WIN475 Accelerometer Calibration Systems

MB’s Win475 is a turnkey, fully-functional, vibration transducer calibration system used to perform low uncertainty, automated calibration of accelerometers and velocity transducers. Calibration specialists deploy the Win475 to assure repeatable low-uncertainty calibrations, slash calibration costs and calibration times, and maximize productivity of the metrology lab. The Win475 calibrates virtually all accelerometer technologies regardless of size and weight including: Charge, Low Impedance, Voltage, Servos, Strain Gage, Piezoresistive, Capacitive, MEMS, TEDS, and AC- and DC-coupled. It can calibrate displacement and velocity transducers, even those with a built-in meter and no AC output. System Transfer Uncertainty matches or surpasses more expensive alternatives.

The Win475 calibrates over the frequency range of 1Hz to 10kHz; uses FFT processing and filtering at each calibration frequency for low uncertainty measurements; makes DC measurements of transducers including ZMO, Z-in and Z-out plus shunt calibration; and minimizes operator error by automatic software-controlled gain settings of the signal conditioner channels for maximum signal-to-noise during calibrations. The Win475 and its CAL50 exciter perform calibrations up to 35g’s pk and displacements up to 25mm peak-to-peak, depending on the frequency and weight of the DUT. DUTs weighing up to 900 grams can be calibrated within their performance specifications.

The designation “Win475-Standard” means the Reference Standard Accelerometer (REF), a single-ended standard embedded within the CAL50 Vibration Exciter, is calibrated according to ISO 16063-11 (Primary Calibration) by using a laser vibrometer. Laser calibration of the REF results in lower DUT uncertainties when the Win475-Standard is used for back-to-back calibrations of DUTs. MB also offers the “Win475-Basic” where the REF is calibrated using secondary or back-to-back methods. The Win475 is a proven product family with an installed base exceeding 185 systems. The
Win475-Standard is cost-justified with as few as 50 transducers needing calibration.

The Win475 Calibration Product Family includes options for calibrating down to 0.1Hz; air bearing shakers allowing sensitivity and phase calibrations out to 20kHz; Win475 system configurations in compliance with ISO 16063-21; resonant search of a transducer to 50kHz; measurement of a transducer’s transverse sensitivity; simultaneous calibration of up to 8 DUTs; shock calibrations up to 13,000g’s; and calibrations at extremes of temperature from -185 degC to +800 degC; and accelerometer amplitude linearity measurements up to 600g’s pk.

ISO 16063-21 Compliance

ISO 16063-21 “Vibration calibration by comparison to a reference transducer” describes the calibration of rectilinear vibration transducers by comparison to a standard calibrated by primary methods. The frequency range is from 0.4Hz to 10kHz, or as may be specified by a metrology lab. Per this ISO typical values for electrodynamic exciters designed for the frequency range of 10Hz to 10kHz are 200 m/s^2 – 1000 m/s^2 r.m.s. acceleration and 10mm peak-to-peak displacement. The vibration exciter has demanding requirements including transverse, bending and rocking acceleration that shall be ≤10% at frequencies ≤1kHz and ≤30% at frequencies >1kHz. Total harmonic distortion over the whole frequency range shall be ≤10%. MB’s Win475-Standard with any of MB’s air bearing exciters – CAL25HF, CAL25AB and CAL212AB – complies with ISO 16063-21.

MB can supply an uncertainty budget for the Win475-Standard. The MB uncertainty budget takes into consideration uncertainties associated with laser calibration of the REF, drift of the REF over time, transverse acceleration of the CAL25HF exciter, voltage ratio measurements, the gain match in the REF and DUT conditioning amplifiers, etc.

For users to develop their own uncertainty budgets, they would start with the MB-supplied Win475-Standard uncertainty budget. Then, in accordance with the methods in ISO 16063-21, users combine the significant sources of uncertainty in their lab including the DUT to determine the attainable expanded uncertainties of their calibrations.

Win475-Low Frequency Calibration and Performance Verification

Low-frequency accelerometers, vibration meters and velocity transducers are used for seismic measurements, bridge & building monitoring, shipboard measurements, suspension & ride quality, tilt/orientation and motion detection, safety systems, modal studies, train and off-highway equipment measurements, measuring rigid body motion, whole body vibration monitoring, and making measurements where the data are integrated to yield velocity or displacement. Amplitudes in milli-g’s and frequency ranges near DC are common.

The Win475 Low Frequency Option, Win475-LF, calibrates from 0.1Hz to 200Hz at g levels from 0.006 g’s – 1.25 g’s pk and at displacements as long as 280mm p-p as shown below. It uses a REF that is calibrated via primary methods gravimetrically in the range 0.07Hz – 0.5Hz and using a laser vibrometer from 0.5Hz to 10Hz. This helps achieve extremely small uncertainties.

MB achieves this impressive performance using its CAL2-300H actuator and innovative software control. The CAL2-300H uses a linear motor with friction-less air bearings under position control with a very-high resolution encoder in combination with acceleration control using a 1,200 mV/g reference accelerometer. The horizontal air bearing stage can calibrate transducers and meters weighing up to 5kg.

Download Win475-LF Data Sheet

Win475 “Extreme Range

Vibration monitoring transducers operate continuously at temperatures above 400 degC, for intermittent duty at over 700 degC, and over large 600 degC thermal cycling excursions. Such applications include gas turbine, jet engine and automotive engine development and monitoring. Prolonged exposures to the bitter cold of the Arctic tundra and high altitudes are harsh environmental conditions at the other end of the temperature scale.

Under such end-use environments, test, calibration, and measurement needs include validating the stability and reliability of the transducer & cabling, characterizing their thermal performance, and developing temperature sensitivity curves over this “extreme range” of end-use temperatures. The MB Win475 Extreme Range calibration option provides this functionality. This Option exposes accelerometers being calibrated (DUTs) to controlled temperatures over the range of +800 degC to -185 degC. It measures DUT temperature sensitivity with good repeatability while exciting at 160 Hz and is capable of vibrating at frequencies from 10 Hz – 1,000 Hz depending on DUT mass.

Download Win475 Extreme Range Data Sheet

Win475 Transverse Sensitivity

Vibration sensors are designed to measure motion in one principal axis perpendicular to the mounting base. But an accelerometer or velocity pick-up’s signal output is contaminated by motion in other directions. The transverse effect varies depending on the direction and amplitude of off-axis vibration. Transverse sensitivity refers to such output caused by cross-axis motion, expressed as a % of the nominal sensitivity with direction dependence. ISO 16063-31:2009 “Methods for the calibration of vibration and shock transducers — Part 31: Testing of transverse vibration sensitivity” was written to specify details of the instrumentation and methods to measure transverse sensitivity of vibration transducers.

The MB Dynamics Win475-TS (Transverse Sensitivity) Option enables measuring a sensor’s transverse sensitivity in accordance with ISO 16063-31 “Section 4, Determination of transverse sensitivity using a single-axis vibration generator”. The Win475-TS determines the sensitivity of a transducer to vibration perpendicular to its sensing axis. The magnitude of this transverse sensitivity varies with the direction of the off-axis vibration. The Win475-TS determines, reports and plots the maximum value, the angle at which the maximum occurs, and computes the ratio of the transverse sensitivity to the nominal sensitivity at user-selected frequencies.

Other transverse sensitivity measurement systems work ONLY at one frequency, but the Win475-TS is applicable over the frequency range from 30 Hz to 2000 Hz at 100 m/s^2 (frequency dependent). The Win475-TS works without mounting / re-mounting the transducer during the measurement, thus avoiding uncertainties that may be encountered in methods requiring repeated mounting. This makes it easier for the end-user and expedites and automates the transverse sensitivity measurement process.

Download Win475-TS Data Sheet

Win475 Multi-DUT Calibration Option

The Win475-Basic and Win475-Standard provide low uncertainty, broad frequency range calibrations on one transducer, or DUT, at a time. However, some end-users use transducers over a narrower bandwidth or do not require very low uncertainty calibrations every time a DUT is calibrated or require frequent verification of accelerometer performance where rapid turnaround on calibration time can be traded off against bandwidth and uncertainty. For those applications, MB provides its MB Win475-Multi-DUT Calibration Option in 2 versions. For end-users with charge, IEPE, voltage mode, and capacitive accelerometers the 4-DUT Option enables simultaneous calibration of 4 identical model transducers. The nominal frequency range is 5Hz – 4000Hz at up to 10g’s Pk, and over the 10Hz – 2000Hz the uncertainty is under 3%. This option uses a CAL50, the exciter in the Win475-Basic and Win475-Standard, with one REF at the center for conventional one-DUT calibrations plus 4 satellite REFs for each of the 4 DUTs. The REFs mount under the Test Instrument Mounting Fixture or TIMF which bolts to the CAL 50 armature.

For end-users with piezo resistive bridge-type accelerometers the 8-DUT Option enables simultaneous calibration of 8 PR transducers of the same model. This Option is used in multiple calibration labs supporting automotive crash tests where many, many PR transducers are used on dummies and whose sensitivities and valid outputs are measured before and after a test. This 8-DUT Option performs sensitivity calibration over the frequency range of 10Hz – 4000Hz at up to 10g’s RMS plus it performs static measurements on all DUTs including ZMO, Zin / Zout and shunt. 6 different shunt resistors can be selected plus there is an external socket for a customer-selected resistor. This Option also reads an electronic ID on the sensor. This Option uses one of MB’s three air bearing shakers, either the CAL25HF (from the ISO 16063-21 Option) or a CAL25AB or a CAL12AB – see the Calibration Exciter page for more details. This Option uses one REF at the center for conventional one-DUT calibrations and the same REF for each of the 8 DUTs. The REF mounts under the Test Instrument Mounting Fixture or TIMF which bolts to the air bearing exciter armature.

Win475 600g Accelerometer Amplitude Linearity & Sine Calibration Option

The Win475 calibration system performs comparison calibration of accelerometers and velocity transducers using sine and random vibration. The Win475-Basic and Win475-Standard perform sine calibrations up to 20g’s Pk depending on the exciter, frequency range, and weight of DUT. For accelerometers used in shock and ballistic applications, users desire to perform calibration and performance verification checks at higher amplitudes than 20g’s. The MB 600g Accelerometer Amplitude Linearity Option for the Win475 Calibration System (600g Option) calibrates and validates accelerometer amplitude linearity, or non-linearity, at amplitudes from 50g’s to 600g’s peak at frequencies below 1000Hz using sine vibration. With this Option added to MB’s Win475 Calibration System, sensitivity deviations can be measured over a user-selected range of high amplitudes and up to four sine frequencies, yielding actual high-amplitude sensitivity results augmenting those from low-g sine calibrations.

The graphic below shows calibration sensitivities can be provided with the 600g Option over a wider range of usage amplitudes than normal 10g calibrations. A metrologist’s uncertainty budget may include a term to account for the uncertainty of calibrations at 10g’s when the user tests at significantly higher g’s. This 600g Option enables that metrologist to reduce this uncertainty by actual sensitivity measurements at higher amplitudes and multiple frequencies.

The 600g Option uses structural resonance of specially designed metal beams that have very low damping to create these high vibration levels at the end of a beam. The beam is vibrated by an electro-dynamic shaker controlled by the Win475 software. The vibration at the end of the beam is measured by a REFerence accelerometer mounted underneath the beam with the DUT mounted directly above the REF. Four beams are supplied with the 600g Option. Each beam has one frequency, its nominal frequency which coincides with its first flexible mode, where the vibration created by the shaker is highly amplified.

Win475-Shock Secondary Calibration of Shock Transducers Using ShockDrop Exciter Option

The Win475 calibration system performs comparison calibration of accelerometers and velocity transducers using sine and random vibration. The Win475-Basic and Win475-Standard perform sine calibrations up to 20g’s Pk depending on the exciter, frequency range, and weight of the accelerometer being calibrated, or DUT. The Win475-600g Sine Calibration and Amplitude Linearity Option uses sine vibration to perform calibrations from 50g’s to 600g’s Pk at up to four frequencies below 1000Hz. For accelerometers used in shock and ballistic applications, users wish to perform calibration and performance verification checks at higher amplitudes than 20g’s or even 600g’s to increase their confidence level in the measured test results at amplitudes much higher than those nominally used to calibrate the DUT. The Win475-Shock Calibration Option performs repeatable shock calibrations of accelerometers measuring as large as 40mm X 40mm X 40mm and weighing up to 200 grams from 100g’s Pk to 13,000 g’s Pk using transient events, not sine or random vibration. This Option measures the sensitivity and amplitude linearity of the DUT with repeatability <±5% and is in accordance with Section 5.2.3 of ISO 16063-22 “Shock calibration by comparison to a reference standard transducer”. DUTs may be charge, differential charge, IEPE, voltage mode, PR, capacitive, and MEMS accelerometers. Target amplitudes in g’s peak are: 100, 200, 500, 1000, 2000, 5000, 10000, and 13000. Representative durations are 100g's (2msec), 2,000g's (0.36msec), 10,000g's (0.08msec), and 13,000g's (0.08msec). The Win475-Shock Option uses a ShockDrop exciter with a REF installed on the bottom of a special mounting plate and a DUT on the top of the mounting plate. This mounting plate rides in a rail cart which free falls into contact with a padded stop on an anvil located at the base of the ShockDrop apparatus. Various combinations of anvil pads and drop heights are used to achieve the desired peak g events for a selected calibration. The ShockDrop exciter includes a series of anvil pads or mitigators to control pulse amplitude. Pulse rep rate or duty cycle is 1 pulse every 10 -- 15 sec. The single-ended REF design greatly reduces mass loading effects common with double-ended REFs used in other shock calibration apparatus. In competitive systems the DUT mounts piggy-back to the REF which aggravates the mass loading effect. In MB’s ShockDrop exciter, the Shock REF is an IEPE-type with a sensitivity of 0.25mV/g, ±20,000 g's F.S., natural frequency >90kHz, 6 gram weight, calibrated at 100, 500, 1000, 5000 and 10000 g’s with reported sensitivities at each amplitude.

Data Sheets for Download

AirBearing Shakers Data Sheet: Download PDF
CAL50 Powered by MB500VI & P7000S Amplifiers Data Sheet: Download PDF
Model 8705M05 & 8706M06- Kistler Accelerometers Data Sheet: Download PDF
Model 405-X Signal Conditioner Data Sheet: Download PDF
Win475- CAL20300H, 50 kHz Data Sheet: Download PDF
Win475 Extreme Range Temperature Calibration & Performance Characterization System for Accelerometers Data Sheet: Download PDF
Win475 Low Frequency Calibration System Data Sheet: Download PDF
Win475 Transverse Sensitivity Data Sheet: Download PDF