Instrument selection and specification process map

What is in this map

13 steps across 4 swimlanes and 5 phases, with 2 decision points.

Swimlanes (who does the work)

Sales / Account Management, Instrumentation Engineering, Compliance / QA and Procurement

Phases (left to right)

Intake, Requirements & constraints, Selection & compliance, Customer proposal & approval and Quotation & order

Why map this process

This map treats the customer's requirement as advisory rather than an order for a named part, and that framing shows up in row 1's own language: it captures a tag number and a service description, not a model number. The reason is that two customers describing what sounds like the same duty can land on different measurement technologies once their actual medium, pressure, temperature and accuracy needs are compared — the selection has to be engineered, not looked up.

Putting the compliance check as its own decision, separate from the measurement-principle selection that precedes it, is what stops a technically excellent choice from being proposed to a customer it cannot legally be sold to. Certificates, hygienic fittings and industry-specific requirements are checked here as their own gate, with a documented loop back to reselection when they are not met — compliance is not treated as a footnote to the engineering choice.

Every step in the map

This is the spreadsheet behind the diagram. The numbers in “Goes to” are row numbers, which is exactly what the editor’s “Line to” column holds — so you can read the flow here and retype any part of it.

The decision points

Every branch in the map, with the label on each outgoing line. These are the questions the process has to be able to answer.

• 7. **Compliance** requirements met?

  Owned by Compliance / QA · Selection & compliance

  • Yes → step 9
  • No → step 8

• 10. Customer **technical approval**?

  Owned by Sales / Account Management · Customer proposal & approval

  • Approved → step 12
  • Changes requested → step 11

Notes on specific steps

These notes travel with the map. In the editor they live in the Notes column and appear when you open a box.

1. Customer requirement received

Captures the tag number, service description and, where one exists, the instrument being replaced. Treated as the trigger for an advisory selection process, not an order for a named part.

5. Select *measurement principle*

The choice here, e.g. differential-pressure vs. Coriolis vs. vortex for a flow point, or RTD vs. thermocouple for a temperature point, follows from the medium, constraints and accuracy already gathered upstream. Two customers with the same nominal duty can land on different technologies once their conditions are compared.

6. Check compliance requirements

Covers customer-industry and regulatory requirements such as material certificates or hygienic fittings. Where the installation location is a classified hazardous area, ATEX certification is verified separately under the ATEX Instrument Selection & Installation SOP rather than duplicated here.

11. Revise instrument selection with customer feedback

Typical feedback is a different process connection, a tighter accuracy class, or a request to match an existing installed base, rather than a rejection of the measurement principle itself.

Making it yours

Both loops in this chart return to the same kind of place they started from: a failed compliance check (row 7, 'No') loops back to measurement-principle selection at row 5, and customer-requested changes after proposal (row 10, 'Changes requested') loop back to re-proposing at row 9, not back to square one. When you adapt this map, keep those loops tight to the step that actually needs revisiting — collapsing them into one generic 'redo the selection' box loses the information about how far back the rework actually needs to go.

What to watch out for

• Do not conflate the ATEX certification check with the general compliance check at row 6. This chart's own note explicitly carves that out: where the installation location is a classified hazardous area, ATEX certification is verified separately under its own SOP rather than duplicated here — folding it back in here means checking it twice, inconsistently, in two different places.
• Customer technical approval (row 10) is a real decision with a real loop, not a rubber stamp on the way to quoting. Typical feedback the chart anticipates is a different process connection, a tighter accuracy class, or matching an existing installed base — none of which reject the measurement principle chosen, which is why the loop returns to re-proposing rather than re-selecting from scratch.
• Do not skip straight from measurement-principle selection to proposing the instrument. Compliance sits between them as a hard gate specifically so nothing gets proposed to a customer that would need to be walked back once a certificate requirement is discovered.

Frequently asked questions