Shock Tolerance Band Analysis

The function is organized around three overlaid traces: reference pulse, tolerance band and measured pulse. It consists of a standard pulse library, tolerance settings, the overlay display, automatic alignment, exceedance statistics and multi-channel continuous recording.

Standard reference pulses

Five nominal shock pulses are built in. They correspond to the pulses defined in widely used shock test standards.

The reference amplitude (peak acceleration in g) and pulse duration (ms) are entered directly. The duration setting covers 0.313 ms to 80 ms, from component-level to packaged-product tests. The corresponding velocity change is displayed as soon as the values are entered, for comparison with the standard.

Tolerance templates and custom bands

Tolerance requirements from common shock standards are available as templates.

A custom band is divided into a pulse region and left and right edge regions, each with its own upper and lower percentage (for example 15 % in the center and 20 % on the edges). The software generates the upper and lower limit lines from these values. Each parameter set can be saved as the default.

Overlay display

• Reference pulse: the nominal shape the shock should have.
• Upper and lower tolerance limits: the variation permitted by the standard.
• Measured pulse: the waveform from the current measurement channel.

An indicator shows “over upper limit” or “below lower limit” as soon as the measured pulse leaves the band.

Automatic alignment

The position of a shock in the time window shifts with early or late triggering. A fixed reference would then report false exceedances. Automatic alignment shifts the reference and band along the time axis to the position with the fewest exceedances and the best waveform match, so no manual positioning is needed.

Exceedance statistics

When enabled, the measured waveform is compared with the limits point by point across the sample window. The software counts out-of-band points, reports the exceedance ratio and reports how closely the matched channel follows the reference. The result can be used as a quantified record of pulse quality.

Multi-channel and continuous recording

• Synchronous multi-channel measurement; the reference can be bound to any channel.
• Continuous and single-shock modes; up to 341 shocks are recorded automatically per channel in continuous mode.
• Each shock is saved as a separate record for replay, overlay comparison and export.
• Trigger level, pre-trigger points and trigger interval can be set to capture the complete event.
• Low-pass or band-pass software filtering, configurable from the sampling rate, keeps the comparison within the required measurement bandwidth and suppresses high-frequency ringing.

A shock machine never reproduces the ideal pulse exactly. Pendulum, drop and pneumatic shock machines are affected by structural elasticity, programmer materials and specimen mounting, so the output always varies around the nominal pulse. Test standards therefore specify a nominal pulse with a tolerance band: the measured pulse must stay inside the band, and integral quantities such as velocity change must stay within their tolerances, for the test to be valid.

• Test validity: a pulse outside the band does not apply the specified stress, so the test result cannot be relied on.
• Repeatability: consistent excitation across laboratories and machines makes results comparable.
• Objective evidence: the overlay and point-by-point statistics replace a visual judgment with a recorded, traceable result.
• Protection of specimen and machine: overshoot, spikes or a collapsed plateau often indicate a machine problem that should be corrected before further tests.

The analysis chain has four automatic steps: reference generation, segmented band construction, automatic alignment, and exceedance and velocity-change evaluation.

Reference pulse generation

From the selected pulse type, amplitude A and duration D, the software generates the nominal pulse defined by the standard: half a sine period for a half-sine; a linear ramp with a steep edge for the sawtooth pulses; a symmetric triangle; or a flat-top pulse with ramped edges for a trapezoid.

Segmented tolerance band

• Baseline segments before and after the pulse use a small percentage of the amplitude (for example 5 %) to limit baseline noise and drift.
• Transition segments ramp linearly between the baseline and the pulse region.
• In the pulse region, the set percentage (for example +15 % / −15 %) is applied along the reference contour, so the peak and both edges have the permitted variation.
• Pulse-specific corrections extend the limit plateaus at features such as the trapezoid top and the sawtooth drop, matching the geometry of the standard tolerance drawings.

Automatic alignment

The reference and band are shifted along the time axis. For each position the software counts out-of-band points. The position with the fewest exceedances is selected first, and the highest normalized correlation second. This removes the effect of random trigger position and evaluates only the pulse itself.

Exceedance ratio and velocity change

At the selected position, each measured point is compared with the limits and the out-of-band points are converted to an exceedance ratio. The measured pulse is also integrated over the specified interval to obtain the actual velocity change, which is compared with the nominal value (for example ±15 %) as a second conformity criterion.

• Built-in tolerance templates for widely used shock standards. Selecting a standard generates the band without manual drawing or calculation.
• Reference, limits and measurement on one display, with immediate exceedance indication.
• Automatic alignment removes trigger-position effects and avoids false exceedances and unnecessary retests.
• Point-by-point exceedance ratio for a quantified record of pulse quality.
• Automatic recording of up to 341 shocks per channel, with record-by-record replay and comparison.
• A 0.313–80 ms reference duration range for components, boards, complete units and packages.
• Curves and results export to Excel, text or image files for test reports and quality records.

Before the test: measurement settings, reference and tolerance page

1. Select the measurement channel that the reference pulse is bound to.
2. Select the pulse type required by the test specification.
3. Enter the peak acceleration (g) and duration (ms). Check the displayed velocity change against the standard.
4. Select the tolerance template for the standard, or select Custom and enter the left, center and right percentages.
5. Enable automatic alignment and exceedance statistics.
6. Enable the reference and tolerance display and confirm. The main window shows the three overlaid traces.

Run the measurement

1. Select continuous or single-shock mode and set the trigger parameters.
2. Start the test. The system waits for the trigger and captures each shock.
3. Check the overlay: the pulse conforms when the measured trace stays inside the band with no exceedance indication.
4. In continuous mode, check each record, or replay records from the list after the test.
5. Where needed, apply software filtering and review again to exclude high-frequency ringing.

Results

• Mark or annotate conforming and non-conforming records.
• Export curves and statistics to Excel, text or image files for the test report.
• Save the settings as a template for similar tests.

A control module is verified with a half-sine shock to IEC 60068-2-27 (15 g / 11 ms). The values below are example data.

1. Settings: half-sine, amplitude 17.0 g (example value), duration 11 ms, template IEC 60068-2-27 / GB/T 2423.5 (peak ±15 %, velocity change ±15 %), automatic alignment and exceedance statistics enabled.
2. Display: the information bar shows amplitude 17.000 g, pulse width 11 ms and velocity change 1.161 m/s. The reference is centered with the band around it; outside the pulse region the band narrows to the baseline limits.
3. First shock: the measured peak is slightly below the reference but inside the band; exceedance ratio 0 %, no indication. The pulse conforms.
4. Second shock, after the programmer pad is changed: the trailing edge shows ringing that crosses the lower limit; the display shows “below lower limit” and an exceedance ratio of 3.2 %. The pulse does not conform. The pad preload is checked and the test repeated.
5. Record: the number of conforming shocks, the exceedance ratio of each shock and the velocity-change deviation are entered in the test report.