8271-485 - Two-Channel Digital Speed Switch

SPECIFICATIONS:

Part Number: 8271-485
Manufacturer: Woodward
Series: Digital Speed Switch
Product Type: Dual-Channel Speed Switch
Input Signal: Magnetic Pickup (MPU) or Proximity Probe
Channels: 2 Independent Relay Channels
Input Voltage: 18–40 Vdc (24 Vdc Nominal)
Frequency Range: 10 Hz to 25,000 Hz
Output Type: Form C Relay Contacts
Operating Temperature: -40 °C to +70 °C
Mounting: DIN Rail or Chassis Mounted
Availability: In Stock

FUNCTIONAL DESCRIPTION:

The 8271-485 is a high-precision Two-Channel Digital Speed Switch designed for the protection and sequencing of rotating machinery. Its primary role is to monitor the rotational frequency of an engine or turbine via a Magnetic Pickup (MPU) and trigger internal relays at user-defined speed setpoints. This module is essential for automated control functions such as crank termination, underspeed/overspeed protection, and auxiliary equipment sequencing (e.g., turning on oil pumps or engaging clutches at specific RPMs).

DUAL-CHANNEL VERSATILITY:

Featuring two completely independent channels, the Two-Channel Digital Speed Switch allows for the configuration of two distinct speed events. For example, Channel 1 can be set for Crank Termination to automatically disengage the starter motor once the engine reaches its self-sustaining speed, while Channel 2 can be set for Overspeed Protection to trigger an emergency shutdown if the machine exceeds its safe operating limit. The digital architecture ensures high accuracy and eliminates the drift often associated with older analog speed switches.

CALIBRATION AND SAFETY:

The 8271-485 is designed for ease of use in the field. Setpoints are typically adjusted via internal switches or potentiometers, allowing for precise calibration without the need for complex software in many applications. The module also features built-in safety diagnostics, including signal loss detection. If the speed signal from the MPU is lost while the machine is running, the switch can be configured to trigger a fault relay, preventing the machine from operating in an unprotected state.

AVAILABILITY AND SUPPORT:

World of Controls offers the 8271-485 Digital Speed Switch in both unused and professionally rebuilt conditions. Every unit is subjected to rigorous bench testing across its full frequency range to ensure relay transition accuracy and signal integrity. We provide a comprehensive warranty and 24/7 technical support to assist with wiring, setpoint calibration, and troubleshooting. Contact us today for pricing, availability, and expedited global shipping to keep your critical assets protected.

FREQUENTLY ASKED QUESTIONS:

What is the Woodward 8271-485?

It is a 2-channel Digital Speed Switch used in Woodward control systems to monitor machine RPM. It triggers internal relays at specific frequency setpoints to manage automated sequences like crank termination or to provide safety-critical overspeed protection.

Can I use one sensor for both channels?

Yes. The 8271-485 is designed to accept a single MPU or Proximity sensor input and use that frequency signal to drive both independent relay setpoints.

How do I test the overspeed setpoint without overspeeding the engine?

The module typically includes a Test or Verify mode. By using a frequency generator to simulate the MPU signal, maintenance personnel can verify the exact relay trip point without actually putting the turbine or engine at risk.

What happens if the speed sensor fails?

The 8271-485 includes a signal failure sensing circuit. If the input frequency drops to zero unexpectedly or the signal strength becomes insufficient, the module can flag a fault, ensuring the system does not remain in a potentially dangerous state.