Detecting double sheets is a common pain point in payroll automation. We've ranked solutions based on material properties for cost-effectiveness.
Metal sheet double sheet detection solutions ranked by cost-effectiveness: Metal double sheet detector > Ultrasonic double sheet sensor > Load cell
Non-metal sheet double sheet detection solutions ranked by cost-effectiveness: Ultrasonic double sheet sensor > Load cell
Below, we compare the principles, inspectable materials, detection accuracy, detection speed, and cost.
1. Principle
Metal double-sheet detection primarily involves two technical approaches: dual-probe and single-probe.
Dual-probe: Utilizes the shielding effect of metal sheets against electromagnetic fields.
Single-probe: Utilizes the eddy current effect. Changes in sheet thickness cause corresponding changes in inductance, allowing the controller to calculate sheet thickness.
Ultrasonic: Different materials and thicknesses have varying shielding effects on ultrasonic waves. Single and double sheets are distinguished by comparing the sound wave intensity of the sheet.
Weighing: Also a traditional gravity sensor, it primarily distinguishes single and double sheets by comparing sheet weight.
2. Inspectable Sheet Materials
Metal double-sheet: Specifically designed for detecting various metal sheets; it cannot detect non-metallic sheets. (P.S.: Magnetic, for simplicity, means it can be attracted by a magnet.)
Ultrasonic: Primarily used for detecting thin, lightweight objects, regardless of material. (Disadvantages: Poor stability when dealing with hollow or thick sheets.)
Weighing: Suitable for both metal and non-metal sheets.
3. Detection Accuracy
Double-sheet Metal Sensor: High accuracy (High detection accuracy for all types of metal sheets, including those with regular hollows).
Ultrasonic Sensor: High accuracy
Weighing Sensor: Relatively large error (Large error, requiring the sheet to stabilize before retesting).
4. Detection Speed
Double-sheet Metal: 1200 pcs/min (Detection is complete as soon as the sheet passes through the center of the probe).
Ultrasonic: 500 pcs/min or higher (Suitable for common use).
Weighing: 12 pcs/min or lower (Requires sheet to be placed on a tray for weighing - workflow: place sheet, wait for sheet to stabilize, weigh, then re-grab the sheet).
5. Cost
Double-sheet Metal Detector: A high-quality double-sheet detector is priced at over 1700 yuan, with prices varying depending on the model.
Ultrasonic Sensors: High-quality ultrasonic sensors generally cost over 2,000 yuan.
Weighing Sensors: Testing standard metal sheets generally costs around 300 yuan per set; these typically require replacement within a year.
6. Thickness Detection
Metal Double Sheet Detector: For standard metal sheets, 0.05-4.5mm; for aluminum sheets, 0.1-40mm.
Ultrasonic Sensors: For metal sheets, within 1mm.
Weighing Sensors: For single sheets, a sheet has a certain weight, but it's not excessively heavy.
In actual comparisons,
For metal sheet detection, we recommend the Astro Boy Metal Double Sheet Detector, which is more cost-effective.
For non-metallic and very thin sheet detection, we recommend ultrasonic sensors.
For applications that can tolerate larger space requirements, three additional mechanical movements, sheet wear from contact, and require fewer than 10 sheets per minute, weighing sensors may be a good option.