Description
Foxboro FBM217 RH914TR | 32-Channel Discrete Input Module
Product Introduction
A 32-point discrete input card is easy to describe incorrectly. With the Foxboro FBM217, the electronics module is only one part of the signal chain—the termination assembly determines whether the cabinet is handling low-voltage DC contact sensing, 120 VAC/125 VDC, or 240 VAC input signals.
The FBM217 RH914TR provides 32 discrete input channels and converts field contact or voltage-monitor signals into data for the Foxboro Module Fieldbus. Schneider documents support for 15–60 VDC, 120 VAC/125 VDC, and 240 VAC applications through the appropriate termination assemblies.
The architecture is also migration-oriented. With the correct TAs, one FBM217 can reproduce functions formerly provided by selected 100 Series FBMs, including FBM07A/B, FBM08, FBM20, and FBM24A/B/C. This makes the FBM217 useful in staged I/O migration projects where existing field wiring needs to remain largely intact.
For redundant applications, two FBM217 modules can operate as a redundant pair through the RH926ZY redundant adapter. The pair shares one termination assembly, while the Foxboro control software validates the redundant input information and selects the higher-quality signal.
FBM217
Key Technical Specifications
- Model:
- Current module part number: RH914TR
- Function: Discrete input
- Input channels: 32
- Primary input architecture: 32 group-isolated channels
- Supported field signals: 15–60 VDC, 120 VAC/125 VDC, 240 VAC, depending on TA
- Low-voltage ON-state: 15–30 VDC
- Low-voltage OFF-state: 0–5 VDC
- Typical input current: 2.2 mA at 30 VDC
- Maximum ON-state source resistance: 1 kΩ at 15 VDC
- Minimum OFF-state source resistance: 100 kΩ at 30 VDC
- Input filter/debounce: None, 4, 8, 16, or 32 ms
- Maximum pulse-count rate: 250 Hz
- Fieldbus: Redundant 2 Mbps Module Fieldbus
- Power supply: 24 VDC +5% / -10%
- Maximum module consumption: 3 W at 24 VDC
- Maximum heat dissipation: 5 W at 24 VDC, including field-power contribution
- Operating temperature: -20 to +70°C (-4 to +158°F)
- Storage temperature: -40 to +70°C (-40 to +158°F)
- Relative humidity: 5–95%, noncondensing
- Contamination environment: ISA S71.04 Class G3
- Vibration: 0.75 g from 5–500 Hz
- Approximate module weight: 284 g
- Dimensions: 102 × 45 × 104 mm
- Height including mounting lugs: 114 mm
- Maximum termination cable length: 30 m / 98 ft
- Baseplate-to-main-TA cable: Type 4
- Main-TA-to-expansion-TA cable: Type 6
- Redundant adapter: RH926ZY
- Field termination: Compression or applicable ring-lug TA configuration
These figures are from Schneider Electric’s current PSS 41H-2S217, Rev B, dated May 2025.
Input Signal Architecture
The itself provides the low-level digital acquisition circuitry. The termination assembly provides the signal conditioning required for the particular field voltage.
For low-voltage applications below 60 VDC, Schneider specifies passive termination assemblies for either voltage monitoring or contact sensing. Voltage-monitor configurations use an external field voltage source, while contact-sense configurations can use the FBM auxiliary +24 VDC supply to wet the field contacts.
For higher-voltage applications, the TA becomes even more important. The available architectures include 120 VAC/125 VDC and 240 VAC inputs, with the TA providing voltage attenuation and, depending on configuration, optical isolation.
This means is not a universal-voltage input card by itself. The correct specification is always:
+ correct TA + correct termination cable + correct controller configuration.
Low-Voltage 30 VDC Configuration
With the appropriate low-voltage TA, the accepts:
- 0–5 VDC as logic OFF
- 15–30 VDC as logic ON
- Approximately 2.2 mA typical input current at 30 VDC
- Maximum 1 kΩ ON-state source resistance
- Minimum 100 kΩ OFF-state source resistance
The input filter can be configured for no filtering, 4 ms, 8 ms, 16 ms, or 32 ms. The module can also execute pulse-count processing up to 250 Hz.
That makes the more flexible than a simple dry-contact acquisition card. However, filtering and pulse-count functions should be selected according to the actual field signal. A 32 ms debounce setting that is perfectly acceptable for a valve limit switch can be completely inappropriate for a fast pulse signal.
Termination Assembly Selection
The TA determines the field interface.
Schneider’s current documentation identifies several termination options, including:
- RH916CA — 32-channel 30 VDC voltage monitor
- RH916XZ — 32-channel 24 VDC contact sense
- RH916YA — 32-channel 132 VAC/150 VDC voltage monitor with channel isolation
- RH916YB — 32-channel 132 VAC/150 VDC contact sense with external excitation
- RH916PU — 32-channel 240 VAC voltage monitor with channel isolation
- RH916QA — 32-channel 240 VAC contact sense with external excitation
The current specification also documents specialized TAs for migration from 100 Series FBM07, FBM08, FBM20, and FBM24 variants.
This is one of the most important procurement checks for an .
Do not order only by “32-channel digital input.”
100 Series Migration
One reason the remains relevant in brownfield Foxboro installations is its ability to emulate selected 100 Series I/O functions through the appropriate termination hardware.
A single can handle the I/O communication for both a migrated 100 Series main FBM and its expansion TA. Where additional field terminals are needed, a second TA is connected as an expansion TA through the appropriate Type 6 cable.
Schneider also provides a Termination Assembly Adapter option for certain 100 Series upgrade applications. This can reduce the amount of field-wiring disruption during a migration project.
The practical engineering rule is simple: identify the legacy FBM being replaced before selecting the TA.
Redundant Architecture
The can operate as either:
- A single discrete input module
- A redundant pair of two modules
For redundancy, the two modules occupy adjacent odd/even baseplate positions, such as positions 1/2, 3/4, 5/6, or 7/8. The RH926ZY redundant adapter provides the common termination-cable interface.
The field input current is doubled when two modules are operating redundantly. Contact-sense power from the two modules is diode-OR’d in the redundant adapter, providing redundant excitation for applicable contact-sense configurations.
The control system uses the associated redundant digital-input logic to validate the two module readings and select the higher-quality signal.
This is module-level redundancy—not simply a second copy of the same software point.
Fieldbus Communication
The communicates with its associated Fieldbus Communications Module or Control Processor through the 2 Mbps Module Fieldbus.
Both Fieldbus paths, A and B, are accepted. If one path becomes unsuccessful or is switched at the system level, the continues communication through the active path.
For troubleshooting, separate three different failure domains:
- Field device or contact circuit
- /TA signal path
- Module Fieldbus/controller path
A healthy LED does not prove that all three are healthy.
Sequence of Events and Logic Functions
The can support software functions including:
- Discrete Input
- Ladder Logic
- Pulse Count
- Sequence of Events
Input filter time and fail-safe configuration are available as configurable options.
For Sequence of Events applications, Foxboro documentation states that the SOE software package can acquire, store, display, and report digital-input events. With optional GPS-based time synchronization, acquisition across control processors can reach intervals of up to 1 ms depending on the signal source.
That capability should not be interpreted as a blanket 1 ms hardware response specification for every field signal. The actual timing chain depends on the input source, TA, filtering, SOE configuration, Fieldbus, and control-system architecture.
Isolation and Safety
The base architecture is described as having 32 group-isolated channels. Certain termination assemblies provide additional channel isolation, while other TAs use group isolation.
For specified group-isolated combinations, the module/TA arrangement can withstand 600 VAC for one minute between the isolated group and ground.
