6 testo NanoMet Operation
18
Fig. 6.2: testo NanoMet control menu in software control mode
6.1.3.
Measurement state
In the MEASUREMENT state the disk starts to rotate. The system is ready to measure.
6.1.4.
Leak Test
UN-ECE R83 reglementations require a system leakage test to be executed prior to each
measurement test cycle. This leakage test is effected by feeding filtered air into the inlet of the
entire particle sampling system. The particle counter shall then report a measured concentration
of less than 0.5
#/cm
3
.
This test can be performed automatically selecting the LEAK TEST state in the testo NanoMet
control menu. In this state all parameters are set as in the measurement state except that the
primary diluter disk is not rotating.
This means no raw gas is added and therewith the filtered dilution air passes the dilution system
instead of measuring gas. If the detected particle concentration does not recede to zero, either
the secondary dilution air flow is set too low which leads to ambient air sucked through the
excess air outlet port, or some leakage occurs, probably caused by a filter defect, by a failure at
the diluter disk, an untight connection, or by a sensor defect.
The leak test will start when 'start data logging' is clicked if the LEAK TEST state is selected.
After 2 minutes test duration the system returns to the STANDBY state. The data logged during
the leak test are saved in the selected data folder.
6.1.5.
Zero Test
A PNC zero test is required once a day for UN-ECE R83 applications. In terms of this test filtered
air has to be feeded to the particle counter PNC. The PNC shall then report a measured
concentration of
≤
0.2
#/
cm
3
. The PNC shall show an increase in measured concentration to at
least 100
#/
cm
3
when challenged with ambient air and return to
≤
0.2
#/
cm
3
when filtered air is
applied again.
The ZERO TEST state of the testo NanoMet software cannot supply ambient air to the PNC but
filtered air can be provided by the testo ASET15-1 when the primary dilution air supply is turned
off and neither measuring gas nor dilution air passes the evaporation tube and only dilution air
enters and leaves the secondary mixing chamber. If the amount of secondary dilution air exceeds
the inlet flow of the PNC, it can only draw filtered air. Ambient air can be provided by manually
pulling off the tube connector from the testo ASET15-1 measuring gas outlet.
If the PNC signal does not recede to zero during the zero test, either the secondary dilution air
filter or the sensor might be faulty.
The indicated particle concentration values during the zero test are recorded and saved in the
selected data folder during 2 minutes when 'start data logging' is clicked.
The ZERO TEST can also be used to isolate the reason for leakage found in a leak test. If the
signal turns to zero in the zero test but not in the leak test, the leakage will probably be found in
the primary dilution subsystem.
