Maintaining Your Measuring Equipment: Servicing Your Portable Measuring Arm

by Sam O’Prey on June 4, 2019 From Ask The Experts

In the previous blog of this series, we explored how to enhance the flexibility of your CMM with a retrofit. In this blog, we’ll look at the steps we take when servicing a portable measuring arm to keep your equipment working at peak performance.

Our Absolute Arm systems are designed to deliver excellent usability and versatility directly within the manufacturing environment. But they are also technologically complex tools and often called upon to perform in harsh conditions for long periods.

That’s why planning for the care of your portable measuring arm is essential to protect your investment. Regular maintenance increases confidence in your measurement results by ensuring that the arm performs to its specifications.

Hexagon Manufacturing Intelligence offers servicing specially designed for portable measuring arms to help users prolong the lifespan of their equipment and keep it in good condition.

What Happens in a Portable Measuring Arm Service?

A thorough check of the portable measuring arm should include a number of key tests.


A service from Hexagon involves a complete inspection of the portable measuring arm, including tests of:

  • All cables
  • TESA kinematic joint connectors (arm and all probes)
  • Control/Feature Pack (including batteries)
  • Buttons on the arm wrist and base
  • LCD wrist display (newer 7-Axis models)
  • Feedback LEDs and pictograms
  • Gas shocks
  • Any accessories and artefacts


Before calibration and alignment, the performance of the arm and scanner (if applicable) are checked. To confirm the machine performs to accuracy requirements, the counterbalance undergoes a compliance inspection.

Alignment, Calibration and Certification

After the arm’s probes have been aligned, tests and calibrations are performed to ensure fulfilment of four accuracy values specified in the ISO 10360-12 standard:

  1. The length test (Euni): ensures the arm doesn’t exceed the maximum permissible error for unidirectional length. The Euni value therefore most closely reflects most measurement needs.
  2. Sphere test one (Ldia): ensures the arm doesn’t exceed the maximum permissible error for the articulation location. The Ldia value indicates the arm’s repeatability.
  3. Sphere test two (Psize): ensures the arm doesn’t exceed the maximum permissible error for measuring the diameter of a sphere. The Psize value represents the accuracy of feature measurements.
  4. Sphere test three (Pform): ensures the arm doesn’t exceed the maximum permissible error for measuring the form of a sphere. The Pform value defines the arm’s dispersion accuracy.

Following this testing and calibration process, new certifications are also provided if required.


All firmware, for both the portable measuring arm and all accessories, is fully updated as part of the service process.


Following the service, the inside of the arm and all cases, cables, artefacts and accessories are fully cleaned, including the replacement of any labels if required.

Key Considerations When Servicing Your Portable Measuring Arm

The factory-recommended maintenance interval is 12 months, but you might want to consider more frequent maintenance if the arm is used for many hours each day and/or in a harsh environment.

Depending on model, size and performance of the arm, a service can take between one and three days. All arms that leave our service centres after a calibration service are shipped with an ISO 10360-12, B89.4.22 or VDE/VDI certificate.

Hexagon’s Absolute Arms can be fitted with optional RDS data collector software, which enables users to perform fast accuracy checks and calibration with a certified length artefact.

We have certified service centres all over the world ready to provide quick and local support. To discuss what service might be right for you, contact customer service and a local representative will be in touch.

In the next blog, we will explore the confidence and supported to be gained from software maintenance agreements.

Sam O’Prey

Sam O’Prey is responsible for sales and marketing for Hexagon Manufacturing Intelligence metrology service and support business in the UK & Ireland. Sam joined the company in 2010 and has 14 years’ experience in digital and direct sales and marketing within the manufacturing and technology sectors, with an additional nine years’ experience as an engineering technician and manager within manufacturing and design.

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