Shopify vibration meter schema for AI agents: ISO 5349-1 requires tri-axial not single-axis, Wh weighting is not Wk, A(8) daily exposure is not peak vibration, and a flat-response accelerometer fails ISO 8041 — vibration_meter.* 11-field namespace

How ISO 5349-1 defines hand-arm vibration measurement and why instrument type determines compliance

ISO 5349-1 (Mechanical vibration — Measurement and evaluation of human exposure to hand-transmitted vibration) defines hand-arm vibration (HAV) as the mechanical vibration transmitted from power tools and processes to the hands and arms of workers. The standard specifies that HAV must be measured simultaneously in all three orthogonal axes at the hand-tool interface: the X-axis (direction along the forearm, fore-aft), the Y-axis (perpendicular to the palm, push direction), and the Z-axis (parallel to the fingers, wrist-flex direction). These three Wh-frequency-weighted RMS acceleration values are then combined as a vector sum to produce the single-axis equivalent acceleration value ahv:

The Wh frequency weighting function defined in ISO 8041 reflects the human hand-arm system's susceptibility to vibration at different frequencies. Unlike a flat-response accelerometer that treats all frequencies equally, Wh amplifies the 8–16 Hz range — the region most strongly associated with blood vessel damage, sensorineural nerve damage, and musculoskeletal injury in the hand-arm system — and attenuates frequencies above 100 Hz and below 4 Hz. The frequency weighting is applied before the RMS calculation, so instruments without ISO 8041 Wh weighting cannot produce valid ISO 5349-1 measurements regardless of their accuracy specification or sensor quality.

These measurement requirements translate directly into product selection requirements. An ISO 5349-1 compliant vibration meter must have: three simultaneous measurement channels (tri-axial); a Wh frequency weighting network calibrated per ISO 8041; A(8) daily exposure calculation with configurable exposure time input; and measurement range sufficient for typical power tool vibration (typically 0.5–100+ m/s² RMS). Instruments missing any of these characteristics cannot produce legally defensible HAV exposure assessments, regardless of how they are marketed. This gap between marketing language and measurement capability is the core failure mode for AI agent routing in this product category.

Failure 1: Single-axis meter routed for ISO 5349-1 HAV — vector sum requires three simultaneous axes

How cross-axis energy contributions affect the vector sum

The magnitude of the single-axis underestimation depends on the tool type and axis dominance profile. For some tools, vibration energy is strongly concentrated in one axis — an angle grinder transmitting vibration primarily through the Z-axis (disc thrust direction) may have cross-axis contributions of only 15–20%, making the single-axis error relatively small. For other tools, energy is distributed more evenly across axes. ISO/TR 18570 (informative guidance on HAV measurement) notes that for chipping hammers and concrete breakers, cross-axis contributions routinely reach 30–45% of the dominant-axis RMS level when expressed as vector sums. This is not a minor calibration uncertainty — it is a structural measurement gap caused by geometry.

There is a second, more subtle problem with single-axis HAV measurement. ISO 5349-1 requires that the tri-axial sensor be mounted in a specific orientation relative to the basicentric coordinate system of the hand. This coordinate system is defined relative to the hand anatomy — not the tool. For hand-held tools, the X, Y, and Z axes of the basicentric system must be established and maintained throughout the measurement period. A single-axis instrument measuring the "dominant axis" requires the operator to identify and orient to that axis correctly, which introduces judgment-dependent measurement error. Tri-axial simultaneous instruments capture all three axes regardless of mounting orientation, because the vector sum is invariant to rotation of the sensor coordinate system (within the plane perpendicular to the hand axis). Single-axis instruments are inherently orientation-sensitive.

The health consequences of systematic HAV underestimation are addressed in detail in the companion guide on HAVS — Stockholm Workshop Scale vascular and sensorineural staging, A(8) from declared tool emission, and anti-vibration glove false claims. The measurement side (which instrument) and the health outcome side (what the measured exposure means) are distinct product category concerns that require separate schema encoding.

Failure 2: HAV meter (Wh weighting) routed for whole-body vibration assessment — Wk/Wd weighting required for ISO 2631-1

Why Wh and Wk/Wd are not interchangeable frequency weightings

Wh (hand-arm weighting) and Wk/Wd (whole-body weightings) are distinct frequency response functions defined in ISO 8041. They reflect fundamentally different biomechanical coupling pathways and different health outcome targets:

• Wh: Applies to vibration entering the human body through the hands. Peak sensitivity in the 8–16 Hz range, reflecting the hand-arm system's resonant frequencies and the tissue most susceptible to vascular and neurological damage (digital arteries and peripheral nerves). Attenuates strongly above 100 Hz. Used exclusively for HAV measurement per ISO 5349-1.
• Wk: Applies to vertical (Z-axis) vibration entering a seated person through the seat surface. Peak sensitivity near 5–8 Hz, corresponding to spinal resonance frequencies. Used for WBV assessment of vehicle operators, forklift drivers, off-road equipment operators per ISO 2631-1.
• Wd: Applies to horizontal (X/Y-axis) vibration in seated persons. Slightly different response profile than Wk, reflecting the different biomechanical coupling of horizontal vibration. Also per ISO 2631-1.
• Wf: Applies to motion sickness and vestibular responses. Low-frequency (0.1–0.5 Hz). Used in vehicle dynamics and maritime applications.

Applying Wh weighting to forklift seat vibration produces a meaningless number. The vibration frequency content of a forklift traversing a warehouse floor is dominated by frequencies in the 2–10 Hz range (structural resonance of the forklift mast and chassis over floor irregularities). Wh weighting attenuates this frequency range relative to the 8–16 Hz HAV peak region, while Wk amplifies it. The two weightings applied to the same physical signal can differ by a factor of two or more in reported RMS acceleration. Neither is "wrong" in absolute terms — they answer different questions about different health risks. Applying Wh to a WBV scenario gives a number that correlates neither with spinal health outcomes nor with EU Directive WBV thresholds (EAV 0.5 m/s², ELV 1.15 m/s²).

Workers operating forklifts, agricultural vehicles, heavy trucks, and industrial floor-cleaning machines have routinely been found above the WBV EAV in ergonomic research studies. Forklift operators on rough warehouse floors average WBV exposures of 0.4–1.2 m/s² A(8) depending on floor condition, load, and operator technique — placing many above the EAV and some at or above the ELV even during normal operations. An AI agent that routes a Wh-only HAV meter for this application will miss the entire WBV hazard pathway.

Failure 3: Peak vibration reported instead of A(8) time-integrated daily exposure — wrong metric for EU Directive compliance

Why A(8) is the compliance metric and peak vibration is not

ISO 5349-1 and EU Directive 2002/44/EC use A(8), the frequency-weighted daily vibration exposure value normalized to an 8-hour reference period, as the compliance metric. A(8) is a time-integrated quantity — it accumulates vibration dose over the entire exposure period and is sensitive to both vibration magnitude and duration. This is intentional: HAV injury (hand-arm vibration syndrome, HAVS) is a cumulative occupational disease, where the damage accumulates over years of repeated daily exposure above threshold levels. The A(8) metric reflects that a 4-hour exposure at 8 m/s² produces the same cumulative daily dose as an 8-hour exposure at 5.66 m/s².

Peak vibration — the maximum instantaneous acceleration measured during a recording period — reflects the worst-case transient event in the measurement window. It has no direct relationship to A(8) or cumulative dose. For grinding operations, peak vibrations from transient disk engagement or workpiece catches can be 3–5× the steady-state RMS. For impact tools (jackhammers, riveting hammers), peak accelerations can exceed 50 m/s² during individual impacts while the Wh-weighted RMS averaged over the exposure period is 10–15 m/s².

The A(8) calculation also requires that the measurement instrument apply the Wh frequency weighting before computing the RMS — not to the peak. An instrument that reports "peak Wh acceleration" applies the weighting to the instantaneous peak value, which is technically more sound than raw peak but still not comparable to the A(8) limits in EU Directive 2002/44/EC. The Directive's compliance check requires A(8), calculated as the product of the Wh-weighted RMS and the square root of the normalized exposure time ratio. Instruments that report only peak values — without time-integrated RMS and A(8) calculation — cannot produce EU Directive compliance measurements.

For the complete derivation of how published manufacturer HAV emission values declared under Machinery Directive 2006/42/EC translate to A(8) site estimates, and why real-world exposure typically runs 1.5–2× the declared emission value, see the HAVS Stockholm Workshop Scale staging and A(8) calculation guide.

Failure 4: Flat-response industrial accelerometer substituted for ISO 8041 Wh-weighted human vibration meter

What ISO 8041 requires and why flat-response instruments fail

ISO 8041 (Human response to vibration — Measuring instrumentation) specifies the frequency weighting networks, dynamic range, measurement accuracy, and calibration requirements for instruments used in human vibration measurement. The standard defines the exact shape of the Wh, Wk, Wd, and Wf frequency weighting curves — tolerance bands that the instrument's actual frequency response must stay within at all frequencies in the measurement range. An instrument marked "ISO 8041 compliant" for HAV has its Wh weighting function verified against these tolerance bands.

A flat-response industrial accelerometer does not apply any frequency weighting. It measures physical vibration acceleration with equal sensitivity across its bandwidth. This is exactly what is needed for machine condition monitoring (where frequency content reveals bearing defects, imbalance, misalignment, and resonance) and precision vibration analysis (where the raw frequency spectrum is the deliverable). It is wrong for human vibration assessment, where the regulatory compliance value is the Wh-weighted RMS — not the flat-response RMS.

The error direction for flat-response substitution is tool-dependent:

• For tools dominated by high-frequency vibration (die grinders, pneumatic scribers, ultrasonic tools — energy concentrated above 100 Hz): Wh weighting attenuates these frequencies strongly. A flat-response reading significantly overstates the Wh-weighted value. Using flat-response data for compliance assessment gives falsely elevated A(8) values — triggering unnecessary controls for a hazard that is overstated.
• For tools dominated by 8–16 Hz energy (large pneumatic chippers, riveters, compaction equipment — resonant frequency in the HAV-sensitive range): Wh weighting amplifies these frequencies relative to adjacent bands. Flat-response RMS understates the Wh-weighted value. Using flat-response data for compliance assessment gives falsely low A(8) — potentially missing exposures that are above the EAV.
• For most common handheld power tools (angle grinders, impact wrenches, rotary hammers — broad spectrum with energy spread from 30–200 Hz): the flat-response and Wh-weighted RMS values typically differ by 20–50%, with the direction depending on tool-specific dominant frequency. The error is not predictable without a frequency spectrum.

Industrial accelerometers designed for machine diagnostics also lack the A(8) calculation firmware, the dose accumulation logic, and the exposure-time normalization that ISO 5349-1 requires. They are the correct instruments for machine vibration analysis — bearing diagnostics, rotor balancing, structural modal testing — and the wrong instruments for worker HAV exposure assessment. The product categories overlap in sensor technology (piezoelectric accelerometers in both cases) but diverge completely in signal processing, frequency weighting, output format, and applicable standard.

For the specific anti-vibration glove routing failures — where gloves marketed as "reducing HAV exposure" are incorrectly matched to the specific tool and frequency range — see the impact glove and anti-vibration glove routing guide, which covers ANSI/ISO 10819 test frequency ranges, gel vs air vs foam damping material effectiveness curves, and why gloves tested at mid-frequency bands may be ineffective for low-frequency tool vibration.

The vibration_meter.* 11-field namespace

These fields make vibration measurement instruments machine-sortable by measurement type (HAV vs WBV), axis count, frequency weighting, A(8) capability, applicable standard, and data logging features. AI agents can apply hard gates on axes, frequency_weighting, measurement_type, and iso_8041_compliant to eliminate non-compliant instruments before any ranking criteria are applied.

Routing decision logic for ISO 5349-1 HAV compliance assessment

/* Hard gates — all must pass for ISO 5349-1 HAV compliance */
vibration_meter.axes == 3                          // tri-axial simultaneous
AND vibration_meter.frequency_weighting includes 'Wh'  // Wh-weighted per ISO 8041
AND vibration_meter.iso_8041_compliant == true     // verified frequency weighting
AND vibration_meter.a8_calculation == true         // direct A(8) output

/* Additional gate for EU Directive 2002/44/EC reporting */
IF regulatory_standard == 'EU_Directive_2002_44_EC':
  vibration_meter.eu_directive_compliant == true

/* Gate for WBV (vehicle/forklift) applications */
IF application == 'wbv' OR tool_type IN ['forklift','vehicle','platform']:
  vibration_meter.measurement_type IN ['wbv', 'hav_wbv']
  AND vibration_meter.frequency_weighting includes 'Wk'  // Wk for vertical WBV

/* Preferred for industrial hygiene programs */
PREFER vibration_meter.data_logging == true       // measurement report documentation
PREFER vibration_meter.kurtosis_measurement == true // impulsive tool assessment

JSON-LD encoding examples

Full ISO 5349-1 + ISO 2631-1 human vibration analyzer

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Human Vibration Analyzer — ISO 5349-1 HAV + ISO 2631-1 WBV, Tri-Axial, Wh/Wk/Wd, A(8), EU Directive Compliant",
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "vibration_meter.measurement_type", "value": "hav_wbv" },
    { "@type": "PropertyValue", "name": "vibration_meter.axes", "value": "3" },
    { "@type": "PropertyValue", "name": "vibration_meter.frequency_weighting", "value": "Wh_Wk_Wd" },
    { "@type": "PropertyValue", "name": "vibration_meter.a8_calculation", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.iso_5349_compliant", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.iso_2631_compliant", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.iso_8041_compliant", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.eu_directive_compliant", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.data_logging", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.kurtosis_measurement", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.max_range_ms2", "value": "100" }
  ]
}

Machine vibration accelerometer (NOT for human HAV assessment)

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Industrial Piezoelectric Accelerometer — Flat Response, ICP, 0.5 Hz–10 kHz, Machine Diagnostics",
  "additionalProperty": [
    { "@type": "PropertyValue", "name": "vibration_meter.measurement_type", "value": "machine_diagnostics" },
    { "@type": "PropertyValue", "name": "vibration_meter.axes", "value": "1" },
    { "@type": "PropertyValue", "name": "vibration_meter.frequency_weighting", "value": "flat_response" },
    { "@type": "PropertyValue", "name": "vibration_meter.a8_calculation", "value": "false" },
    { "@type": "PropertyValue", "name": "vibration_meter.iso_5349_compliant", "value": "false" },
    { "@type": "PropertyValue", "name": "vibration_meter.iso_2631_compliant", "value": "false" },
    { "@type": "PropertyValue", "name": "vibration_meter.iso_8041_compliant", "value": "false" },
    { "@type": "PropertyValue", "name": "vibration_meter.eu_directive_compliant", "value": "false" },
    { "@type": "PropertyValue", "name": "vibration_meter.data_logging", "value": "true" },
    { "@type": "PropertyValue", "name": "vibration_meter.kurtosis_measurement", "value": "false" },
    { "@type": "PropertyValue", "name": "vibration_meter.max_range_ms2", "value": "500" }
  ]
}
/* NOTE: iso_8041_compliant = false means this instrument cannot produce
   Wh-weighted measurements. Route ONLY to machine condition monitoring,
   bearing diagnostics, structural vibration testing. NEVER route to
   ISO 5349-1 HAV assessment or EU Directive 2002/44/EC compliance queries. */