Foxboro FBM212 Thermocouple/mV Differential Input Module

Foxboro FBM212 Thermocouple/mV Differential Input Module

DESCRIPTION

The Differential Thermocouple/mV Input Module (FBM212) contains 14 differentially isolated thermocouple input channels, and one differentially isolated RTD reference junction temperature compensation channel (for terminal temperature sensing). Each thermocouple/mV channel accepts standard thermocouples for various temperature ranges, and each provides thermocouple burnout detection (up-scale). Each channel has a differential input to allow voltage differences between channels without introducing errors.

The module performs the signal conversion required to interface the electrical input signals from the field sensors to the optionally redundant Fieldbus. It executes an analog input application program, which provides configurable options for Conversion Time and Rate of Change Limits.

FEATURES 

Key features of the FBM212 are:

 Fourteen channels for input of thermocouple signals 

 One isolated RTD reference junction compensation channel (for terminal temperature sensing) 

 Each channel has a differential input 

 Rugged design suitable for enclosure in Class G3 (harsh) environments 

 Execution of an analog input application program that provides conversion time and configurable options for Rate of Change Limits 

 High accuracy achieved by sigma-delta data conversions for each channel 

 Termination Assemblies (TAs) for locally or remotely connecting field wiring to the FBM212.

HIGH ACCURACY

For high accuracy, the module incorporates a multiplexed Sigma-Delta converter, which can provide new analog input readings every 500 ms, and a configurable integration period to remove any process noise and power line frequencies. Each update time period, the FBM converts each analog input to a digital value, averages these values over the time period and provides the averaged value to the controller.

STANDARD DESIGN

FBM212 has a rugged extruded aluminum exterior for physical protection of the circuits. Enclosures specially designed for mounting the FBMs provide various levels of environmental protection, up to harsh environments, per ISA Standard S71.04.

FIELDBUS COMMUNICATION

A Fieldbus Communications Module or a Control Processor interfaces to the redundant 2 Mbps module Fieldbus used by the FBMs. The FBM212 accepts communication from either path (A or B) of the 2 Mbps Fieldbus — should one path fail or be switched at the system level, the module continues communication over the active path.

MODULAR BASEPLATE MOUNTING

The module mounts on a 200 Series baseplate, which accommodates up to four or eight Fieldbus Modules. The Modular Baseplate is either DIN rail mounted or rack mounted, and includes signal connectors for redundant Fieldbus, redundant independent DC power, and termination cables. For applications which require CE certification, the baseplate and power supplies must be installed in a metal rack. Open wall mounting in that case is not allowed.

FUNCTIONAL SPECIFICATIONS

Accuracy

MILLIVOLT INPUT：±0.03% of span (±27 µV) at 25°C

RTD CHANNEL：±0.03% of span

RTD REFERENCE JUNCTION CONFORMITY：±0.25°C

THERMOCOUPLE CONFORMITY：±0.25°C

ACCURACY TEMPERATURE COEFFICIENT：±50 ppm/°C

RTD REFERENCE JUNCTION MEASUREMENT ACCURACY(B)：±0.50°C (When using the RTD internal to the Foxboro® supplied termination blocks)

INPUT VOLTAGE RANGE (REDUNDANT)：24 V DC +5%, -10%

CONSUMPTION：3 W (maximum) at 24 V DC

HEAT DISSIPATION：3 W (maximum) at 24 V DC