AI-Tek 70085 Passive Speed Sensors

Technical Dossier

Product Details And Specifications

AI-Tek 70085 Series: Comprehensive Module Range and Technical Overview

The AI-Tek 70085 series of passive speed sensors occupies a well-established position in global heavy industry installations, including petrochemical refineries, nuclear power facilities, pulp and paper mills, steel rolling mills, and offshore platforms. These variable reluctance (VR) sensors operate without an internal power supply, generating a sinusoidal AC voltage signal proportional to the rotational speed of a ferromagnetic target wheel. Their passive architecture eliminates failure modes associated with active electronics, making them a preferred choice for safety-critical rotating machinery monitoring — turbines, compressors, pumps, fans, and conveyor drives — where signal reliability over decades of service is a primary specification requirement.

The 70085 series is manufactured by AI-Tek Instruments (formerly known as Airpax / Electro Corporation), a U.S.-based OEM with a long-standing catalog in industrial tachometry and speed sensing. The series covers a broad range of connector configurations, cable lengths, thread sizes, and temperature ratings, allowing direct cross-referencing against legacy installations without mechanical modification.

The Evolution of 70085 Architecture

The 70085 series traces its lineage to the Electro Corporation variable reluctance sensor designs of the 1970s, which were adopted widely in the first generation of DCS-integrated turbine control systems. When AI-Tek Instruments absorbed the Electro Corporation product line, the 70085 numbering convention was retained to preserve backward compatibility with existing plant documentation, spare parts lists, and DCS I/O wiring schedules.

Early 70085 variants used a two-wire flying lead output with a simple threaded body (typically 3/8-24 UNF or M18x1.5), designed for direct insertion into proximity housings on gear teeth or toothed wheels. Subsequent revisions introduced MIL-spec connector terminations (MS3106 series), extended temperature ratings (–55°C to +150°C), and potted construction for IP67 ingress protection. The current catalog spans both legacy connector types and modern M12 circular connector variants, ensuring compatibility across control system generations from Honeywell TDC 3000, Foxboro I/A Series, ABB Advant, and Emerson DeltaV installations.

As the 70085 series has entered the mature/end-of-life phase of its product lifecycle, AI-Tek no longer actively promotes new design-ins. However, the installed base across global process industries remains substantial, and demand for exact-replacement spare parts continues. DriveKNMS maintains a dedicated inventory buffer for this series to support long-term maintenance contracts and unplanned outage requirements.

AI-Tek 70085 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked models within the AI-Tek 70085 passive speed sensor series. Each model is a variable reluctance sensor; functional differentiation is driven by connector type, cable configuration, thread specification, and temperature/environmental rating.

70085-1010-056: Passive VR speed sensor, 2-wire flying lead, 3/8-24 UNF thread, standard temperature range, general industrial use.
70085-1010-057: Passive VR speed sensor, 2-wire flying lead, extended 12-inch cable, 3/8-24 UNF thread, panel-mount compatible.
70085-1010-058: Passive VR speed sensor, 2-wire output, M18x1.5 metric thread body, IP65 rated, European plant standard.
70085-1010-060: Passive VR speed sensor, MS3106 MIL-spec connector, 3/8-24 UNF, potted construction, vibration-resistant.
70085-1010-061: Passive VR speed sensor, MS3106 connector, extended temperature –55°C to +150°C, suitable for turbine housings.
70085-1010-062: Passive VR speed sensor, MS3106 connector, M18x1.5 thread, high-temperature potted, refinery-grade.
70085-1010-065: Passive VR speed sensor, 2-wire shielded cable, 3/8-24 UNF, EMI-shielded for variable frequency drive environments.
70085-1010-070: Passive VR speed sensor, M12 4-pin circular connector, 3/8-24 UNF, IP67, modern DCS retrofit compatible.
70085-1010-072: Passive VR speed sensor, M12 connector, M18x1.5 thread, IP67, stainless steel body option.
70085-1010-075: Passive VR speed sensor, 2-wire, 3/8-24 UNF, extended 36-inch armored cable, hazardous area rated.
70085-1010-080: Passive VR speed sensor, MS3106 connector, 1/2-20 UNF thread, heavy-duty compressor and pump shaft monitoring.
70085-1010-082: Passive VR speed sensor, MS3106 connector, 1/2-20 UNF, high-output coil winding, low tooth-count target wheels.
70085-1010-085: Passive VR speed sensor, 2-wire flying lead, 1/2-20 UNF, standard temperature, paper mill and steel mill service.
70085-1010-090: Passive VR speed sensor, M12 connector, 1/2-20 UNF, IP67, nuclear plant qualified documentation available.
70085-1010-095: Passive VR speed sensor, MS3106 connector, M24x1.5 metric thread, high-vibration offshore platform specification.
70085-1010-100: Passive VR speed sensor, 2-wire, M24x1.5 thread, extended temperature, subsea and marine drive monitoring.

Sourcing Hard-to-Find & Obsolete AI-Tek 70085 Parts

The 70085 series is no longer in active production at AI-Tek Instruments. Lead times through standard distribution channels are extended or indefinite for many sub-variants. DriveKNMS operates a dedicated lifecycle extension program for this series, maintaining physical stock of both common and low-volume variants sourced through authorized surplus channels, OEM overstock acquisitions, and decommissioned plant asset recovery.

For end-users operating under long-term maintenance agreements (LTMA) or multi-year service contracts, DriveKNMS can provide consignment stock arrangements, ensuring that critical 70085 replacement sensors are available on-site or within 24-hour dispatch. Cross-reference support is available for legacy part numbers from Electro Corporation, Airpax, and early AI-Tek catalog revisions that predate the current 70085-XXXX-XXX numbering format. Functional equivalents and dimensional cross-references are verified against original OEM datasheets prior to shipment.

Quality Control for the AI-Tek 70085 Range

Each 70085 series sensor processed through DriveKNMS undergoes a structured verification protocol prior to dispatch. Coil resistance is measured against the OEM-specified nominal value (typically 150–2,500 Ω depending on variant) using a calibrated LCR meter. Insulation resistance between the coil winding and the sensor body is tested at 500 VDC to confirm potting integrity and absence of moisture ingress. Output voltage linearity is verified on a calibrated gear tooth test rig, confirming that the sensor generates a clean sinusoidal signal across the specified RPM range without harmonic distortion or signal dropout.

Connector terminations are inspected for pin corrosion, contact retention force, and shell thread integrity. For MS3106-terminated variants, coupling ring torque is verified. For M12 variants, IP67 sealing is confirmed by visual inspection of the O-ring and overmold condition. All units are tagged with a DriveKNMS inspection reference number traceable to the test record, and documentation packages (test report, datasheet, certificate of conformance) are available upon request for nuclear and safety-instrumented system (SIS) applications.