National Instruments SCXI-1327 Installation Manual

INSTALLATION GUIDE

™

SCXI -1327 H
T

ERMINAL

Introduction

B

LOCK

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.

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
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.

IGH

-V

OLTAGE

A

TTENUATOR

or ±300 VDC with the SCXI-1120,

rms

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

on the excitation channels.

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

For correct operation with the SCXI-1121 module, you must bypass the attenuators

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-1327 Installation Guide 2 ni.com

– SCXI-1120D

– SCXI-1121

– SCXI-1125

– SCXI-1126

❑ Number 1 and 2 Phillips-head screwdrivers

❑

1/8 in. flathead screwdriver

❑

Long-nose pliers

❑

Wire cutter

❑

Wire insulation stripper

Safety Information

Cautions

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 II
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 operate the device in an explosive atmosphere or where there may be

1

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.

1

Category II refers to local-level power distribution, such as that provided by a standard wall outlet.

© National Instruments Corporation 3 SCXI-1327 Installation Guide

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 V

and42.4V

rms

or 60 VDC) are present, you must connect

peak

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

• Set both switches to the 1:1 position to bypass the attenuator of the

SCXI-1327 Installation Guide 4 ni.com

channel. This setting places a precision 100:1 divider in the circuit to
divide the voltage by 100 before the voltage enters the module.

appropriate channel. This setting removes the 100:1 divider from the
input stage.

Table 1. SCXI-1327 High-Voltage Attenuator Configuration

Switch Position Description

Note

For correct operation with the SCXI-1121 module, you must bypass the attenuators

on the excitation channels.

Connecting Signals

100:1

1:1

100:1

1:1

Enables the attenuator for a specific channel.
This is the default setting.

Bypasses the attenuator for a specific channel.

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.

© National Instruments Corporation 5 SCXI-1327 Installation Guide

6

7

5

4

3

1

2

1 Top Cover Screws
2TopCover

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.

3Thumbscrew
4 Mating Connector

5 Strain-Relief Bar
6 Strain-Relief Screws

7 Safety-Ground Lug

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.

SCXI-1327 Installation Guide 6 ni.com

9

7

6

5

4

3

18

2

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

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.

6 Screw Terminals
7 Switches to Enable or Bypass the Attenuator
8 Product Name, Assembly Number, and Revision Letter
9 Voltage Dividers

Figure 2. SCXI-1327 Signal Connections

11. Connect the terminal block to the module front connector as explained

© National Instruments Corporation 7 SCXI-1327 Installation Guide

in the Installing the Terminal Block section.

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

extreme temperature differential.

For accurate cold-junction compensation, place the SCXI chassis away from an

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
Calibration Procedures.

ni.com/calibration

Specifications

and follow the link for Manual

All specifications are typical at 25 °C unless otherwise specified.

Electrical

Compatible modules

SCXI-1327 Installation Guide 8 ni.com

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

Cold-junction temperature-sensor circuitry

Sensor type...................................... Thermistor

Output range ................................... 1.91 to 0.65 VDC

from0to50°C

Accuracy

1

........................................ ±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 V

or ±300 VDC

rms

of the ground

Channel-to-channel voltage ............ Each channel to remain

within 300 V

or ±300 VDC

rms

of the voltage applied
to any other channel

1

This 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).

© National Instruments Corporation 9 SCXI-1327 Installation Guide

Mechanical

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

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

Safety

Operating temperature ............................0 to 50 °C

Storage temperature................................–20 to 70 °C

Relative humidity ...................................5 to 90% noncondensing

Altitude (maximum) ...............................2000 m

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

SCXI-1327 Installation Guide 10 ni.com

Electromagnetic Compatibility

EMC/EMI............................................... CE, C-Tick, and FCC Part 15

Electrical emissions................................ EN 55011 Class A at 10 m

Electrical immunity................................ Evaluated to EN 61326:1998,

(Class A) Compliant

FCC Part 15A above 1 GHz

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,usethe
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:

Thermistor_Convert

function. The VI takes

where T

a = 1.295361 × 10
b = 2.343159 × 10
c = 1.018703 × 10

R

T

© National Instruments Corporation 11 SCXI-1327 Installation Guide

T°C() T

is the temperature in Kelvin

K

T

–

3

–

4

–

7

----------------------------------------------------------------=

K

ab R

++[]

K

ln()cR

T

= resistance of the thermistor in ohms

V



T

5000

=

,

R

--------------------------------------



2.5 V

–

273.15–=

1

ln()

TEMPOUT

TEMPOUT

3

T

V

TEMPOUT

= output voltage of the temperature sensor

T

°

C()[]9

T

°

F()

----------------------- 32+=

5

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 V
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:

TEMPOUT

depends on which

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.

SCXI-1327 Installation Guide 12 ni.com

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.

+5 V

4.7 k
1%

2.5 V

2

5k

LM 4040

2.5 V

0.1%

0.1 µF

0.1%

o

5k

-t
at 25

o

C

MTEMP

1

+

10 µF
16 V

2

1

0.1 µF

2

Figure 3. Temperature Sensor Circuit Diagram

© National Instruments Corporation 13 SCXI-1327 Installation Guide

Technical Support Resources

NI Web Support

National Instruments Web support is your first stop for help in solving
installation, configuration, and application problems and questions. Online
problem-solving and diagnostic resources include frequently asked
questions, knowledge bases, product-specific troubleshooting wizards,
manuals, drivers, software updates, and more. Web support is available
through the Technical Support section of

Worldwide Support

National Instruments has offices located around the world to help address
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Worldwide Offices section of
up-to-date contact information, support phone numbers, e-mail addresses,
and current events.

If you have searched the technical support resources on our Web site
and still cannot find the answers you need, contact your local office or
National Instruments corporate. For telephone support in the United States,
dial 512 795 8248. For telephone support outside the United States, contact
your local branch office:

ni.com

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SCXI-1327 Installation Guide 14 ni.com