Liquid Level Measurement Devices
1.Using graphical man-machine interface , intuitive and concrete
2.The processing speed is fast, the inspection accuracy is high, the fastest speed can reach 50000 BPH
3.Simple operation, easy to production line staff
4.Multi angle inspection, no dead angle, less manual intervention, low false tick rate
5.Using high brightness LED light source, adjustable brightness, long lfe, energy saving,maintenance free
I. Project Equipment Overview
Project Name: PET Bottle Cap, Anti-theft Ring, Liquid Level, and Inkjet Printing Inspection System
Project Description: This system performs online inspection of PET bottles, automatically identifying and rejecting defective products with issues related to caps, anti-theft rings, liquid levels, or inkjet printing quality.
Maximum Throughput: Up to 60,000 bottles per hour
Applicable Bottle Type: PET bottles
Product Volume Range: 200 mL – 2 L
II. Environmental Conditions
Recommended Altitude: 5–3000 m above sea level
Operating Temperature: 5°C – 40°C
Relative Humidity: 50% – 65% RH
Factory Infrastructure: Floor flatness, load-bearing capacity, and other parameters must comply with national standards to ensure proper machine operation.
Storage Conditions: After delivery, equipment and parts must be stored in facilities that meet relevant national standards. During storage, proper lubrication and maintenance are required to avoid surface damage, corrosion, or deformation that could affect installation, commissioning, or operation.
III. Equipment Operating Conditions
Power Supply: 220V, 50Hz, single-phase (provided by customer; special voltage requirements must be specified in advance, as they may impact specifications, lead time, and pricing).
Total Power Consumption: Approx. 2.4 kW
Control Voltage: 24 VDC
Compressed Air: 4–12 Pa (pipeline connection between air source and equipment main unit to be provided by the customer).
IV. Equipment Introduction
Installation Location
The inspection system is installed directly on the PET bottle production line for online detection and rejection.Inspection Scope
Missing cap
Over-height cap
Tilted cap
Broken anti-theft ring
Low liquid level
Absence of inkjet printing
Excessive inkjet printing
Detection Principle
As each PET bottle passes a positioning sensor, the system records the bottle ID along with the encoder signal through the control unit.
The positioning sensor then triggers the camera to capture images of the bottle cap, liquid level, and inkjet marking. These images are analyzed by the image processor, and results are transmitted simultaneously to the HMI (Human-Machine Interface) for real-time monitoring and to the PLC for further processing.
If a defect is detected, the PLC issues a rejection command, and the rejector automatically removes the corresponding defective bottle based on its recorded ID.
4. Equipment mechanical components
model
| Name | Components | Functional Description | Remark
|
1 | Distribution cabinet | Composed of an image processor, an interface processor, a strobe controller, and a PLC. | Provides power to the entire system, processes images, and controls the rejection of defective products. | |
2 | Detection module | LED light source, industrial CCD camera, and sensor. | Dynamically captures images of PET bottles. | |
3 | Rejection device | Main components include solenoid valves and mechanical components. | Receives signals and controls the rejection of defective products. |
5. Electrical composition of the equipment
model
| Name | Unit | Brand Notes | Quantity |
1 | Embedded imaging industrial computer (4 Ethernet ports) i5+4G+120G | Unit | Taiwan Chaoen, dust-proof, fast processing speed, and excellent stability | 1 |
2 | DAHUA high-speed gigabit digital camera | Unit | Resolution 680x480, imported from Canada, industry-leading brand | 4 |
3 | Camera I/O module | Set | Made-in-China | 4 |
4 | Lens | Piece | COMPUTAR 6MP, 12mm | 4 |
5 | Camera-50/30line cable | Piece | Made-in-China, 5m | 4 |
6 | MW.24v DC power supply 75/120W (DRP-75/120-24) | Piece | Taiwan Mean Well | 2 |
7 | PLC | Piece | Maotong independently developed | 1 |
8 | Touchscreen display | Piece | Taiwan IEI 15-inch | 1 |
9 | Light source controller | Unit | Customized in China, 4-way asynchronous triggering, screen flicker control technology, significantly extending light source life | 1 |
10 | Photo light source | Unit | Customized surface lighting, infrared, and blue | 4 |
11 | Power distribution cabinet | Piece | Made-in-China, 304 material, brushed, pickled, oxidized, and brushed finishes | 1 |
12 | Single-stage rejector Mono | Piece | Customized, air-push type, 304 material | 1 |
13 | Reject unit cylinder | Piece | Norgren high-speed cylinder, UK | 1 |
14 | Reject unit solenoid valve | Piece | MAC high-speed solenoid valve, US, 4.9ms response speed | 1 |
15 | Encoder | Piece | Made-in-China, Hode, incremental type | 1 |
16 | Low-voltage electrical components | Piece | Schneider, France | Several |
17 | Image processing system | Piece | Maotong independently developed, can develop V3.0 according to customer needs | 1 |
18 | Special equipment refrigeration unit - industrial air conditioner | Piece | Shanghai Highly Special, cooling capacity 320W | 1 |
19 | Terminal blocks | Piece | Honeywell, USA | Several |
20 | Photoelectric sensor | Piece | Leuze, Aurora PNP | 1 |
21 | Other electrical components | Piece | - | Several |
22 | Cabinet material and surface treatment | Piece | 304 material, igus® mechanical parts, brushed, pickled, oxidized, and brushed finishes. | 1 |
23 | Alarm light | - | Several | |
24 | Oil-water separator | - | Schneider tri-color tower light | Several |
25 | Relay | Piece | 1 | |
26 | Glass material | Piece | AirTac | 1 |
6. Testing cabinet structure diagram
Capping liquid level detection (capping liquid level detection at stations one and three)
Inkjet printing inspection (station 2, single-camera inkjet printing inspection)
This module uses three CCD cameras to capture images of bottles from different angles, reducing blind spots. Special optical lenses filter light from all directions to ensure efficient image acquisition. Its primary function is to detect defective bottles such as missing caps, overhanging caps, crooked caps, and broken caps.
PET bottle capping images captured by CCD camera
8. Liquid Level Detection
This module uses a CCD camera to capture liquid level images from the front, ensuring that the liquid level in the bottle is nearly horizontal when the bottle is stationary. This module employs image processing principles that render the portion below the liquid level black in the image and the portion above the empty bottle white. A special method is used to distinguish between levels below and above the specified liquid level.
Sample image recognition processing effect
9. Inkjet Printing Inspection
This module uses a CCD camera to capture images of the inkjet printing on bottles and caps from the front. It then digitally analyzes the captured images and automatically and accurately rejects bottles with unqualified inkjet printing. It is compatible with both yellow caps with black ink and black caps with white ink.
10. Detection accuracy
Inspection Items | Inspection Contents | Detection accuracy
| Rejection rate
|
| No cap | —— | ≥99.99% |
High cap | ＞0.8 mm | ≥99.98% | |
Crooked cap | ＞0.8 mm | ≥99.5% | |
Safety ring 100% disconnected | ＞1mm gap | ≥99.99% | |
Safety ring >70% broken | ＞1mm gap | ≥98.32% | |
Safety ring >50% broken | ＞1mm gap | ≥95.78% | |
Safety ring 100% missing | —— | ≥99.99% | |
Safety ring 70% missing | —— | ≥98.21% | |
Safety ring 50% missing | —— | ≥95.78% | |
Inspection Items | Liquid level detection (high and low) | 3mm below (or above) the standard
| ≥99.92% |
Bottle Cap Inspection | No inkjet print | ≥99.99% | |
Overall inkjet print 50% missing | ≥99.95% | ||
Overall inkjet print 30% missing | ≥99.9% | ||
Overall inkjet print 20% missing | ≥99.8% | ||
Inkjet print is blurred enough to remove the inkjet characters after processing | ≥99.99% |
