Ring Proximity Sensor

Ring Proximity Sensors are generally used for detecting small objects(e.g., minimum detectable object diameter 0.5mm), such as small nuts, steel balls, springs, rivets, and wire breaks, as well as for product counting, presence detection, and other applications. The accuracy of the detection object varies depending on the material.

The output of a general ring proximity switch can be divided into NPN and PNP outputs. NPN means output low level (negative voltage), and PNP means output high level (positive voltage). NO means normally open, and NC means normally closed.

1. High sensitivity: able to accurately perceive small physical position changes.

2. No mechanical wear: Because it does not involve physical contact, there is no wear problem, and the maintenance cost is low.

3. Long lifespan: Due to its simple structure and lack of moving parts, it has a relatively long service life.

4. Easy to install: It can be easily installed on various devices as needed, with strong adaptability.

 

Case Study 1: Parts Counting and Presence Detection in an Automated Feeding System

Application Scenario: On an automated fastener assembly line, small metal parts such as bolts, nuts, and rivets are sorted by a vibratory feeder and then conveyed at high speed (up to 35 m/s) via a feeding hose using compressed air. Traditional mechanical contact detection is prone to jamming or missed detection.

Solution: Install a ring-shaped capacitive proximity switch on the feeding hose. The sensor utilizes a ring structure for 360-degree detection without blind spots. When a part passes through the center of the ring, the switch signal is immediately triggered, achieving non-contact and wear-free counting.

Key Values: This solution can accurately detect parts as small as 2mm; installation and maintenance can be quick without disassembling the hose; the ring structure effectively avoids missed detections and false triggers, achieving stable flow control. Some hoses can even be installed non-contactly using a strap-type sensor, without compromising the hose's integrity.

Case Study 2: Pharmaceutical Powder Level Control in Pharmaceutical Equipment

Application Scenario: In a fully automated capsule filling machine, pharmaceutical powder enters the "powder-holding ring" of the metering device from a stainless steel hopper. Precise control of the powder level is crucial during the filling process. Excessive powder level leads to overflow and waste, while insufficient level results in inadequate capsule filling, powder waste, and reduced production efficiency. Traditional contact-type level switches are susceptible to powder adhesion, while photoelectric sensors are prone to failure due to dust accumulation.

Solution: A capacitive proximity sensor is installed on the side of the powder-holding ring. When the powder rises to the specified height, the capacitive sensor outputs a switching signal to the PLC due to a change in dielectric constant, automatically stopping the filling process.

Key Values: Non-contact detection avoids direct contact between the sensor and the powder, maintaining hygiene standards and eliminating the risk of cross-contamination; high sensitivity accurately identifies the difference in dielectric constant between the powder and air, enabling precise control; the dustproof design provides excellent adaptability to dusty environments. 

Case Study 3: Missing Medicine Bottle Detection After Packaging

Application Scenario: On automated pharmaceutical packaging lines, after medicine bottles are placed into sealed cardboard boxes, traditional photoelectric sensors cannot penetrate the outer packaging to verify whether the box actually contains a bottle because the boxes are completely sealed. If an empty box is not detected in time, it will lead to a recall of the entire batch of products, customer claims, and damage to brand reputation.

Solution: Install capacitive proximity sensors above or on the side of the sealed conveyor belt. This utilizes capacitive technology to penetrate non-metallic packaging materials and directly detect the presence of a medicine bottle inside.

Key Value: Detection can be performed through plastic walls or non-metallic outer packaging without damaging the packaging; it is unaffected by packaging color or printed patterns, ensuring high detection accuracy. In this type of application, the Garantta series capacitive sensors can effectively detect medicine bottles inside sealed cardboard boxes through sensitivity adjustment, with a maximum switching distance of 25mm.

The working principle of the annular capacitive proximity switch is based on the capacitance effect. When no object approaches, the capacitance value between the two electrodes is fixed. Once a conductive object enters the electric field range of the capacitor plates, it changes the effective distance between the electrodes, causing a change in the capacitance value. This change will be detected by the internal electronic circuit and converted into a switch signal output, achieving detection and control of the object.

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