Differences Between Metal Double-Sheet Detectors, Ultrasonic Double-Sheet Sensors, and Weighing Sensors

Detecting double-sheet stacks is a common pain point in automated feeding. For cost-effectiveness we rank solutions by material type.

Cost-effectiveness ranking for metal sheets: Metal Double-Sheet Detector > Ultrasonic double-sheet sensor > Weighing sensor

Cost-effectiveness ranking for non-metal sheets: Ultrasonic double-sheet sensor > Weighing sensor

Below we compare principle, detectable materials, detection accuracy, detection speed and cost.

1. Principle

Metal double-sheet solutions use either dual-probe or single-probe techniques:

Dual-probe: based on the shielding effect of metal on electromagnetic fields.

Single-probe: uses eddy current effects where thickness changes alter the induced coefficient and the controller estimates sheet thickness.

Ultrasonic: differentiates single/double sheets by comparing transmitted acoustic intensity through the material.

Weighing: compares weight to distinguish single vs multiple sheets.

2. Detectable materials

Metal detectors: dedicated to metal sheets and cannot detect non-metallic sheets.

Ultrasonic: works on thin lightweight objects regardless of material, but stability can decrease with perforated or thick sheets.

Weighing: material-agnostic.

3. Detection accuracy

Metal double-sheet sensors: high accuracy (able to detect patterned or perforated sheets).

Ultrasonic sensors: high accuracy.

Weighing sensors: relatively larger error and require waiting for the part to settle before measurement.

4. Detection speed

Metal double-sheet: up to 1,200 pcs/min (detection completes as the sheet passes between probes).

Ultrasonic: above 500 pcs/min (adequate for many applications).

Weighing: below 12 pcs/min (requires placing, settling, weighing, and re-grasp by the robot).

5. Cost

Metal double-sheet detectors: quality models commonly priced above ¥1,700; prices vary by model.

Ultrasonic sensors: quality units typically above ¥2,000.

Weighing sensors: conventional sets for sheet detection around ¥300; however, frequent replacements are common within a year.

6. Detectable thickness

Metal double-sheet detectors: general metal sheets 0.05–4.5 mm; aluminum: 0.1–40 mm.

Ultrasonic sensors: effective for metal sheets within about 1 mm.

Weighing sensors: suitable when single-sheet weight is measurable but not very large.

Recommendation: for metal sheets choose Atonm Metal Double-Sheet Detectors for cost effectiveness; for very thin non-metal sheets choose ultrasonic sensors; consider weighing sensors only if large footprint, extra mechanics, and slow throughput are acceptable.