National Instruments SCXI-1327 User manual

CVI™, LabVIEW™, National Instruments™,ni.com
™,NI-DAQ ™, and SCXI™are trademarks of National Instruments Corporation. Product and company
names mentioned herein are trademarks or trade names of their respective companies.
321930C-01 ©Copyright 1998, 2000 National Instruments Corp. All rights reserved. October 2000
INSTALLATION GUIDE
SCXI -1327 HIGH-VOLTAGE ATTENUATOR
TERMINAL BLOCK
This guide describes how to install and use the SCXI-1327 high-voltage
attenuator terminal block with the SCXI-1120, SCXI-1120D, SCXI-1121,
SCXI-1125, and SCXI-1126 modules.
Introduction
The SCXI-1327 high-voltage attenuator terminal block is shielded and has
screw terminals that connect to the SCXI-1120, SCXI-1120D, SCXI-1121,
SCXI-1125, or SCXI-1126 input connector. Each SCXI-1327 channel has
a precision 100:1 resistive voltage divider that you can use to measure
voltagesofupto300V
rms or ±300 VDC with the SCXI-1120,
SCXI-1120D, SCXI-1121, SCXI-1125, or SCXI-1126. You can
individually bypass these dividers for low-voltage measurement
applications.
The terminal block has 18 screw terminals for easy signal connection.
One pair of screw terminals connects to the SCXI-1120, SCXI-1120D,
SCXI-1121, SCXI-1125, or SCXI-1126 chassis ground. When used with
the SCXI-1120, SCXI-1120D, SCXI-1125, or SCXI-1126, the remaining
eight pairs of screw terminals connect signals to the eight module inputs.
When used with the SCXI-1121, four pairs of SCXI-1327 screw terminals
connect signals to four module inputs and the remaining four pairs of
SCXI-1327 screw terminals connect signals to four module excitation
outputs.
Note For correct operation with the SCXI-1121 module, you must bypass the attenuators
on the excitation channels.
™

SCXI-1327 Installation Guide 2 ni.com
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.
bold Bold text denotes items that you must select or click on in the software,
such as menu items and dialog box options.
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, and code excerpts.
What You Need to Get Started
To set up and use your SCXI-1327 terminal block, you need the following
items:
❑SCXI-1327 high-voltage attenuator terminal block
❑SCXI-1327 High-Voltage Attenuator Terminal Block
Installation Guide
❑SCXI chassis
❑One of the following modules:
– SCXI-1120
– SCXI-1120D
– SCXI-1121
– SCXI-1125
– SCXI-1126

©National Instruments Corporation 3 SCXI-1327 Installation Guide
❑Number 1 and 2 Phillips-head screwdrivers
❑1/8 in. flathead screwdriver
❑Long-nose pliers
❑Wire cutter
❑Wire insulation stripper
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 can 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.
Equipment described in this document must be used in an Installation Category II1
environment per IEC 60664-1. 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 it until service-trained personnel can check its safety.
If necessary, return the device to National Instruments for service and 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.
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 minimum voltage rating of 300 V and a temperature value of 60 °C for measuring up
to 300 V.
1Category II refers to local-level power distribution, such as that provided by a standard wall outlet.

SCXI-1327 Installation Guide 4 ni.com
When connecting or disconnecting signal lines to the SCXI terminal block screw terminals,
make sure the lines are powered off. Potential differences between the lines and the SCXI
ground can 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 hazardous voltages (≥30 Vrms and42.4V
peak or 60 VDC) are present, you must connect
a safety earth-ground wire to the terminal block safety-ground 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 lug, run an earth-ground wire 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 lug hardware when connecting the
safety-ground wire; to do so reduces the safety isolation between the high voltage and
safety ground.
Clean the module and accessories by brushing off light dust with a soft non-metallic brush.
Remove other contaminants with a stiff non-metallic brush. The unit must be completely
dry and free from contaminants before returning it to service.
The terminal block must be used with a UL-listed SCXI chassis.
Configuring the High-Voltage Attenuator
Each channel has a 100:1 high-voltage attenuator that you can enable or
disable by changing switch settings as shown in Table 1. Each channel
requires two switches that you must set in the same position for the
attenuator to operate correctly. The switches are behind their corresponding
terminals.
•Set both switches to the 100:1 position to attenuate the appropriate
channel. This setting places a precision 100:1 divider in the circuit to
divide the voltage by 100 before the voltage enters the module.
•Set both switches to the 1:1 position to bypass the attenuator of the
appropriate channel. This setting removes the 100:1 divider from the
input stage.

©National Instruments Corporation 5 SCXI-1327 Installation Guide
Note For correct operation with the SCXI-1121 module, you must bypass the attenuators
on the excitation channels.
Connecting Signals
Caution Refer to the Safety Information section before removing equipment covers
or connecting or disconnecting any signal wires.
To connect the signal to the terminal block, perform the following steps,
referringtoFigures1and2asnecessary:
1. Unscrew the top cover screws and remove the top cover.
2. Loosen the strain-relief screws and remove the strain-relief bar.
3. Prepare your signal wire by stripping the insulation no more than
7mm.
Table 1. SCXI-1327 High-Voltage Attenuator Configuration
Switch Position Description
Enables the attenuator for a specific channel.
This is the default setting.
Bypasses the attenuator for a specific channel.
100:1
1:1
100:1
1:1

SCXI-1327 Installation Guide 6 ni.com
Figure 1. SCXI-1327 Parts Locator Diagram
4. Run the signal wires through the strain-relief opening. You can add
insulation or padding if necessary.
Note When connecting your signals to the SCXI-1327, follow the labeling on the
SCXI-1327 for the appropriate module, as indicated in Figure 2.
1 Top Cover Screws
2TopCover
3Thumbscrew
4 Mating Connector
5 Strain-Relief Bar
6 Strain-Relief Screws
7 Safety-Ground Lug
2
7
1
4
3
5
6

©National Instruments Corporation 7 SCXI-1327 Installation Guide
Figure 2. SCXI-1327 Signal Connections
5. Connect the signal wires to the screw terminals by inserting the
stripped end of the wire fully into the terminal. No bare wire should
extend past the screw terminal. Exposed wire increases the risk of short
circuits and equipment failure.
6. Configure your high-voltage attenuator as explained in the
Configuring the High-Voltage Attenuator section.
7. Tighten the screws to a torque of 5–7in.-lb.
8. Connect the safety earth-ground to the safety-ground lug. Refer to the
Safety Information section for connection information.
9. Reinstall the strain-relief bar and tighten the strain-relief screws.
10. Reinstall the top cover and tighten the top cover screws.
11. Connect the terminal block to the module front connector as explained
in the Installing the Terminal Block section.
1 Serial Number
2 Chassis Ground
3Thermistor
4 Channel Labeling for the SCXI-1121
5 Channel Labeling for the SCXI-1120,
SCXI-1120D, SCXI-1125, SCXI-1126
6 Screw Terminals
7 Switches to Enable or Bypass the Attenuator
8 Product Name, Assembly Number, and Revision Letter
9 Voltage Dividers
9
3
18
5
6
7
42

SCXI-1327 Installation Guide 8 ni.com
Installing the Terminal Block
To connect the terminal block to the SCXI 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.
Cleaning the Terminal Block
Clean the terminal block 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 it to service.
Calibrating the Terminal Block
For information on calibrating the SCXI-1327, see the SCXI-1327
High-Voltage Attenuator Terminal Block Calibration Procedure located
online at ni.com/calibration and follow the link for Manual
Calibration Procedures.
Specifications
All specifications are typical at 25 °C unless otherwise specified.
Electrical
Compatible modules
SCXI-1120/1120D...........................8 input channels
SCXI-1121.......................................4 input channels,
4 excitation output channels
SCXI-1125.......................................8 input channels
SCXI-1126.......................................8 input channels

©National Instruments Corporation 9 SCXI-1327 Installation Guide
Cold-junction temperature-sensor circuitry
Sensor type...................................... Thermistor
Output range ................................... 1.91 to 0.65 VDC
from0to50°C
Accuracy1........................................ ±0.9 °Cfrom15to35°C
±1.3 °Cfrom0to15°C
and35to50°C
Repeatability ................................... ±0.5 °Cfrom15to35°C
Maximum temperature gradient
between sensor and any terminal .... ±0.4 °C (non-isothermal)
High-voltage attenuator
Attenuation ratio ............................. 100:1 or 1:1 (selectable
on a per-channel basis
using slide switches)
Attenuation ratio accuracy .............. ±0.06% (for 100:1 setting)
Attenuation ratio
temperature drift ............................. 15 ppm/°C
Resistance between
CH–and CH+ terminals
1:1 attenuation setting.............. Determined by attached module
100:1 attenuation setting.......... 1 MΩ
Coupling................................................. DC only
Current-receiver resistors....................... Resistors not included,
resistor sockets not provided
Maximum working voltage
(signal + common-mode)
Channel-to-ground voltage ............. Each channel to remain
within 300 Vrms or ±300 VDC
of the ground
Channel-to-channel voltage ............ Each channel to remain
within 300 Vrms or ±300 VDC
of the voltage applied
to any other channel
1This includes the accuracy of the temperature sensor itself (±0.5 °C) and the temperature difference between the sensor and
any screw terminal (which may be as large as ±0.4 °C).

SCXI-1327 Installation Guide 10 ni.com
Field-wiring connectors
Screw terminals
Signal terminals........................16 (8 pairs)
Functional ground terminals.....2
Maximum wire gauge...............16 AWG
Terminal spacing ......................0.5 cm (0.2 in.) center-to-center
Dimensions of front entrance ..........1.2 by 7.3 cm (0.47 by 2.87 in.)
Solder pads
for additional components ...............None
Safety earth-ground lugs..................1
Strain relief ......................................Strain-relief bar at
terminal-block entrance
Mechanical
Dimensions .............................................17.8 by 7.94 by 3.0 cm
(7.0 by 3.125 by 1.2 in.)
Weight ....................................................200 g (7 oz)
Environmental
Operating temperature ............................0 to 50 °C
Storage temperature ................................–20 to 70 °C
Relative humidity ...................................5 to 90% noncondensing
Altitude (maximum) ...............................2000 m
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.
Installation category II
Pollution degree 2

©National Instruments Corporation 11 SCXI-1327 Installation Guide
Electromagnetic Compatibility
EMC/EMI............................................... CE, C-Tick, and FCC Part 15
(Class A) Compliant
Electrical emissions................................ EN 55011 Class A at 10 m
FCC Part 15A above 1 GHz
Electrical immunity................................ Evaluated to EN 61326:1998,
Table 1
Note This device should only be operated with shielded cabling for full EMC and EMI
compliance. See the Declaration of Conformity for this product for any additional
regulatory compliance information.
Temperature Sensor Output and Accuracy
The SCXI-1327 temperature sensor outputs 1.91 to 0.65 V from 0 to 50 °C.
Converting a Thermistor Voltage to a Temperature
National Instruments software can convert a thermistor voltage to
the thermistor temperature for the circuit diagram shown in Figure 3.
In LabVIEW, you can use the Convert Thermistor Reading VI that is found
in the Data Acquisition»Signal Conditioning palette. If you are using
CVIorNI-DAQ,usetheThermistor_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:
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
T
°
C() TK273.15–=
TK
1
ab R
T
ln()cR
T
ln()
3
++[]
----------------------------------------------------------------=
RT5000 VTEMPOUT
2.5 VTEMPOUT –
--------------------------------------


,
=

SCXI-1327 Installation Guide 12 ni.com
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.
Reading the Temperature Sensor in LabVIEW
In LabVIEW, the channel string used to read VTEMPOUT depends on which
module is connected to the SCXI-1327. For more information about
channel-string arrays and the SCXI channel-addressing syntax, see the
LabVIEW Measurements Manual.
Note This section is not applicable to the SCXI-1126.
•With the SCXI-1120, SCXI-1120D, or SCXI-1121, use the address
string:
obx ! scy ! mdz ! mtemp
This channel-address string cannot be in the same channel-string array
as other channels on the module that is being addressed.
•With the SCXI 1125, use the address string:
obx ! scy ! mdz ! cjtemp
This channel-address string can be in the same channel-string array as
other channels on the same SCXI-1125 module and may be called
multiple times within the same channel-string array.
T
° F() T
°
C()[]9
5
----------------------- 32+=

©National Instruments Corporation 13 SCXI-1327 Installation Guide
Temperature Sensor Circuit Diagram
Yo u d o not need to read this section to operate the SCXI-1327. The circuit
diagram in Figure 3 is optional information that you can use if you want
more details about the SCXI-1327 temperature sensor.
Figure 3. Temperature Sensor Circuit Diagram
4.7 k
1%
5k
0.1%
MTEMP
1
2
1
2
2
+
5k
at 25 oC
10 µF
16 V 0.1 µF
0.1 µF
-to
+5 V
2.5 V
LM 4040
2.5 V
0.1%

SCXI-1327 Installation Guide 14 ni.com
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