Smart I/O Modules

The cFP-TC-12x and cFP-RTD-12x modules offer 16-bit resolution for

high-accuracy measurements, and you can connect directly to industrial

sensors or units under test with the safety isolation available. The

modules filter, calibrate, and scale raw sensor signals to engineering

units, as well as perform self-diagnostics to look for problems such as

open thermocouples. With cFP-TC-12x and cFP-RTD-12x modules, your

software application reads a linearized, calibrated, scaled value from the

I/O module, eliminating the error-prone step of converting binary values

to temperature. For increased accuracy and noise rejection, the modules

use a16-bit delta-sigma analog-to-digital converter (ADC) with an

integrated notch filter on each channel, which is configured for 50 and

60 Hz rejection. With high-accuracy 16-bit delta-sigma ADCs on the I/O

modules, you also get instrument-quality measurements on an industrially

rugged, distributed, embedded system. The cFP-TC-12x and cFP-RTD-12x

modules offer a variety of update rates to fit your application, ranging

from 0.22 s with filters off and 1.08 to 1.13 s with filters enabled. Overall

data throughput depends on filter settings across all channels, software

loop speeds, and network speeds.

cFP-TC-120

The cFP-TC-120 includes eight differential inputs for thermocouples.

It also provides cold-junction compensation using a thermistor embedded

in the connector block. An onboard microcontroller compensates and

linearizes the thermocouple reading to the NIST ITS-90 standard,

using an advanced linearization routine for maximum accuracy.

cFP-TC-125

In addition to the thermistor and linearization features of the cFP-TC-120,

applications where differences in voltages might exist between connected

thermocouples. The cFP-TC-125 also offers 0.22 s update rates when the

50/60 Hz filter is not enabled.

cFP-RTD-122

The cFP-RTD-122 includes eight inputs for 2- and 3-wire RTDs.

The module uses a stable current source for sensor excitation and an

onboard microcontroller that linearizes and scales the measurements to

temperature units. You can configure each channel of the module to

return data scaled to temperature (°C, °F, or °K) or resistance. The 3-wire

configuration used with the cFP-RTD-122 eliminates errors caused by

lead wire resistance but does not reduce errors caused by noise. If your

application involves high noise or long wires, you should use 4-wire RTDs

with the cFP-RTD-124.

cFP-RTD-124

The cFP-RTD-124 includes eight inputs for 2- and 4-wire RTDs. The module

uses a stable current source for sensor excitation and an onboard

microcontroller that linearizes and scales the measurements to temperature

units. You can configure each channel of the modules to return data scaled

to temperature (°C, °F, or °K) or resistance. Four-wire RTDs used with the

cFP-RTD-124 are ideal for applications involving long signal wires or high

signal noise. The 4-wire configuration eliminates the voltage drop caused

by lead wire resistance and reduces errors caused by noise.

Isothermal Connectivity for cFP-TC-12x Modules

For maximum accuracy, NI recommends using an isothermal connector

block with a cFP-TC-12x. The cFP-CB-3 isothermal connector block

minimizes the temperature gradient across wiring connections,

improving the accuracy of the cold-junction measurement, and,

therefore, of thermocouple measurements.

Compact FieldPoint I/O Connections

Compact FieldPoint modules include a built-in power distribution bus

that provides multiple power connections on the module. A field-wired

power supply connected to the voltage (V) and common (C) terminals is

internally connected to a power distribution bus that features additional

breakout terminals for voltage supply (VSUP) and common (COM). These

terminals offer a convenient way to distribute power to field devices that

require external power.

Each cFP-TC-12x input channel has two terminals for differential input:

1. Thermocouple positive input (IN+)

2. Thermocouple negative input (IN-)

Each cFP-RTD-122 input channel has three terminals:

1. Excitation output (EXCITE)

2. Sensing input (SENSE)

3. Common input (COM)

Each cFP-RTD-124 input channel has four terminals:

1. Excitation output (EXCITE)

2. Positive sensing input (SENSE+)

3. Negative sensing input (SENSE-)

4. Common input (COM)

Thermocouple and RTD Modules for Compact FieldPoint

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