All You Need To Know About Capacitive Proximity Sensors


 

A capacitive proximity sensor is an electronic device that detects objects by changing their capacitance when they come near an object. The sensor is composed of an insulator and two detection targets, with one switch in the middle. When the target is near the sensor, oscillations cause the insulator to change in capacitance, triggering an output signal. In addition, the proximity sensor can be adjusted to activate within a predetermined range.

Functions

Non-contact capacitive proximity sensors are often used to detect objects, such as ferrous metals, by generating an oscillating magnetic field. As the metal approaches the sensing area, it induces eddy currents, which reduce the reluctance of the magnetic circuit. The oscillation amplitude decreases as more metal enters the field. The sensor triggers a switch only when the object is within the sensing area.

Operating Frequency refers to the number of switching events per second in one second. It is a critical distance in which the switch is activated. The device is calibrated by measuring the number of switching events within a specified range. This value is determined by the device's sensitivity. This value is usually given as a percentage of the measured operating distance. The repeatability value is the variation between observed operating distance values over 8 hours.

Effective Sensing Distance

A capacitive proximity sensor is a device that detects a change in capacitance when an object is near the sensitive side. The sensor detects this oscillation and the voltage applied to it by a threshold circuit. The sensor's voltage output is amplified by an external load. The sensor is adjustable via a screw-on its back. Among other uses, capacitive proximity sensors are useful in storage tanks for liquid-level sensing.

The effective sensing distance of a capacitive proximity sensor varies depending on the type of target material. For example, a capacitive proximity sensor with a 10 mm sensing distance can detect an object that is only 0.8 mm in diameter. The dielectric constant of a capacitive proximity sensor is a property that makes it easy to detect materials that are in the vicinity.

Circuitry

A capacitive proximity sensor is an electronic device that produces an analog or voltage signal when the object near it is close enough to cause a charge to be stored in its capacitor. There are four basic component groups of this sensor. They are typically concentric electrodes mounted on either end of a cylinder or a metal plate mounted on the active sensing face. They are available in various configurations, including dual-mode, single-pole, and three-pole, and they can output either a voltage or contact closure. The operating frequency describes the number of times the device can cycle on and off in a second. To calculate the frequency, the manufacturer can use a dynamic method, as described in EN 50010: fig. 1. The sensor's position is shown in fig. 1, and the operating distance is represented by S and m. The formula for the frequency is shown in fig. 2. The repeatability measures the variation in the operating distance measured over eight hours. The measurement is performed at 15oC-30oC, and the supply voltage is with a 5% deviation.

Applications

The applications of capacitive proximity sensors are diverse. They are sensitive to a wide variety of objects, with the easiest targets being those with high density and high dielectric constant, such as water. Furthermore, they are versatile, allowing the sensors to detect different levels of liquid or solid materials. Here are some common uses of capacitive proximity sensors. Read on to learn more. The first application of capacitive proximity sensors is to detect the status of food or beverage products hidden behind opaque surfaces. The second type of proximity sensor uses light rather than a photon to detect objects. These sensors can detect objects, even plain plastic labels. Their advantage is that they are resistant to general contaminants, such as dust and other particles. They are also inexpensive and can be applied in small locations and automated systems. Both types of proximity sensors contain a light source and sensor. The light source is normally a semiconductor device called a photodiode. When light is present, the photodiode will emit a small amount of light and vice versa.

Cost

The cost of capacitive proximity sensors varies widely, depending on their size and sensitivity. A typical capacitive proximity sensor has two conductive elements, one inside the sensor and one outside the object. A dielectric material or air gap is located between the two plates and the gap between the sensor and target functions as an insulator. The capacitance values of the electrodes change when an object is placed between them, indicating the presence of an object. Inductive and capacitive proximity sensors both depend on the ability of objects to store an electrical charge. The capacitance of a sensor is the measurement of its capacity to hold a charge. Depending on the design, capacitive proximity sensors detect changes in this capacitance when an object approaches. The range of capacitance is huge, ranging from 0.1 to several hundred micrometers. To ensure the highest possible sensitivity, the sensing field should be large.

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