Measurement-based control for industrial systems in the digital world

New series of standards for better testing of industrial and process measurement transmitters

By Roberto Redaelli, Product Manager, Gefran (Italy), Morand Fachot

Industrial automation is not new: it has evolved over the years from simple functions as technologies have improved. Measurement-based control has always been at the core of industrial automation. As the nature of manufacturing changes rapidly, new standards are needed for making accurate measurements for industrial control systems.

Gefran pressure transmitter IEC 62828 provides reference conditions and procedures for testing industrial and process measurement transmitters, such as pressure transmitters (Photo: Gefran)

From basic to intelligent automation

Modern industrial automation in the form of programmable robots (first introduced in the US automotive industry in the early 1960s) has, until recently, relied mainly on analogue control systems. Manufacturing is moving rapidly away from analogue technologies, instead adopting “intelligent” digital systems and processes such as computerized controls, connected devices – the so-called internet of things (IoT) – and machine learning, and evolving into what is being termed smart manufacturing (or Industry 4.0).

This new industrial environment calls for new control systems and standards for equipment designed to provide accurate measurements.

IEC SC 65B: Measurement and control devices, a Subcommittee (SC) of IEC Technical Committee (TC) 65: Industrial-process measurement, control and automation, is developing a series of International Standards, IEC 62828, Reference conditions and procedures for testing industrial and process measurement transmitters. Two Standards have already been published; more are being developed and will be published in coming months.

When it is completed, the IEC 62828 series will replace IEC 60770, Transmitters for use in industrial-process control systems, which will be withdrawn.

IEC 62828 will also be used to revise the IEC 61298 series, Process measurement and control devices, which is applicable to all process measurement and control devices. This will ensure the harmonization of the two series.

Underlying principles and reasons for this new series

The reasons that led to the development of the IEC 62828 series are explained in the introduction to the two Standards that have been available since November 2017:  

“Most of the current IEC International Standards on industrial and process measurement transmitters are rather old and were developed bearing in mind devices based on analogue technologies. Today’s digital industrial and process measurement transmitters are quite different from those analogue transmitters: they include additional functions and newer interfaces, both in the computing section (mostly digital electronic) and in the measuring section (mostly mechanical). Even if some Standards dealing with digital process measurement transmitters already exist, they are insufficient, since some aspects of the performance are not covered by appropriate test methods.

“In addition, existing IEC test Standards for industrial and process measurement transmitters are spread over many documents, so that for manufacturers and users it is difficult, impractical and time-consuming to identify and select all the Standards to be applied to a device measuring a specific process quantity (pressure, temperature, flow, level, etc.). To help manufacturers and users, it was decided to review, complete and reorganize the relevant IEC Standards and to create a more suitable, effective and comprehensive Standard series that provides, in a systematic way, all the necessary specifications and tests required for different industrial and process measurement transmitters”.

Roberto Redaelli, a product manager for pressure transducers with Italy-based Gefran, a company specializing in automation components and industrial process control systems, gave e-tech the information given below on this new series of IEC International Standards. Redaelli is an expert with Working Group (WG) 6 of IEC SC 65B. IEC SC 65B/WG 6: Testing and evaluation performance, prepares "methods of evaluating the performance of system elements and functions used in industrial process measurement and control with special regard for harmonization".

Move from analogue to digital main driver to work on new Standards

Measuring physical variables such as pressure and temperature is becoming increasingly important in industrial and process automation today. The move to the so-called Industry 4.0, or smart manufacturing environment that results from the increased digitization of systems and the introduction of IoT in industrial environments makes this particularly relevant.

This means that it is more necessary than ever to define precisely what a process measurement transmitter (PMT) such as a pressure or a temperature transmitter has to do, what are the conditions in which it has to work and what is the best procedure for testing it.

Speaking a “common language” on both the manufacturer and the user sides is the best path to follow to avoid making mistakes, obtain the best results and achieve the optimum outcome. The new IEC 62828 series is leading the way, and aims to be both useful and beneficial for all players in a demanding market.

To help manufacturers and users, it was decided to review, complete and reorganize the relevant IEC Standards and to create a more suitable, effective and comprehensive series that would provide, systematically, all the necessary specifications and tests required for different industrial and process measurement transmitters.

The new series on industrial and process measurement transmitters solves these issues and adds value for stakeholders by covering:

  • applicable normative references
  • specific terms and definitions
  • typical configurations and architectures for the various types of industrial and process measurement transmitters
  • hardware and software aspects
  • interfaces (to the process, the operator and the other measurement and control devices)
  • physical, mechanical and electrical requirements and relevant tests; clear definition of the test categories: type tests, acceptance tests and routine tests
  • performance (specification, tests and verification)
  • environmental protection, hazardous areas application, functional safety, etc.
  • structure of the technical documentation

Multiple parts address various issues

To address systematically all the issues that need including, the series is organized in several parts.

The following two IEC 62828 Standards for reference conditions and procedures for testing industrial and process measurement transmitters are currently (as of November 2017) available from the IEC webstore:

These parts will be published in 2018:

  • IEC 62828-3: Specific procedures for temperature transmitters
  • IEC 62828-4: Specific procedures for level transmitters
  • IEC 62828-5: Specific procedures for flow transmitters

In preparing the IEC 62828 series, many test procedures were taken from the IEC 61298 series and improved upon.

International effort to develop a common language, assess accuracy

Clause 3 of IEC 62828-1, covering terms, definitions and abbreviated terms, is used to define the PMT properties, with recommendations as to what a technical data sheet should contain. This is intended to help with speaking “a common language” and to make it easier for users to understand product specifications.

Another interesting feature is defined in clause 7, which introduces the total probable error (TPE) concept, giving a guideline as to how to assess the overall accuracy of a PMT. This will make it easier, especially for end users, to compare PMTs from different manufacturers so that they can make the right choice according to their specific needs.

The development of IEC 62828 Standard is the fruitful result of the participation of experts from several IEC National Committees (from Germany, Japan, China and France) working for primary manufacturing industries and end users associations.

Italian experts on SC 65B/WG 6 have also played a central role in the development of this Standard, with more than a third of the WG experts, including the convenors, working on it.

To celebrate the success of the publication of IEC 62828-1 and IEC 62828-2 and define the work still needed to complete the remaining three parts (temperature, flow and level), scheduled to be published in the near future, Gefran invited IEC SC 65B/WG 6 to hold its latest official meeting at the Gefran Headquarters in Lombardy, Italy, in October 2017.

Gallery
Gefran pressure transmitter IEC 62828 provides reference conditions and procedures for testing industrial and process measurement transmitters, such as pressure transmitters... (Photo: Gefran)
Siemens temperature transmitters ...and temperature transmitters
IEC SC 65B/WG 6 experts at Gefran headquarters, October 2017 IEC SC 65B/WG 6 met at Gefran headquarters in Italy in October 2017