Field inspection manual—volumetric measuring devices
Part 3, section 1— Performance— return-to zero test
This test applies to all measuring devices equipped with registers that are resettable to zero.
R. 249, R.252 and R.256.
Reset the device to zero.
In the case of mechanical registers where the digits are returned to zero by mechanical (progressive) advancement, ensure that the elements of registration are obscured until the zero position is reached.
Mechanical printers must be interlocked so that they can print only the delivered / displayed volume.
In the case of devices that use a push-button, or other similar mechanisms, to initiate the reset-to-zero process, ensure that the process cannot be stopped until the zero position is reached.
All means of indication and recording of a device (gross volume, net volume, printed volume) including money register on price computing devices, must all return to zero when the reset-to-zero mechanism is activated. This requirement applies as well to computers interfaced to measuring devices.
The ability of a device to properly return to zero can be assessed every time the device is reset-to-zero following performance tests.
Interpretation of results
All means of registration of a device must return to zero accurately (without ambiguity).
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