AS 4422:2016 – Playground surfacing-Specifications,requirements and test method. Length measuring equipment
In the case of free-fall impact tests, means shall be provided so that when conduding an impact lest, the drop height can be measured directly prior to release of the missile.
NOTE: Calculating the drop height from the measured time between release and contact of the missilc with thc surface may bc not sufficient bccaus of possible time differences between the start of time measurement and the effective release of the missile (e.g. caused by pennanenr magnetism in a magnetic rclcasc system).
In all cases, the drop height shall be measured with an uncertainty of not greater than 1%. Velocity meusuring equipment
In the case of guided impact tests, means shall be provided so that thc theoretical drop height can be calculated by measuring the velocity of the missile immediately prior to the impact.
In all cases, the velocity shall be measured with an uncertainty of not more than ±1%.
NOTE: To allow for frictional losca. h velocity of the misiIe immediately prior to impact is recorded in order to calculate the equivalent drop height as if the missile had been in free fall.
2.2.2 Impact measuring equipment Genera!
Impact measuring equipment shall consist of an accelerometer measurement system
(see Clause, a recording device (see Clause and a HIC calculation program
(sec Clause
The accelerometer measurement system shall be capable of measuring all frequencies in the range 0.3 Hz to 1000 Hz and having a sufficient response at all frequencies to keep amplitude crn)rs below 5%, in accordance with ISO 6487 Channel Class 1000. It shall be capable of measuring, recording and displaying the acceleration and lime duration of each complete impact. Recording device
The recording device shall be capable of capturing and recording the acceleration time signals produced during an impact at a minimum sampling rate of 20 ku.
Signal conditioning and filtering shall be compatible with the accelerometer and the data channel specified. This process shall conform to ISO 6487.
NOTE: According to ISO 64117. the analoguc anti-aliasing filters should havc an attenuation minimum of 30 d13 at half the sampling rate.
2.21.4 Program for calculating the HIC value
The apparatus shall include a program for calculating the IIIC. IlIC duration. g,,, time and date for the recorded acceleration time history of each impact in accordance with Clause
2.3.1 Calibration measuring device
Apparatus shall be equipped with calibrated measuring devices.
Laboratory measurement equipment including the signal processing equipment and the measuring of drop height shall be validated at a minimum every six months.
On-site measurement equipment shall be validated before and after each set of measurements using a reference rile. If thc validation value is greatcr than 10% the unit shall be re-calibrated.
Testing in accordance with this Standard shall be undertaken by a laboratory that fulfils the requirements of AS ISOIEC 17025,
I A laboratory may demonstrate that it fulfils the requirements of AS ISO IEC 17025 through accreditation as a signatory member of the International Laboratory Accreditation Cooperation (ILAC). %lutual Recognition Arrangcmcnt IMRA) with a relevant scope of accreditation to cover the tests being performed.
2 In Australia. the signatory member of the II.AC MRA is the National Association of Testing Authorities. Australia (SATA).
2.3.2 Calibration criteria
Apparatus shall be calibrated based on the following criteria:
(a) Accelerometers shall be calibrated for the whole frequency range. Recalibration shall be carried out at time intervals recommended by the manufacturer of the accelerometer or at a minimum every iwo years. Accelerometers shall have an uncertainty no greater than 5% Ut the 95% confidence level.
(b) Velocity measurement systems shall be calibrated for the whole velocity range (up to 3 m drop height).
(c) The computer algorithm used for the calculation shall be checked by imposing a half-sine curve and the result, when compared with an independent mathematical calculation of this curve, shall not deviate by more than ±1%.
(d) Reactions from the release system on the missile shall be tested by a minimum series of three consecutive drop tests on a defined reference surface with constant properties. The HIC values obtained shall not differ more than ±5%.
I These tests are for checking any deviations or anomalies in the components and replace neither calibration nor the validation for compliance of the apparatus with this Standard,
2 Experience has shown that comparative testing on defined surfaces ntight not be sufficient and that an external calibration of the measuring device is required.