Furness controls FCO770, Руководство пользователя

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FCO770 Users Guide Issue 1 Page 91
When the minimum stabilisation time has been established, leave the leak tight test item
vented for at least five minutes. Once the test item is back at the same conditions as the
normal production items, start a test with the “Learn Offset” input enabled. The leak detector
will measure the pressure offset caused by the reduced stabilisation time and, provided it is
less than 40% of the instrument’s full scale differential pressure, store it in the appropriate
test number.
The track filter should now be set so that the instrument will remove any signal caused by
slow changes of ambient conditions. A value of 5 is a good starting point to be small enough
to cater for most temperature changes experienced in a factory environment, yet large enough
to prevent the masking of consecutive leaks.
At least ten production items should now be tested and the variation between tests monitored.
If the variation is too great and it is not caused by genuine leaks in the products, then the
stabilisation time should be increased until the variation is acceptable. When the stabilisation
time is altered, the offset will need to be re-learnt.
If during production, there is significant temperature variation causing rapid drift in the
stability curve of one test item to the next and the instrument is unable to track the change,
then the track filter value should be reduced.
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Once the initial setting up procedure has been completed and the required fill, stabilise and
test times have been established, it should only be necessary to learn the offset whenever a
new batch of test components are started or if there is a break in production.
Fit a master leak tight test component. This must be of the same construction as the normal
production items and must be stored at the same conditions as the production items. The item
must not be tested more than once without allowing time for it to relax back to the same
conditions as an untested component (normally greater than five minutes).
The learn phase can be initiated from the instrument front panel or by an external switch
contact. When an external switch is used it should be closed whilst the START button is
pressed.
The digital filter is reset when the product is changed.