6. Substitute Materials
In many instances for high capacity instruments, it may be uneconomic to transport the quantity of weights needed to reach maximum/working capacity; in such cases it will be necessary to use substitute materials.
For all calibration, the amount of calibrated test weights used before substitute materials are employed should be as high as is practicably possible; only in exceptional circumstances should substitute materials be used to calibrate instruments with a maximum capacity of 500kg or less.
Suitable materials will depend upon local conditions and availability. Vehicles, both empty and loaded, sand, ballast, water, or loose materials may all be used in appropriate conditions.
The test procedure when using substitute material is to carry out as much of the testing as possible using the calibrated weights and then remove the weights and add substitute material to the same weight or as near as is practicably possible below that value. The calibrated weights are then used to reach the next point(s). This procedure is repeated until the maximum (working) capacity of the machine has been reached.
Use of substitute materials requires that the error found during that part of the test using calibrated test weights be carried forward.
The use of substitute materials shall be noted in the comments section of the calibration certificate.