Description
Core Product Summary (Brand / Model / Key Attributes)
The Foxboro FBM202 is an 8-channel Thermocouple/mV Input Module for the Foxboro I/A Series and EcoStruxure Foxboro DCS 200 Series I/O subsystem. It accepts low-level millivolt signals from standard thermocouples and provides galvanically isolated analog input conversion to the redundant module Fieldbus.
Each of the eight channels is independently isolated and supports common thermocouple types together with direct millivolt inputs. A dedicated isolated RTD channel performs reference-junction (cold-junction) compensation at the termination assembly. The module uses per-channel Sigma-Delta conversion, offers configurable integration time and rate-of-change limits, and includes thermocouple burnout detection that drives the input to full upscale on open circuit.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Product Type | Thermocouple/mV Input Module (channel isolated) |
| Input Channels | 8 isolated thermocouple/mV channels + 1 isolated RTD reference-junction channel |
| Input Range | –10.5 to +69.5 mV DC (0 to 64 000 raw counts; 71.419 mV = full scale) |
| Supported Thermocouples | B, E, J, K, N, R, S, T and other millivolt signals |
| Reference Junction | 4-wire 100 Ω platinum RTD (IEC 751 Class B) at termination assembly |
| Accuracy (Millivolt) | ±0.03 % of span at 25 °C |
| Accuracy (RTD Channel) | ±0.03 % of span |
| Reference-Junction Conformity | ±0.25 °C |
| Thermocouple Conformity | ±0.25 °C |
| Accuracy Temperature Coefficient | ±50 ppm/°C |
| RTD Measurement Accuracy | ±0.50 °C (with Foxboro termination assemblies) |
| Differential Input Impedance | 10 MΩ |
| Common-Mode Voltage | Up to 30 V ac or 60 V dc |
| A/D Conversion | Independent Sigma-Delta converter per channel |
| Update Capability | New readings every 25 ms (integration period configurable) |
| Burnout Detection | Full upscale on open thermocouple |
| Isolation | Galvanic isolation, channel-to-channel and channel-to-ground |
| Power Supply (Redundant) | 24 V DC +5 % / –10 % |
| Power Consumption | 3 W maximum |
| Communication | Redundant 2 Mbps module Fieldbus |
| Application Program | Analog Input with configurable integration time and Rate of Change Limits |
| Environmental Rating | Suitable for Class G3 (harsh) environments |
Detailed Product Overview
The Foxboro FBM202 provides precise acquisition of thermocouple and low-level millivolt signals within the 200 Series Fieldbus Module architecture. Field sensors connect through a termination assembly that also houses the 100 Ω platinum RTD used for reference-junction compensation. Each of the eight measurement channels is galvanically isolated from the others and from system ground, minimizing ground-loop errors and noise pickup in industrial environments.
Signal conversion is performed by an independent Sigma-Delta analog-to-digital converter on every channel. This architecture supports update rates as fast as 25 ms while allowing the integration period to be configured in software to reject process noise or power-line frequencies. The module executes the standard Analog Input application program, which also provides configurable rate-of-change limits. Open-circuit (burnout) conditions on any thermocouple drive the reported value to full upscale, giving a clear diagnostic indication.
The FBM202 communicates with the associated Fieldbus Communications Module or Field Control Processor over the redundant 2 Mbps module Fieldbus. It is designed for DIN-rail or baseplate mounting and is rated for Class G3 harsh environments. Termination assemblies are available in both compression and ring-lug styles to match plant wiring practices and can be located locally or remotely from the module.
Because the reference-junction RTD is integral to the Foxboro termination assembly, overall temperature measurement accuracy includes the documented ±0.50 °C contribution of that sensor when the official assemblies are used. The module requires no field calibration under normal operating conditions.
FBM202
FBM202
Engineering Selection Highlights
- Choose FBM202 when the application requires direct connection of thermocouples or low-level millivolt sources without external transmitters.
- Confirm that the expected thermocouple types (B, E, J, K, N, R, S, T) or millivolt range fall inside the –10.5 to +69.5 mV input span.
- Verify that the termination assembly includes the required 4-wire 100 Ω platinum RTD for reference-junction compensation.
- Use the configurable integration period to balance update speed against noise rejection for the specific process.
- Account for the 3 W power consumption and Class G3 environmental rating when allocating baseplate slots and cabinet cooling.
- Ensure the control software is configured for the Analog Input application program with the desired rate-of-change limits.
- Plan wiring and shielding to stay within the common-mode voltage limits of 30 V ac / 60 V dc.
Dimensions, Mounting & Connection Notes
The FBM202 is a standard 200 Series Fieldbus Module form factor designed for plug-in mounting on a DIN-rail baseplate or modular baseplate. Field wiring is terminated on a dedicated Termination Assembly that also contains the reference-junction RTD. Both compression-type and ring-lug-type termination assemblies are supported and may be mounted locally or remotely. The module requires no special orientation beyond normal baseplate practices. Adequate ventilation should be provided consistent with the 3 W heat dissipation. Installation must remain within the environmental limits specified for Class G3 service.
System Compatibility & Integration Requirements
| Item / Dependency | Verified Compatibility or Requirement | Practical Note |
|---|---|---|
| System Family | Foxboro I/A Series / EcoStruxure Foxboro DCS | 200 Series Fieldbus Module subsystem |
| Fieldbus | Redundant 2 Mbps module Fieldbus | Connects to FCM or FCP |
| Power Supply | Redundant 24 V DC +5 % / –10 % | 3 W maximum consumption |
| Termination Assembly | Foxboro TA with integral 100 Ω Pt RTD (e.g., P0916AC/AD series) | Required for reference-junction compensation |
| Mounting | DIN-rail baseplate or standard 200 Series baseplate | Compact and standard versions available |
| Software | Analog Input application program | Configurable integration time and Rate of Change Limits |
| Environmental | Class G3 (harsh) | Suitable for industrial process areas |
FAQ
What is the Foxboro FBM202?
The Foxboro FBM202 is an 8-channel isolated Thermocouple/mV Input Module for the I/A Series and EcoStruxure Foxboro DCS that converts thermocouple and millivolt signals to digital values on the module Fieldbus.
How many channels does the FBM202 have?
It provides eight isolated thermocouple/mV input channels plus one dedicated isolated RTD channel for reference-junction temperature compensation.
Which thermocouple types are supported?
Standard types B, E, J, K, N, R, S and T, as well as general millivolt signals within the –10.5 to +69.5 mV range.
Does the module include cold-junction compensation?
Yes. Reference-junction compensation is performed by a 4-wire 100 Ω platinum RTD located in the Foxboro termination assembly.
What is the input accuracy?
Millivolt accuracy is ±0.03 % of span at 25 °C. Thermocouple and reference-junction conformity are each ±0.25 °C; overall RTD measurement accuracy with Foxboro TAs is ±0.50 °C.
What happens on thermocouple burnout?
An open thermocouple is detected and the channel is driven to full upscale value.
What power supply is required?
A redundant 24 V DC supply (+5 % / –10 %). Maximum consumption is 3 W.
Is the module suitable for harsh environments?
Yes. It is rated for Class G3 (harsh) industrial environments.
Verification & Troubleshooting Notes
- Confirm module identity by the FBM202 designation and part number on the label and by successful recognition on the Fieldbus.
- Verify that the correct termination assembly containing the 100 Ω platinum RTD is installed and properly connected.
- Check that the 24 V DC redundant power is present and within tolerance.
- Observe channel status and diagnostic indicators; an open thermocouple will report full upscale.
- If readings are noisy, review the configured integration period and the quality of field wiring and shielding.
- Confirm that common-mode voltage on any channel remains within 30 V ac or 60 V dc.
- Module-level communication or power faults appear as Fieldbus diagnostics at the control processor; replace the module only after confirming power, Fieldbus integrity, and correct termination assembly.
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