National Instruments SCC-68 User manual

USER GUIDE
SCC-68
I/O Connector Block with 4 SCC Signal Conditioning Slots for DAQ Devices
The SCC-68 is an I/O connector block for easy signal connection to a
National Instruments M Series or E Series DAQ device. The SCC-68
features screw terminals and a general breadboard area for I/O signal
connection, and bus terminals for external power and grounding. The
SCC-68 has four SCC slots for use in integrating thermocouple, strain
gauge, RTD input, frequency input, current input, voltage attenuator,
lowpass filter, load cell input, accelerometer, feedthrough, SPDT relay,
isolated digital I/O, and isolated voltage input SCC modules into the
measurement system.
Contents
Conventions ............................................................................................ 3
Using the SCC-68 Enclosure .................................................................. 4
Opening the Enclosure..................................................................... 4
Closing the Enclosure ...................................................................... 5
Stacking and Wall Mounting ........................................................... 6
Installing Rubber Feet...................................................................... 7
Connecting to the DAQ Device .............................................................. 8
Using the SCC-68 with 16 AI Channel M Series Devices .............. 8
Using the SCC-68 with 32 AI Channel M Series Devices .............. 8
Using the SCC-68 with a 68-Pin E Series Device ........................... 9
Using the SCC-68 with the NI 6025E, NI 6033E, or NI 6071E...... 10
SCC-68 Features ..................................................................................... 11
Screw Terminals .............................................................................. 12
Device Pinouts .......................................................................... 12
Wiring to Screw Terminals....................................................... 12
Integrated Strain Relief.................................................................... 12
SCC Modules................................................................................... 13
Breadboard Area .............................................................................. 13
Using the Temperature Sensor for Cold-Junction
Compensation (CJC) ..................................................................... 14
Cold Junction Temperature Measurement Accuracy ............... 15

SCC-68 User Guide 2 ni.com
Bus Terminals...................................................................................15
Power Supply....................................................................................16
Using SCC Modules with the SCC-68 ....................................................16
Supported SCC Modules ..................................................................17
Connecting Signals to SCC Modules in the SCC-68 .......................17
Power Supply Considerations...........................................................19
LED ...........................................................................................20
Installing the SCC Modules in the SCC-68......................................21
SCC Connector Pinouts.............................................................21
Direct Access to SCC signals....................................................23
Analog Input Measurement Considerations ............................................23
Differential .......................................................................................24
Single-Ended ....................................................................................24
Non-Referenced Single Ended (NRSE) ...........................................25
Grounded Signal Sources ..........................................................25
Floating Signal Sources.............................................................26
Ground-Referenced Single Ended (RSE).........................................26
Grounded Signal Sources ..........................................................26
Floating Signal Sources.............................................................26
Taking Measurements with NI-DAQmx .................................................27
Configuring the SCC-68...................................................................28
Configuring the SCC-68 as an SCC Carrier..............................28
Configuring the SCC-68 as a Screw Terminal Accessory ........28
Configuring Channels and Tasks......................................................29
Configure a Task .......................................................................29
Configure Global Virtual Channels...........................................31
Using Your Task in an Application..................................................32
Specifications...........................................................................................33
Quick Reference Guides ..........................................................................38

©National Instruments Corporation 3 SCC-68 User Guide
Conventions
The following conventions are used in this manual:
<> 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.
SCC-XX This name refers to any SCC module.

SCC-68 User Guide 4 ni.com
Using the SCC-68 Enclosure
Caution Refer to the Read Me First: Safety and Radio-Frequency Interference document
before removing equipment covers or connecting/disconnecting any signal wires.
Figure 1. SCC-68 Parts Locator Diagram
Opening the Enclosure
To open the SCC-68, use a flathead screwdriver to loosen the captive screw
at the front of the device. After the screw is loosened, pull up on the front
of the enclosure cover to open. The top half of the SCC-68 enclosure can
be removed completely.
1SCCSlots
2 Screw Terminals
3 68-Pin I/O Connector
4EnclosureCover
5 Quick Reference Guide
6 Enclosure Base
7 External Power Screw Terminal
8 External Power Switch
9 Strain Relief Wire Entry
4
5
6
3
2
2
1
8
7
9

©National Instruments Corporation 5 SCC-68 User Guide
Closing the Enclosure
To close the SCC-68, align the two back tabs into the corresponding holes
at the back of the base, as shown in the detail in Figure 2. With the cover
and base of the enclosure aligned, snap the SCC-68 closed. To secure the
SCC-68 enclosure, use a flathead screwdriver to push the screw down
against the spring resistance and tighten the screw.
Caution The captive screw must be used to secure the enclosure when connecting
hazardous voltage (>30 Vrms/42.4 Vpk/60 VDC) signals to an SCC-RLY01 module.
Note For safest operation of the SCC-68, NI recommends always using the captive screw
to keep the SCC-68 in a closed position.
Figure 2. SCC-68 Enclosure Features
1 Strain Relief Posts
2 Snapping Latches
3 Captive Screw
4 Hinge Tabs
5 Strain-Relief Holes for Cable Ties
4
1
5
2
3

SCC-68 User Guide 6 ni.com
Stacking and Wall Mounting
The SCC-68 has grooves on the bottom of the enclosure that allow the
device to be stacked on top of other SCC-68 connector blocks.
Note The SCC-68 cannot be securely stacked onto another SCC-68 if the rear rubber feet
are attached.
The SCC-68 also has mounting holes on the bottom of the device for secure
wall-mounting. The third mounting hole allows you to mount the SCC-68
onto a wall sideways or inverted. Refer to Figures 3 and 4 for more
information about the location and use of these enclosure features.
Figure 3. SCC-68 Mounting Dimensions
1 Mounting Holes
2 Directional Mounting Hole
3 I/O Connector Cable
24.46 cm
(9.63 in.)
17.78 cm
(7.00 in.)
17.78 cm
(7.00 in.)
12.70 cm
(5.00 in.) 2.54 cm
(1.00 in.)
12.70 cm
(2.50 in.)
3.51 cm
(1.38 in.)
1
2
3

©National Instruments Corporation 7 SCC-68 User Guide
Installing Rubber Feet
Rubber non-skid feet are shipped with the device that can be attached for
secure desktop use. To install the rubber feet, remove adhesive backing and
affix to the SCC-68 where indicated in Figure 4.
Figure 4. SCC-68 Mounting Features
1 Rubber Feet
2 Wall-Mounting Holes
3 Stacking Grooves
21
3
1
1
2

SCC-68 User Guide 8 ni.com
Connecting to the DAQ Device
The following sections describe how to connect the SCC-68 to the DAQ
device. The SCC-68 is designed to be used with M Series and E Series
DAQ devices only. Other 68-pin devices may not function properly with
the SCC-68.
Using the SCC-68 with 16 AI Channel M Series Devices
To use the SCC-68 with a 16 AI channel M Series device, complete the
following steps:
1. Attach the quick reference guide, shown in Figures 21 and 22, to the
top of the SCC-68 enclosure as shown in Figure 1. The quick reference
guide for Connector 0 (included in the SCC-68 kit) shows the pin
assignments of the SCC-68 and other useful information.
2. Attach the SCC-68 to the DAQ device using one of the following
cables:
• SHC68-68-EPM
• SHC68-68
• RC68-68
3. Proceed to the Taking Measurements with NI-DAQmx section for
information about using the SCC-68 in measurement applications.
Note Some M Series devices are available with a 37-pin connector. The SCC-68 cannot
be used with these devices.
Using the SCC-68 with 32 AI Channel M Series Devices
The 32 AI channel M Series DAQ device has two connectors.
• Connector 0 (AI 0-15)
• Connector 1 (AI 16-31)
The SCC-68 can be used with Connector 0 or Connector 1.
To use the SCC-68 with a 32 AI channel M Series device using
Connector 0, complete the following steps:
1. Attach the quick reference guide, shown in Figures 21 and 22, to the
top of the SCC-68 enclosure as shown in Figure 1. The quick reference
guide for Connector 0 (included in the SCC-68 kit) shows the pin
assignments of the SCC-68 and other useful information.

©National Instruments Corporation 9 SCC-68 User Guide
2. Attach the SCC-68 to Connector 0 of the DAQ device using one of the
following cables:
• SHC68-68-EPM
• SHC68-68
• RC68-68
3. Proceed to the Taking Measurements with NI-DAQmx section for
information about using the SCC-68 in measurement applications.
To use the SCC-68 with a 32 AI channel M Series device using
Connector 1, complete the following steps:
1. Attach the SCC-68 to Connector 1 of the DAQ device using one of the
following cables:
• SHC68-68-EPM
• SHC68-68
• RC68-68
2. Refer to Figure 22 in the Quick Reference Guides section for the quick
reference guide for the SCC-68 connected to Connector 1 of the DAQ
device. The guide shows the pin assignments of the SCC-68 and other
useful information. Attach a copy of this guide to the top of the
SCC-68 enclosure as shown in Figure 1.
Using the SCC-68 with a 68-Pin E Series Device
To use the SCC-68 with a 68-pin E Series device, complete the following
steps:
1. Attach the SCC-68 to the DAQ device using one of the following
cables:
• SH68-68-EP
• R68-68
2. Refer to Figure 23 in the Quick Reference Guides section for the quick
reference guide for the SCC-68 connected to the E Series DAQ device.
The guide shows the pin assignments of the SCC-68 and other useful
information. Attach a copy of this guide to the top of the SCC-68
enclosure as shown in Figure 1.

SCC-68 User Guide 10 ni.com
Using the SCC-68 with the NI 6025E, NI 6033E, or NI 6071E
To use the SCC-68 with the NI 6025E, NI 6033E, or NI 6071E, complete
the following steps:
1. Attach the SCC-68 to the DAQ device using an SH1006868 cable. This
cable has two 68-pin connectors labeled MIO 16 and Extended I/O.
Connect the MIO 16 connector to the SCC-68. Refer to Figure 5.
Figure 5. Connecting a 100-Pin DAQ Device to an SCC-68 Connector Block and
Another Terminal Block
You cannot use the Extended I/O connector with an SCC-68. Use
another terminal block such as the SCB-68 or CB-68LPR with the
Extended I/O connector.
2. Refer to Figure 23 in the Quick Reference Guides section for the quick
reference guide for the SCC-68 connected to the E Series DAQ device.
The guide shows the pin assignments of the SCC-68 and other useful
information. Attach a copy of this pinout to the top of the SCC-68
enclosure as shown in Figure 1.
E Series
100-Pin Device
SH1006868 Cable
SCC-68
Extended
I/O Connector
MIO Connector
SCB-68 or
Other
Terminal
Block

©National Instruments Corporation 11 SCC-68 User Guide
SCC-68 Features
The following sections describe the hardware features of the SCC-68.
Figure 6. SCC-68 Features
1SCCSlots
2 SCC Screw Terminals
3 68-Pin I/O Connector
4 External Power Switch
5 External Power Screw Terminals
6 DIO Screw Terminals
7AIScrewTerminals
8 Bus Screw Terminals
9 AO Screw Terminals
10 Strain-Relief Wire Entry
SCC
Mod 1
SCC
Mod 2
SCC
Mod 3
SCC
Mod 4
ROUTE SCC SIGNAL WIRES
ON THIS SIDE
SCC Mod 1 SCC Mod 2 SCC Mod 3 SCC Mod 4
USE SCC CONNECTOR BACKSHELL FOR HAZARDOUS
LIVE SIGNALS (>42.4 Vpk / 60VDC)
68
34
24
4
52
33
66
27
7
17
65
31
29
9
49
30
63
32
12
47
13
39
15
1
18
40
35
2
36
46
44
45
8
50
53
69
72
73
70
71
3
37
38
5
6
41
42
43
10
11
48
16
51
19
74
75
76
77
78
79
80
81
82
83
57
23
56
25
58
59
60
26
64
28
61
62
67
20
22
54
21
55
NI SCC-68
10
3
2
4
1
7
8
9
6
5
SCC-68
FOR PATENTS: NI.COM/PATENTS
SELF POWER (DEFAULT)
EXTERNAL POWER +5V GND
FRONT
SW1
4.75-5.25V
2A MAX

SCC-68 User Guide 12 ni.com
Screw Terminals
The SCC-68 provides screw terminals for easy I/O connectivity.
Device Pinouts
For a list of pins and their corresponding signal assignments, refer to the
quick reference guide for the device, which can be found in the Quick
Reference Guides section of this document. Refer to the DAQ device
documentation for additional details about the DAQ device signals.
Wiring to Screw Terminals
To connect signals to the SCC-68, complete the following steps while
referring to Figure 1.
1. Disconnect the 68-pin cable from the SCC-68.
2. Remove the top cover as directed in the Opening the Enclosure section.
3. Slide the signal wires through the wire entry strain-relief opening. For
more information about using strain relief with the SCC-68, refer to
the Integrated Strain Relief section.
4. Connect the wires to the screw terminals by stripping off 7 mm
(0.28 in.) of the insulation, inserting the conductors into the terminals,
and tightening the screws.
5. Close the top cover.
You can now connect the SCC-68 to the 68-pin I/O connector.
Integrated Strain Relief
Strain relief for the I/O connector wires is provided through a
labyrinth-style wire entry at the front of the SCC-68 device. For larger
gauge connector wires and jacketed cables, bundle the wires together and
secure the wires to the holes in the wire entry opening using the provided
cable ties.
For smaller gauge connector wires (26 AWG–30 AWG), thread the wires
through the strain-relief posts located on the side opposite the wire entry.
By lacing the connector wires through these posts, movement is limited.
Note Route all SCC signals through the left wire-entry side of the SCC-68. Route all other
signals through the right wire-entry side.

©National Instruments Corporation 13 SCC-68 User Guide
Figure 7. SCC-68 Strain Relief
SCC Modules
The SCC-68 can accept SCC modules for integrating signal conditioning
into your application. Refer to the Using SCC Modules with the SCC-68
section for more information.
Breadboard Area
The SCC-68 features a general breadboard area for custom circuitry such
as filtering or attenuation. For soldering components to the underside of the
breadboard, remove the printed circuit board by carefully snapping it loose
from the SCC-68 enclosure. To desolder on the SCC-68, vacuum-type tools
work best.
1 Small Gauge Strain Relief Posts 2 Larger Gauge Cable Tie Holes
11
SCC-68
ROUTE SCC SIGNAL WIRES
ON THIS SIDE
SCC Mod 1 SCC Mod 2 SCC Mod 3 SCC Mod 4
USE SCC CONNECTOR BACKSHELL FOR HAZARDOUS
LIVE SIGNALS (>42.4 Vpk / 60VDC)
NI SCC-68
45
8
50
53
69
72
73
11
48
16
51
19
74
75
76
77
78
79
80
81
82
83
28
61
62
67
20
22
54
21
55
2
Right Wire EntryLeft Wire Entry

SCC-68 User Guide 14 ni.com
Using the Temperature Sensor for Cold-Junction Compensation (CJC)
The SCC-68 has a temperature sensor connected to screw terminals 70 and
71 as shown in Figure 8. Refer to the Specifications section for the formula
for converting the measured voltage on CJC+ to temperature.
Figure 8. SCC-68 Temperature Sensor Connection
To use the temperature sensor for cold-junction compensation of
thermocouple measurements, connect CJC+ (terminal 70) to AI channel 7
of the SCC-68. Figure 9 shows the temperature sensor connected to AI 7.
Figure 9. Connecting the CJC Sensor to Channel AI 7
You must also ensure that the temperature sensor is powered by one of the
following:
• The DAQ device. Move the power switch to SELF POWER (shown in
item 4 of Figure 6).
• An external power supply. Refer to the Power Supply Considerations
section for more information.
70
71
CJC+
AI GND
4,870 Ω
5 kΩat 25 ˚C
R1
RT
+5V
71
56
70
3
37
38
5
6
41
42
43
10
57
23
25
58
59
60
26
CJC+
AI GND
AI 7
AI 15
AI GND

©National Instruments Corporation 15 SCC-68 User Guide
To remove power from the temperature sensor, complete the following
steps:
1. Move the power switch to EXTERNAL POWER, shown in item 4 of
Figure 6.
2. Leave the external power screw terminals, shown in item 5 of Figure 6,
unconnected.
Cold Junction Temperature Measurement Accuracy
Note For the most accurate thermocouple measurements, NI recommends using an
SCC-TC series module. For more information, refer to ni.com/products.
Temperature differences between the cold-junction temperature sensor and
the actual cold junction formed by a thermocouple connected to the screw
terminals will directly contribute to thermocouple measurement errors.
With minimal loading on the SCC-68 ±15V power supply, the temperature
difference between the screw terminals of the SCC-68 is typically less than
1 °C. Variations in the ambient temperature, SCC module heat dissipation,
and heat conducted along thermocouple wire can all contribute to
isothermal errors across the screw terminals.
For more information on thermocouple theory and use, refer to the Taking
Thermocouple Temperature Measurements tutorial at ni.com/zone.
Bus Terminals
The bus terminals provide an easy interface for supplying external power,
extra ground terminals, or grounding to any sensors or custom circuits used
in the SCC-68. There are two buses—Bus A and Bus B—where all four
screw terminals on each side are connected together internally. To use these
terminals, you may connect the power supply from an external source, and
then use the remaining three terminals to connect sensors or circuits inside
the SCC-68.
Figure 10. Bus Terminals
76
77
78
79
80
81
82
83
Bus A
Bus B
Bus A and Bus B are not connected to
any other signals on the SCC-68.

SCC-68 User Guide 16 ni.com
The bus terminals do not provide external power to the SCC modules
installed in the SCC-68 or to the +5V terminal. Refer to the Power Supply
Considerations section for information about providing power to SCC
modules in your application.
Power Supply
In most situations, the SCC-68 is powered by the DAQ device, eliminating
the need for an external power supply. The +5V power provided by the
DAQ device is distributed to all components in the SCC-68, including the
+5V screw terminal (pin 8). The +5V power on the DAQ device is current
limited. For more information about the power supply and possible
limitations, refer to the Power Supply Considerations section.
Using SCC Modules with the SCC-68
The SCC-68 has four SCC slots for integrating signal conditioning into
your applications. Each SCC slot can be used with any analog input or
digital I/O SCC modules. The SCC-68 is not compatible with analog output
or counter SCC modules.
Note If you use analog input SCC modules with the SCC-68, you must connect
AI SENSE to AI GND, as shown in Figure 11.
Figure 11. Connecting AI SENSE to AI GND
20
62
67
22
54
21
55
AI SENSE
AI GND

©National Instruments Corporation 17 SCC-68 User Guide
Supported SCC Modules
The SCC-68 supports all analog input and digital I/O SCC modules.
Table 1 shows all SCC modules that are compatible with the SCC-68.
Connecting Signals to SCC Modules in the SCC-68
Caution Always refer to the specifications in the SCC-XX module user guide before
connecting signals. Exceeding specified module ratings can create a shock or fire hazard
and can damage any or all of the devices connected to the module.
Caution The captive screw must be used to secure the enclosure when connecting
hazardous voltage (>30 Vrms/42.4 Vpk/60 VDC) signals to an SCC-RLY01 module.
Disconnect the 68-pin cable for the DAQ device before installing or removing any
SCC modules.
Table 1. SCC-68-Compatible SCC Modules
SCC Module Type
SCC-AI0xIsolated Voltage Input
SCC-TC0xThermocouple Input
SCC-LP0xLowpass Filters
SCC-SG0xStrain Gauge Input
SCC-SG24 Load Cell Input
SCC-ACC01 Accelerometer Input
SCC-FT01 Feedthrough
SCC-RTD01 RTD Input
SCC-FV01 Frequency Input
SCC-CI20 Current Input
SCC-A10 Voltage Attenuation
SCC-DI01/DO01 Isolated Digital I/O
SCC-RLY01 SPDT Relay

SCC-68 User Guide 18 ni.com
Caution You must use an SCC connector backshell when connecting hazardous voltage
(>30 Vrms/42.4 Vpk/60 VDC) signals to an SCC-RLY01 module. Refer to Figure 12.
Figure 12. SCC Connector Backshell
Refer to the SCC-XX user documentation for additional safety information.
To connect an SCC module to the SCC-68, complete the following steps:
1. Remove power from the signal lines.
2. Strip insulation from the ends of the signal wires. Refer to the SCC-XX
user documentation for the exact strip length for the module.
3. Insert the conductors into the screw terminals. The SCC-XX module
has a fixed screw-terminal receptacle and a removable screw-terminal
block, as shown in Figure 13.
Figure 13. SCC-XX Two-Part Screw-Terminal System
4. Tighten the screws to 0.5 to 0.6 N · m (4.4 to 5.3 lb · in.) of torque.
1 SCC Screw-Terminal Receptacle 2 Removable Screw-Terminal Block
3
2
1
4
1
2
SCC-
XXXX

©National Instruments Corporation 19 SCC-68 User Guide
Power Supply Considerations
The +5V power provided by the DAQ device is distributed to all
components in the SCC-68 and is also used to generate ±15V power for
SCC modules. Figure 14 shows the power distribution of the SCC-68.
If your application exceeds the current limitation of the DAQ device, you
will need to connect an external power supply—such as the External Power
Supply for the SCC-68 Accessory (Part Number 779641-01)—to the
SCC-68. To use an external power supply with the SCC-68, connect the
power supply to the screw terminals shown in item 5 of Figure 6 and move
the power switch (shown in item 4 of Figure 6) to EXTERNAL POWER.
You may need an external power supply if you have SCC modules installed
and any of the following conditions apply to your application:
• More than two SCC-AI0xor SCC-SG24 modules are installed in the
SCC-68
• The cable connecting the DAQ device to the SCC-68 is longer
than2m
• You measure less than 4.50 V between terminals 8 and 50 when the
SCC-68 is under full load1
• You are using a PCMCIA device such as the NI DAQCard-6024E
• You are using +5V to power custom circuitry on the breadboard area
1 If the +5V power from the DAQ device drops below about 4.5 V, SCC modules installed in the SCC-68 will not operate
properly. The LED in the SCC-68 will flash seven times per second to indicate this condition. There is no error or notification
in software.

SCC-68 User Guide 20 ni.com
Figure 14 shows the power supply path and power distribution of the
SCC-68.
Figure 14. SCC-68 Power Distribution Block Diagram
LED
The LED in the SCC-68 shows the status of the power supply. The SCC-68
monitors the voltage of the +5V signal from the DAQ device, as shown in
Figure 14. Table 2 shows the correlation between power levels in the
SCC-68 and the LED status.
Table 2. SCC-68 Power Levels
Voltage on +5V Signal LED Status Meaning
≥4.5 V*On Power on
≥2 V and <4.5 V*Blinking Power insufficient†
<2 V Off Power is off or power
insufficient
*Due to component variations, the threshold for the LED can vary between 4.25 V
and 4.5 V.
†Refer to the Power Supply Considerations section for more information about supported
SCC module configurations and other SCC-68 power supply issues.
SCC
Mod 1
+15V
+5V Screw
Terminal
(Pin 8)
SCC-68
LED
Voltage
Monitor
Switching
Power Supply –15V
+5V (Filtered)
SCC
Mod 2
SCC
Mod 3
SCC
Mod 4
Current
Limiter
PC or PXI
Chassis
Power
Supply
DAQ Device
+5V
GND
Filter
External
Power Supply
GND
GND
+5V
SW1