 The large Strainstall designed test machine has recently been recalibrated by the National Physical Laboratory (NPL). It was first calibrated when new, in December 2006, when it achieved excellent results, with a 0.5 Grade (0.5% of reading) from 12MN down to 300MN to BS EN ISO 7500-1:2004. Since that time it has worked hard without any problem, initially on some load cells where almost the full capacity of the machine was used for proof loading at 1701 tonnes.
To provide the recalibration, NPL needed a reference load cell calibrated to the necessary standards, and this was done at the German National test house. The calibration machine there suffered severe damage last year, requiring major repairs. As a result, the recent visit by NPL was the earliest recalibration date that was possible for the machine.
The outcome has been a great success. The test machine load monitoring system required no adjustment at all, and the grading results matched those achieved in the original calibration. The numerical results were slightly better than last time. | 
