By means of the adjustment values 1 and 2, the original measurement curve
(raw values) is associated with an actual leakage. This is necessary because a
"volume factor" is created by the overflow method and the overflow buffer
between buffer volume and total volume. This is also noticeable at the pressure
ratio of the buffer pressure to the test pressure.
The calibration is essential for correct working. For this purpose, a leakage
calibrator is required as measuring means.
First, determine the pressure ratio between the buffer pressure and the
overflow pressure after the overflow. With this ratio, the correct buffer
pressure for the desired test pressure must then be entered into the
Then measure the first raw value (original value) for the leakage zero
(calibration value 1)
Next, set a nominal leakage with the leakage calibrator and measure the
second raw value (original value) for the nominal leakage (adjustment value 2)
Assign the nominal leakage in the parameters to the measured raw values
The answer to this question depends on the load on the devices:
Under heavy load (every day in multi-shift operation) the device should be
checked and calibrated at least once a year
Under less severe stress, this cycle can be extended at once in two
This calibration does not replace a regular check or the update / upgrade by
the manufacturer. In addition, it says nothing about the condition of the
device. It reproduces only a snapshot of the measuring systems of the device at
a certain point in time.
During the filling process, thermo-dynamic processes occur in the test gas
(test air), which are to be compensated at a later time by the environment. If
shorter filling times are used, the test gas (test air) on the two sides of
the differential pressure sensor (test volume and comparison volume) can not
compensate and a curved differential pressure characteristic is produced
during the resting or measuring phase. Depending on the parameters, the curve
can be either upwards (direction positive values) or downwards (direction
negative values). By means of a corresponding filling pressure adjustment in
the filling phase 1, this effect can be counteracted somewhat.
There are actual leaks e.g. In the testing device. In this case, however,
you should first remove the leakage before setting a master value, since
otherwise incorrect measurements can occur.
There is a temperature influence. Cooling the test gas (test air) results
in negative and heating to positive values. In this case as well, it is
necessary to determine exactly where this temperature influence originates. In
the case of constant operations, the setting of a master value can be used to
counteract this effect. However, an incorrect application also leads to
incorrect measurements here!
The PMD02 in the variant DIFFERENTIAL PRESSURE can detect and evaluate
leakage not only as pressure change per time (e.g., as Pa / s) but also as
volume flow per time (e.g., ccm / min). For this conversion to be possible
correctly, the PMD02 requires the value of the total test volume connected to
the test side. This consists of a test piece, hose and internal device volume.
This total value must be entered in the corresponding parameter of the test
For more information on the calculation of the volume flow from a pressure
drop, please click
For a detailed description, refer to the device
A simple protocol is possible via the serial interface RS232 "Serial 2". The
device can be set in such a way that a result telegram is sent here after each
measurement. The telegrams can be recorded with a simple printer or a terminal
program. In addition, it is possible to record and evaluate the data as curves
and / or data records with the APT software PMD02-ANALYZE.
For a detailed
description, refer to the device documentation.