Dewesoft Technologies Update: PoE and PTP v2 in Data Acquisition

Power over Ethernet

What is PoE?

Power over Ethernet (PoE) technology delivers data and electrical power over a single Ethernet cable. It powers devices via their data connection and eliminates the need for separate power cables. PoE is widely used for devices like IP cameras, wireless access points, VoIP phones, network switches, and several data acquisition systems from Dewesoft, where it’s beneficial to have flexible placement without needing a separate connection to a power outlet.

How does PoE work?

PoE uses Ethernet cables (usually CAT5e, CAT6, or higher) with four copper wire twisted pairs. A PoE-enabled network switch or injector sends both data and power over these pairs, which is then received by a compatible device (often called a Powered Device or PD).

Here’s a breakdown of how it works:

1. Power Sourcing Equipment (PSE): This device provides power, which can be a PoE switch or injector. A PoE switch is often used in setups where multiple devices need power, while a PoE injector adds power to a standard Ethernet line if the switch itself does not support PoE.

2. Powered Device (PD): This device receives power over Ethernet, such as an IP camera or access point. PoE-compatible devices are designed to detect the presence of a PoE signal and safely receive power while maintaining data transfer integrity.

3. Power Transmission: The Ethernet cable can carry power over specific pairs of wires, depending on the type of PoE:

   1. PoE (IEEE 802.3af): Up to 15.4 watts, with power delivered over two pairs.

   2. PoE+ (IEEE 802.3at): Up to 30 watts delivered over two pairs.

   3. PoE++ (IEEE 802.3bt): Up to 60 watts (Type 3) or 100 watts (Type 4), using all four pairs.

4. Power Detection and Negotiation: When a device is plugged into a PoE switch or injector, the PSE checks if the connected device is PoE-compatible. If so, it negotiates the power required to operate, usually done in defined power classes. This prevents the PSE from delivering excess power, ensuring device safety and efficient power use.

5. Power and Data Separation: Inside the powered device, circuitry separates the data and power components, routing data to the network interface and power to the device's power system.

Applications of PoE

PoE provides power and data in situations where deploying multiple cables is inconvenient or impractical, such as:

• DAQ Instruments: Several Dewesoft data acquisition (DAQ) instruments use PoE to simplify wiring in remote and challenging locations.

• IP Cameras: Widely used for surveillance in locations where AC power isn’t readily available.

• Wireless Access Points (WAPs): This technology enables the flexible placement of Wi-Fi access points in ceilings or high walls, optimizing coverage.

• VoIP Phones: Allows phones to work anywhere there’s a network outlet, often simplifying moves and installations.

• IoT Devices: PoE provides power to IoT devices like sensors and controllers in intelligent building systems.

Benefits of PoE

• Flexibility: Devices can be placed in optimal locations without an electrical outlet.

• Simplicity: It eliminates the need for additional power infrastructure, which reduces installation costs and complexity.

• Reliability: PoE power can often be centralized and backed up, reducing the impact of power failures.

• Safety: The PoE’s negotiation protocols prevent overloading devices and ensure safe power levels.

Overall, PoE technology simplifies installations, saves on wiring costs, and enables greater flexibility in network design, making it a popular choice for both small and large network environments.

Passive vs. Active PoE

Passive PoE and Active PoE are two different methods of delivering Power over Ethernet to devices. They differ primarily in terms of power regulation and compatibility.

Passive PoE

• Fixed voltage: Passive PoE operates at a fixed voltage, typically 24V or 48V, regardless of the device’s power requirements.

• No Power Negotiation: Passive PoE delivers power continuously without checking if the connected device is PoE-compatible or needs a specific voltage.

• Compatibility: It only works safely with devices specifically designed to accept passive PoE at the set voltage. It should not be used with devices designed only for Active PoE.

• More straightforward, Lower-Cost Option: This option is less expensive and more straightforward for installations that use only Passive PoE-compatible devices.

Active PoE

• Standards-Based (IEEE 802.3af/at/bt): Active PoE conforms to IEEE standards and supports multiple power levels (15.4W, 30W, 60W, or 100W, depending on the standard).

• Power Negotiation: Active PoE devices initiate a handshake to determine if the connected device is PoE-compatible and at what power level it should operate. Power is delivered only to devices that request it.

• Higher Safety and Flexibility: It suits larger, mixed installations with diverse equipment.

• Used in Enterprise Settings: It is often found in corporate, industrial, or relatively complex network setups.

Active PoE is standards-compliant, negotiates power needs, and is safer for various devices. Passive PoE is more straightforward, usually at a fixed voltage, and is compatible only with specific equipment.

Dewesoft products that support PoE

Active PoE

• SIRIUS X

• IOLITE X

Passive PoE

• DS-CAM-POE-SPLITTER

• DS-LAN Network Switches

• NEMOSENSE

• SIRIUSi-XHS-PWR 

• IOLITE modular

PTP V2 synchronization

What is PTP synchronization?

PTP (Precision Time Protocol) Version 2, also known as IEEE 1588v2, is a protocol that enables high-precision synchronization of clocks across a network. PTP v2 is an upgrade from the original PTP (IEEE 1588-2002) and is widely used in sectors where accurate timing is critical, such as telecommunications, industrial automation, power utilities, and financial services.

How does PTP v2 synchronization work?

PTP v2 synchronizes clocks on devices (known as nodes) within a network using a master-slave hierarchy. The protocol enables nodes to align their clocks to a Grandmaster Clock (the main time source), ensuring they share the same precise time down to the microsecond or nanosecond.

The synchronization process involves several steps:

1.Clock Hierarchy Selection:

• PTP v2 uses a hierarchical model to identify the best clock in the network, called the Grandmaster Clock. This is determined through a process called the Best Master Clock (BMC) algorithm, which considers factors like clock accuracy, stability, and priority.

• The Grandmaster Clock sends time data to all other clocks.

2.Synchronization Messages:

• PTP v2 achieves synchronization by exchanging Sync, Delay Request, Delay Response, and Follow-Up messages between the Grandmaster and slave clocks. These messages allow the protocol to measure and account for network delays and ensure accurate time alignment.

• Sync Message: The Grandmaster Clock periodically sends a Sync message with its current timestamp to the other clocks.

• Follow-Up Message: This is a subsequent message with precise timing details, helping other clocks adjust for delays in the Sync message’s transmission.

3.Delay Measurement:

• Other clocks send Delay Request messages to the Grandmaster, which responds with Delay Response messages. The time stamps from these exchanges allow the other clocks to calculate the time delay between them and the Grandmaster.

• Other clocks can precisely align their time with the Grandmaster Clock by measuring and accounting for these delays.

4.Offset Calculation and Adjustment:

• Using the time stamps from these messages, the other clocks calculate offsets (the time difference between the slave and Grandmaster) and the network transmission time delay.

• Other clocks adjust their local time to match the Grandmaster, achieving synchronization.

PTP v2 applications

PTP v2 is essential in industries where precise timing is crucial for coordination, data accuracy, and system performance:

1. DAQ and Industrial Automation: PTP v2 synchronizes machines and processes in these applications. Processes and data are accurately time-stamped and aligned.

2. Telecommunications: PTP v2 synchronizes cellular base stations, supporting efficient handovers and time-sensitive network services.

3. Financial Services: Precise time stamping of trades is required to comply with international regulations and ensure transaction traceability.

4. Power Utilities: Electrical grid synchronization requires precise timing for monitoring and control for power distribution stability, event analysis, and fault detection.

5. Broadcasting: PTP v2 supports synchronizing audio, video, and data streams, essential for live broadcasts and multimedia distribution.

PTP v2 benefits

1. High Precision: PTP v2 offers microsecond to nanosecond accuracy in applications that require high precision for safety and related imperatives.

2. Network Efficiency: PTP v2’s multicast messaging reduces the need for point-to-point connections and lowers bandwidth usage.

3. Reduced Costs: Operating over Ethernet, PTP v2 eliminates specialized cabling and infrastructure.

4. Scalability: PTP v2 supports large networks by allowing multiple layers of time distribution.

5. Flexibility Across Networks: PTP v2 can be deployed alongside other time-synchronization protocols when needed.

PTP v2 L2 and L3

The PTP v2 L2 and L3 versions are widely used. Selecting the better one for each application depends on the network architecture and precision requirements.

L2 is preferred in environments where low latency and high precision are critical, such as industrial automation, telecom, and audio/video production. It eliminates the overhead of IP and UDP layers, offering minimal jitter and latency.

L3 offers greater scalability due to IP-based routing. It can leverage existing network infrastructure, including multicast routing protocols.

Dewesoft Products that Support PTP

• SIRIUS X 

• IOLITE X 

• SIRIUS XHS 

• OBSIDIAN

• DS-LAN Network Switches

Summary

Dewesoft has embraced PTP v2 and active power over Ethernet technologies to make daisy-chained, distributable data acquisition systems easy to configure.

Dewesoft uses these and other emerging technologies to add capability, reliability, and value to our DAQ instrument ecosystem, benefiting our valued customers. Synchronization has been our special focus for decades and has only become more critical over the years. These technologies allow us to design and build robust DAQ instruments that handle the most challenging applications and interoperate in a cohesive ecosystem. Products like the X line are openDAQ compliant, an open-source SDK that allows them to be integrated into any software environment, further enhancing their versatility and interoperability.

If you have questions about how these technologies can be applied to your measurement needs, please contact your closest Dewesoft application engineer for guidance.