100% Employee Owned, Founded 1954


100% Employee Owned, Founded 1954


100% Employee Owned, Founded 1954


Specification Documents: Pay Now or REALLY Pay Later

Robbie Peoples, P.E. | May 13th, 2015

Navigating the dark, rocky waters of control system development can be challenging for even the very experienced project managers. Control system activities such as estimating, planning, and building seems like some kind of black box magic. Many aspects of an automation project can easily be miscommunicated, not thoroughly understood, or the wrong control strategy is applied to achieve the overall production requirements.

There are so many pitfalls that can turn a basic control system project into a sinking ship. However, the risk can be removed by following the “Beacon Light of Specifications.” A proven, structured approach to developing an automation project can keep your ship sailing to smooth waters.

What Are Specification Documents?

Specification documents provide a written description that uses laymen terms to allow the end-user to understand what is being defined without having to be proficient at DCS or PLC programming. These documents are comparable to a set of house plans. Would you write a check to your contractor and say, “build me a house” without providing a floor plan? I didn’t think so!

The same is true for building an automation system. If you want a project to be successful and to get what you expect, then you need to plan what should be achieved. Planning a control system can be implemented using specification documents that are formatted very simply and easily understood by the non-control system engineers. Using common, laymen’s language, these documents provide very specific target functions to allow all stakeholders involved to grasp a thorough understanding of a potentially intimidating process.

Functional Specifications (FS) & Detail Design Specifications (DDS)

Specification documents for an automation system generally come in two flavors: Functional Specifications (FS) & Detail Design Specifications (DDS).

The Functional Specifications generally define the big picture or overall functionality of system-wide functions. An example of Functional Specifications documents are Software Specifications or Batch Specifications. These typically define the common elements and/or tools that are utilized across multiple instances in the system.

Detail Design Specifications documents typically are more focused on specific application or process related functions such as: Equipment Module Sequences, Interlock Matrix functions, and automated logic conditions. A typical control system has both the Functional Specifications & Detail Design Specifications to completely encompass all of the functions.

In addition, the Functional Specifications can be developed and used for bidding purposes for accurate quoting and bid comparison. Once the project is awarded, the Detail Design Specifications can be developed to outline the details of how to achieve the functions identified in the Functional Specifications.

Benefits of Owning Specification Documents

  1. Provide means to generate an accurate quote.
  2. Defines exactly what end-user will be getting.
  3. Establishes a scope boundary for the project.
  4. Enables generation of a preliminary schedule.
  5. Determines the automation goals for the project to be successful.
  6. Generates reference documents for acceptance testing.

Best Practices When Developing Specification Documents

  1. Get all parties involved early. Engineering, Production, Maintenance, Quality, etc.
  2. Define terminology so that everyone is on the same page.
  3. Organize documents and provide a road map so that everyone understands the overall objectives.
  4. Identify how exception conditions are handled from a general standpoint.
  5. Utilize class based approach as much as possible to reduce design, implementation, and testing time.
  6. Perform one example of each type of document first, and review to ensure everyone’s efforts are efficient.


Specification documents are a critical part of a successful automation project. The benefits of planning and documenting the software/hardware functions will ensure the end-user will receive exactly what is needed to meet the production requirements.

Designing a system on paper allows for everyone to assimilate the available features and provide a mechanism to account for details to ensure nothing is overlooked or missed. Developing an overall Functional Specification early on allows for accurate quoting and development of a general timeline to ensure the project is delivered on on-budget and on-time.

Developing accurate specifications for an automation project can be an exhaustive effort, but with proper organization and support from all stakeholders, this task can be streamlined and efficient as possible. Specifications allow for the removal of the unknown and provide a navigational beacon to avoid the rocky waters of risk. Not all projects require the GAMP validation model level of documentation, but with a customer focused approach, specification documents will set your project up for success.

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