HeMaTech 3925-0050 - Setting up the Device for Specimen

Setting up the device for specimen Testing and Setup
EN 3925-0060 V207-00 MANUAL R03.doc
HeMaTech Prüftechnik
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Setting up the device for specimen
Testing with filling pressure
When testing under filling pressure (shock filling) set the filling pressure approx. 0.2
bar/ü or 10 % higher than the test pressure. However, the exact filling pressure can
only be determined with a specimen connected. To do so:
 Connect an absolutely leak tight specimen, position 20, to the specimen connec-
tion on the back of the tester.
The following applies as rule of thumb for the determination of the test times: filling
time and stabilization time together must make up approx. 2/3 and the measuring
time approx. 1/3 of the test sequence.
Stabilization time and filling time must be considered as independent functions:
− The filling time may set a trend for the measurement.
− The stabilization time stabilizes the measurement and thus the repetitive accu-
racy.
Example trend measurement
After the filling time has been set to 3 seconds the the stabilization time to 5 seconds,
the measuring value indicator moves with constant speed to 50 Pa over a measuring
time of 5 seconds.
When extending the filling time, the trend will be reduced e.g. to 5 … 10 Pa with un-
changed measuring time.
If the filling time is too long, the sign of the measuring value display for the trend
measurement will change; the measuring value display moves below 0 Pa to the nega-
tive range.
Once you have determined the optimal filling time, you can exactly adjust the stabili-
zation time. You can carry on reducing the stabilization time, as long as the measuring
values remain repeatable with sufficient accuracy.
This measuring time depends on the leak rate to be measured and the setting of the
limit contacts. This setting is bet be made with a specimen with limiting leak.
Testing without filling pressure
For testing without filling pressure (shock filling) you must consider the filling and stabi-
lization times as connected times.
Filling and stabilization times must be dimensioned in such a way, that the measuring
value display does neither jump, nor move for more than 5 Pa over a measuring peri-
od of 3 seconds, after the stabilization time has elapsed.
NOTE!
The cycle time can be reduced by shortening the filling or the stabili-
zation time and to run a so-called trend measurement.
Example:
With a leak tight specimen the measuring value display moves for 10 Pa and with a
specimen with limit leak it moves up to 20 Pa.
This measuring time depends on the leak rate to be measured and the setting of the
limit contacts. This setting is bet be made with a specimen with limiting leak.