DAIDISIKE AC 2-wire inductive proximity sensors (M12/M18/M30) detect metal targets without contact, wired in series directly into a 20–250 V AC load circuit. The IP67 metal housing resists moisture, dust, and vibration. Sensing range 2–16 mm, LED indicator, NO (A1) / NC (A2) output, 400 mA maximum load current with a 5 A / 20 ms inrush rating and leakage current below 1.8 mA. Supplied with a 2 m cable, in flush (P) or non-flush (T) mount. Cost-effective, rugged, ideal for machinery, assembly lines, robotic arms, and conveyors.
The DAIDISIKE AC two-wire inductive proximity sensor series is a non-contact metal detection device for industrial automation, including M12, M18, and M30 models. It supports AC two-wire power supply and detects metals like iron, steel, and aluminum. The brand is known for high reliability, durability, and cost-effectiveness, widely used in mechanical manufacturing, assembly lines, robotic arms, and conveyor systems. Sensors have a metal housing with IP67 protection for stable operation in harsh environments like humidity, dust, or vibration. Outputs are NO (A1) or NC (A2) for easy integration. Two-wire design simplifies wiring and reduces costs while maintaining precision. Key advantages: 2-16mm sensing range, LED indicators, 400 mA maximum load current with a 5 A / 20 ms inrush rating, leakage current below 1.8 mA and an overload current protection point of 120 mA. Supplied with a 2-metre cable (longer on request), with flush (P) / non-flush (T) mounting for optimized performance.
Specifications Table
The following is a detailed specifications table for the DAIDISIKE AC two-wire inductive proximity sensor series, organized by size:
Parameter
M12
M18
M30
Model Size
M12
M18
M30
Sensing Distance (Flush, P)
2 / 4 mm
5 / 8 mm
10 / 16 mm
Sensing Distance (Non-Flush, T)
4 / 8 mm
8 / 16 mm
8 / 16 mm
Supply Voltage
20-250V AC
20-250V AC
20-250V AC
Wiring
2-wire, in series with the AC load
2-wire, in series with the AC load
2-wire, in series with the AC load
Output Type
NO (A1) / NC (A2)
NO (A1) / NC (A2)
NO (A1) / NC (A2)
Max Load Current
400 mA
400 mA
400 mA
Inrush Current
5 A for 20 ms
5 A for 20 ms
5 A for 20 ms
No-load / Leakage Current
< 1.8 mA
< 1.8 mA
< 1.8 mA
Voltage Drop
< 8 V AC at 400 mA
< 8 V AC at 400 mA
< 8 V AC at 400 mA
Switching Frequency
< 25 Hz
< 25 Hz
< 25 Hz
Response Time
10 ms
10 ms
10 ms
Switching Hysteresis
< 15 % (Sr)
< 15 % (Sr)
< 15 % (Sr)
Repeat Accuracy
< 5 % (Sr)
< 5 % (Sr)
< 5 % (Sr)
Temperature Drift
< 10 % (Sr)
< 10 % (Sr)
< 10 % (Sr)
Overload Protection Point
120 mA
120 mA
120 mA
Indicator
LED
LED
LED
Protection Rating
IP67
IP67
IP67
Operating Temperature
-25°C to +70°C
-25°C to +70°C
-25°C to +70°C
Connection Method
2 m cable (longer on request)
2 m cable (longer on request)
2 m cable (longer on request)
Housing Material
Metal housing — exact material: contact factory
Metal housing — exact material: contact factory
Metal housing — exact material: contact factory
Body Length / Thread
M12×1 × 60 mm
M18×1 × 55 mm
M30×1.5 × 55 mm
Weight
Contact factory
Contact factory
Contact factory
Certifications
Contact factory
Contact factory
Contact factory
Note: Specifications may vary slightly by specific model; please refer to the product manual for exact values. Sensing distance is for standard iron targets (size twice the sensing distance). This series features waterproof design.
Technical Parameters
The technical parameters of the DAIDISIKE AC two-wire inductive proximity sensors are as follows, ensuring high performance and reliability in industrial environments:
Supply Voltage Range: 20-250V AC, wired in series with the AC load using only the brown (BN) and blue (BU) leads.
Maximum Load Current: 400mA, with a rated inrush current of 5A for 20ms.
No-load / Leakage Current: below 1.8mA — confirm the AC load tolerates it and draws enough holding current for the sensor.
Voltage Drop: below 8V AC at 400mA.
Switching Frequency: below 25Hz; response time 10ms.
Switching Hysteresis: below 15% (Sr).
Repeat Accuracy: below 5% (Sr).
Temperature Drift: below 10% (Sr).
Overload Current Protection Point: 120mA.
LED Indication: built-in LED for output status display, convenient for on-site debugging.
Output: NO (model code A1) or NC (model code A2).
Protection Rating: IP67; operating temperature -25°C to +70°C.
Cable: 2m standard, longer lengths available on request.
Target Material: metal targets. Rated Sn assumes a standard mild-steel target; non-ferrous metals are detected at a shorter distance — contact the factory for reduction factors.
Body size: M12×1 × 60 mm, M18×1 × 55 mm, M30×1.5 × 55 mm.
Housing material detail, weight and certification: contact the factory (not published in the current catalogue for this series).
The figures above are transcribed from the factory selection table for the AC two-wire series; items not published there are marked as "contact the factory" rather than estimated.
Working Principle
The working principle of the DAIDISIKE AC two-wire inductive proximity sensor is based on electromagnetic induction. Specifically, the sensor contains a high-frequency oscillation circuit internally, which generates an alternating magnetic field. When a metal object (target) enters the sensor's sensing area, eddy currents are induced in the target, altering the impedance and amplitude of the oscillation circuit. The sensor detects this change and, through an internal amplifier and comparator circuit, converts the signal into a switch output.
Detailed process:
1. Oscillator Generates Magnetic Field: The front-end coil of the sensor produces a high-frequency magnetic field (typically several hundred kHz).
2. Target Approaches: The metal object enters the magnetic field, absorbs energy, and generates eddy currents, causing field attenuation.
3. Detects Change: The oscillator's amplitude or frequency change is captured by the detection circuit.
4. Signal Processing: Through threshold comparison, outputs a switch signal (NO or NC).
5. Two-Wire Design: Power and signal are transmitted via the same pair of wires, simplifying the circuit; the load is connected in series in the power loop, and when the sensor activates, current changes drive the load. Since it is AC-powered, the sensor accommodates alternating current supply, with output directly switching the AC load.
This non-contact detection avoids mechanical wear, extending service life compared with mechanical limit switches. In professional terms, this is an "Inductive Proximity Sensor," designed with reference to the general industry specification for proximity switches (IEC 60947-5-2), commonly used for "Position Sensing" and "Presence Detection." Compared to DC versions, AC two-wire sensors are better suited for high-voltage environments and offer stronger resistance to electrical noise, though with lower switching frequencies. The core of detection is energy transfer via eddy current losses, applicable to ferromagnetic and non-ferromagnetic metals.
Frequently Asked Questions
What is an AC two-wire inductive proximity sensor and how is it wired?
It is a non-contact metal-detection switch powered directly from a 20–250 V AC supply using just two wires. The load is connected in series in the AC loop, so wiring is simple and there is no separate NPN/PNP sourcing/sinking decision. A small leakage current (< 1.8 mA) flows even when off, so check your AC load tolerates it — and that the load draws enough current to keep the sensor's internal circuit powered.
How do I choose between M12, M18, and M30 sizes?
Pick the size by required sensing distance and mounting space. Flush versions are rated 2 / 4 mm (M12), 5 / 8 mm (M18) and 10 / 16 mm (M30); non-flush versions are rated 4 / 8 mm (M12), 8 / 16 mm (M18) and 8 / 16 mm (M30). Larger bodies give longer range and easier targeting on conveyors and presses; the smaller M12 fits tight fixtures and robotic arms.
What is the difference between flush and non-flush mounting?
Flush (shielded, P suffix) sensors mount level with surrounding metal and resist side interference but generally have a shorter range. Non-flush (unshielded, T suffix) sensors need a metal-free clear zone around the face and generally deliver a longer sensing distance. Check the rating per model rather than assuming: in this AC series the M30 is rated 10 / 16 mm flush and 8 / 16 mm non-flush, so the longest M30 distance is 16 mm either way.
Can it replace an Omron, Balluff, or Autonics AC proximity switch?
Usually yes. It shares the standard M12/M18/M30 thread, IP67 rating, 20–250 V AC two-wire operation, and NO/NC output, so it fits the same bracket and AC load circuit. Match the size, flush/non-flush type, sensing distance and 2 m cable to the unit being replaced, and confirm the new sensor's 400 mA maximum load current suits your AC load.
Does the Sn sensing distance change for stainless steel or aluminum?
Yes. The rated Sn is specified for a standard mild-steel target at least twice the sensing distance in size. Non-ferrous metals such as stainless steel and aluminium are detected at a shorter distance than the rated value — contact the factory for reduction factors on a specific model, and size your target and mounting gap with margin.
