1 Year Warranty
Description
WOODWARD A8516-038: Engine Speed Sensor or Magnetic Pickup
Critical Speed Sensing Component for Prime Mover Control Systems
The WOODWARD A8516-038 is a magnetic pickup (MPU) or passive speed sensor, a fundamental component used to detect the rotational speed (RPM) of engines, turbines, or other rotating machinery. It is a key input device for Woodward engine governors, control systems, and protection devices.
Product Overview
This sensor is a passive, two-wire device that generates a small alternating current (AC) voltage signal when a ferrous metal target (such as a gear tooth) passes through its magnetic field. The frequency of this AC signal is directly proportional to the rotational speed of the target. Woodward A8516 series sensors are known for their durability and reliability in harsh industrial environments.
Core Features & Benefits
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Passive & Rugged Design: Contains no active electronics, making it highly resistant to extreme temperatures, vibration, and electrical noise. Requires no external power supply.
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Reliable Speed Detection: Generates a clean, sinusoidal voltage signal ideal for digital speed detection circuits in Woodward governors and speed switches.
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Wide Operating Gap: Allows for a reasonable air gap between the sensor tip and the target gear, simplifying installation and accommodating minor mechanical run-out.
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Environmentally Sealed: Typically features a stainless steel body with a sealed, epoxy-potted connector or cable exit, providing protection against moisture, oil, and contaminants.
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Temperature Resistant: Designed to operate reliably across the wide temperature ranges found in engine rooms and industrial facilities.
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Direct Compatibility: Engineered to provide the correct signal characteristics (voltage and waveform) for Woodward control systems, ensuring accurate speed measurement.
A8516-040
Technical Specifications (Typical for A8516 Series)
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Parameter
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Specification / Description
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Manufacturer Part Number
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Woodward A8516-038
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Type
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Passive Magnetic Speed Sensor (Magnetic Pickup / MPU)
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Operating Principle
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Variable Reluctance. Generates an AC voltage proportional to the rate of change of magnetic flux.
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Output Signal
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AC sine wave (approximately). Amplitude increases with speed and decreases with air gap.
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Target
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A ferrous metal gear (typically 60-tooth or other specified). Must have a minimum tooth height and width.
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Air Gap (Typical)
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0.010 to 0.040 inches (0.25 to 1.0 mm) from the tip of the sensor to the top of the gear tooth. Critical for proper signal strength.
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Pole Piece
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The **”-038″ suffix often specifies the thread size and length of the sensor body (e.g., 3/8″-24 UNF thread).
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Connector / Cable
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Likely a 2-pin, military-style (MS) connector or a integrated, shielded cable with stripped leads. The exact termination is defined by the suffix.
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Temperature Range
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-40°C to +150°C (-40°F to +300°F) or similar.
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Resistance (Coil)
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Typically 100 to 500 ohms (measured between the two pins at room temperature).
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Output Voltage
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Varies with speed, gap, and gear tooth size. Can range from <1 VAC at low speed to >50 VAC at high speed.
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Body Material
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Stainless steel.
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System Context & Application
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Role: It is the primary speed feedback device for Woodward control systems such as:
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Governors: UG-8, UG-10, 2301A, 723PLUS, etc.
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Digital Controls: ProAct, EasyGen, NetCon.
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Speed Switches & Monitors: SPM-A, SSL.
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Installation: Mounts radially or axially to a gear on the engine’s flywheel, accessory drive, or dedicated speed sensing gear. The gear must be made of ferromagnetic material (steel).
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Signal Path: The sensor’s two wires connect directly to the speed input terminals on the Woodward controller. The controller internally conditions this signal to determine RPM.
Typical Applications
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Generator Set Control: Measuring engine RPM for governing (frequency control) and overspeed protection.
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Industrial Engine Control: Speed sensing for compressors, pumps, and mechanical drive engines.
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Marine Propulsion: Engine speed feedback for propulsion control systems.
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Turbine Control: Speed sensing for small gas turbines or steam turbines.
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Any rotating equipment where precise speed measurement is required for control or protection.
Installation & Commissioning Notes
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Air Gap is Critical: The gap between the sensor tip and the gear tooth must be set with a non-magnetic feeler gauge while the gear is stationary. An incorrect gap will cause a weak or no signal.
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Gear Specifications: The gear must meet Woodward’s specifications for tooth size, pitch, and material. A common standard is a 60-tooth gear.
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Wiring: Use shielded, twisted-pair cable. Connect the shield at the controller end only to prevent ground loops. Keep sensor wires away from high-voltage cables.
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Signal Verification: During startup, the output voltage (VAC) should be measured with a multimeter. It should increase smoothly with engine speed. Most Woodward controllers require a minimum signal strength (e.g., 1.0 Vrms) for reliable detection.
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Polarity: For two-wire sensors, polarity is generally not critical.
Troubleshooting
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No Speed Reading / Engine Overspeed:
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Check air gap.
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Check sensor resistance (should be within spec; infinite = open coil, 0 = shorted coil).
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Check for broken wires or poor connections at the connector.
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Verify gear is ferrous and rotating.
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Erratic Speed Reading:
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Check for loose sensor mounting.
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Check for excessive gear run-out or damaged teeth.
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Check for electrical noise interference (ensure proper shielding).
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Package Includes
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1 x Woodward A8516-038 Magnetic Speed Sensor.
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May include a mating connector, lock washer, and sealing washer.
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Note: Mounting hardware (nuts) and the target gear are not included.
