Dimensional metrology
Traceability to the SI unit of length: the metre
The metre is realized in accordance with its definition: "The metre is the length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of a second." In practice, length is measured in terms of the wavelength of light from a laser that is highly stabilized in its output frequency. The wavelengths of lasers that are used by the NRC for dimensional calibrations are calibrated by comparing them to optical frequency/wavelength standards maintained by the NRC. These standards include an ensemble of three helium-neon lasers that are stabilized on a transition component of the 11-5 band, R (127) line of iodine-127, with a relative expanded uncertainty (2s) of 4.2 x 10-11. They are used to calibrate the optical frequency/wavelength of helium-neon lasers in the red at 633 nm, which are widely used in precision interferometric dimensional metrology. Their accuracy is guaranteed through periodic comparisons with each other and through direct calibration, with traceability to the SI second and SI metre, provided by means of an optical frequency comb that is maintained by the NRC. Lasers at other wavelengths that are used by the NRC are calibrated directly by means of the optical frequency comb.
Facilities
The dimensional metrology facilities are temperature-controlled clean rooms maintained at 20.00 °C ± 0.05 °C with relative humidity controlled to 40 ± 2 percent.
Limitations
Dimensional and related calibrations are performed at 20 °C. The artifact must be in substantially new condition and of a quality that warrants the requested calibration. The acceptable accuracy-grade for a specific artifact can usually be judged from the uncertainty of the measurements described below; lower-grade artifacts and measuring instruments such as micrometers and vernier calipers should be referred to secondary laboratories accredited under the ARCHIVED - Calibration Laboratory Assessment Service.
Uncertainties
The uncertainties quoted in the descriptions below are expanded uncertainties representing a confidence level of approximately 95 percent. They were obtained assuming a normal distribution and multiplying the standard uncertainty (one standard deviation) by a coverage factor of k = 2.
Calibration services and fees
If you wish to order a calibration service, please request a quote from the following technical contact:
Dr. Brian Eves
Telephone: 613-991-3279
Email: Brian.Eves@nrc-cnrc.gc.ca
Note that the calibration costs quoted DO NOT include shipping, insurance or the cost of a customs broker. The client must arrange and pay for these services separately.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-00-00 | Custom dimensional metrology services | Fee on request |
| A33-04-00-01 | Handling fee, for processing items found not suitable for calibration. A charge is levied for any instrument or standard found to be unsuitable for calibration. This fee covers opening, inspection and return, and is based on the work done prior to discovery of the fault. | $250 |
| A33-04-00-02 | Some items require special jigs and set-ups to adapt to existing calibration facilities and the client may be asked to pay for all or a portion of the cost. | Fee on request |
Laser wavelength/frequency
The frequency and vacuum wavelength are routinely determined for helium-neon lasers stabilized at a vacuum wavelength of 633 nm and 543 nm. Calibrations at other vacuum wavelengths may be possible by special arrangement.
Laser wavelength and frequency calibrations are carried out by the NRC metrologists. Please see the "Optical frequency" calibration services for more information.
End-standards (gauge blocks and length bars)
The NRC end-standard interferometer accepts end standards made from any suitable material, such as steel, carbides, and ceramics. Interferometric length calibrations are done using the method of exact fractions and three or more wavelengths from at least two radiation sources. Only the best grades of blocks are admitted for interferometric measurements. Gauges are first inspected to ensure that the end surfaces are flat, parallel, and will wring to a reference optical flat. Gauge blocks up to 100 mm are calibrated in a vertical orientation, wrung to an optical flat. Up to 38 gauge blocks can be loaded into the instrument at a time. Long bars over 100 mm and up to 1 m are calibrated one at a time in a horizontal orientation, supported at their airy points and with a small optical flat wrung to one end. Calibration uncertainty is commensurate with the quality of the gauges and under optimal conditions is limited to (20 + 300L) nm, where L is the length of the gauge in metres. Steel gauges are demagnetized and given a rust-preventative coating prior to being returned.
Short rectangular gauge blocks (between 1 mm and 100 mm) are the easiest to calibrate. Thin gauges (less than 1 mm) and hoke-type (square section) gauges are more difficult to inspect and measure.
Calibration of a set of one or more gauges consists of the preparation (unpacking, administration, instrument set-up and repacking) for which the handling fee applies, plus the inspection and calibration of each type of gauge in the set.
Research publications:
- Gauge Block Calibration by Optical Interferometry at the National Research Council Canada (NRC Doc. No. 40002)
Authors: J.E. Decker and J.R. Pekelsky - Uncertainty Evaluation for the Measurement of Gauge Blocks by Optical Interferometry (NRC Doc. No. 41374)
Authors: J.E. Decker and J.R. Pekelsky - Updates to the NRC gauge block interferometer (NRC Doc. No. 42753)
Authors: J.E. Decker, K. Bustraan, S. de Bonth, J.R. Pekelsky
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-02-01 | Handling fee | Fee on request |
| A33-04-02-21 | Inspect a short (= 1 mm, = 100 mm), rectangular gauge block | Fee on request |
| A33-04-02-22 | Inspect a thin (< 1 mm), rectangular gauge block | Fee on request |
| A33-04-02-23 | Inspect a short, hoke-type gauge block | Fee on request |
| A33-04-02-24 | Inspect a thin, hoke-type gauge block | Fee on request |
| A33-04-02-25 | Inspect a length bar (> 100 mm, =1000 mm) | Fee on request |
| A33-04-02-31 | Calibrate a short (= 1 mm, =100 mm), rectangular gauge block | Fee on request |
| A33-04-02-32 | Calibrate a thin (< 1 mm), rectangular gauge block | Fee on request |
| A33-04-02-33 | Calibrate a short, hoke-type gauge block | Fee on request |
| A33-04-02-34 | Calibrate a thin, hoke-type gauge block | Fee on request |
| A33-04-02-35 | Calibrate a length bar (> 100 mm, = 1000 mm) | Fee on request |
| A33-04-02-41 | Set of 112 (1 mm base) rectangular metric gauge blocks (111 short, 1 thin) | Fee on request |
| A33-04-02-42 | Set of 88 (1 mm base) rectangular metric gauge blocks (87 short, 1 thin) | Fee on request |
| A33-04-02-43 | Set of 88 (2 mm base) rectangular metric gauge blocks (87 short, 1 thin) | Fee on request |
| A33-04-02-44 | Set of 17 (thin set) rectangular metric gauge blocks (17 thin) | Fee on request |
| A33-04-02-51 | Set of 88 rectangular imperial gauge blocks (88 short) | Fee on request |
| A33-04-02-52 | Set of 81 rectangular imperial gauge blocks (81 short) | Fee on request |
| A33-04-02-55 | Set of 9 rectangular imperial gauge blocks (9 short) | Fee on request |
| A33-04-02-61 | Set of 8 metric length bars (125, 150, 175, 200, 250, 300, 400, and 500 mm) | Fee on request |
| A33-04-02-62 | Set of 8 imperial length bars (5, 6, 7, 8, 10, 12, 16, and 20 in.) | Fee on request |
| A33-04-02-70 | Rental of calibrated gauge block set for characterization of mechanical comparator linearity. | $200 per week |
Precise scales
The NRC line-standard interferometer accepts precise scales up to 1 m long on metal or glass substrates having either dark lines on a highly reflective plane, such as metre bars formerly used to define the metre, or high-reflectance lines on a dark plane, such as microscope stage micrometers and moir encoder scales. Calibration of the length of intervals between the lines is done by counting the number of reference optical wavelengths as the scale is traversed under a photoelectric line-detecting microscope. Calibration uncertainty is commensurate with the quality of the scales. The lowest uncertainty (not less than 20 nm) is achieved in the labour-intensive stationary-mode and is used only for the best scales. The scanning mode is more automated, but has a greater uncertainty (not less than 100 nm). The fee depends on the number of intervals to be calibrated.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-03-01 | Line scale: uncertainty class U = 0.1 µm. Stationary-mode calibration of intervals is performed on a precise scale, with an uncertainty not less than 20 nm depending on scale quality and length of interval. | Fee on request |
| A33-04-03-02 | Line scale: uncertainty class U = 0.3 µm. This service covers scanning-mode calibration of intervals on a precise scale, with an uncertainty not less than 100 nm depending on scale quality and length of interval. | Fee on request |
Grating pitch
Gratings with structures in the range 10 µm down to a few nanometers are used to calibrate the lateral scale of scanning probe microscopes used in nanotechnology. Using an optical diffractometer, our current capability is for nominal pitch values of p=350 nm or greater with expanded measurement uncertainty of 10-5 P.
The NRC imaging diffractometer measures the angle made by diffraction orders when the grating is illuminated by a laser beam. Diffractometer instruments measure the pitch of a grating within the area illuminated by the laser beam, yielding an evaluation of an average pitch value based on hundreds, even thousands of grating lines. The technique offers direct traceability to the SI definition of the metre with small uncertainty, obtained by the use of a calibrated laser and a calibrated angle measurement facility. The technique does not give information about the uniformity of the grating, since the variations in uniformity can be orders of magnitude poorer than the uncertainty of the average pitch measurement. The NRC diffractometer calibration service draws upon expertise in classical laser and angle metrology to provide a solid foundation for delivering the SI metre at the nanoscale to clients.
Level rods and target bars
Three-metre level rods with scales on an invar ribbon and 60-inch target bars for optical triangulation systems are calibrated using a long-bed Abbé comparator equipped with a laser interferometer. Under optimal conditions, these artifacts can be calibrated to an uncertainty commensurate with the quality of the gauge, but not less than 10 µm.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-05-01 | Level rod or target bar, one interval | $1640 |
| A33-04-05-02 | Level rod or target bar, each additional interval | $820 |
Diameter and roundness standards
Diameters from 5 mm to 300 mm are measured on a Mitutoyo Legex 707 CMM using a gauge-block substitution technique. Smaller external diameters, down to 0.1 mm are measured on a 1-D mechanical comparator (SIP305M). The best-measurement capability uncertainty depends on the size and quality of the artifact:
- external cylinders (plugs), 5 mm to 300 mm: U = [0.15 + 0.7D/1000] µm, D is diameter in millimetres;
- external cylinders (pins, wires), 0.1 mm to 5 mm: U = [0.25 + 0.01D] µm, D is diameter in millimetres;
- internal cylinders (rings), 5 mm to 300 mm: U = [0.15 + 0.7D/1000] µm, D is diameter in millimetres;
- balls, spheres, 5 mm to 250 mm: U = [0.15 + 0.7D/1000] µm, D is diameter in millimetres.
Diameter of a cylinder is usually measured in the marked reference direction across the circle, taken at three elevations. Special diameter measurements are available, and additional work can be done at cost in order to reduce the quoted routine uncertainties. Roundness and sphericity of artifacts up to 350 mm in diameter and 406 mm in height are measured on a vertical-spindle rotating-stylus type instrument (TR73 HPR). Routine calibrations are offered for:
- external cylinders (plugs), 5 mm to 350 mm diameter;
- internal cylinders (rings), 5 mm to 300 mm diameter;
- spheres and hemispheres, 5 mm to 250 mm diameter.
With roundness variations not exceeding 400 mm. Best measurement capability uncertainty is u= [17 + 11R] nm, R is the roundness in micrometres. Roundness of cylinders is usually measured at three elevations (charged as separate traces). Special roundness measurements are available, and additional work can be done at cost in order to reduce the quoted routine uncertainties.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-06-10 | Diameter, special calibration | Fee on request |
| A33-04-06-20 | Roundness, special calibration | Fee on request |
Fees for diameter and/or roundness standard calibration are calculated by adding the fees for the specific aspect measurements requested (A33-04-05-3x series) to the base fee (A33-04-06-30).
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-06-30 | Diameter and/or roundness standard base fee | $300 |
| A33-04-06-31 | First diameter (3 elevations) | $480 |
| A33-04-06-32 | Additional diameter, same artifact (3 elevations) | $310 |
| A33-04-06-33 | Roundness, per trace | $180 |
| A33-04-06-40 | Roundness, precision glass hemisphere | $1320 |
Angle standards
The angle calibration facility uses an interferometric optical sine-bar to generate angles over a 10 degree range to an uncertainty of 0.005 seconds. Combined with a 2-axis autocollimator and a precise indexing table, a variety of angle devices can be calibrated. These include: 1- and 2-axis autocollimators, angle gauge blocks, optical polygons and index tables. Calibration uncertainty is commensurate with the quality of the angle standard, but not less than 0.1 seconds for routine calibrations.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-07-00 | Angle calibration, special | Fee on request |
| A33-04-07-11 | Autocollimator, 1-axis | $2410 |
| A33-04-07-12 | Autocollimator, 2-axis | $3590 |
| A33-04-07-21 | Angle gauge, one | $1816 |
| A33-04-07-22 | Angle gauge, each additional | $435 |
| A33-04-07-31 | Square polygon | $2805 |
| A33-04-07-32 | Regular polygon, n-sided | Fee on request |
| A33-04-07-41 | Index table, (30o intervals) | Fee on request |
Surface roughness standards
Measurements of surface roughness are made using stylus equipment (RTH Form Talysurf) and a wide range of surface-roughness parameters can be determined (Ra, Rq, Ry, Rz, etc.). The instrument resolution is 10 nm over a 6 mm range. Roughness patches, steps or grooves can be measured to an uncertainty commensurate with the quality of the standard, but not less than 2 percent + 4 nm for any parameter.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-08-01 | Roughness transfer standard | $670 |
| A33-04-08-02 | Roughness transfer standard, each additional patch | $255 |
General form and profile measurements
General form (shape and size) within an envelope of 700 mm x 700 mm x 450 mm can be measured on the high-precision coordinate measuring machine (Mitutoyo Legex 707 CMM) with a linear uncertainty commensurate with the quality and size of the standard, but not less than 0.5 µm, and volumetric uncertainty not less than 0.8 µm. Smaller profiles, up to 6 mm high x 120 mm long, can be measured using the RTH Form Talysurf Stylus-type profiling instrument. The measurement uncertainty is given by (5L) nm, where L is the length of the profile in millimetres, but is not less than 100 nm.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-10-01 | Dimensional metrology of a test object | Fee on request |
Nation-wide measurement assurance program (ball plate)
The program provides access to calibrated CMM verification artifacts for companies who cannot afford to buy and maintain them. NRC offers a ball plate (list price of $20 000 plus $10 000 for yearly calibrations) for $500/week.
The ball plate is available for customers who wish to verify the accuracy of their measuring equipment (CMM, portable arm, laser scanner, etc). The calibration uncertainty of the ball plate parameters is less than 1.5 micrometres.
The client does blind measurements of the ball plate, which are then compared to NRC's results, and a measurement report is issued. The reported deviations are an indication of the general performance of the CMM and create a direct traceability to national standards.
| Calibration number | Description | Fee |
|---|---|---|
| A33-04-10-02 | Use of ball plate and analysis of 1 set of results | $625 |
| A33-04-10-03 | Analysis of an additional set of results | $100 |
Contact
Dr. Brian Eves
Telephone: 613-991-3279
Email: Brian.Eves@nrc-cnrc.gc.ca
Business Office: inmsbusino@nrc-cnrc.gc.ca
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