Chapter 8: Power Over Ethernet Overview

Line Detection

Before power is applied, safety dictates that it must first be ensured that a valid PD is connected to the PSE's output. This process is referred to as "line detection", and involves the PSE seeking a specific, 25 KO signature resistor. Detection of this signature indicates that a valid PD is connected, and that provision of power to the device may commence.

The signature resistor lies in the PD's PoE front-end, isolated from the rest of the the PD's circuitries till detection is certified.

Classification

Once a PD is detected, the PSE may optionally perform classification, to determine the maximal power a PD is to consume. The PSE induces 15.5-20.5 VDC, limited to 100 mA, for a period of 10 to 75 ms responded by a certain current consumption by the PD, indicating its power class.

The PD is assigned to one of 5 classes: 0 (default class) indicates that full 15.4 watts should be provided, 1-3 indicate various required power levels and 4 is reserved for future use. PDs that do not support classification are assigned to class 0. Special care must be employed in the definition of class thresholds, as classification may be affected by cable losses.

Classifying a PD according to its power consumption may assist a PoE system in optimizing its power distribution. Such a system typically suffers from lack of power resources, so that efficient power management based on classification results may reduce total system costs.

Start-up

Once line detection and optional classification stages are completed, the PSE must switch from low voltage to its full voltage capacity (44-57 Volts) over a minimal amount of time (above 15 microseconds).

A gradual startup is required, as a sudden rise in voltage (reaching high frequencies) would introduce noise on the data lines.

Once provision of power is initiated, it is common for inrush current to be experienced at the PSE port, due to the PD's input capacitance. A PD must be designed to cease inrush current consumption (of over 350 mA) within 50 ms of power provision startup.

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Graco GE-DS-242-POE manual Line Detection, Classification, Start-up
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GE-DS-242-POE specifications

The Graco GE-DS-242-POE is an advanced electric diaphragm pump designed to cater to a wide range of industrial applications. This model stands out for its reliability, efficiency, and innovative technology, making it an ideal choice for demanding environments such as automotive, food processing, and chemical handling.

One of the main features of the GE-DS-242-POE is its robust construction. Built from durable materials, it is designed to withstand harsh operating conditions, ensuring a long service life. The pump is powered by a reliable electric motor that guarantees consistent performance with minimal downtime. This electric design offers a significant advantage over air-operated pumps, as it eliminates the need for compressed air, reducing operational costs.

The GE-DS-242-POE utilizes a double-diaphragm design that allows for precise fluid transfer and improved efficiency. This technology enables the pump to handle a variety of fluids, including viscous materials, slurries, and abrasive substances, without compromising performance. The dual diaphragm feature also enhances the pump's ability to handle fluctuating pressures, making it suitable for diverse applications.

Another key characteristic of this model is its versatile port configuration. The pump is available with various inlet and outlet sizes, allowing for easy integration into existing systems. This adaptability also means that the GE-DS-242-POE can be used in both temporary and permanent installations, further extending its utility.

Ease of maintenance is a crucial aspect of the GE-DS-242-POE. The design incorporates accessible service points, which simplify routine inspections and repairs. This user-friendly approach reduces maintenance time and costs, ultimately boosting productivity.

Additionally, the GE-DS-242-POE is equipped with advanced safety features. These include pressure relief valves and electronic controls that help prevent overpressurization, ensuring safe operation under all conditions. The pump also meets various industry standards, reinforcing its reliability and suitability for compliance with safety regulations.

In conclusion, the Graco GE-DS-242-POE is a technologically advanced electric diaphragm pump that excels in performance, durability, and versatility. Its robust construction, efficient double-diaphragm technology, and user-friendly design make it an indispensable tool for businesses in various sectors, enhancing operational efficiency while ensuring safety and reliability in fluid handling processes.
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