
1Pin1 2Pin2 3PWBKey 4 Pin 19 5Pin20
Table 1. SCC-CI20 Pin Signal Assignments
Pin Number Signal
1E Series AI (X)
2E Series AI GND
3 —
4E Series AI (X+8)
5 —
6E Series AI GND
7 —
8E Series AI GND
5
4
2
1
3

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© 2001–2004 National Instruments Corp. All rights reserved.
371068B-01 Mar04
*371068B-01*
9 —
10 —
11 E Series A GND
12 —
13 +15 V
14 –15 V
15 —
16 —
17 AI (X)– (from first stage)
18 AI (X+8)+ (from first stage)
19 AI (X)+ (from first stage)
20 AI (X+8)– (from first stage)
Table 1. SCC-CI20 Pin Signal Assignments (Continued)
Pin Number Signal