Product Overview
The AI-TEK 70085-1010-037 is a high-sensitivity passive variable reluctance speed sensor, a magnetic pickup that converts the rotation of a ferrous target — a gear tooth, tone wheel, shaft keyway or bolt head — directly into an AC voltage without needing any external power supply. Manufactured by AI-TEK Instruments, LLC, formerly marketed under the Airpax brand, the AI-TEK 70085-1010-037 belongs to the 70085 family of passive speed sensors that has been used for decades in control and protection circuits, from aircraft engine controls operating near 425 °C to automobile wheel hubs exposed to severe shock and vibration. Inside its stainless steel threaded barrel are only three elements: a permanent magnet, a pole piece and a coil of wire, which is why the sensor is so difficult to break and so easy to trust.
When a ferrous target passes the sensor tip, it alternately increases and decreases the reluctance of the magnetic circuit, and this disturbance induces a voltage in the coil whose frequency is directly proportional to rotational speed and whose amplitude rises with surface speed. The AI-TEK 70085-1010-037 therefore provides both a speed signal — the pulse frequency counted by a tachometer, governor or PLC high-speed counter — and, because output grows with speed, a useful indication of whether the machine is turning at all. Fitted with a 3/8-24 UNF thread and integral lead wires, the AI-TEK 70085-1010-037 screws into a drilled and tapped hole, is set with a small air gap to the target, and then runs for years without adjustment, making it a standard choice for overspeed protection, zero-speed detection and speed feedback on turbines, compressors, pumps, gearboxes and engines.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 70085-1010-037 |
| Manufacturer | AI-TEK Instruments, LLC (formerly Airpax), USA |
| Product Type | High Sensitivity Passive (VR) Speed Sensor / Magnetic Pickup |
| Sensor Technology | Variable reluctance, self-generating (no external power required) |
| Body Shape | Cylindrical threaded barrel, stainless steel housing |
| Mounting Thread | 3/8-24 UNF (fine thread) |
| Output Signal | AC voltage, frequency proportional to rotational speed |
| Typical Output Voltage | Approximately 13 V peak-to-peak at rated surface speed (speed and gap dependent) |
| DC Resistance | Approximately 190 ohms maximum |
| Output Polarity | White lead positive (housing ground identified by tracer) |
| Measurement Range | Application dependent, typically usable to approximately 10,000 RPM |
| Target Requirement | Ferrous steel gear, tone wheel, shaft keyway or similar ferrous discontinuity |
| Recommended Air Gap | Approximately 0.005 in to 0.015 in (0.13 mm to 0.38 mm) to the target |
| Operating Temperature | –55 °C to +107 °C (–67 °F to +225 °F) |
| Electrical Connection | Integral lead wires, approximately 18 in (457 mm) standard |
| Approximate Weight | Approximately 0.14 kg (5 oz) or less |
Main Features and Advantages
Self-powered operation: The AI-TEK 70085-1010-037 generates its own signal from the motion of the target, so there is no supply wiring, no excitation card and no polarity-sensitive electronics at the sensing point. This is a genuine advantage in remote skids, hazardous areas and machine-mounted junction boxes, where running power to a sensor is often more expensive than the sensor itself, and it also removes a whole class of failure modes associated with active electronics.
No moving parts and long service life: With only a magnet, pole piece and coil inside a sealed stainless steel body, there is nothing to wear, nothing to contact and nothing to lubricate. The AI-TEK 70085-1010-037 is therefore specified for continuous-duty service on machines where access is poor and a sensor failure means a production stoppage, and its non-contact principle means measurement accuracy does not degrade with running hours.
Survives heat, shock and contamination: Rated from –55 °C to +107 °C, the AI-TEK 70085-1010-037 works next to turbine casings, engine blocks and compressor cylinders where active sensors with integrated electronics would drift or fail. Its sealed construction resists oil, moisture, dirt and industrial contaminants, and because the sensing element contains no semiconductor, the sensor is largely immune to the electrical noise that plagues long cable runs in plants with variable-frequency drives.
Simple mechanical installation and alignment: The threaded barrel of the AI-TEK 70085-1010-037 screws into a standard tapped hole and is locked with a nut, so axial position — and therefore air gap — can be set precisely and repeatably. Alignment is forgiving, output rises predictably as the gap is reduced, and commissioning is essentially a matter of backing the sensor out until a clean, stable signal is obtained, which keeps installation time short even for technicians unfamiliar with the equipment.
High sensitivity for low-speed and long-cable applications: As a high-sensitivity variant of the 70085 family, the AI-TEK 70085-1010-037 produces usable amplitude at lower surface speeds and over longer cable runs than a general-purpose pickup. This matters on large, slow-turning machines and on installations where the monitor or governor sits far from the measurement point, where a weaker signal would fall below the input threshold of the receiving instrument.
