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. Each thread size is offered in a 35 mm short body and a 55 mm standard body, in flush (P) or non-flush (T) mounting, with detection distances from 5 mm to 40 mm. The housing is nickel-plated brass 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 has an IP67 protection rating, and is suitable for harsh industrial environments.
The series includes M18 and M30 variants — each thread size in a 35 mm short body and a 55 mm standard body, and each body in flush (P) or non-flush (T) mounting — with detection distances ranging from 5 mm to 40 mm. The sensor housing is made of nickel-plated brass 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 | Flush (P) / Non-flush (T) | Flush (P) / Non-flush (T) |
| Body lengths available | M18×1 × 35 mm (short) · M18×1 × 55 mm (standard) | M30×1.5 × 35 mm (short) · M30×1.5 × 55 mm (flush) / 58 mm (non-flush) |
| Detection distance (std iron target) | Flush: 5 / 8 / 12 mm · Non-flush: 8 / 16 / 20 mm | Flush: 10 / 15 / 22 mm · Non-flush: 15 / 25 / 40 mm |
| Sensing distances on the 35 mm short body | 5 mm (flush) · 8 mm (non-flush) | 10 mm (flush) · 15 mm (non-flush) |
| Output mode | NPN / PNP — NO (code 1) / NC (code 2) | NPN / PNP — NO (code 1) / NC (code 2) |
| Operating voltage | 10 – 30 V DC (three-wire) | 10 – 30 V DC (three-wire) |
| Switching frequency | 1 kHz (5 mm P) / 500 Hz (8 mm P) / 300 Hz (12 mm P) · 700 Hz (8 mm T) / 150 Hz (16 mm T) / 100 Hz (20 mm T) | 500 Hz (10 mm P) / 300 Hz (16 mm P) / 150 Hz (22 mm P) · 400 Hz (15 mm T) / 150 Hz (25 mm T) / 80 Hz (40 mm T) |
| Response time | 0.2 ms (5 mm P) / 0.5 ms (8 mm P) / 0.8 ms (12 mm P) · 0.5 ms (8 mm T) / 1 ms (16 & 20 mm T) | 0.5 ms (10 mm P) / 1 ms (16 & 22 mm P) · 0.5 ms (15 mm T) / 1 ms (25 mm T) / 2 ms (40 mm T) |
| Switch hysteresis | < 15 % (Sr) | < 15 % (Sr) |
| Repeatability | < 3.0 % / < 5.0 % (Sr) | < 3.0 % / < 5.0 % (Sr) |
| Indicator light | LED switching-state indicator | LED switching-state indicator |
| Protection rating | IP67 | IP67 |
| Operating temperature | −25 °C to +70 °C | −25 °C to +70 °C |
| Temperature drift | < 10 % (Sr) | < 10 % (Sr) |
| Short-circuit protection | Yes | Yes |
| Overload protection point | 180 mA | 180 mA |
| Shell material | Nickel-plated brass | Nickel-plated brass |
| Standard wire length | 2 m (longer on request) | 2 m (longer on request) |
| Connection method | Pre-wired cable | Pre-wired cable |
| Maximum load current | 150 mA | 150 mA |
| No-load (idle) current | < 10 mA | < 10 mA |
| Leakage current | < 0.01 mA | < 0.01 mA |
| Voltage drop across sensor | < 1.5 V | < 1.5 V |
| Supply ripple | < 10 % | < 10 % |
| Weight | Contact factory | Contact factory |
| Compliance / certification | Contact factory | Contact factory |
Technical Parameters
Detection distance depends on installation method, target material, and environmental factors. Values listed are rated for a standard iron target; non-ferrous metals such as stainless steel, aluminium, brass and copper reduce the achievable distance. Power supply is DC 10 – 30 V three-wire (brown = V+, blue = 0 V, black = output). This family is three-wire DC only — it does not include 2-wire DC or AC variants. Output types are NPN (open-collector, common positive, output negative) or PNP (open-collector, common negative, output positive), in NO (code 1) or NC (code 2) logic.
Switching frequency ranges from 80 Hz on the M30 40 mm non-flush variant up to 1 kHz on the fastest M18 variant. Response time runs from 0.2 ms (M18, 5 mm flush) to 2 ms (M30, 40 mm non-flush). Protection features include short-circuit protection and an overload current protection point of 180 mA. Environmental adaptability is strong: temperature drift < 10 % (Sr), switching hysteresis < 15 % (Sr), repeatability < 3 – 5 % (Sr).
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, while non-ferrous metals such as aluminium and copper are detected at a shorter distance than the rated value. 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.
Frequently Asked Questions
What is the difference between flush (shielded) and non-flush (unshielded) M18 / M30 sensors?
Flush sensors mount level with surrounding metal and give a shorter range — 5 / 8 / 12 mm on M18 and 10 / 15 / 22 mm on M30. Non-flush types need metal-free side clearance but reach 8 / 16 / 20 mm on M18 and 15 / 25 / 40 mm on M30. Choose flush for embedded installation and non-flush when you need a longer sensing distance.
Should I order NPN or PNP, and NO or NC output?
These are DC three-wire sensors offered in NPN (sinking) or PNP (sourcing), with NO (model code 1) or NC (model code 2) switching logic. PNP is the default for most modern PLCs, especially in Europe, while NPN is common in some Asian controls. Wiring is brown = V+, blue = 0 V, black = output. Match the output type to your controller input.
What is the difference between the 35 mm and 55 mm body variants?
Both M18 and M30 are available in a 35 mm short body and a 55 mm standard body. The 35 mm short body carries a reduced set of sensing distances (M18: 5 mm flush, 8 mm non-flush; M30: 10 mm flush, 15 mm non-flush), while the 55 mm standard body offers the full range of sensing distances for each thread size.
How does target material affect the sensing distance?
Rated detection distance is specified for a standard mild-steel (iron) target. Non-ferrous metals such as stainless steel, brass, aluminium and copper reduce the achievable distance. Allow margin and verify with your actual target material — contact the factory for reduction factors on a specific model.
Can the DAIDISIKE M18 / M30 replace an Omron, Balluff, SICK or Autonics sensor?
Usually yes. They share the standard M18 / M30 threaded barrel, DC three-wire NPN/PNP wiring, IP67 rating and pre-wired cable, so they fit the same bracket and lead. Match the flush / non-flush type, sensing distance, body length (35 or 55 mm) and output (NO/NC) to the unit being replaced for a drop-in swap.
What ingress protection and temperature range do these switches have?
The M18 / M30 series is rated IP67 with a nickel-plated brass housing and a −25 °C to +70 °C operating range. Short-circuit protection is built in with an overload current protection point of 180 mA, and every unit carries an LED switching-state indicator and a 2 m cable (longer on request).
What is the response time and switching frequency?
Response time ranges from 0.2 ms on the fastest M18 variant (5 mm flush) to 2 ms on the M30 40 mm non-flush variant. Switching frequency ranges from 80 Hz (M30, 40 mm non-flush) up to 1 kHz on the fastest M18 variant.
Specs reviewed by Engineer Cai, Senior Application Engineer. Company CE & ISO approvals — see certificates.
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