Telemecanique XS618B1MAL2 Inductive Proximity Sensor

M18 Flush-mount Inductive Proximity Switch (2-wire AC/DC universal, Normally Open NO)

1. Model Code Explanation

XS6: General-purpose inductive proximity sensor of XS6 series

18: M18 threaded cylinder

B: Standard sensing distance

1: Normally Open (NO)

M: 2-wire AC/DC universal

A: Cable outlet

L2: 2-meter fixed cable

2. Core Electrical & Mechanical Specifications

3. Installation Guidelines
4. Flush Mount (Shielded Type): The sensor can be fully embedded inside a metal mounting seat without false triggering caused by side metal.
5. Mounting hole M18, supplied with double lock nuts.
6. Minimum spacing between adjacent sensors of the same model ≥3×Sn (≥24mm) to prevent mutual interference.
7. Target metal plate thickness ≥1mm, area ≥30×30mm for stable detection.
8. Wiring Instructions

2-wire design, non-polarized (AC/DC universal):

Connect two wires in series between power supply and load.

When metal approaches the sensing face → switch turns ON (NO contact closed).

Note: 2-wire sensors carry standby leakage current. False actuation may occur with low-power loads (high-resistance relay coils). Load calculation is required during selection.

5. Typical Application Scenarios

Metal detection on conveyor lines, machine tool limit positioning, material presence detection, hydraulic/cylinder position feedback, food processing washdown equipment (IP69K for high-pressure cleaning), packaging machinery.

6. Alternative / Equivalent Models within the Series

XS618B1MBL2: 2-wire Normally Closed NC, other parameters identical

XS618B1PAM12: 3-wire PNP Normally Open, M12 connector type

XS618B1NAM12: 3-wire NPN Normally Open, M12 connector type

7. Common Troubleshooting
8. No output: Verify supply voltage within 24~240V; confirm metal target enters the 8mm sensing range; inspect cable for breakage.
9. False triggering: For flush mounting, ensure mounting metal does not cling to the sensing face; check interference from neighboring sensors.
10. Cannot turn off: Too small load; leakage current of 2-wire sensor keeps relay energized. Replace with 3-wire PNP/NPN version.

Operating Principle of Flush-mount Inductive Proximity Switches (such as XS618B1MAL2)

Basic Principle

Inductive proximity switches work based on the eddy current effect, with a high-frequency oscillating coil as the core component.

1. Internal circuit generates a high-frequency alternating magnetic field, radiating outward from the front sensing face.
2. When a metal target approaches the sensing face, the alternating magnetic field induces eddy currents on the metal surface.
3. Eddy currents generate a reverse magnetic field to counteract the original oscillating magnetic field of the sensor.
4. The amplitude of the oscillation circuit attenuates; detection circuit identifies this change and outputs switching signal (ON/OFF).

✅ Core difference between Flush-mount (Shielded) and Non-flush (Unshielded): A metal shielding ring surrounds the coil

Structural Features of Flush-mount (Shielded Type)

A metal shielding layer wraps the sides of the sensing coil for flush-mount sensors:

Restricts magnetic field to directly in front of the sensor, nearly no magnetic field on lateral sides.

Therefore, it can be fully screwed into metal mounting brackets with sensor end face flush to mounting surface and no false triggering from surrounding metal.

Trade-off: Under identical specifications, sensing distance is shorter than non-flush type (Sn=8mm for XS618B1MAL2 flush model).

Non-flush type: Magnetic field exists on sides; cannot be embedded in metal seat, otherwise continuous triggering occurs, with longer sensing distance.

Signal Output Flow (2-wire NO model XS618B1MAL2)

1. Power on → internal oscillator starts oscillation.
2. No metal nearby → stable oscillation, switch open (NO Normally Open).
3. Metal approaches and reaches rated sensing distance Sn → oscillation attenuates, detection circuit actuates and the 2-wire circuit conducts.
4. Metal moves away → oscillation recovers, switch opens.

Key Characteristics

1. Only detects metal: Plastic, wood and glass cannot produce eddy currents and will not be detected. Ferromagnetic metals (steel, iron) deliver optimal sensing distance; effective distance attenuates for non-ferrous metals such as copper and aluminum.
2. Fast response speed, suitable for high-speed counting and position detection.
3. Flush mounting resists side metal interference, preferred for machine tools, conveyor metal frame installations.
4. 2-wire version carries leakage current; load selection needs attention.

Simple Comparison Table

Common Application Scenarios of Inductive Proximity Switches

Core features: Detect metal only, non-contact, no mechanical wear, resistant to dust and oil; Flush type (XS618B1MAL2) suitable for flush installation on metal frames

1. Position Detection / Travel Limit (Most Common)
2. Cylinder position feedback: Detect extended/retracted end position of cylinder piston rod to confirm completion of cylinder action, standard fitting for pneumatic automation; M18 flush sensors widely used on cylinder mounting seats.
3. Machine tool travel limit: Soft limit and hard overtravel protection for CNC machine slides and worktables; turret and tool magazine positioning, tool change confirmation; fixture clamping verification to judge workpiece seating status.
4. Valve, baffle and safety door status detection: Detect closure of metal safety gates for safety interlock; equipment startup prohibited when door open.
5. Robot positioning: Homing and station in-place detection for robotic arms.
6. Counting, Speed Measurement & Rotational Speed Monitoring
7. Metal workpiece counting on conveyor lines: Count metal parts, screws, metal caps and metal pallets on production lines for output statistics.
8. Rotational speed / line speed acquisition: Gear tooth disc fitted on motor shaft; proximity sensor detects gear teeth pulses, PLC collects pulses to calculate rotation speed and line speed, widely used for conveyors and reducer spindle monitoring.
9. Material break / shortage detection: Monitor feeding of metal rods to confirm material delivery and breakage.
10. Conveying & Logistics Sorting
11. Detect arrival of metal workpieces on belt conveyors to trigger cylinder actions for transfer and sorting;
12. Metal pallet presence detection and rack positioning in automated warehouses;
13. Jam monitoring: Alarm for material accumulation and blockage.
14. Packaging & Food Machinery (Suitable for XS618B1MAL2 with IP68/IP69K)

Detection of cans, metal caps and aluminum foil seals to verify cap presence;

Trigger filling when metal containers arrive at filling stations;

High-pressure washdown capability; flush sensors preferred for food & beverage cleaning lines.

5. Automotive Manufacturing

Workpiece positioning at welding stations and fixture clamping confirmation for welded car bodies;

Gear position detection for gearboxes and presence check of wheel hubs;

Stable performance under welding slag and heavy dust; inductive sensors outperform photoelectric sensors in contaminated environments.

6. Hydraulic & Construction Machinery

Hydraulic cylinder position detection and metal float liquid level monitoring;

Position feedback for machinery doors and buckets;

Adapt to heavy vibration and oily harsh environments.

7. Other Segmented Applications
8. Stamping equipment: Mold closure detection and safety interlock;
9. Electronic equipment: Metal component detection on SMT lines;
10. Pump & fan: Shaft stall monitoring via gear tooth speed measurement.

Selection Tips (For XS618B1MAL2)

✅ Flush-mount (Shielded Type): Can be installed flush within metal mounting seats, free from false triggering by surrounding metal; preferred for machine frames and cylinder mounts.

⚠️ Limitation: Only identifies metal, plastic, paper and non-metallic workpieces cannot be detected; effective sensing distance shortens for copper and aluminum.

⚠️ 2-wire models (e.g. XS618B1MAL2) have leakage current, which may cause false pull-in of small-load relays.

Telemecanique XS618B1 Series Full Model List (M18 Flush Mount, Sn=8mm)

Unified Base Specification: XS618B1 = XS6 series, M18 threaded, flush shielded type, nominal sensing distance 8mm, nickel-plated brass housing, IP68/IP69K, -25~+70℃

Model Coding Rule: XS618B1 + Output Code + Outlet Type + Length/Connector

M = 2-wire AC/DC; P=PNP; N=NPN

A=Normally Open NO; B=Normally Closed NC

L2=2m cable; L5=5m cable; M12=M12 circular connector; AU20=1/2″UNF connector

1. 2-wire AC/DC (Branch of XS618B1MAL2, 24~240V AC/DC)

2. 3-wire DC PNP (12~48VDC, most common for PLC)

3. 3-wire DC NPN (12~48VDC, for NPN-type PLC)

4. ATEX Dust Explosion-proof Versions (Explosive Atmosphere)

Quick Selection Guide

1. 2-wire models starting with M (XS618B1MAL2): Universal AC/DC, no polarity distinction; ⚠️ leakage current exists, prone to false relay pull-in for tiny loads, suitable for heavy loads.
2. 3-wire P/N prefix: DC12~48V, PNP/NPN, short-circuit protection, standard PLC selection, preferred replacement for 2-wire sensors.
3. Suffix L2/L5: Fixed cable; M12/AU20: Detachable connector for easier maintenance.
4. A=NO Normally Open, B=NC Normally Closed: When metal approaches, NO closes and NC opens.

Extended M18 Flush Models in the Same Series (Longer Sn, Non-B1)

XS618B4PAL2: Flush mount, Sn12mm, PNP NO, 2m cable