Instrumentation Questions

Mastering DeviceNet Industrial network protocol: Top Interview Questions and Answers – Part 2

Table of Contents

1.What are the benefits of using DeviceNet?

Advantages of employing DeviceNet include simplified cabling, resistance to noise, versatile network topologies, integrated power and data transmission, and support for numerous nodes.

2.What protocol does DeviceNet utilize for its transport and network layers?

DeviceNet utilizes the Common Industrial Protocol (CIP) for its transport and network layers, offering services like explicit messaging and I/O messaging.

3.How does DeviceNet differ from Ethernet/IP?

DeviceNet and Ethernet/IP both use the Common Industrial Protocol (CIP), but they differ in their physical and data link layers. DeviceNet is based on the CAN bus and is designed for low-level device communication, while Ethernet/IP utilizes Ethernet for higher-level device and system integration.

4.How can a DeviceNet system be safeguarded from overvoltage or transients?

Overvoltage and transient protection can be achieved by using surge protection devices, which limit voltage levels on the DeviceNet network.

5.What is a DeviceNet scanner module?

A DeviceNet scanner module is a hardware component that can be installed in a PLC or controller, enabling it to manage DeviceNet communication as the network’s master.

6.Can a PC be connected to a DeviceNet network?

Yes, a PC can be connected to a DeviceNet network through a PC interface card or a USB-to-DeviceNet adapter, facilitating network monitoring and management.

7.What happens if a DeviceNet termination resistor is absent?

The absence of a termination resistor can result in signal reflections on the network, potentially leading to communication errors or network failure.

8.Can a regular Ethernet cable be used for a DeviceNet network?

No, a standard Ethernet cable should not be used for a DeviceNet network. DeviceNet requires a specialized cable capable of carrying both power and data.

9.What is meant by ‘drop line’ in a DeviceNet network?

A ‘drop line’ in a DeviceNet network is a shorter cable connecting a device to the main trunk line, typically using thinner cable than the trunk line.

10.What tools can be employed to design a DeviceNet network?

Various network design tools offered by manufacturers can aid in DeviceNet network design, helping calculate power requirements, assess network load, select suitable devices and cables, and plan the overall network layout.

11.How can issues in a DeviceNet system be identified?

Problems in a DeviceNet system can be detected using diagnostic tools, observing LED indicators on devices, checking error codes, and utilizing network analysis software.

12.Can a USB device be connected to a DeviceNet network?

Directly connecting a USB device to a DeviceNet network is not possible. However, USB-to-DeviceNet adapters are available to enable communication between a PC with a USB interface and the DeviceNet network.

13.How can the length of a DeviceNet network be extended?

To extend the length of a DeviceNet network beyond its maximum allowed length, repeaters can be used to regenerate the signal and enable longer cable distances.

14.What does the DeviceNet specification define?

The DeviceNet specification defines the physical and data-link layers based on the CAN protocol and includes definitions for the transport, session, and application layers using the Common Industrial Protocol (CIP).

15.How can a DeviceNet device be configured?

DeviceNet devices can be configured using manufacturer-provided software tools, allowing the adjustment of parameters such as MAC ID and baud rate.

16.Can DeviceNet support peer-to-peer communication?

Yes, DeviceNet can support peer-to-peer communication, enabling direct communication between any devices on the network, provided they support this communication model.

17.What happens when a DeviceNet device malfunctions?

When a DeviceNet device malfunctions, it can disrupt network communication. The network master (scanner) can detect the failure and inform the control system to take appropriate action.

18.What is the typical power consumption of a DeviceNet device?

The power consumption of a DeviceNet device varies depending on its type and model, but most devices typically use a modest amount of power, usually a few hundred milliamps at most.

19.Can DeviceNet be used in a hazardous location?

Yes, DeviceNet can be employed in hazardous locations, provided that devices and installation methods are rated and approved for such use. This often involves using intrinsically safe barriers or isolators and devices designed for hazardous locations, adhering to local codes and regulations.

20.Can DeviceNet be integrated with other Fieldbus protocols in a hybrid network?

Yes, gateways or bridges can be utilized to connect a DeviceNet network with networks using other Fieldbus protocols, facilitating data exchange between the networks.

21.What is a “DeviceNet card”?

The capability to communicate with a DeviceNet network is provided by a hardware component known as a DeviceNet card. This component can be installed in a computer or an industrial device.

22.Are there industry-specific versions of DeviceNet?

Yes, there are specialized variants of DeviceNet designed for specific industries, such as Marine DeviceNet and Safety DeviceNet.

23.What error detection mechanisms does DeviceNet employ?

DeviceNet uses error detection mechanisms inherited from the CAN protocol, including frame checking, acknowledgment checks, and cyclic redundancy checks (CRC).

24.Can DeviceNet be used for motion control applications?

Yes, DeviceNet can be used for basic motion control applications, but for more complex or high-speed requirements, a dedicated motion control network may be more suitable.

25.Can fiber optic cable be used with DeviceNet?

Yes, fiber optic cables can be used with DeviceNet, but media converters are required to convert electrical signals from DeviceNet devices to optical signals and vice versa.

26.What is a “DeviceNet star topology”?

A DeviceNet star topology is a network configuration where each device is directly connected to a central point, such as a hub or a switch. However, this topology is generally not recommended for DeviceNet due to the increased risk of reflection issues.

27.How does DeviceNet handle network arbitration?

DeviceNet, like CAN, employs non-destructive bitwise arbitration, where messages with higher priority (lower arbitration ID) are transmitted first in the event of simultaneous transmissions, ensuring data integrity.

28.What are common causes of network faults in a DeviceNet system?

Network faults in a DeviceNet system can result from factors like incorrect wiring, duplicate MAC IDs, device failures, lack of termination, and electromagnetic interference.

29.Is it advisable to run DeviceNet and power wires in the same conduit?

It is generally not recommended to run DeviceNet and high-voltage power wires in the same conduit due to the risk of electrical noise interference. Compliance with local codes and regulations for cable installation is essential.

30.What is a “DeviceNet EDS file”?

An Electronic Data Sheet (EDS) file is a text file used in DeviceNet to describe a device’s features. Configuration software uses EDS files to identify devices and display their configurable parameters.

31.What is the maximum current capacity supported by a DeviceNet network?

Typically, a DeviceNet network can handle a maximum current capacity of 8 Amps on the trunk line, but this capacity may vary based on factors such as cable length and diameter.

32.How can you ensure that a single device failure does not disrupt the entire DeviceNet network?

Effective network design, which includes segment isolation, can prevent a single device failure from impacting the entire network. Additionally, devices equipped with built-in short-circuit protection can safeguard the network from the consequences of a single device short-circuit.

33.What is the purpose of a ‘DeviceNet traffic analyzer’?

A DeviceNet traffic analyzer serves the function of monitoring and diagnosing the network. It is capable of capturing and decoding network traffic, aiding in the identification and resolution of issues while optimizing network performance.

34.What do we mean by ‘DeviceNet error codes’?

DeviceNet error codes refer to codes generated by devices when they encounter errors. These codes provide valuable information for diagnosing and rectifying issues within the network.

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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