Speed Sensor

    Speed Sensor

    Woodward Speed Sensors

    SIL-3 Speed Sensors for Safety Systems


    These speed sensors are designed for use in SIL-3, SIL-2, or SIL-1 (safety integrity level) rated turbine or engine safety systems. When applied with a SIL rated logic solver and final element, users can easily create an overspeed safety instrumented function (SIF) which meets the required safety integrity level for the specific application.

    Rotating machinery requires speed sensing for rotor control, monitoring, and safety.  Speed sensing is accomplished using a variety of technologies. Variable-reluctance based MPUs (magnetic pickups) are commonly selected because of their simplicity, reliability, and low cost. MPUs are passive probes in the sense that there are no active signal conditioning electronics in the probe. VR (passive) sensors also do not require an external supply, simplifying the overall system and increasing system reliability values.

    To simplify application and installation concerns, these sensors have been validated to be directly compatible with Woodward’s ProTech® and MicroNet™ safety logic solvers when used in SIL-3 or SIL-2 certified safety systems, including:

    ·        ProTech-GII—Overspeed Detection System (SIL-3 certified)

    ·        ProTech-SX—Simplex Safety Logic Solver (SIL-2 certified)

    ·        ProTechTPS—Safety Logic Solver including Overspeed Detection (SIL-3certified)

    ·        MSM—MicroNet Safety Logic Solver (SIL-3 certified)

    These sensors are single-channel, variable-reluctance speed sensors consisting of a single inductive coil and a permanent magnet.  A ferrous gear tooth passing the sensor pole piece changes the magnetic field strength, inducing an AC voltage. The frequency of the output signal is proportional to the velocity of the gear tooth passing the sensor’s pole piece. The amplitude of the signal depends on the following:

    ·        Angular speed

    ·        Air gap between sensor face (pole piece) and target (gear tooth)

    ·        Target (gear tooth) geometry

    ·        Target (gear tooth) ferrous material properties

    ·        Load impedance of the electrical circuit used to sense output signal

    Depending on the application, these sensors can be ordered with imperial or metric threads and different thread lengths (determined by part number).




    These sensors have been validated for the following EMC conditions. Tests have been performed with increased

    requirements for safety products with either a longer test time or a greater number of test impulses (according to IEC



    Electrostatic discharge according to IEC 61000-4-2 and IEC 61326-3-1:

    ·        Up to ±8 kV air discharge

    ·        Up to ±6 kV contact discharge


    Electrical fast transients/bursts according to IEC 61000-4-4 and IEC 61326-3-1 direct coupling:

    ·        Up to ±2 kV peak, 5/50 ns, 5 kHz, 75 ms


    Surges according to IEC 61000-4-5 and IEC 61326-3-1:

    ·        ±2 kV 1.2/50 μs (line to ground)

    ·        ±1 kV 1.2/50 μs (line to line)



    These sensors are certified by TÜV SÜD Product Service GmbH to be used in SIL-2 and SIL-3 applications according to IEC 61508, IEC 61511, and ANSI/ISA 84.00.01.  TÜV’s SIL certificate and corresponding report can be provided by Woodward upon request.  The sensors are designed to be integrated into a safety-related system or subsystem.  Voting between individual sensors is required in accordance with IEC 61508 SIL2/SIL3 and ISO 13849-1 CAT 3 PL e.   Impedance measurement to detect open circuit and channel trips shall be realized in accordance to IEC 61508 SIL2/SIL3 and ISO 13849-1 CAT 3 PL e.


    Temperature & Humidity 

    ·        Operating temperature range of entire sensor: –40 °C to +150 °C

    ·        Storage temperature range of entire sensor: –40 °C to +150 °C

    ·        Relative humidity in ambient atmosphere: 95% maximum


    Vibration & Shock Immunity

    ·        Sine sweep: ±0.35 mm in the range 5 to 57 Hz, 5G in the range of 57 to 2000 Hz, 1 oct/min, 10 cycles according to IEC 60068-2-6

    ·        Noise: 0.0125 g²/Hz in the range of 5 to 2000 Hz, 30 min/axis according to IEC 60068-2-64, 50 g for 11 ms, half sine wave, 3 shocks + and – for 3 axes, 18 shocks total according to IEC 60068-2-27