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Conformance testing for Ethernet-APL products: ensuring interoperability

July 1, 2021
In addition to providing the specifications for Ethernet-APL, the APL Project has also developed conformance testing plans for Ethernet-APL devices. However, Ethernet has existed for many years and has been integrated into many products. Why is special testing needed?

Conformance testing has traditionally been a key way for end users to gain assurance that the products they are sourcing from different vendors will interoperate. However, as we think of it in our offices or in the industrial space today, Ethernet is a four-wire Ethernet with separate power, and conformance testing services by network organizations has typically focused on the protocols. With Ethernet-APL, both data and power are being introduced over only two wires. Therefore, a way to measure conformance to the specifications needs to be provided for end users to have the same assurance of interoperability. In addition, there are also special requirements in process automation that are not found in other industries, which must be considered. 

Special requirements for hazardous areas

Perhaps the most common special requirement involves deployment in unsafe areas. Process automation has very specific demands that must be met to assure the safe installation of products when they involve power and are used in hazardous areas. It is typically accomplished with the two-wire power and data type standard with a technique called intrinsic safety (IS). Intrinsic safety is an IEC specification and not handled within the IEEE. This means that the Ethernet physical layer of an Ethernet product is governed by the IEEE—but the intrinsic safety and the discrete power requirements for the industrial space are driven by the IEC. Therefore, there is an additional set of requirements above what is defined by the IEEE and generally acceptable for consumer and light industrial applications that must be examined.

In addition, the APL Project has developed specifications for port profiles for Ethernet-APL in order to define the power and signaling requirements. These port profile specifications, which are integrated into the network specifications for the key industrial networks, also outline expectations for immunity to noise in support of different links and cables that would be necessary for the industrial space. The end result is that there are IEEE requirements and Ethernet-APL specific requirements. This means that a product that is conformant to IEEE may not meet all the requirements of Ethernet-APL. However, an Ethernet-APL product must meet all requirements for IEEE usage as well as those for APL. 

Furthermore, the Ethernet-APL port profile specifications allow for discrete power classes including those for intrinsic safety as well as non-intrinsically safe applications. Suppliers can create higher power instruments that in turn can only be used with specific high-power ports on an Ethernet-APL switch or suppliers can allow for an additional power supply in their device. 

Testing program: IEEE and Ethernet-APL specific operations

FieldComm Group, Profibus/Profinet International, ODVA, and the OPC Foundation will implement a testing program around the physical layer which will confirm both: 

  • the IEEE operations of the product
  • the Ethernet-APL specific operations of the product, including power and signal as well as noise immunity and other requirements

These items are all addressed within the conformance test specifications. 

Common set of tests will be accepted by all organizations

Furthermore, if a company tests an Ethernet-APL pressure transmitter for Profinet, for example, and then creates a version for HART-IP on the same physical layer, then the company would only need to have the HART-IP functionality tested. The Ethernet-APL physical layer will face a common set of tests at each organization and those test results will be recognized by each of them.

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