4. Installation prerequisites

Before a Q-Series Child Dummy is mounted on a sled, buck, or impactor rig, three independent readiness domains must be confirmed: the test fixture that carries and constrains the dummy, the dummy itself as a physical and instrumented article, and the calibration status of every measurement channel that will be recorded. A deficiency in any one of these domains invalidates the run regardless of how well the other two are prepared. This chapter explains what to inspect, how to inspect it, and what acceptance criteria to apply, so that the installation step begins from a verified baseline rather than an assumed one.

Fixture inspection: geometry, restraint interfaces, and instrumentation routing

Fixture inspection begins with the mounting interface. The seat pan and back pan surfaces must match the drawing-defined geometry within the tolerances stated in the test specification — typically flatness and angular position of the pan relative to the sled reference frame. Check the pan surfaces for dents, weld distortion, or previous-run witness marks that indicate local deformation; a deformed pan changes the dummy's pelvis and spine loading path and will bias both kinematics and injury criteria. Verify that the H-point reference fixture, if used, locates repeatably and that its mounting holes are not elongated.

Next, confirm the restraint interfaces. For a belted configuration, inspect the belt routing anchors, retractor mounting points, and any D-ring or slip-ring hardware for wear, correct orientation, and freedom of rotation. Belt webbing should be inspected for fraying, contamination, and prior-set folds; a belt that has been loaded in a previous test develops a set that alters its force–elongation behavior. For a child restraint system (CRS) installation, verify that the CRS anchorages on the fixture — ISOFIX/latch bars or belt paths — are undamaged and that the anchorage positions correspond to the intended seating row and position code.

Finally, inspect instrumentation routing on the fixture. Cable paths for the dummy's internal transducers, load cells, and any on-fixture accelerometers must be dressed so they cannot be pinched by the dummy during installation, cannot load the dummy through cable stiffness, and cannot be severed by belt or CRS contact. Confirm that connector breakout points are labeled and that strain relief is present at each transition from moving to fixed structure. A useful practice is to photograph the empty fixture with routing in place before the dummy is installed; this photograph becomes the reference for post-test comparison.

Dummy condition checks: physical integrity and channel continuity

The dummy condition check has two layers: physical and electrical. Physically, inspect the dummy for damage from previous use — skin tears at the pelvis, chest, and head; deformation of the neck or lumbar spine; looseness at joint centers; and contamination of the jacket or flesh. Any skin damage that exposes the internal structure or alters the contact surface must be repaired or the component replaced before installation. Check that the dummy's mass is within the manufacturer's stated tolerance for the build configuration; a dummy assembled with the wrong limb set or missing internal ballast will produce plausible-looking but invalid kinematics.

Electrically, perform a channel continuity and offset check with the dummy in a known, static attitude. With the data acquisition system powered and the dummy at rest, record a short static sample — 2 to 5 seconds is sufficient — and verify that every channel reports a stable offset within its expected range and that no channel is saturated, floating, or showing excessive noise. A channel that reads a plausible value but drifts during the static sample usually indicates a loose connector or a damaged cable; a channel that reads zero or full-scale usually indicates an open or shorted lead. Resolve these before installation, because fault isolation after the dummy is belted into the fixture is far more time-consuming.

Calibration status verification: traceability and validity windows

Calibration verification is a documentary and metrological check, not a physical adjustment. For each measurement channel, confirm three things: that a calibration certificate exists, that the certificate's validity window covers the scheduled test date, and that the certificate's sensitivity and channel identification match the physical channel actually connected. The third point is where errors most often occur — a certificate may be valid but issued for a different serial-numbered transducer, or the sensitivity entered in the acquisition software may not match the certificate value.

Build a channel-by-channel cross-check between the certificate, the transducer label, and the acquisition software entry. The table below shows the structure of such a cross-check for a representative subset of channels; the values are illustrative examples, not measured data.

Two failure modes deserve emphasis. First, an expired certificate does not mean the transducer is broken, but it does mean the channel cannot be used for a compliance-relevant result; the correct action is to replace the transducer with a calibrated spare or to reschedule. Second, a sensitivity mismatch between certificate and software is silent — the run will complete and produce data, but every result from that channel will be scaled incorrectly. The cross-check above catches both before the run begins.

How the three domains interact

The three readiness domains are not independent in their consequences. A fixture with a deformed seat pan will load the dummy differently, which can push a marginal transducer channel outside its expected range and mimic an instrumentation fault. A dummy with a loose neck joint can produce kinematics that look like a fixture alignment error. A mis-scaled channel can make a correctly installed dummy appear to have failed a criterion. The figure below shows the dependency structure and the decision points that gate the installation step.

The dashed feedback path in the figure reflects a practical point: when a domain fails, re-verify only the affected domain and any domain whose interpretation depends on it. If the calibration cross-check reveals a sensitivity mismatch, the dummy's static offset sample should be re-examined, because the offset was recorded through the same acquisition path. If the fixture inspection reveals a deformed pan, the dummy's physical condition should be re-checked for contact damage at the pelvis and back. Treating the three domains as a single coupled system, rather than three isolated checklists, is what prevents the most common pre-test escapes.

Documenting the readiness state

Close the prerequisite phase by recording the outcome in a form that the installation technician and the test engineer can both read at a glance. At minimum, record: the fixture inspection result with any deviations noted, the dummy serial number and build configuration, the static offset values per channel with ambient temperature, and the calibration cross-check result per channel with certificate identifiers and validity dates. Where a deviation was accepted under engineering judgment, record the rationale and the compensating action. This record becomes the baseline against which post-test anomalies are diagnosed — if a channel behaves unexpectedly during the run, the pre-test offset and calibration entry are the first two facts to consult.

With all three domains verified and documented, the dummy can be installed with confidence that the baseline is sound. The installation itself — positioning, belt or CRS application, and pre-test attitude confirmation — then proceeds from a known-good starting state, and any anomaly observed during or after the run can be attributed to the installation or the test event rather than to an unverified prerequisite.