Dräger X-act 7000 Manual Tecnico página 42

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Description
data integrity. The RFID/NFC tag contains metadata on the MicroTubes (e.g.
substance designation, measuring range, part number, lot number), which are
displayed to the user, parameters for sampling (e.g. mass flow, image lighting), and
parameters for evaluating the image data using the front tracking algorithm, among
other things. The X-act 7000 is now ready to perform a measurement in line with
the specifications of the inserted MicroTubes.
3.1.7.2 Checks
Before starting the actual measurement, the capillary to be used undergoes several
checks to ensure the receipt of a reliable concentration calculation at the end of the
measurement. First, a check confirms whether the capillary remained intact on its
path from production to final use and that no ambient air penetrated prematurely,
which could have led to a premature change in the discoloring chemical
preparation. To do so, the pump is activated with a defined power in order to
determine the resulting mass flow as a reference using the mass flow sensor. The
tip of the capillary facing the pump is then broken and an air-tight connection is
simultaneously established between the capillary and the pneumatic system
consisting of the mass flow sensor and the pump. The mechanical contact is
confirmed by an initial 'cracking' sound. The pump is re-activated and the resulting
mass flow is compared with the previously determined reference. If the capillary is
intact, no significant mass flow can be created; rather, a slight negative pressure
forms in the air-tight path between the pump and the capillary tip on the inlet side. If
this is the case, the leak test is successfully completed. The inlet side of the
capillary is now also mechanically contacted and an air-tight connection between
the device inlet and the pneumatic system is established via the capillary. This
process can be detected by a second, cracking sound. The capillary can now be
exposed to ambient air for measurement in the specified manner. The remaining
negative pressure can lead to an initial penetration of ambient air into the capillary
in this process. If the concentrations of the target analyte are very high, a large part
of the chemical preparation is already irreversibly discolored and is thus no longer
available in the actual measurement to determine the concentration. To still be able
to inform the user of the potentially hazardous situation early on in this case,
another preliminary test was integrated into the process. For this purpose, photos
are taken with the camera before and after the complete integration of the capillary
into the gas-conducting path. These are compared with one another and, in the
event of excessive discoloration after the leak test, the measurement is completed
prematurely with the result "Overrange".
3.1.7.3 Measurement
At the start of the actual measurement, a photo is taken of the as yet non-discolored
capillary. The pump, regulated by the mass flow sensor, then generates the mass
flow through the capillary as specified for the MicroTubes. If the target analyte is
present, this reacts with the chemical preparation in the capillary, causing a
discoloration. This process is recorded by the camera in the photos, which are then
analyzed by the front tracking algorithm. Every new photo is compared with the
reference photo taken at the start. The speed of migration of the discoloration by
the capillary is extracted and the existing concentration is calculated with the lot-
dependent calibration curve created on the RFID/NFC tag.
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Technical Manual
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X-act 7000