M18 / M30 Series Metal Sensing Proximity Switches — Three-Wire Type
The M18 / M30 series metal inductive proximity switch is a high-performance cylindrical electromagnetic proximity sensor designed for industrial automation. The series uses DC three-wire power supply, supports NPN / PNP outputs, and detects metal objects without physical contact. Variants include M18 × 35 (shielded), M18 × 55 (unshielded), M30 × 50 (shielded) and M30 × 60 (unshielded), with detection distances from 5 mm to 40 mm. The housing is stainless steel or copper nickel-plated for corrosion resistance, and a built-in LED makes status monitoring straightforward.
Product Introduction
The DAIDISIKE M18 & M30 series metal inductive proximity switch is a high-performance cylindrical electromagnetic proximity sensor designed for industrial automation applications. The series uses DC three-wire power supply, supports NPN and PNP output modes, and detects metal objects without physical contact. It complies with RoHS standards, has an IP67 protection rating, and is suitable for harsh industrial environments.
The series includes M18 and M30 variants — M18 × 35 (shielded), M18 × 55 (unshielded), M30 × 50 (shielded) and M30 × 60 (unshielded) — with detection distances ranging from 5 mm to 40 mm. The sensor housing is made of stainless steel or copper nickel-plated material for high corrosion resistance, and is equipped with an LED indicator for easy status monitoring. The product is widely used in mechanical manufacturing, automotive industry, food processing and similar fields for object position detection, counting and limit control.
Specifications — M18 vs M30
| Parameter | M18 Series | M30 Series |
|---|---|---|
| Brand | DAIDISIKE | DAIDISIKE |
| Product name | M18 Metal Inductive Proximity Switch | M30 Metal Inductive Proximity Switch |
| Installation method | Shielded (Flush) / Unshielded (Non-flush) | Shielded (Flush) / Unshielded (Non-flush) |
| Detection distance (std iron target) | Shielded: 5 / 8 / 12 mm · Unshielded: 8 / 12 / 16 / 20 mm | Shielded: 10 / 15 mm · Unshielded: 15 / 20 / 25 / 40 mm |
| Output mode | NPN / PNP — NO / NC / NO+NC | NPN / PNP — NO / NC / NO+NC |
| Operating voltage | 10 – 30 V DC (some models support 5 – 40 V DC) | 10 – 30 V DC (some models support 20 – 250 V AC / 10 – 300 V DC) |
| Maximum load current | 150 mA / 200 mA / 300 mA | 200 mA / 300 mA |
| No-load current | < 10 mA | < 15 mA |
| Voltage drop | < 1.5 V / < 2 V | < 2 V / < 3 V |
| Leakage current | < 0.01 mA | < 0.1 mA |
| Switching frequency | 50 Hz / 100 Hz / 500 Hz / 1000 Hz / 2000 Hz | 50 Hz / 90 Hz / 100 Hz / 200 Hz / 500 Hz |
| Response time | < 0.5 ms / < 1 ms | < 1 ms / < 2 ms |
| Switch hysteresis | < 15 % (Sr) | < 15 % (Sr) |
| Repeatability | < 3.0 % (Sr) / < 5 % | < 3.0 % (Sr) / < 5 % |
| Indicator light | Yellow LED — on when detecting | Yellow LED — on when detecting |
| Protection rating | IP67 / IP68 | IP67 / IP68 |
| Operating temperature | −25 °C to +70 °C / −40 °C to +85 °C | −25 °C to +70 °C / −40 °C to +85 °C |
| Storage temperature | −40 °C to +85 °C | −40 °C to +85 °C |
| Temperature drift | < 10 % (Sr) | < 10 % (Sr) |
| Short-circuit protection | Yes | Yes |
| Reverse-polarity protection | Yes | Yes |
| Overload protection point | 180 mA / 220 mA | 220 mA / 350 mA |
| Shell material | Stainless steel / copper nickel-plating / brass nickel-plating | Stainless steel / copper nickel-plating / brass nickel-plating |
| Sensing-face material | PBT / Polyester | PBT / Polyester |
| Standard wire length | 2 m (PVC cable) | 2 m (PVC cable) |
| Connection method | Cable / M12 connector | Cable / M12 connector |
| Dimensions | M18 × 35 – 50 mm (shielded) · M18 × 55 – 65 mm (unshielded) | M30 × 50 – 60 mm (shielded) · M30 × 60 – 80 mm (unshielded) |
| Weight | ≈ 50 – 100 g | ≈ 100 – 150 g |
| Compliance | RoHS · CE · UL | RoHS · CE · UL |
| Vibration resistance | 10 – 55 Hz, 1 mm amplitude | 10 – 55 Hz, 1 mm amplitude |
| Shock resistance | 500 m/s², 10 times | 500 m/s², 10 times |
| Electromagnetic compatibility | IEC 61000 series | IEC 61000 series |
Technical Parameters
Detection distance depends on installation method, target material, and environmental factors. Values listed are typical for standard iron targets with correction factors for other metals — stainless steel 0.9, aluminum 0.4, brass 0.5, copper 0.4. Power supply is DC 10 – 30 V three-wire (brown = V+, blue = 0 V, black = output); some models support AC / DC dual power. Output types are NPN (open-collector, common positive, output negative) or PNP (open-collector, common negative, output positive), with NO / NC / NO+NC combinations.
The sensor offers high switching frequency — up to 2000 Hz on M18 and 500 Hz on M30 — suitable for high-speed applications. Response time is < 0.5 – 2 ms, ensuring real-time detection. Protection features include short-circuit protection (auto-reset), reverse-polarity protection, overload protection (trigger point 180 – 350 mA), and surge suppression. Environmental adaptability is strong: temperature drift < 10 %, repeatability < 3 – 5 %. Selected models support analog output options (4 – 20 mA or 0 – 10 V) for continuous distance measurement. Electromagnetic compatibility complies with IEC 61000 standards.
Working Principle
The inductive proximity sensor is based on the law of electromagnetic induction (Faraday). Internally it contains a high-frequency oscillator made up of an inductive coil (LC oscillation circuit), oscillation circuit and output amplifier. The coil generates an alternating electromagnetic field (typically hundreds of kHz to MHz). When a conductive metal object enters this field, it induces eddy currents on the object surface that produce a counter-field, absorbing energy from the original field — causing the oscillator amplitude to attenuate, frequency to shift or stop oscillating. The detection circuit (e.g. a Schmitt trigger) captures this change and converts it into a digital high / low switching signal.
Detection distance is influenced by the conductivity and permeability of the target — iron (high permeability) has the longest sensing distance; non-ferrous metals such as aluminum and copper reach roughly 40 – 50 % of iron's distance. The sensor does not detect non-metallic objects, has strong anti-interference (electromagnetic shielding), no contact wear, and resists oil and dirt. Shielded sensors concentrate the field at the front and are suitable for embedded installation; unshielded types have a broader field and longer sensing distance but require more side clearance.
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