High-accuracy reference bridge CMM for calibration and form measurement
Reference-class bridge CMMs · sub-micron E0, form measurement, 20–22 °C rooms, Zerodur scales, probe and stylus changing
A high-accuracy reference CMM is a bridge coordinate measuring machine built and specified for sub-micron work: calibrating gauges and test specimens, measuring roundness and cylindricity, and serving as the reference in a measuring laboratory. Ask three things first: the ISO 10360 errors the maker will accept at your lengths, the temperature band and gradients that hold them, and the probing and stylus changing the machine will use.
Bridge CMMs specified in the sub-micron class for calibration, form measurement and reference measuring rooms, with their scanning probes and stylus or module change racks. Production bridge, gantry and similar Cartesian CMMs with general ISO 10360-2 acceptance are covered on the Coordinate measuring machines (CMM) page; portable arms, laser trackers and vision machines are outside this page.
CNFX editorial research · Sources checked October 12, 2026 · 3 sources
ZEISS states a length measurement error of 0.5 + L/500 µm for PRISMO ultra and positions it for research, quality assurance and the calibration of gauges or test specimens in reference measuring rooms; the machine uses ZERODUR scales with 20 nm resolution, thermal bending compensation, active pneumatic damping and improved air bearings. [1]
TNO publishes the figures for its own installed PRISMO ultra: E0 = 0.5 + L/500 µm at 20–22 °C and repeatability range R0 of 0.4 µm under ISO 10360-2:2009, scanning error THP of 0.9 µm under ISO 10360-4:2000, single-stylus probing error PF of 0.5 µm and multi-stylus errors PFTH 1.9 µm, PSTM 0.6 µm and PLTM 1.2 µm under ISO 10360-5:2010, a roundness form measurement error of 0.5 µm and a probing form tolerance PFTU of 1.0 µm. [2]
Editorial calculation: with E0 = 0.5 + L/500 µm, the permitted length error is 1.5 µm at L = 500 mm and 2.5 µm at L = 1000 mm, so the constant term dominates only on short lengths. [1] Ask for every figure in the set, not E0 alone, because multi-stylus and scanning errors on TNO's machine are larger than its single-stylus PF. [2]
ZEISS states that with its optional form measurement package, which includes a special probe set, the machine guarantees calibration of a ring gauge to 0.2 µm or better, and that roundness and cylindricity tolerances from 2 to 3 µm can be measured under the golden rule of measurement technology. [1]
Give the supplier the features and tolerances you must measure, the longest lengths, the probing method (single point, scanning, multi-stylus), and the ISO 10360 parts and values you will use for acceptance.
02
Plan the room, acclimatization and acceptance
ZEISS lists 20–22 °C for PRISMO ultra, and TNO quotes its E0 at 20–22 °C. [1][2] TNO's machine stands in a cleanroom classed 6/7 with an ESD-safe floor. [2]
ZEISS states that every PRISMO ultra granite plate is acclimatized for three months before delivery, the final inspection takes place in an air-conditioned chamber, and after installation a precision test is followed 4 to 6 weeks later by an acceptance test by an expert. [1] Editorial note: build that interval into the commissioning plan; the machine is not accepted on the day it is installed.
TNO's machine has a measuring volume of 900 × 1300 × 650 mm, a table height of 860 mm, a machine weight of 2770 kg and a maximum workpiece mass of 1500 kg; ZEISS lists sizes from 700 × 1000 × 500 mm to 1600 × 3000 × 1000 mm. [2][1] Editorial calculation: a 2770 kg machine carrying a 1500 kg part puts 4270 kg on the floor, which the foundation and any isolation must carry.
03
Choose the probe and the change rack
Renishaw's SP25M combines a scanning and a touch-trigger sensor in a 25 mm diameter housing, with five scanning modules carrying M3 styli from 20 to 400 mm and an adaptor for TP20 touch-trigger modules. [3]
Renishaw's FCR25 change racks store any SP25M element in each port, as a triple-port unit for its MRS modular rack or as 3-port and 6-port stand-alone units. [3] TNO's PRISMO ultra carries the ZEISS VAST Gold active scanning probe head. [2] Ask which probe and rack the quoted accuracy figures were measured with.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What length error does a reference-class bridge CMM reach?
ZEISS states E0 = 0.5 + L/500 µm for PRISMO ultra; at 1000 mm that is 2.5 µm by editorial calculation. [1]
Which other errors should be quoted?
TNO lists R0 0.4 µm, THP 0.9 µm, PF 0.5 µm, PFTH 1.9 µm, PSTM 0.6 µm and PLTM 1.2 µm for its machine. [2]
What stylus lengths can a scanning probe module carry?
Renishaw's SP25M modules carry M3 styli from 20 to 400 mm across five modules. [3]
Sources and what still needs a direct check
Sources checked 2026-10-12. ZEISS and Renishaw describe their own machine and probe; TNO, the Netherlands research organisation, publishes the specification of the machine in its laboratory.
