Length bar and long gauge block calibration services
Calibration of length bars and long gauge blocks by interferometry.
NPL services for interferometric calibration of length bars and long gauge blocks
Length bars and long gauge blocks are among the most commonly used standards for maintaining traceability in engineering. Before use, all length bars and long gauge blocks must themselves be calibrated according to various specification standards such as BS 1790, BS 5317 and ISO 3650. Length bars and long gauge blocks must also be re-calibrated periodically to maintain their accuracy. In order to satisfy these requirements NPL offers comprehensive UKAS-accredited calibration services for length bars and long gauge blocks from 25 mm to 1500 mm in length. These services are available by prior booking.
Calibration service details
NPL's calibration service offers the following features:
- interferometric calibration of central length by comparison against known standard absolute interferometric calibration of central length (lower uncertainty)
- verification of measurement face flatness
- verification of parallelism or variation in length
- interferometric calibration of coefficient of thermal expansion (lengths > 100 mm)
- calibration of long gauge blocks to ISO 3650 and BS EN ISO 3650
- calibration of length bars to BS 1790 and BS 5317
- calibration of steel or ceramic length bars and long gauge blocks
Download flyer outlinking length bar & gauge block calibration services [PDF]
Gauge block and length bar types we can calibrate for you
NPL can measure the following grades of length bar and long gauge block:
- Reference and Calibration grades of BS 5317 (Metric)
- Reference and Calibration grades of BS 1790 (Inch)
- Grades 00, 0 and Calibration of ISO 3650 (Metric)
- Grades 00, 0 and K of BS EN ISO 3650 (Metric & Inch)
A PDF note on the types of gauge blocks and length bars we can measure (
PDF 282 KB) is also available.
Measurement uncertainty
Measurement by interferometric comparison:
- Lengths, L, up to 100 mm : ±(0.065, 0.00042L) µm
- Lengths, L, above 100 mm: ±(0.116 + 0.000263L) µm
Measurement by absolute interferometry:
- Lengths 150 mm - 1500 mm: ±(0.049 µm, 0.000083L) µm
Length measurement uncertainties are quoted at 95 % confidence level (where L is the length of the gauge in mm).
NPL's length bar and long gauge block services are covered buy the CIPM MRA and are UKAS-accredited.
Further information
- Contact us for more details, to request a quotation or to schedule a calibration
- Details of thermal expansion measurements on long gauge blocks
- Notes on the care and use of gauge blocks ( PDF 18 KB)
Publications
- Lewis, A J, Long-term study of gauge block interferometer performance and gauge block stability, Metrologia, 2010, 47, 473-486
- Lewis, A J, Measurement of length, surface form and thermal expansion coefficient of length bars up to 1.5 m using multiple-wavelength phase-stepping interferometry, Meas. Sci. Technol., 1994, 5, 694 – 703
- Lewis A J, Pugh D J, Interferometer light source and alignment aid using single-mode optical fibres, Meas. Sci. Technol., 1992, 3, 929-930
- Lewis A J, Absolute length measurement using multiple-wavelength phase-stepping interferometry, PhD Thesis, 1993, Imperial College, University of London
- Lewis A J, Key Comparison CCL-K2 – Measurement of long gauge blocks – Final Report, Metrologia, 2003, 40 Tech. Suppl. 04004
- Lewis A J, Final Report on EUROMET Key Comparison EUROMET.L-K2: Calibration of long gauge blocks, Metrologia, 2006, 43 Tech. Suppl. 04003
Contact
Customer Service tel: 020 8943 8631
E-mail: dimensional_enquiries@npl.co.uk