National Instruments NI 9214 User manual

OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9214 with NI TB-9214
16-Channel Thermocouple Input Module with
Terminal Block
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NI 9214 Operating Instructions and Specifications 2 ni.com
This document describes how to use the National Instruments 9214 in
conjunction with an NI TB-9214 terminal block and includes
specifications for the NI 9214 and terminal assignments for the
NI TB-9214. Visit ni.com/info and enter rdsoftwareversion
to determine which software youneed for the modules youare using.
For information about installing, configuring, and programming the
system, refer to the system documentation. Visit ni.com/info and
enter cseriesdoc for information about C Series documentation.
Visit ni.com/info and enter compatibility for information
about chassis and carrier compatibility for the modules youare
using.
Note The safety guidelines and specifications in this
document are specific to the NI 9214 used in conjunction
with an NI TB-9214. The other components in the system
might not meet the same safety ratings and specifications.
Refer to the documentation for each component in the
system to determine the safety ratings and specifications
for the entire system. Visit ni.com/info and enter
cseriesdoc for information about C Series
documentation.
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© National Instruments Corp. 3 NI 9214 Operating Instructions and Specifications
Safety Guidelines
Operate the NI 9214 only as described in these operating
instructions.
Hot Surface This icon denotes that the component may be
hot. Touching this component may result in bodily injury.
Safety Guidelines for Hazardous Voltages
If hazardous voltages are connected to the module, take the
following precautions. A hazardous voltage is a voltage greater
than 42.4 Vpk or 60 VDC to earth ground.
Caution Ensure that hazardous voltage wiring is
performed only by qualified personnel adhering to local
electrical standards.
Caution Do not mix hazardous voltage circuits and
human-accessible circuits on the same module.
Caution Make sure that devices and circuits connected to
the module are properly insulated from human contact.
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NI 9214 Operating Instructions and Specifications 4 ni.com
Caution When module terminals are hazardous voltage
LIVE (>42.4 Vpk/60 VDC), youmust ensure that devices
and circuits connected to the module are properly
insulated from human contact. Youmust use the
NI TB-9214 terminal block included with the NI 9214
to ensure that the terminals are not accessible.
Figure 1 shows the NI TB-9214 terminal block.
Figure 1. NI TB-9214 Terminal Block
Note The NI TB-9214 contains a plastic insert to prevent
accidental wire contact with the metal enclosure.
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© National Instruments Corp. 5 NI 9214 Operating Instructions and Specifications
Safety Guidelines for Hazardous Locations
The NI 9214 is suitable for use in Class I, Division 2, Groups A, B,
C, D, T4 hazardous locations; Class I, Zone 2, AEx nA IIC T4, and
Ex nA IIC T4 hazardous locations; and nonhazardous locations
only. Follow these guidelines if youare installing the NI 9214 in a
potentially explosive environment. Not following these guidelines
may result in serious injury or death.
Caution Do not disconnect I/O-side wires or connectors
unless power has been switched off or the area is known
to be nonhazardous.
Caution Do not remove modules unless power has been
switched off or the area is known to be nonhazardous.
Caution Substitution of components may impair
suitability for Class I, Division 2 and Zone 2.
Caution For Division 2 and Zone 2 applications, install
the system in an enclosure rated to at least IP 54 as
defined by IEC 60529 and EN 60529.
Caution For Division 2 and Zone 2 applications,
connected signals must be within the following limit:
Capacitance .......................... 0.2 F max
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NI 9214 Operating Instructions and Specifications 6 ni.com
Special Conditions for Hazardous Locations Use in Europe
This equipment has been evaluated as Ex nA IIC T4 equipment
under DEMKO Certificate No. 07 ATEX 0626664X. Each module
is marked II 3G and is suitable for use in Zone 2 hazardous
locations, in ambient temperatures of –40 °C Ta 70 °C. If you
are using the NI 9214 in Gas Group IIC hazardous locations, you
must use the device in an NI chassis that has been evaluated as
Ex nC IIC T4, EEx nC IIC T4, Ex nA IIC T4, or Ex nL IIC T4
equipment.
Electromagnetic Compatibility Guidelines
This product was tested and complies with the regulatory
requirements and limits for electromagnetic compatibility (EMC)
as stated in the product specifications. These requirements and
limits are designed to provide reasonable protection against
harmful interference when the product is operated in its intended
operational electromagnetic environment.
This product is intended for use in industrial locations. There is no
guarantee that harmful interference will not occur in a particular
installation, when the product is connected to a test object, or if the
product is used in residential areas. To minimize the potential for
the product to cause interference to radio and television reception
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© National Instruments Corp. 7 NI 9214 Operating Instructions and Specifications
or to experience unacceptable performance degradation, install and
use this product in strict accordance with the instructions in the
product documentation.
Furthermore, any changes or modifications to the product not
expressly approved by National Instruments could void your
authority to operate it under your local regulatory rules.
Caution When operating this product, use shielded
cables and accessories.
Special Guidelines for Marine Applications
Some products are Lloyd’s Register (LR) Type Approved for
marine (shipboard) applications. To verify Lloyd’s Register
certification for a product, visit ni.com/certification and
search for the LR certificate, or look for the Lloyd’s Register mark
on the product label.
Caution In order to meet the EMC requirements for
marine applications, install the product in a shielded
enclosure with shielded and/or filtered power and
input/output ports. In addition, take precautions when
designing, selecting, and installing measurement probes
and cables to ensure that the desired EMC performance is
attained.
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NI 9214 Operating Instructions and Specifications 8 ni.com
Connecting the NI 9214
The NI TB-9214 provides connections for 16 thermocouple
channels on the NI 9214.
Figure 2. NI TB-9214 Terminal Reference
TC0+
TC0–
TC1+
TC1–
TC5+
TC5–
TC6+
TC6–
TC2+
TC4–
TC4+
TC3+
TC3–
TC2–
TC7+
TC9–
TC9+
TC8+
TC8–
TC7–
TC10+
TC12–
TC12+
TC11+
TC11–
TC10–
TC13+
TC15–
TC15+
TC14+
TC14–
TC13–
COM
COM
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© National Instruments Corp. 9 NI 9214 Operating Instructions and Specifications
Youcan connect thermocouple input signals to the NI 9214.
Connect the positive lead of the thermocouple to the TC+ terminal
and the negative lead of the thermocouple to the TC– terminal. If
youare unsure which of the thermocouple leads is positive and
which is negative, check the thermocouple documentation or the
thermocouple wire spool.
The NI 9214 also has two common terminals, COM, that are
internally connected to the isolated ground reference of the
module. A connection to COM is not necessary for most
applications. Specifically, leave COM unconnected for
configurations in which all thermocouples are floating, all
thermocouples are referenced to the same common-mode voltage,
or one thermocouple is referenced to a common-mode voltage and
all others are floating.
However, for configurations in which two or more thermocouples
are referenced to different common-mode voltages, connecting
COM according to the following guidelines improves
common-mode rejection performance. Connect COM to chassis
ground if the common-mode to chassis voltages are smaller than
±1.2 V. Otherwise, connect COM to a valid common-mode voltage
reference that is within ±1.2 V of the common-mode voltages of all
the thermocouple inputs.
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NI 9214 Operating Instructions and Specifications 10 ni.com
Connecting the Signals
To connect thermocouple wires to the NI TB-9214, complete the
following steps while referring to Figure 3.
1. Loosen the captive screws and remove the top cover.
2. Remove the foam pad from the NI TB-9214 opening.
3. Prepare the screw-terminal wire by stripping the outer
insulation and inner insulation. Refer to the Specifications
section for more information on screw-terminal wiring.
4. Insert the stripped end of the wire fully into the appropriate
terminal. Make sure no exposed wire extends past the screw
terminal.
5. Secure the connection by tightening the screw for the terminal.
Refer to the Specifications section for information on
screw-terminal torque.
6. Route the wire through the NI TB-9214 opening.
7. Remove slack in the NI TB-9214 wiring and secure the wires
by threading a zip tie through the two strain relief holes on the
NI TB-9214 opening.
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© National Instruments Corp. 11 NI 9214 Operating Instructions and Specifications
8. Replace the foam pad in the NI TB-9214 opening to fill any
excess space in the opening.
9. Reinstall the top cover on the NI TB-9214 and tighten the four
captive screws to secure the cover and compress the foam pad.
Figure 3. Connecting Wires to the NI TB-9214
1TopCover
2FoamPad
3Terminals
4 Strain Relief Holes
5 Ground Lug
1
245
3
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NI 9214 Operating Instructions and Specifications 12 ni.com
Youcan connect a shielded thermocouple to the NI 9214. Connect
the shield to the ground lug on the NI TB-9214 and COM to a
common-mode voltage reference on the thermocouple. A valid
common-mode voltage reference is a voltage that is within ±1.2 V
of the common-mode voltage of the thermocouple. If COM is left
floating, the internal common-mode voltage of the input circuitry
is the average of all the inputs. Refer to the Specifications section
for more information about the common-mode voltage. The shield
grounding methodology can vary depending on the application.
Refer to Figure 4 for an illustration of a typical shielding
configuration.
Figure 4. Connecting a Shielded Thermocouple Input Signal to the NI 9214
Thermocouple
TC–
COM
TC+
Shield
NI TB-9214
NI 9214
ChassisGround
Ground
Lug
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© National Instruments Corp. 13 NI 9214 Operating Instructions and Specifications
Installing the NI TB-9214
Connect the NI TB-9214 to the NI 9214 front connector as shown
in Figure 5. Tighten the two jackscrews on the NI TB-9214 to hold
it securely in place. Do not overtighten the jackscrews.
Figure 5. Installing the NI TB-9214
NI 9214 Circuitry
The NI 9214 passes 16 thermocouple input channels and one
autozero channel through a differential filter. Each channel is then
multiplexed and sampled by a 24-bit analog-to-digital converter
(ADC). Refer to Figure 6 for an illustration of the input circuitry
for one channel of the NI 9214.
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NI 9214 Operating Instructions and Specifications 14 ni.com
Figure 6. Input Circuitry for One Channel of the NI 9214
Each thermocouple channel has a programmable open
thermocouple detection (OTD) circuit, which consists of a current
source between the TC+ and TC– terminals. If an open
thermocouple is connected to the channel, the current source forces
a full-scale voltage across the terminals. Youcan configure the
OTD circuit in software. Refer to the software help for information
about configuring the OTD circuit. Visit ni.com/info and enter
cseriesdoc for information about C Series documentation.
TC+
TC–
COM
NI 9214
Input
Impedance
10 MΩ
10 MΩ
Open
Thermocouple
Detection
Current
Filtered
Differential
Amplifier
and
Multiplexer
Isolated
ADC
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© National Instruments Corp. 15 NI 9214 Operating Instructions and Specifications
Each thermocouple channel also has a resistor between the
TC+ and COM terminals and between the TC– and COM
terminals. Because long thermocouple wires can act like resistors,
the bias current from the OTD circuit can cause small offset errors.
The gain and offset errors resulting from the source impedance of
connected thermocouples are negligible for many applications.
Thermocouples with a higher lead resistance can introduce more
significant errors. Refer to the Compensating for OTD Current
section for information about compensating for offset errors
caused by bias current and lead resistance. Refer to the
Specifications section for more information about errors resulting
from source impedance.
The channels share a common ground, COM, that is isolated from
other modules in the system. The NI 9214 common-mode range is
the maximum voltage allowed between any channel and COM. The
NI 9214 measures the common-mode voltage level of each channel
and returns a warning in the software if the signal is outside the
common-mode voltage range. Refer to the Specifications section
for more information about the common-mode voltage range.
The NI 9214 supports high-resolution and high-speed timing
modes. High-resolution timing mode optimizes accuracy and noise
and rejects power line frequencies. High-speed timing mode
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NI 9214 Operating Instructions and Specifications 16 ni.com
optimizes sample rate and signal bandwidth. Refer to the
Specifications section for more information about the high-speed
and high-resolution timing modes. Refer to the software help for
information about setting the timing mode, or conversion time,
in software. Visit ni.com/info and enter cseriesdoc for
information about C Series documentation.
Temperature Measurement Accuracy
Considerations
Temperature measurement errors depend partly on the
thermocouple type, the accuracy of the thermocouple, the
temperature being measured, the resistance of the thermocouple
wires, and the cold-junction temperature. Refer to the Temperature
Measurement Accuracy section in the Specifications section for the
module accuracy for each thermocouple type when connected to
the NI 9214.
For the best accuracy results, keep temperature gradients across
NI 9214 terminals to a minimum, null the lead wire resistance, and
enable the autozero channel. Refer to the Minimizing Thermal
Gradients section, the Compensating for OTD Current section,
and the Using the Autozero Channel section for more information.
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© National Instruments Corp. 17 NI 9214 Operating Instructions and Specifications
Cold-Junction Temperature Measurement Accuracy
The NI TB-9214 has three cold-junction compensation channels.
Heat dissipated by adjacent modules or other nearby heat sources
can cause errors in thermocouple measurements by heating up the
NI 9214 terminals to a different temperature than the cold-junction
compensation sensor. The thermal gradient across the terminals
can cause the terminals of different channels to be at different
temperatures, in which case the resulting measurement creates
errors not only in absolute accuracy but also in the relative
accuracy between channels. Refer to the Specifications section for
the cold-junction compensation accuracy specifications. The
thermocouple accuracy specifications include the errors caused
by the thermal gradient across the NI 9214 terminals for
configurations with the NI 9214 terminals facing forward or
upward. Refer to the Temperature Measurement Accuracy section
in the Specifications section for the thermocouple accuracy
specifications.
Minimizing Thermal Gradients
Thermal gradients can be caused by changes in the ambient air
temperature near the front connector or by the thermocouple wire
if it conducts heat or cold directly to the terminal junctions. For the
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NI 9214 Operating Instructions and Specifications 18 ni.com
best accuracy results, follow these guidelines for minimizing
thermal gradients:
• Use small-gauge thermocouple wire. Smaller wire transfers
less heat to or from the terminal junction.
• If youare using a low channel count on the module, insert the
foam pad in the NI TB-9214 opening. Refer to the Connecting
the Signals section for more information.
•Run thermocouple wiring together near the NI TB-9214 to
keep the wires at the same temperature.
•Avoidrunning thermocouple wires near hot or cold objects.
• Minimize adjacent heat sources and air flow across the terminals.
• If possible, use the foam pad in the NI TB-9214 opening to
restrict airflow around the terminals.
• Keep the ambient temperature as stable as possible.
• Make sure the module terminals are facing forward or upward.
Keep the module in a stable and consistent orientation.
• Allow the thermal gradients to settle after a change in system
power or in ambient temperature. A change in system power
can happen when the system powers on, the system comes out
of sleep mode, or youinsert/remove modules. Refer to the
warm-up time in the Specifications section for more
information.
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© National Instruments Corp. 19 NI 9214 Operating Instructions and Specifications
Compensating for OTD Current
The OTD current causes a voltage error on the input when pushing
against a source resistance. This error is minimal for many
applications, but can be significant for some applications that
require high accuracy and use long, narrow gauge thermocouple
wires that cause large source resistances. Refer to the
Specifications section for more information about the OTD bias
current.
Youcan also eliminate the OTD bias current by disabling the OTD.
Refer to the software help for information about configuring the
OTD circuit. Visit ni.com/info and enter cseriesdoc for
information about C Series documentation.
Youcan compensate for the OTD bias current if your application
requires high accuracy, high resistance thermocouple wires, and
the ability to detect open thermocouples. Take a measurement with
the OTD enabled and a second measurement with the OTD
disabled. The voltage difference between the measurements is
the error voltage due to the OTD bias current. Subtract the error
voltage from subsequent measurements.
Visit ni.com/info and enter 9214OTD for more information
about compensating for the OTD errors.
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NI 9214 Operating Instructions and Specifications 20 ni.com
Using the Autozero Channel
The NI 9214 has an internal autozero channel, which can be
subtracted from each thermocouple reading to compensate for
offset errors. Use of the autozero channel is optional, however the
NI 9214 specifications assume that autozero is applied to every
sample. Refer to the software help for information about using the
autozero channel. Visit ni.com/info and enter cseriesdoc for
information about C Series documentation.
Sleep Mode
This module supports a low-power sleep mode. Support for sleep
mode at the system level depends on the chassis that the module is
plugged into. Refer to the chassis manual for information about
support for sleep mode. If the chassis supports sleep mode, refer
to the software help for information about enabling sleep mode.
Visit ni.com/info and enter cseriesdoc for information
aboutCSeriesdocumentation.
Typically, when a system is in sleep mode, youcannot
communicate with the modules. In sleep mode, the system
consumes minimal power and may dissipate less heat than it does
in normal mode. Refer to the Specifications section for more
information about power consumption and thermal dissipation.
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