AI-Tek 70085-1010-205 Speed Sensor – 70085 Series

AI-Tek 70085-1010-205: Variable Reluctance Speed Sensor for High-Reliability Industrial Speed Measurement

The AI-Tek 70085-1010-205 is a self-generating passive magnetic pickup (variable reluctance type) engineered for continuous-duty speed measurement in turbomachinery, reciprocating engines, and rotating process equipment. Unlike active Hall-effect sensors, this device requires no external excitation voltage — the coil-and-magnet assembly generates a sinusoidal AC voltage directly from the passage of ferrous gear teeth through its magnetic field. The amplitude of the output signal scales with rotational velocity, while the frequency is a direct function of tooth-pass rate, making it inherently linear and immune to supply voltage variation.

The -205 suffix designates a factory-terminated integral cable of 2.05 m, eliminating field splicing at the sensor body — a common failure point in high-vibration installations. The stainless steel housing provides mechanical resistance to hydraulic fluid, lubricating oil, and mild chemical exposure. Thread engagement depth and air gap between sensor tip and gear tooth crown are the two primary installation variables that govern signal amplitude; AI-Tek specifies a nominal air gap of 0.25–1.27 mm (0.010–0.050 in) for the 70085 series, with output voltage rising steeply as gap decreases.

In control system architectures, the 70085-1010-205 feeds directly into frequency-to-voltage converters, PLC high-speed counter modules, or DCS speed input cards. Its sinusoidal output is compatible with zero-crossing detection circuits, which extract pulse frequency with sub-millisecond resolution. This characteristic makes the sensor suitable for overspeed protection relays, governor feedback loops, and process historians requiring high-fidelity shaft speed data.

siemensplc.com maintains verified stock of the AI-Tek 70085-1010-205 sourced through traceable supply channels. Each unit is inspected for physical integrity and connector condition prior to dispatch. Orders ship from Xiamen, China via DHL Express, FedEx International Priority, or freight consolidation, with typical transit times of 3–7 business days to major industrial hubs in Southeast Asia, the Middle East, and Europe.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

Electromagnetic Transduction Mechanism: The 70085-1010-205 operates on Faraday’s law of electromagnetic induction. A permanent magnet within the sensor body creates a static flux field that extends through the sensor tip. As each ferrous gear tooth passes through this field, the reluctance of the magnetic circuit changes, inducing a voltage in the wound coil proportional to the rate of flux change (dΦ/dt). At low RPM, the rate of change is slow and output amplitude is low — typically 0.5–2 V peak at speeds below 100 RPM. At operational speeds (500–10,000 RPM), output amplitude rises to 10–80 V peak depending on gear geometry and air gap, providing a robust signal margin well above the noise floor of standard signal conditioning inputs.

EMC Design Characteristics: The passive architecture inherently rejects common-mode electrical noise. Because the sensor generates its own signal voltage, there is no DC supply rail to couple switching transients from adjacent VFDs or solenoid drivers. The twisted-pair integral cable provides differential signal transmission, and the stainless steel housing acts as a partial Faraday shield for the coil assembly. In installations with severe electromagnetic interference, a shielded cable extension with drain wire grounded at the signal conditioner end (single-point ground) is recommended to prevent ground loop currents from corrupting the sinusoidal waveform.

Mechanical Robustness: The 70085 series housing is machined from corrosion-resistant stainless steel with a hex wrench flat for torque-controlled installation. The integral cable exit is sealed with an elastomeric compound rated to IP67, preventing ingress of lubricating oil, coolant, and wash-down water. The sensor tip geometry is optimized for M18 mounting bosses common in turbine bearing housings and engine timing covers, with a thread engagement depth sufficient to maintain air gap stability under thermal expansion cycles of ±0.05 mm.

System Integration Benefits

• Zero-power operation: No 24 VDC supply wiring required at the sensor, reducing cable count in junction boxes and eliminating supply-side fault modes that affect active sensors.
• Direct PLC counter module compatibility: Sinusoidal output interfaces directly with Siemens FM350-1/FM351, Allen-Bradley 1756-HSC, and equivalent high-speed counter modules via zero-crossing detection — no intermediate signal converter needed in most installations.
• Deterministic frequency output: Tooth-pass frequency is a mathematically exact function of shaft RPM and gear tooth count, enabling PLC ladder logic to compute speed with single-scan-cycle latency without floating-point approximation errors.
• Wide dynamic speed range: Functional from approximately 60 RPM (minimum voltage threshold for most signal conditioners) to beyond 15,000 RPM, covering the full operating envelope of gas turbines, diesel engines, and high-speed centrifugal pumps.
• Overspeed relay integration: The analog amplitude characteristic of the sinusoidal output allows dedicated overspeed relays (e.g., Woodward 9907-series, Bently Nevada 3500/25) to detect both frequency (speed) and amplitude anomalies, providing a secondary diagnostic channel beyond simple frequency counting.
• Diagnostic transparency: Signal amplitude degradation over time — caused by increasing air gap from bearing wear or gear tooth erosion — is directly observable on a process historian trend, enabling predictive maintenance scheduling before signal loss occurs.
• Thermal stability across process extremes: Rated to −55 °C / +150 °C, the sensor maintains coil resistance within ±15% across the full temperature range, ensuring consistent signal amplitude in arctic outdoor installations and engine compartment environments without recalibration.
• Redundancy architecture support: Two 70085-1010-205 sensors can be mounted 180° apart on the same gear wheel and wired to separate input channels, providing 1oo2 (one-out-of-two) or 2oo2 voting logic in SIL-rated overspeed protection systems without additional hardware.
• Long cable drive capability: Coil impedance of ~130–200 Ω allows signal transmission over cable runs up to 300 m with standard shielded twisted-pair (0.5 mm²) without significant amplitude attenuation, supporting remote sensor placement in large turbine halls.

Quality Assurance & Global Logistics

Every AI-Tek 70085-1010-205 unit supplied by siemensplc.com is sourced through verified distribution channels with full part traceability. Pre-shipment inspection covers physical housing integrity, cable jacket condition, connector pin seating, and coil continuity measurement. Units failing any inspection criterion are quarantined and not dispatched.

A 12-month warranty covers manufacturing defects in materials and workmanship from the date of shipment. Certificate of Conformance (CoC) is available upon request for quality management system documentation requirements.

Logistics operations are based in Xiamen, China — a major international freight hub with direct air cargo connections to Singapore, Dubai, Frankfurt, Los Angeles, and Sydney. Standard export documentation includes commercial invoice, packing list, and HS Code 8543.70.9000 classification. DHL Express and FedEx International Priority are the primary carriers for single-unit and small-quantity orders, with typical door-to-door transit of 3–7 business days. Freight consolidation via sea is available for bulk orders exceeding 50 kg. All shipments are fully insured and tracked from dispatch to delivery confirmation.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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