National Instruments SCC-RTD01 User manual

USER GUIDE
SCC-RTD01 Resistance
Temperature Detector
The SCC-RTD01 resistance temperature detector (RTD) input module
accepts up to two RTD input signals from 2-, 3-, or 4-wire RTDs. Each
module consists of two RTD input channels, a 30 Hz Butterworth lowpass
filter for each channel and a 1 mA excitation current source. Each input
channel includes an instrumentation amplifier with differential inputs and
a fixed gain of 25.
The SCC-RTD01 filters RTD inputs and passes them through a differential
amplifier with a fixed gain of 25 resulting in a maximum input voltage of
400 mVDC. The output of the amplifier passes through a three-pole, 30 Hz
Butterworth lowpass filter. The SCC-RTD01 provides a 1 mA excitation
current source for RTDs.
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. 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.

SCC-RTD01 Resistance Temperature Detector Input Module 2 ni.com
ADE Application Development Environment
bold Bold text denotes items that you must select in 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. 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.
SC-2345 SC-2345 refers to both the SC-2345 connector block and the SC-2345 with
configurable connectors.
SCC SCC refers to any SCC Series signal conditioning module.

©National Instruments Corporation 3 SCC-RTD01 Resistance Temperature Detector Input Module
What You Need to Get Started
To set up and use the SCC-RTD01, you need the following items:
❑SC-2345/2350 with one of the following:
– SCC-PWR01
– SCC-PWR02 and the PS01 power supply
– SCC-PWR03 (requires a 7 to 42 VDC power supply, not included)
❑One or more SCC-RTD01 modules
❑Read Me First: Safety and Radio-Frequency Interference
❑SCC-RTD01 Resistance Temperature Detector Input Module
User Guide
❑SC-2345/2350 User Manual, available at ni.com
❑SCC Quick Start Guide, available at ni.com
❑SC-2345 Quick Reference Label
❑68-pin E Series data acquisition (DAQ) device, documentation, and
68-pin cable
❑1/8 in. flathead screwdriver
❑Numbers 1 and 2 Phillips screwdrivers
❑Wire insulation strippers
❑NI-DAQ (current version) for Windows 2000/NT/XP/Me
Note If you do not have the current version of NI-DAQ or one of the documents, you can
download them from the National Instruments Web site at ni.com or contact an NI sales
representative. Software scaling of measurements is not supported on the Macintosh
operating system. Refer to the Specifications section for information about software
scaling.

SCC-RTD01 Resistance Temperature Detector Input Module 4 ni.com
Device Specific Information
Note For general SCC module installation and signal connection information, and
information about the SC-2350 carrier, refer to the SCC Quick Start Guide, available for
download at ni.com/manuals.
Installing the Module
Caution Refer to the Read Me First: Safety and Radio-Frequency Interference document
before removing equipment covers or connecting/disconnecting any signal wires.
You can plug the SCC-RTD01 into any AI socket on the SC-2345.
The SCC-RTD01 can function as a single-stage module or as the first stage
of a dual-stage signal conditioning configuration. The socket you choose
determines which E Series DAQ device channels receive the SCC-RTD01
signals, as explained in the SCC Quick Start Guide.
For single-stage input conditioning, plug the SCC-RTD01 into any socket
J(X+1), where Xis 0 to 7, and connect the input signals to the module as
described in the SCC Quick Start Guide.
If you use the SCC-RTD01 in a dual-stage configuration, the SCC-RTD01
must be the first stage. Plug the SCC-RTD01 into any socket J(X+9) and
plug the second-stage SCC into socket J(X+1), where Xis 0 to 7. Connect
the input signals to the SCC-RTD01 as described in the SCC Quick Start
Guide. The SC-2345 connects the output signals of the first-stage SCC to
the inputs of the second-stage SCC. An example of dual-stage conditioning
is an SCC-AIXX isolated analog input module followed by an SCC-LPXX
lowpass filter module.
Note Refer to the SC-2345/2350 User Manual for more information on single-stage and
dual-stage signal conditioning and configuration.

©National Instruments Corporation 5 SCC-RTD01 Resistance Temperature Detector Input Module
Connecting the Input Signals
Note The signal names have changed. Refer to ni.com/info and enter rdtntg to
confirm the signal names.
The SCC-RTD01 has six pins and provides two differential AI channels for
measuring the voltage across RTDs. Pins 1 and 2 form a differential
channel routed to E Series DAQ device channel X+8, and pins 3 and 4 form
a second differential channel routed to E Series DAQ device channel X,
where Xis 0 to 7 depending on the socket of the SCC-RTD01. Pins 5 and 6
carry the 1 mA constant-current excitation source.
For information on how the I/O pins on the bottom of the SCC-RTD01
correspond to signals on the E Series DAQ device, refer to the I/O
Connector Pin Assignments section.
Signal sources can be floating or ground-referenced. The SCC-RTD01 has
high-impedance bias resistors typically required for floating sources.
Therefore, floating signal sources do not require external bias resistors
connected to ground.
Note For floating signal sources in high-noise environments, connect the negative
terminal of the signal source to the AI SENSE terminal on the SC-2345 screw-terminal
block to reduce common-mode noise.
You can connect one or two RTDs to the SCC-RTD01 in 2-, 3-, and 4-wire
configurations. Figure 1 contains wiring diagrams for connecting one 2-,
3-, or 4-wire RTD to the SCC-RTD01.

SCC-RTD01 Resistance Temperature Detector Input Module 6 ni.com
Figure 1. SCC-RTD01 Single-Channel Wiring Diagrams
IEX (1 mA)
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
4-Wire, 1 Channel
Red
Red
Black
Black
RTD
IEX (1 mA)
E Series
AI (
X )
E Series
AI (
X +8)
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
2-Wire, 1 Channel
Red
Black
RTD
IEX (1 mA)
E Series
AI (
X )
E Series
AI (
X +8)
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
3-Wire, 1 Channel, Remote Sensing
Red
Black
Black
RTD
IEX (1 mA)
E Series
AI (
X )
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
3-Wire, 1 Channel
Red
Black
Black
RTD
E Series
AI (
X +8)
E Series
AI (
X )
E Series
AI (
X +8)

©National Instruments Corporation 7 SCC-RTD01 Resistance Temperature Detector Input Module
Figure 2 contains wiring diagrams for connecting two 2-, 3-, or 4-wire
RTDs to the SCC-RTD01.
Figure 2. SCC-RTD01 Two-Channel Wiring Diagrams
Note Use 4-wire transducer connections for a more accurate measurement. Lead
resistance in 2- and 3-wire connections can introduce measurement errors.
For information about configuring the SCC-RTD01 module using
NI-DAQmx, refer to the SCC Quick Start Guide.
I
EX
(1 mA)
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
4-Wire, 2 Channels
Red
Red
Red
Red
Black
Black
Black
Black
RTD
RTD
I
EX
(1 mA)
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
3-Wire, 2 Channels
Red
Red
Black
Black
Black
Black
RTD
RTD
I
EX
(1 mA)
+
–
+
–
+
–
6
5
4
3
2
1
SCC-RTD01
2-Wire, 2 Channels
Red
Red
Black
Black
RTD
RTD
E Series
AI (
X )
E Series
AI (
X +8)
E Series
AI (
X )
E Series
AI (
X +8)
E Series
AI (
X )
E Series
AI (
X +8)

SCC-RTD01 Resistance Temperature Detector Input Module 8 ni.com
Using the SCC-RTD01
Note If you have an RTD that is not supported in Measurement & Automation
Explorer (MAX), Read Voltage Data and scale it in your ADE.
Converting Voltage Measurements to Temperature Measurements
If you use MAX to configure the SCC-RTD01, the reading you get from
the E Series DAQ device is properly scaled. Otherwise, you must scale the
readings and convert the voltage measurement to temperature by
performing the following steps to use the standard equations for platinum
RTDs:
1. Measure the RTD voltage.
a. Read the RTD channel on the E Series DAQ device and call the
value VESERIES[CH(X)].
b. Calculate the RTD voltage using the following formula:
where
VRTD is the SCC-RTD01 input voltage.
VESERIES is the E Series DAQ device voltage.
2. Use polynomial expressions or a conversion table provided by the RTD
vendor to convert the RTD voltage to temperature.
Note NI programming environments include RTD conversion utilities that implement the
voltage-to-temperature conversions. Refer to the ADE documentation for more
information on these utilities.
Although the RTD resistance-versus-temperature curve is relatively
linear, accurately converting resistance to temperature requires curve
fitting. The Callendar-Van Dusen equation is commonly used to
approximate the RTD curve:
Rt= R0[1 + At+ Bt2+ C(t– 100)3]
where
Rtis the resistance of the RTD at temperature t.
R0is the resistance of the RTD at 0 °C.
A, B, and C are the Callendar-Van Dusen coefficients shown in
Table 1.
tis the temperature in °C.
VRTD
VESERIES
25
---------------------=

©National Instruments Corporation 9 SCC-RTD01 Resistance Temperature Detector Input Module
For temperatures above 0 °C, the C coefficient equals 0. Therefore, for
temperatures above 0 °C, this equation reduces to a quadratic. If you
pass a known current, IEX, through the RTD and measure the voltage
developed across the RTD, V0,you can use the following formula to
solve for t:
where
V0is the measured RTD voltage.
IEX is the excitation current.
Most platinum RTD curves conform to one of the following three
standardized curves:
• DIN 43760 standard
• U.S. Industrial or American standard
• International Temperature Scale (ITS)–90 (for use with
wire-wound RTDs)
Table 1. Callendar-Van Dusen Coefficients for Platinum RTDs
Standard
Temperature
Coefficient A B C
DIN 43760 0.003850 3.9080 ×10–3 –5.8019 ×10–7 –4.2735 ×10–12
American 0.003911 3.9692 ×10–3 –5.8495 ×10–7 –4.3235 ×10–12
ITS-90 0.003926 3.9848 ×10–3 –5.870 ×10–7 –4.0000 ×10–12
t
2V0IEXR0
–()
IEXR0AA
24BV
0IEXR0
–()()IEXR0 ()⁄++[]
---------------------------------------------------------------------------------------------------------------=

SCC-RTD01 Resistance Temperature Detector Input Module 10 ni.com
Specifications
These ratings are typical at 25 °C unless otherwise stated.
Analog Input
Number of input channels.......................2 DIFF
Input range ..............................................±400 mVDC (fixed gain of 25 on
each channel)
Overvoltage protection ...........................±42 VDC powered on
±25 VDC powered off
Input impedance
Normal powered on .........................2 MΩin parallel with 4.7 nF
Powered off .....................................20 kΩ min
Overload ..........................................20 kΩmin
Filter type................................................3-pole Butterworth lowpass filter
–3 dB cutoff frequency....................30 Hz
System noise ...........................................4.5 µVrms (referred to the input
[RTI]1)
Transfer Characteristics
Gain ........................................................25
Gain error................................................±1.2%
Gain-error temperature coefficient .........±10 ppm/°C
Offset error .............................................±250 µV (RTI)
Offset-error temperature coefficient .......±1.6 µV/°C
Nonlinearity ............................................10 ppm of full scale
Recommended warm-up time.................5 min
Amplifier Characteristics
Common-mode rejection ratio................110 dB at 60 Hz
Output range ...........................................±10 V
1 Calculated relative to the input range of the module

©National Instruments Corporation 11 SCC-RTD01 Resistance Temperature Detector Input Module
Excitation
Number of channels ............................... 1
Constant-current source ......................... 1 mA, ± 0.4 µA or 0.04%
Maximum voltage level
without regulation loss ........................... 24 V
Drift........................................................ ±127 ppm/°C
Power Requirement
Analog power......................................... 135 mW max
+15 V .............................................. 4.5 mA max
–15 V............................................... 4.5 mA max
Digital power.......................................... 153 mW max
+5 V ................................................ 30.6 mA max
Physical
Dimensions............................................. 8.89 cm ×2.92 cm ×1.85 cm
(3.50 in. ×1.15 in. ×0.73 in.)
I/O connectors ........................................ 20-pin right-angle
male connector,
6-pin screw terminal
Field-wiring diameter............................. 28 to 16 AWG
Maximum Working Voltage
Maximum working voltage
(signal plus common mode) ................... Each input should remain within
±12 V of ground
Environmental
Operating temperature............................ 0 to 50 °C
Storage temperature ............................... –20 to 70 °C
Humidity ................................................ 5 to 90% relative humidity,
noncondensing
Maximum altitude .................................. 2,000 m
Pollution Degree (indoor use only) ........ 2

SCC-RTD01 Resistance Temperature Detector Input Module 12 ni.com
Safety
The SCC-RTD01 meets the requirements of the following standards
for safety and electrical equipment for measurement, control, and
laboratory use:
• IEC 61010-1, EN 61010-1
• UL 3111-1, UL 6101013-1
• CAN/CSA C22.2 No. 1010.1
Note For UL and other safety certifications, refer to the product label or to
ni.com/hardref.nsf, search by model number or product line, and click the
appropriate link in the Certification column.
Electromagnetic Compatibility
Emissions................................................EN 55011 Class A at 10 m
FCC Part 15A above 1 GHz
Immunity ................................................EEN 61326-1:1997 + A2:2001,
Table 1
CE, C-Tick, and FCC Part 15 (Class A) Compliant
Note For EMC compliance, operate this device with shielded cabling.
CE Compliance
This product meets the essential requirements of applicable European
directives, as amended for CE marking, as follows:
Low-Voltage Directive (safety)..............73/23/EEC
Electromagnetic Compatibility
Directive (EMC) .....................................89/336/EEC
Note Refer to the Declaration of Conformity (DoC) for this product for any additional
regulatory compliance information. To obtain the DoC for this product, visit
ni.com/hardref.nsf, search by model number or product line, and click the
appropriate link in the Certification column.

©National Instruments Corporation 13 SCC-RTD01 Resistance Temperature Detector Input Module
I/O Connector Pin Assignments
Figure 3 shows the I/O connector pins on the bottom of the module.
Figure 3. SCC Module Bottom View
Table 2 lists the signal connection corresponding to each pin. AI (X)
and AI (X+8) are the AI signal channels of the E Series DAQ device.
AI GND is the AI ground signal and is the reference for AI (X) and
AI (X+8). A GND is the reference for the ±15 V supplies and REF 5 V.
AI GND and A GND connect to the SC-2345 at the SCC-PWR connector.
GND is the reference for the +5 V supply.
1Pin1 2Pin2 3PWBKey 4 Pin19 5Pin20
Table 2. SCC-RTD01 Pin Signal Connections
Pin Number Signal
1E Series AI (X)
2 —
3 —
4E Series AI (X+8)
5 —
6AI GND
7 —
8 —
9+5 V
5
4
2
1
3

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© 2002–2004 National Instruments Corp. All rights reserved.
371072B-01 Mar04
*371072B-01*
10 GND
11 A GND
12 —
13 +15 V
14 –15 V
15 —
16 —
17 —
18 —
19 —
20 —
Table 2. SCC-RTD01 Pin Signal Connections (Continued)
Pin Number Signal