The Yokogawa ST2#D, also cataloged as the ST2 Digital Input/Output Module, operates as a dedicated hardware component for discrete signal conditioning and logic state monitoring within Yokogawa DCS platforms.

Hardware Specifications

Process Control and Signal Connectivity

The module utilizes 4-20 mA HART loop protocol standards for compatible analog segments, while facilitating robust channel-to-channel isolation for all discrete inputs. Integrated circuitry provides cold junction compensation (CJC) for associated thermocouple loops, ensuring that on-off contact signals from limit switches and push buttons remain decoupled from system noise. This electrical isolation prevents potential ground loops across the DCS backplane.

Frequently Asked Questions

Q: Does the ST2#D support hot-swapping while the DCS backplane is powered?

A: No. Power must be removed from the specific rack segment before extraction or installation to avoid potential electrical faults on the communication bus.

Q: Are the LED indicators configurable for different logic states?

A: No. The LEDs are hardwired to reflect the physical state of the internal relay coils; they indicate active relay operation status only and cannot be reprogrammed.

Field Installation Guidelines

• Cabinet Mounting: The unit is designed for standard rack-mount installation. Ensure the chassis is securely fastened to the rack rails to mitigate mechanical vibration.
• Grounding Protocols: Connect the module chassis to the system common ground rail using a low-impedance copper conductor to prevent floating potentials.
• Wiring Separation: Maintain a minimum separation of 10 cm between high-voltage AC power wiring and low-voltage signal cabling to reduce electromagnetic interference on the discrete inputs.
• Signal Termination: Ensure all field wiring is properly labeled. When connecting limit switch contacts, verify the loop continuity before powering the module to prevent improper state detection.