National Instruments CFP-TC-120, FP-TC-120 Operating Instructions Manual

FieldPoint Operating Instructions

FP-TC-120 AND CFP-TC-120

8-Channel Thermocouple Input Modules

These operating instructions describe how to install and use the
National Instruments FP-TC-120 and cFP-TC-120 thermocouple
input modules (referred to inclusively as the [c]FP-TC-120). For
details on configuring and accessing the [c]FP-TC-120 over a
network, refer to the user manual for the FieldPoint network
module you are using.

Features

The [c]FP-TC-120 is a FieldPoint thermocouple input module with
the following features:

• Eight thermocouple or millivolt inputs

• Built-in linearization and cold-junction compensation for eight
thermocouple types: J, K, R, S, T, N, E, and B

• Four voltage ranges: ±25, ±50, ±100, and – 20 to 80 mV

• Open-thermocouple detection and indicator LEDs

• 16-bit resolution

• Differential inputs

• Filtering against 50 and 60 Hz noise

• 2,300 V
inter-module communication bus and the I/O channels

•250 V

• –40 to 70 °C operation

• Hot plug-and-play

transient overvoltage protection between the

rms

isolation voltage rating

rms

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Product and compa ny names mentioned herein are trade marks or trade names of their respe ctive companies.
For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software,
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patents.txt file on your CD, or ni.com/p atents.

373344A-01 October 2002

© 2002 National Instruments Corp. All rights reserved.

Installing the FP-TC-120

The FP-TC-120 mounts on a FieldPoint terminal base (FP-TB-x).
Hot plug-and-play enables you to install the FP-TC-120 onto a
powered terminal base without disturbing the operation of other
modules or terminal bases. The FP-TC-120 receives operating
power from the terminal base.

To install the FP-TC-120, refer to Figure 1 and follow these steps:

1. Slide the terminal base key to either position X (for any
module) or position 1 (for the FP-TC-120).

2. Align the FP-TC-120 alignment slots with the guide rails on
the terminal base.

3. Press firmly to seat the FP-TC-120 on the terminal base.
The latch on the terminal base locks the FP-TC-120 into place
when it is firmly seated.

Key

Latch

Alignment

Slot

Guide Rails

Terminal BaseI/O Module

Figure 1. Installing the FP-TC-120

Installing the cFP-TC-120

The cFP-TC-120 mounts on a FieldPoint backplane (cFP-BP-x).
Hot plug-and-play enables you to install the cFP-TC-120 onto a
powered backplane without disturbing the operation of other
modules or connector blocks. The cFP-TC-120 receives operating
power from the backplane.

To install the cFP-TC-120, refer to Figure 2 and follow these steps:

1. Align the captive screws on the cFP-TC-120 with the holes on
the backplane. The alignment keys on the cFP-TC-120 prevent
backward insertion.

FP-TC-120 and cFP-TC-120 2 ni.com

2. Press firmly to seat the cFP-TC-120 on the backplane.

3. Using a number 2 Phillips screwdriver with a shank of at least
64 mm (2.5 in.) length, tighten the captive screws to 1.1 N ⋅ m
(10 lb ⋅ in.) of torque. The nylon coating on the screws prevents
them from loosening.

2 1

4

3

1 cFP Backplane
2 cFP Controller Module

Figure 2. Installing the cFP-TC-120

4

3cFP-TC-120
4 Captive Screws

5

5

5 Screw Holes

Wiring the [c]FP-TC-120

The FP-TB-x terminal bases have connections for each of the eight
differential input channels on the FP-TC-120 and a common
(COM) terminal for connecting a shield to each channel. The
cFP-CB-x connector blocks provide the same connections for the
cFP-TC-120.

Table 1 lists the terminal assignments for the signals associated
with each channel. The terminal assignments are the same for the
FP-TB-x terminal bases and the cFP-CB-x connector blocks.

© National Instruments Corp. 3 FP-TC-120 and cFP-TC-120

Table 1. Terminal Assignments

Terminal Numbers

Channel

0 1 2 18

1 3 4 20

2 5 6 22

3 7 8 24

4 9 10 26

5 11 12 28

6 13 14 30

7 15 16 32

Note On the FP-TB-3 terminal base and the cFP-CB-3

IN(+)

IN(–)

COM

connector block, use the C terminals for COM
connections.

The COM terminals of all the channels are internally connected
and are connected to the terminals labeled C on the terminal base.
You do not need to connect a power source to the V or C terminals
of the terminal base or connector block. The C and COM terminals
are internally connected to the isolated ground reference of the
module and to any shield connections you make, so connecting a
power supply to one of these terminals may create a ground loop
and cause measurements to be misreferenced. Connecting the C
and COM terminals of the [c]FP-TC-120 to the V, C, or COM
terminals of another FieldPoint module defeats the isolation
barriers between the two modules.

Taking Measurements
with the [c]FP-TC-120

The [c]FP-TC-120 has eight differential input channels. All eight
channels share a common ground reference that is isolated from
other modules in the FieldPoint system. Each of the input channels
has a bias resistor to this isolated ground reference on the negative
terminal, IN(–), and a pull-up resistor on the positive terminal,
IN(+), to detect open thermocouples. Each channel has a COM
terminal that connects to the isolated ground reference. Each
channel is filtered, then sampled by a 16-bit analog-to-digital

FP-TC-120 and cFP-TC-120 4 ni.com

converter (ADC). Figure 3 shows the input circuitry on one
channel.

+0.7 V

10 MΩ

IN(+)

Filter

IN(–)

10 MΩ

COM

C

Figure 3. [c]FP-TC-120 Analog Input Circuitry on One Channel

16-Bit

Isolated ADC

[c]FP-TC-120

Connecting Voltage Input Signals

Connect the positive lead of a millivolt signal to the IN(+) terminal
and the negative lead to the IN(–) terminal. If you are using
shielded wiring, connect one end of the shield to the COM
terminal. Figure 4 shows a millivolt source connected to one
channel of the [c]FP-TC-120.

CV

IN(+)

Millivolt
Source

+

IN(–)

–

[c]FP-TC-120

Figure 4. Connecting a Millivolt Source to the [c]FP-TC-120

The input ranges for the voltage inputs are ±25, ±50, ±100, and
–20 to 80 mV. An input signal outside the selected input range
causes the [c]FP-TC-120 to report an

Out of range error for the

affected channel. The [c]FP-TC-120 ignores any configuration of
thermocouple type when you select one of these ranges.

© National Instruments Corp. 5 FP-TC-120 and cFP-TC-120

Connecting Thermocouple Input Signals

Connect the positive lead of a thermocouple to the IN(+) terminal
and the negative lead to the IN(–) terminal. If you are using
shielded wiring, connect one end of the shield to the COM
terminal. Thermocouple wires are color coded. The color code
depends on the thermocouple type and the country of manufacture.
If you are unsure which of the thermocouple leads is the positive
and which is the negative, check the thermocouple documentation
or the thermocouple wire spool. The [c]FP-TC-120 supports
thermocouple types J, K, R, S, T, N, E, and B. Figure 5 shows
a shielded thermocouple connected to one channel of the
[c]FP-TC-120.

CV

Thermocouple

IN(+)

IN(–)

Shield

Figure 5. Connecting a Shielded Thermocouple to the [c]FP-TC-120

To Next

Channel

[c]FP-TC-120

The [c]FP-TC-120 linearizes the thermocouple voltage and returns
a reading in units of temperature. The available ranges are
0 to 2,048 K, – 270 to 1,770 °C, and – 454 to 3,218 °F.
Temperatures outside these ranges result in an

Out of range

error for the affected channels.

Note You must configure each channel of the

[c]FP-TC-120 for the type of thermocouple connected
to it.

The algorithms in the [c]FP-TC-120 linearize measurements
according to the National Institute of Standards and Technology
NIST-175 standard for thermocouple characteristics, based on the
ITS-90 International Temperature Scale. These linearization
algorithms are typically accurate to within ±0.05 °C (0.03 °F) of
the NIST standard over the entire range of temperatures defined
by the NIST for the supported thermocouple types.

FP-TC-120 and cFP-TC-120 6 ni.com