National Instruments SCXI-1328 User manual

CVI™, LabVIEW™, National Instruments™, ni.com™, NI-DAQ™, and SCXI™ are trademarks of National Instruments Corporation. Product and
company names are trademarks or trade names of their respective companies.
321877B-01 ©Copyright 1993, 1999 National Instruments Corp. All rights reserved. November 1999
INSTALLATION GUIDE
SCXI -1328 HIGH-ACCURACY ISOTHERMAL
TERMINAL BLOCK
This guide describes how to install and use the SCXI-1328 high-accuracy
isothermal terminal block with the SCXI-1120, SCXI-1120D, and
SCXI-1121 modules.
Introduction
The SCXI-1328 high-accuracy isothermal terminal block consists of a
shielded board with screw terminals to connect to the SCXI module input
connector. The SCXI-1328 has a high-precision thermistor and an
aluminum isothermal plate to minimize the temperature gradients across
the screw terminals when you measure thermocouples.
The terminal block has 18 screw terminals for easy connection. One pair of
screw terminals connects to the SCXI module chassis ground. With the
SCXI-1120/D or SCXI-1125, the remaining eight pairs of screw terminals
are for signal connection to the eight module inputs. With the SCXI-1121,
four pairs of screw terminals are for the four module inputs and four pairs
are for the module excitation channels.
What You Need to Get Started
To set up and use your SCXI-1322 terminal block, you need the following
items:
❑SCXI-1328 terminal block
❑SCXI-1328 High-Accuracy Isothermal Terminal Block Installation
Guide
❑SCXI chassis
❑SCXI-1120, SCXI-1120D, SCXI-1125, or SCXI-1121 module
™

SCXI-1328 Installation Guide 2 www.ni.com
❑Number 1 and 2 Phillips-head screwdrivers
❑1/8 in. flathead screwdriver
❑Long-nose pliers
❑Wire cutters
❑Wire insulation stripper
Conventions
The following conventions are used in this guide:
»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.
italic Italic text denotes variables, emphasis, a cross reference, or an introduction
to a key concept.This font also denotes textthat 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, and code excerpts.
Safety Information
Cautions Do not operate the device in an explosive atmosphere or where there may be
flammable gases or fumes.
Keep away from live circuits. Do not remove equipment covers or shields unless you are
trained to do so. If signal wires are connected to the device, hazardous voltages may exist
even when the equipment is turned off. To avoid a shock hazard, do not perform procedures
involving cover or shield removal unless you are qualified to do so and disconnect all field
power prior to removing covers or shields.

©National Instruments Corporation 3 SCXI-1328 Installation Guide
Equipment described in this document must be used in an Installation Category II
environment per IEC 664. This category requires local level supply mains-connected
installation.
Do not operate damaged equipment. The safety protection features built into this device
can become impaired if the device becomes damaged in any way. If the device is damaged,
turn the device off and do not use until service-trained personnel can check its safety. If
necessary, return the device to National Instruments for serviceand repair to ensure that its
safety is not compromised.
Do not operate this equipment in a manner that contradicts the information specified in this
document. Misuse of this equipment could result in a shock hazard.
Terminals are for use only with equipment that has no accessible live parts.
Do not substitute parts or modify equipment. Because of the danger of introducing
additional hazards, do not install unauthorized parts or modify the device. Return the
device to National Instruments for service and repair to ensure that its safety features are
not compromised.
When using the device with high common-mode voltages, you must insulate your signal
wires for the highest input voltage. National Instruments is not liable for any damages or
injuries resulting from inadequate signal wire insulation. Use only 26-14 AWG wire with
a voltage rating of 300 V and 60 °C for measuring up to 300 V.
WhenconnectingordisconnectingsignallinestotheSCXIterminalblockscrewterminals,
make sure the lines are powered off. Potential differences between the lines and the SCXI
ground create a shock hazard while you connect the lines.
Connections, including power signals to ground and vice versa, that exceed any of the
maximum signal ratings on the SCXI device can create a shock or fire hazard or can
damage any or all of the boards connected to the SCXI chassis, the host computer, and the
SCXI device. National Instruments is not liable for any damages or injuries resulting from
incorrect signal connections.
If high voltages (≥30 Vrms and 42.4 Vpeak or 60 VDC) are present,you must connect a safety
earth ground wire to the terminal block safety ground solder lug, shown in Figure 1. This
complies with safety agency requirements and protects against electric shock when the
terminal block is not connected to the chassis. To connect the safety earth ground to the
safety ground solder lug, run an earth ground wire in the cable from the signal source to
the terminal block. National Instruments is not liable for any damages or injuries resulting
from inadequate safety earth ground connections.
Do not loosen or re-orient the safety ground solder lug hardware when connecting the
safety ground wire; to do so reduces the safety isolation between the high voltage and
safety ground.
Clean devices and terminal blocks by brushing off light dust with a soft, nonmetallic brush.
Remove other contaminants with deionized water and a stiff nonmetallic brush. The unit
must be completely dry and free from contaminants before returning to service.

SCXI-1328 Installation Guide 4 www.ni.com
Temperature Sensor Output and Accuracy
The SCXI-1328 temperature sensor outputs 1.91 to 0.58 V from 0 to 55 °C
and has an accuracy of ±0.5 °C over the 15 to 35 °C range and ±0.9 °C over
the 0 to 15 °C and 35 to 55 °C ranges1.
National Instruments software can convert a thermistor voltage to the
thermistor temperature for the circuit diagram shown later in this guide.
In LabVIEW, you can use the Convert Thermistor Reading VI in the
Data Acquisition»Signal Conditioning palette. If you are using
LabWindows/CVI or NI-DAQ, use the Thermistor_Convert function.
The VI takes the output voltage of the temperature sensor, the reference
voltage, and the precision resistance and returns the thermistor temperature.
Alternatively, you can use the following formulas:
T(°C) = TK– 273.15
where TKis the temperature in kelvin
a = 1.295361 ×10–3
b = 2.343159 ×10–4
c = 1.018703 ×10–7
RT= resistance of the thermistor in ohms
VTEMPOUT = output voltage of the temperature sensor
where T(°F) and T(°C) are the temperature readings in degrees Fahrenheit
and degrees Celsius, respectively.
Note Use an average of a large number of samples to obtain the most accurate reading.
Noisy environments require more samples for greater accuracy.
1 Includes the combined effects of the temperature sensor accuracy and the temperature difference between the temperature
sensor and any screw terminal. The temperature sensor accuracy includes tolerances in all component values, the effects
caused by temperature and loading, and self-heating.
TK1
ab R
T
ln()cR
T
ln()
3
++[]
--------------------------------------------------------------=
R
T5000 VTEMPOUT
2.5 VTEMPOUT –
--------------------------------------




,=
T
°F() [T(°C)]9
5
----------------------- 3
2
+=

©National Instruments Corporation 5 SCXI-1328 Installation Guide
Signal Connection
Note Refer to the Safety Information section before removing equipment covers or
connecting or disconnecting any signal wires.
When connecting your signals to the SCXI-1328, follow the labeling on the
SCXI-1328 for the appropriate module, as indicated in Figure 2.
To connect the signal to the terminal block, perform the following steps,
referring to Figures 1 and 2 as necessary:
1. Unscrew the top cover screws and remove the cover.
2. Loosen the strain-relief screws and remove the strain-relief bar.
3. Run the signal wires through the strain-relief opening. You can add
insulation or padding if necessary.
4. Prepare your signal wire by stripping the insulation no more than
12 mm.
5. Connect the wires to the screw terminals by wrapping the wires around
the screw. No bare wire should extend past the screw head. Exposed
wire reduces the safety isolation between the high voltage and safe low
voltages.
6. Tighten the screws to a torque of 5–7 in.-lb.
7. Connect safety earth ground to the safety-ground solder lug. Refer to
the Safety Information section for connection information.
8. Reinstall the strain-relief bar and tighten the strain-relief screws.
9. Reinstall the top cover and tighten the top cover screws.
10. Connect the terminal block to the module front connectoras explained
in the Installation section.

SCXI-1328 Installation Guide 6 www.ni.com
Figure 1 shows the SCXI-1328 terminal block parts locator diagram.
Figure 1. SCXI-1328 Parts Locator Diagram
Figure 2 shows the SCXI-1328 signal connections.
Figure 2. SCXI-1328 Signal Connections
1 Strain-Relief Bar
2 Strain-Relief Screws 3 Safety-Ground Solder Lug 4 Mating Connector 5 Thumbscrew 6 Top Cover Screws 7 Top Cover
1 Screw Terminals 2 Berg Connector (W1) 3 Channel Labeling for
the SCXI-1120/D 4 Channel Labeling for the SCXI-1121
2
7
3
6
4
5
1
Back View Front View
++++ ++++
CH0 CH1 CH2 CH3 SCXI-1120
SCXI-1121
SCXI-1328
WARNING: IF HIGH VOLTAGE IS PRESENT, AN
WIRE MUST BE CONNECTED TO EXTERNAL SAFETY EARTH GROUND STRAIN RELIEF EARTH TERMINAL
HIGH ACCURACY ISOTHERMAL TERMINAL BLOCK DTEMP
W1
MTEMP
CH4 CH5 CH6 CH7
CH0 EX0 CH1 EX1 CH2 EX2 CH3 EX3
–––– ––––
!
1
4
3
2

©National Instruments Corporation 7 SCXI-1328 Installation Guide
Installation
ToconnecttheterminalblocktotheSCXI module front connector, perform
the following steps:
1. Connect the module front connector to its mating connector on the
terminal block.
2. Tighten the top and bottom thumbscrews on the back of the terminal
block to hold it securely in place.
Note For accurate cold-junction compensation, place the SCXI chassis away from an
extreme temperature differential.
Specifications
Cold-junction sensor
Accuracy1........................................0.5° from 15 to 35 °C
0.9° from 0° to 15 °C
and35to55°C
Repeatability...................................0.2° from 15 to 35 °C
Output .............................................1.91 to 0.58 V from 0 to 55 °C
Common-mode isolation
Channel to channel..........................300 Vrms
Channel to ground...........................300 Vrms
Environment
Operating temperature............................0 to 50 °C
Storage temperature ...............................–20 to 70 °C
Relative humidity...................................5% to 90% noncondensing
Safety
Designed in accordance with IEC 61010-1, UL 3111-1, and CAN/CSA
C22.2 No. 1010.1 for electrical measuring and test equipment.
Approved at altitudes up to 2000 meters.
Installation Category II
Pollution Degree 2
1 Includes the combined effects of the temperature sensor accuracy and the temperature difference between the temperature
sensor and any screw terminal. The temperature sensor accuracy includes tolerances in all component values, the effects
caused by temperature and loading, and self-heating.

SCXI-1328 Installation Guide 8 www.ni.com
Temperature Sensor Circuit Diagram
You do not need to read this section to operate the SCXI-1328. The circuit
diagram in Figure 3 is optional information you can use if you want more
details about the SCXI-1328 temperature sensor.
Figure 3. Temperature Sensor Circuit Diagram
Technical Support Resources
NI Web Support
To provide you with immediate answers and solutions 24 hours a day,
365 days a year, National Instruments maintains extensive online technical
support resources. They are available to you at no cost, are updated daily,
and can be found in the Technical Support section of our Web site at
www.ni.com/support
Worldwide Support
National Instruments has offices located around the globe. Many branch
offices maintain a Web site to provide information on local services. You
can access these Web sites from www.ni.com/worldwide
For telephone support in the United States, dial 512 795 8248. For
telephone support outside the United States, contact your local branch
office:
Australia 03 9879 5166, Austria 0662 45 79 90 0, Belgium 02 757 00 20,
Brazil 011 284 5011, Canada (Calgary) 403 274 9391,
Canada (Ontario) 905 785 0085, Canada (Québec) 514 694 8521,
+5 V
2.5 V
4.7 k
1%
LM 4040
2.5 V
0.1% 5 k
at 25˚ C
5 k
0.1%
10 µF
16 V
0.1 µF
0.1 µF
-t˚
1
2
1
2
2
1
20.1 µF
1
2
MTEMP

©National Instruments Corporation 9 SCXI-1328 Installation Guide
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