Configured for discrete circuit switching in CENTUM CS / CENTUM VP distributed control architectures, the Yokogawa MRO-234*A (MRO-234 SPDT Relay Output Module) provides direct physical/electrical execution.
Suffix Breakdown & Model Matrix
Parameter / Suffix Code
Specification Breakdown
Base Model (MRO-234)
Single Pole Double Throw (SPDT) Relay Output Module
*Revision Code (A)
Style A hardware revision level
Hardware Specifications
Parameter
Specification
Model
MRO-234*A
Brand
Yokogawa
Origin
Japan
Weight
0.5 kg
Dimensions
99 mm x 100 mm x 40 mm
Operating Temp
0 to 55 deg C
Power Consumption
24 VDC system backplane bus draw
Output Type
SPDT relay contacts
Functionality
Discrete contact switching for external electrical circuits
4-20 mA HART Loop Protocol & Channel Isolation
The module incorporates physical contact isolation barriers to decouple sensitive backplane control logic from external high-voltage field switching circuits. Dedicated inductive load suppression networks prevent contact arcing, reducing high-frequency electrical transients that could interfere with adjacent analog field lines operating on the 4-20 mA HART loop protocol. Galvanic separation across individual contact sets maintains signal integrity and prevents common-mode noise propagation within dense cabinet environments.
Frequently Asked Questions
Q: Can the contact outputs on the MRO-234*A be used to switch both AC and DC load circuits?
A: Yes, the dry SPDT relay contacts provide mechanical isolation, allowing switching of either AC or DC external loads within the rated contact voltage and current boundaries.
Q: What grounding precautions should be followed when wiring inductive field loads to the relay contacts?
A: Inductive field loads must be fitted with external transient suppressors (flyback diodes for DC, RC snubbers for AC) directly across the load, and signal cable shields must terminate at the protective earth (PE) bus bar to prevent noise back-coupling.
Field Installation Guidelines
Mount the MRO-234*A module firmly into the designated I/O slot of the control chassis, verifying complete pin engagement of the backplane connector before securing the locking screws to 0.5 Nm torque. Route all field output contact wiring through dedicated wiring channels, maintaining a minimum 150 mm physical separation from sensitive low-level analog input lines. Ground all cable shielding leads to the central protective earth (PE) bus bar using short conductors with a minimum cross-sectional area of 2.5 mm sq. Maintain cabinet ambient temperature between 0 and 55 deg C to ensure relay coil stability.
