National Instruments SCC-AI Series User manual

USER GUIDE
SCC-AI Series Isolated Analog
Input Modules
The SCC-AI Series isolated analog input modules (SCC-AIXX) can extract
a relatively low-amplitude input signal from a high-common-mode voltage
so the E Series DAQ device can measure the input signal. They also can
amplify and filter the input signal, resulting in higher measurement
resolution and accuracy.
SCC-AIXX modules are available in a range of gains from 0.2 to 200. They
contain lowpass filters of either 10 kHz or 4 Hz bandwidth. Table 1-1 gives
the gain and bandwidth for each module.
Table 1-1. SCC-AIXX Module Input/Output Range, Gain, and Bandwidth
Model Input Range Output Range Gain Bandwidth
SCC-AI01 ±42 V ±8.4 V 0.2 10 kHz
SCC-AI02 ±20 V ±10 V 0.5 10 kHz
SCC-AI03 ±10 V ±10 V 110 kHz
SCC-AI04 ±5 V ±10 V 210 kHz
SCC-AI05 ±1 V ±10 V 10 10 kHz
SCC-AI06 ±100 mV ±10 V 100 10 kHz
SCC-AI07 ±50 mV ±10 V 200 10 kHz
SCC-AI13 ±10 V ±10 V 14 Hz
SCC-AI14 ±5 V ±10 V 24 Hz

SCC-AI Series Isolated Analog Input Modules 2 ni.com
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,
AI <0..7>.
»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 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. 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 the SC-2345
configurable connector.
SCC SCC refers to any SCC series signal conditioning module.

©National Instruments Corporation 3 SCC-AI Series Isolated Analog Input Modules
What You Need to Get Started
To set up and use the SCC-AIXX, 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-SGXX
❑SCC-SG Series Strain-Gauge Modules User Guide
❑SC-2345/2350 User Manual, available at ni.com
❑SCC Quick Start Guide, available at ni.com
❑Read Me First: Safety and Radio-Frequency Interference
❑SC-2345 Quick Reference Label
❑68-pin Basic or E Series DAQ device, documentation,
and 68-pin cable
❑1/8 in. flathead screwdriver
❑Numbers 1 and 2 Phillips screwdrivers
❑Wire insulation strippers
❑NI-DAQ (current version) for Windows 2000/NT/XP/Me
Note Software scaling of measurements is not supported on the Macintosh operating
system. Refer to the SCC-AIXX Module Pin Assignments section.

SCC-AI Series Isolated Analog Input Modules 4 ni.com
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-AIXX into any analog input socket on the SC-2345.
The socket you choose determines which E Series DAQ device channels
receive the SCC-AIXX signals.
For single-stage input conditioning, plug the SCC-AIXX into any socket
J(X+1), where Xis 0 to 7, and connect the input signals to the module as
described in the Connecting the Input Signals section.
If you use the SCC-AIXX in a dual-stage configuration, the SCC-AIXX
must be the first-stage module. Plug it 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-AIXX as described inthe Connecting the Input Signals
section. The SC-2345 connects the output signals of the first-stage SCC to
the inputs of the second-stage SCC. An example of dual-stage conditioning
is an SCC-AI02 followed by an SCC-FV01 frequency input module.
Sockets J9 to J16 are also available for digital input/output (DIO)
conditioning or control. Refer to the SC-2345 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 on the SCC-AIXX is labeled by pin number <1..4>.
Pins 1 and 2 form a channel routed to E Series DAQ device channel X+8,
and pins 3 and 4 form a channel routed to the E Series DAQ device channel
X, where Xis 0 to 7 depending on the socket where you plug in the module.
The SCC-AIXX provides channel-to-ground and module-to-module
isolation only. It does not provide isolation between the two channels of the
SCC-AIXX. Because both channels must have the same reference voltage,
pins 1 and 3 are connected together internally.

©National Instruments Corporation 5 SCC-AI Series Isolated Analog Input Modules
Figure 1-1 shows the SCC-AIXX signal connections.
Figure 1-1. SCC-AIXX Signal Connections
The inputs are designed in a floating (nonreferenced) single-ended
configuration. If the measured signals are floating, connect the negative
input pins, 1 and 3, to AI SENSE on the SC-2345 terminal block through
a10kΩto 100 kΩresistor. Figure 1-2 shows a floating signal connection
on one channel of the SCC-AIXX.
Figure 1-2. Nonreferenced Signal Connection for the SCC-AIXX (One Channel)
+
4
Lowpass
Filter
+
–
–
+
–
+
–
Lowpass
Filter
3
2
1
E Series DAQ Device
Signal
Source
AI (
X )
SCC-AI
XX
AI SENSE
AI GND
AI (
X +8)
+
4
Lowpass
Filter
+
–
–
+
–
Lowpass
Filter
3
2
1
E Series DAQ Device
Signal
Source AI (
X )
SCC-AI
XX
AI SENSE
AI GND
AI (
X +8)
AI SENSE
on SC-2345
terminal block
10–100 kΩ

SCC-AI Series Isolated Analog Input Modules 6 ni.com
If a high common-mode voltage is present, connect the negative input pins,
1 and 3, to the signal reference. Figure 1-3 shows a ground-referenced
signal connection on one channel of the SCC-AIXX.
Figure 1-3. Ground-Referenced Signal Connection for the SCC-AIXX
with High Common-Mode Voltage (One Channel)
For information about how to configure the SCC-AI module using
NI-DAQmx, refer to the SCC Quick Start Guide.
Using the SCC-AIXX when Scaling Voltage Measurements
If you configured the SCC-AIXX using Measurement & Automation
Explorer (MAX) and you are using NI-DAQ, the voltage reading you get
from the E Series DAQ device accounts for the voltage scaling effect of the
SCC-AIXX. Otherwise, because the voltage measurement from the
E Series DAQ device is scaled by the gain given in Table 1-1, you must
divide the voltage reading returned by the E Series DAQ device by this gain
to get the correct input voltage.
+
4
Lowpass
Filter
+
–
–
+
–
Lowpass
Filter
3
2
1
E Series DAQ Device
Signal
Source AI (
X )
SCC-AI
XX
AI SENSE
AI GND
AI (
X +8)
High
CMV
+
–

©National Instruments Corporation 7 SCC-AI Series Isolated Analog Input Modules
Calibrating Gain and Offset Errors
The SCC-AIXX is calibrated at the factory before shipment. If you want to
adjust the gain of the SCC-AIXX in your system using your E Series DAQ
device, you need a voltage source that is several times more accurate than
the SCC itself and capable of providing the DC voltage shown in Table 1-2.
Gain Adjustment
To adjust the gain of the SCC-AIXX, complete the following steps:
1. Select the desired SCC-AIXX channel on the E Series DAQ device.
2. Set the gain on the E Series DAQ device so that its input range is ±10 V.
3. Connect the voltage source to the screw terminals of the desired
channel on the SCC-AIXX.
4. Apply the voltage given in Table 1-2 that corresponds to the
SCC-AIXX module. For example, if you have an SCC-AI03,
you must apply 8 VDC.
5. Using your software, have the E Series DAQ device read the desired
channel on the SCC-AIXX and record the value.
6. Input 0 VDC to the SCC-AIXX.
7. Use the E Series DAQ device to read that channel and record the value.
8. Subtract the values read (first reading – second reading).
Table 1-2. SCC-AIXX Input Voltage Requirements
Module Input Range
SCC-AI01 40 V
SCC-AI02 16 V
SCC-AI03 8 V
SCC-AI04 4 V
SCC-AI05 800 mV
SCC-AI06 80 mV
SCC-AI07 40 mV
SCC-AI13 8 V
SCC-AI14 4 V

SCC-AI Series Isolated Analog Input Modules 8 ni.com
9. Adjust the trimpot labeled Gain located on the top of the SCC-AIXX.
If the value you obtained in step 8 is less than the input voltage, turn
the trimpot clockwise to increase the gain. If it is greater than the input
voltage, turn the trimpot counterclockwise to decrease the gain.
10. Repeat steps 4 through 9 until the difference you get in step 8 equals
the Input Voltage Required value shown in Table 1-2; in this example
the value is 8 V using an SCC-AI03.
For example, assume that you have an SCC-AI03 module. You first connect
8 VDC to the input of CH (X). The E Series DAQ device reads 8.05 V as
the SCC output. You then connect 0 VDC to the input of CH (X) and the
E Series DAQ device reads –0.01 V as the SCC output. You subtract these
readings, 8.05 – (–0.01) =8.06, getting a difference of 8.06 V. Because this
difference is not equal to 8 V, you must adjust the gain trimpot and repeat
the procedure until the difference in outputs equals 8 V.
Note In this example there can be an offset voltage such that the final readings are 8.01 V
and 0.01 V for a difference of 8 V. The gain trimpot adjusted in step 9 of the previous
procedure adjusts only for gain errors and does not compensate for this offset voltage.
Offset Voltage Adjustment
Complete the following steps to adjust the offset voltage of the SCC-AIXX:
1. Select the desired SCC-AIXX channel on the E Series DAQ device.
2. Set the gain on the E Series DAQ device so that the input range
is ±10 V.
3. Connect the screw terminals of your desired channel on the SCC-AIXX
together.
4. Using your software, have the E Series DAQ device read the channel.
5. If the value read is not equal to 0.00 V, adjust the appropriate trimpot
located on the top of the SCC-AIXX, labeled Offset. Turn the trimpot
clockwise to increase the offset.
6. Repeat steps 4 and 5 until the voltage read in step 4 equals 0.00 V.

©National Instruments Corporation 9 SCC-AI Series Isolated Analog Input Modules
Specifications
These ratings are typical at 25 °C unless otherwise stated.
Input Characteristics
Number of input channels ...................... 2 NRSE
Isolation.................................................. Bank isolation (isolation
per module)1
Input/output signal range, gain,
and bandwidth ........................................ Refer to Table 1-1
Input impedance
SCC-AI01, SCC-AI02 .................... 1 MΩ
All others......................................... 100 MΩ
Gain error ............................................... 4.5% max (trimmable to zero)
Gain stability .......................................... 150 PPM/°C
Offset error............................................. 40 mV max (RTI2)
Offset stability........................................ 225 µV/°C
Nonlinearity ........................................... 0.0128% typ
0.0260% max
Common-mode rejection ratio ............... 100 dB typical at 60 Hz
Output slew rate,
dependent on BW (filtering) .................. 0.8 V/µs max
Filter Characteristics
Number of poles..................................... 3
Rolloff .................................................... 60 dB/decade
Cutoff frequency (–3 dB)
AI0X................................................ 10 kHz
AI1X................................................ 4 Hz
1 The SCC-AIXX does not provide isolation between the two channels of the module. For more information,
refer to the Connecting the Input Signals section.
2 This specification is calculated relative to the input range of the module.

SCC-AI Series Isolated Analog Input Modules 10 ni.com
Power Requirement
Analog power .........................................410 mW max
+15 V ...............................................13.67 mA max
–15 V ...............................................13.67 mA max
Digital power (+5 V) ..............................650 mW max
130 mA max
Physical
Dimensions .............................................8.89 cm ×2.92 cm ×1.85 cm
(3.5 in. ×1.15 in. ×0.73 in.)
I/O connectors.........................................One 20-pin right-angle
male connector,
one 4-pin screw terminal,
removable
Screw terminal wire gauge .....................24 to 12 AWG
Maximum Working Voltage
Maximum working voltage refers to the signal voltage plus the
common-mode voltage.
Channel-to-earth .....................................300 V, Installation Category II
Module-to-module ..................................300 V, Installation Category II
Channel-to-channel.................................Not isolated1
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
1 The SCC-AIXX does not provide isolation between the two channels of the module. For more information,
refer to the Connecting the Input Signals section.