Servomex 07931001B, Руководство оператора

Страница: 130 / 221

116
© Servomex Group Limited. 2020 07931001B revision 6
•
Required span-gas valve state
Refer to the Modbus map in section 12.1.14 for the register address.
Note that once the Laser 3 Plus asks for the zero-gas valve to be turned on, it
assumes that this happens correctly and automatically proceeds to the next step
which is zero-gas flush.
The Laser 3 Plus will now wait for the zero-gas to flush through the validation cell.
The flush time is a settable parameter.
There is no involvement from the HMI in this step and the Laser 3 Plus will
automatically proceed to the next step once the zero-gas flush has been completed.
The Laser 3 Plus will now apply baseline subtraction. This will remove the effect of
the process measurement so that the validation span measurement will only
measure the span-gas in the validation cell.
Note that as mentioned in the system overview section, baseline subtraction is not a
perfect process. It takes a snapshot of the measurement spectra and then subtracts
it from all future spectra until you turn off baseline subtraction. If the measurement
does not drift and is not noisy then this should result in a concentration of 0%.
However, in reality the measurement is noisy to a greater or lesser extent and the
process itself will probably drift over time. This means that the concentration will
probably not be exactly zero. Any non-zero component of the process measurement
will appear as an error in the validation measurement.
This is why the first stage of validation (step 4) is to check that the process is stable
enough to allow validation to proceed and to obtain meaningful results.
There is no involvement from the HMI in this step and the Laser 3 Plus will
automatically proceed to the next step once baseline subtraction has been applied.
Once we have applied baseline subtraction, we again have to wait for the
measurement to stabilize. The measurement once it has stabilized should be about
0%.
The process is exactly the same as for step 4.
There is no involvement from the HMI in this step and the Laser 3 Plus will
automatically proceed to the next step once baseline stabilization has been
completed.